Professor Jose Torero provides expert fire engineering testimony on compartment fire dynamics in flat 16, uPVC window surround failure, cavity effects, and vertical flame spread mechanisms that led to the rapid external spread at Grenfell Tower.
00:07:26 good morning everyone if I could just go through the housekeeping announcements with you for today there's no planned fire alarm test today the fire alarm test is usually on a Wednesday at 4:45
00:07:39 test is usually on a Wednesday at 4:45 if the alarm sounds trained fire wardens on the second floor will direct you to evacuate there are two fire exits within the room on the right-hand side facing
00:07:50 the room on the right-hand side facing the chair that's on that side of the room
00:07:53 room joven bar staff and the inquiry team will ensure you are evacuated first before they evacuate the building please do not leave personal possessions in the hearing room overnight any items found
00:08:05 hearing room overnight any items found will be removed by security at the end of the session please remain seated until the chairman and the witness have left the room also please remember to switch your phones to silent in the
00:08:17 switch your phones to silent in the hearing room I've also been asked to advise you that we do have support workers both in this room and on the second floor they are available for anyone that might wish to speak to them
00:08:29 anyone that might wish to speak to them thank you very much
00:10:56 good morning everybody welcome to today's hearing today we're going to start hearing from expert witnesses instructed by the inquiry to advise us
00:11:07 instructed by the inquiry to advise us in relation to various aspects of the fire yes good morning mr. chairman yes we will be hearing today from Professor Jose torero who is one of three experts
00:11:19 Jose torero who is one of three experts who will be giving evidence this week professor Bisbee and dr. Lane will follow tomorrow and Thursday yes so if I can now call professor torero thank you
00:11:33 can now call professor torero thank you yes
00:11:51 I do solemnly sincerely and truly declare and affirm that the evidence I shall give shall be the truth thank you
00:12:07 shall give shall be the truth thank you very much sit down make yourself comfortable and it's grated before you start I think I'm sure the professor is well used to delivering lectures and
00:12:18 well used to delivering lectures and other material for quite the extended periods but I think we should have a break during the middle of the morning yeah I think possibly one break will be sufficient and this you professor indicate that you'd like one any other
00:12:29 indicate that you'd like one any other stage if you do because let me know okay thank you thank you yes yes thank you so please would you give the inquiry your name Jose Luis Toro : and you have
00:12:41 name Jose Luis Toro : and you have provided to the inquiry a preliminary phase 1 report which was dated the 23rd of May and you have updated that report in a revised version dated the 21st of October 2018 and also with an
00:12:53 October 2018 and also with an accompanying two-page addendum document dated the 20th of October is that right yes and that report addresses your preliminary conclusions on the ignition
00:13:04 preliminary conclusions on the ignition of the Graham felt our facade materials far spread to and on the exterior of Graham 'full tower and fire and spray smoke spread within Graham phone tower that's right yes yes that's correct
00:13:15 that's right yes yes that's correct and it's important to note that you have also been instructed to provide a further report at phase 2 which will address forensic fire and smoke spread
00:13:26 address forensic fire and smoke spread throughout Graham tall tower the correlation between the fire safety provisions and the fire safety strategy for Graham phone tower and various aspects of the adequacy of the London
00:13:37 aspects of the adequacy of the London Fire Brigades procedures and training an overview of conclusions to be drawn on a graph about the ground for tower fire an overview of lessons to be learned when comparing the ground for tower fire with
00:13:49 comparing the ground for tower fire with other fires both international and domestic and any recommendations arising from the same is that correct yes that's correct
00:13:56 correct now as you indicate in the declaration in Section 1.5 of your report you have provided it in the same way as you would have
00:14:04 have provided a report to a court is that right yes that's correct and in section 1.4 of your report you have outlined your background and experience relevant to the matters in this inquiry we don't need to rehearse
00:14:16 this inquiry we don't need to rehearse all of that today but I just want to pick out some key points now you specialize in fire safety having originally trained as a mechanical engineer and then gone on to specialize
00:14:27 engineer and then gone on to specialize in fire safety as I suspect you are currently the John L Bryan chair at the department of fire protection engineering and the director of the Center for disaster resilience at the
00:14:39 Center for disaster resilience at the Department of Civil Engineering at the University of Maryland in the USA is that correct yes that's correct and previously you were the professor of civil engineering and head of the school
00:14:50 civil engineering and head of the school of civil engineering at the University of Queensland in Australia between 2012 and 2017 that's great and before moving to Australia you held the land Dalton
00:15:02 to Australia you held the land Dalton company chair for innovation for a sustainable future at the Ecole Polytechnique fédérale de Lausanne in Switzerland in 2012 yes and you also
00:15:14 Switzerland in 2012 yes and you also held the BRE Trust Royal Academy of Engineering chair in fire safety engineering at the University of Edinburgh between 2004 and 2011 yes in
00:15:25 Edinburgh between 2004 and 2011 yes in 2008 you were awarded the Arthur B guys medal by the Society of fire protection engineers in the USA and in 2011 the David Rabbit medal by the institution of
00:15:38 David Rabbit medal by the institution of fire engineers in recognition for eminent achievement in the education engineering and science of fire safety is that correct yes that's correct you were the editor-in-chief of the forest Safety Journal between 2010 and 2016 yes and
00:15:52 Journal between 2010 and 2016 yes and you have been involved in numerous foreign investigations many of which have been landmark studies between 20 2001 and 2010 you were involved in an
00:16:05 2001 and 2010 you were involved in an independent investigation of the World Trade Center buildings one and two collapses yes you have conducted a cause and origin investigation into the Texas City explosion at subsequent fires as well as a damage
00:16:17 at subsequent fires as well as a damage correlation exercise yes you conducted dispersion far modeling supporting the litigation relevant to the bumps field explosion and the surco mine explosion
00:16:28 explosion and the surco mine explosion in the USA yes that's correct and you conducted a post forest structural assessment of the abbé derby plaza fire in Kazakh Stan probably the biggest ever fire of a building under
00:16:40 biggest ever fire of a building under construction is that correct yes that's correct
00:16:43 correct now you've been awarded a number of prizes in this field for your writing and I just want to pick out one you have together with your co-authors being
00:16:54 together with your co-authors being awarded the FM global best paper award for a paper on the precision of fire models and the required skills for fire modeling is that correct yeah that's correct
00:17:03 correct thank you are the factual matters set out annual report true to the best of your knowledge and belief I believe so does your report accurately set out your opinions on matters relevant to this
00:17:15 opinions on matters relevant to this inquiry yes it does thank you so I want to start by just asking you a few general questions about fire safety strategies in high-rise buildings in
00:17:28 strategies in high-rise buildings in section two of your report you have explained the concept of a fire safety strategy for high-rise buildings but you've explained that this and you've explained that this is a concept by
00:17:40 explained that this is a concept by which measures are taken to ensure societally acceptable levels of fire safety is that correct yes that's correct but you have not defined that at this stage by reference to any specific
00:17:51 this stage by reference to any specific document which may have been produced in the context of Grenville Tower you are talking about fire safety strategies generally for high-rise buildings yes that's correct
00:18:02 that's correct page 17 of your report you've explained that the main characteristic that defines a high-rise building is what you call a convergence of timescales yes
00:18:13 call a convergence of timescales yes can you just explain four is what you mean by that yes there's several factors that are happen when you have a fire fire is unusual in the sense that is one
00:18:25 fire is unusual in the sense that is one of the few hazards that actually evolves in space
00:18:28 in space time so it is going to grow as a function of time and it can grow slower or faster normally for example if you were to have a low-rise building egress time so the time that it takes for
00:18:40 time so the time that it takes for people to get out is extremely fast so effectively there is an independent time scale in a few minutes you will get everybody out while the fire can take half an hour or an hour to grow in a
00:18:51 half an hour or an hour to grow in a similar manner the structure is going to take a significant time to heat up so you can separate the time scales and basically get the life safety aspects of the building taking care of in a few
00:19:02 the building taking care of in a few minutes while everything else has a different time scale now in the case of a tall building that is not possible because you have multiple levels so it will normally take a very significant
00:19:13 will normally take a very significant period of time for people to be able to descend through those levels and therefore the number of minutes that it will take to address the life safety issues of people can be well within an
00:19:24 issues of people can be well within an hour and therefore it will converge with the time that it takes for the fire to take its full extent and it will also converge with the time that it will take for the structure to start heating up and start being deteriorated by the fire
00:19:37 and start being deteriorated by the fire so what you get in the case of a high-rise it's a very unique scenario that because the egress timescales are very very long then what you have is a situation with where all the timescales converge so you have to address
00:19:49 converge so you have to address structural behavior fire growth and egress in a simultaneous manner when you address the problem of fire safety and you've said in your report that the time
00:20:02 you've said in your report that the time for occupants occupants to evacuate is often at the same order of magnitude as the time for failure all the time required for fire and rescue service intervention can you just be clear what
00:20:14 intervention can you just be clear what you mean by failure in that context yes so in in a very short period of time you will probably have a situation by which the fire has not yet grown to a point that is affecting any component of the
00:20:27 that is affecting any component of the building so you would not expect for example a structure to fail a door to fail a window to crack you would expect people to be out of those spaces before that in a similar manner we have
00:20:38 that in a similar manner we have pre-stressed specified required times for
00:20:41 for the fire service to arrive on site and depending on which country which jurisdiction you have there will be you know a few minutes five minutes six minutes and and and therefore all life
00:20:52 minutes and and and therefore all life safety aspects of the building in principle would have been taken care of before the firefighters arrived or before anything has failed so people will be out of the building and they
00:21:03 will be out of the building and they will be safe before any of these things happen in a tall building because it takes much longer for people to arrive you would expect that the firefighters would have arrived on scene before everybody is out of the building and you
00:21:16 everybody is out of the building and you would have expected that before everybody is out of the building some components of the building will already be experiencing some element of distress or failure can you explain the
00:21:27 or failure can you explain the significance of that convergence of timescales for a high-rise strategy does it mean for example that you need safe areas to exist in the building yes the
00:21:38 areas to exist in the building yes the because you cannot take everybody out in such a short period of time that they are not being affected by the fire itself people are going to be in the
00:21:49 itself people are going to be in the building while certain areas of the building are already going to be fully compromised so you can have a fire that starts like in the case of grain fill in the kitchen and and that fire has already fully compromised the kitchen
00:22:01 already fully compromised the kitchen before people have had enough time to be able to get out of the building so a way in which we address the problem is we sector eyes the building and we create safe areas so what we are considering us
00:22:14 safe areas so what we are considering us are time to egress is the time that it takes not to get out of the building but the time that it takes to enter a place that is considered to be a safe place so by creating the sectors and separating
00:22:26 by creating the sectors and separating the building in different components we are allowing certain parts of the building to be fully compromised while other parts of the building remained perfectly safe so people can actually be
00:22:37 perfectly safe so people can actually be in those parts while the building is being affected by the fire and you say in your report that the most common safe areas are the stairwells and you also say that there's no limit to the time
00:22:48 say that there's no limit to the time that stairwells need to remain safe can you just expand on that yes because in a high-rise you gonna have a situation in which people are going to be back waiting for a very
00:22:59 are going to be back waiting for a very long period of time there's very significant uncertainty on human behavior
00:23:04 behavior so the timescales are very difficult to predict so it's very difficult to calculate how long will a person be within a building there's been cases for example like the first bombing of the
00:23:16 example like the first bombing of the World Trade Center where effectively people were inside the stairs for many hours and and so we have to make provisions to protect those areas in such a way that they remain viable for
00:23:28 such a way that they remain viable for as long as it is necessary and because as long as it's necessary it's not very well defined you know we have to make that almost a permanent feature of the building so you talk about redundancies
00:23:41 building so you talk about redundancies being necessary for all safety systems and you explain also that lobbies are typical of redundancies built into a fire safety strategy can you explain why those redundancies are so important I
00:23:53 those redundancies are so important I think you'd probably just explain that but with reference to lobbies as well as stairs every time you design a safety system safety systems are not perfect and and there will always be a
00:24:05 and and there will always be a probability of failure so you cannot rely on a single safety system to protect the lives of people so what you do is you always introduce multiple levels of redundancy until you're
00:24:16 levels of redundancy until you're satisfied that the overall probability of the entire chain is so low that you can almost guarantee you know the safety of people so depending on on the
00:24:28 of people so depending on on the complexity of the system you will introduce more levels of redundancy and and if a system is very simple you might need just maybe two levels of redundancy you know but if a system is very complex
00:24:40 you know but if a system is very complex for example if you're dealing with a nuclear power plant you have multiple levels of redundancy to make sure that the system doesn't fail so we we as a common practice in any matter of safety
00:24:53 common practice in any matter of safety we will always introduce to all safety systems levels of redundancy to make sure that in case something doesn't work there is something else to cover you know for us
00:25:05 know for us now in your report in general what you've done is you've broken down the substance of that report into four seminal stages in the progress of the fire at Greenville tower and you say
00:25:16 fire at Greenville tower and you say that these four stages are where distinctive interactions between the fire the building its occupants and the fire brigade were observed I'm just going to establish what these four
00:25:27 going to establish what these four stages are at this stage so stage one is initiation of the fire event through to breach of the compartment of origin which is approximately zero 0:54 a.m. to
00:25:41 which is approximately zero 0:54 a.m. to 1:05 a.m. Stage two is from the breaching of that compartment of origin to the point when the fire reaches the top of the building on the east face approximately 1:05 a.m. to 1:30 a.m.
00:25:55 approximately 1:05 a.m. to 1:30 a.m. stage 3 you characterized as lateral fire spreads and internal migration of the fireman smoke until the full compromise of the interior of the
00:26:07 compromise of the interior of the building including the stairs and again that's approximately 1:30 a.m. to 2:30 a.m. and stage 4 is what you describe as the untenable stage where significant parts of the building are it untenable
00:26:20 parts of the building are it untenable we'll come back to this approximately 2:30 a.m. until extinction is the untenable stage now as I say we're going to come back to each of those stages in detail during your evidence but at this
00:26:32 detail during your evidence but at this stage can you just explain why you have chosen to divide the fire into those four stages in your report yes the I mean beyond just trying to keep a little
00:26:45 mean beyond just trying to keep a little bit of order to all this information I think the different stages have very distinct characteristics that are quite fundamental to the behavior of the building and therefore I believed it was
00:26:58 building and therefore I believed it was very important to separate those the the first stage is to me fundamental because as I explained in my report at the backbone of the fire safety strategy is
00:27:10 backbone of the fire safety strategy is the concept of no spread external spread of the fire so we make this assumption that the fire will be boxed in within one floor and on the basis of
00:27:21 within one floor and on the basis of boxing in the fire within one floor even beyond that within one unit you know we make this assumption that the fire is boxed in and on the basis of that we construct the whole fire safety strategy
00:27:32 construct the whole fire safety strategy so the primary assumption behind every component of the fire safety strategy remains this concept of having the fire boxed and within one unit so that
00:27:43 boxed and within one unit so that initial stage represents the period where the building is actually behaving as designed where effectively the fire is boxed in within the unit and he has not managed to come out and penetrate
00:27:55 not managed to come out and penetrate other units within within the building so so that particular stage effectively represents the building operating as designed now the second stage again it
00:28:06 designed now the second stage again it it is it is fundamental in the sense that the building is now not operating as designed nevertheless within that process of vertical flame spread which is quite rapid there is no significant
00:28:19 is quite rapid there is no significant evidence that the means of egress in the building have been severely compromised so effectively there is still the ability that the redundancies that we have in the building have provided of
00:28:30 have in the building have provided of enabling people to actually migrate out of the building now by the time you get to the third stage of the building the process becomes a very dynamic process in which effectively we have sufficient
00:28:44 in which effectively we have sufficient evidence that the means of egress have been compromised now the the fact that they are compromised doesn't necessarily mean that people cannot get in you know into
00:28:56 that people cannot get in you know into those means of egress and successfully get out all that it means is that there's significant evidence that there is a deterrent for people to do so in the sense that there will be smoke in many ways people will be identifying
00:29:07 many ways people will be identifying smoke so effectively the means of egress are not acting the way they should be acting so we have fundamentally breached all levels of redundancy and we have
00:29:18 all levels of redundancy and we have reached to the core of the safe area you know of the building now the final stage of the fire is when there is a generalized perception that that core
00:29:30 generalized perception that that core safety area of the building has been lost and therefore there is very little evidence so people can actually use the means of egress to exit the building so let's
00:29:41 egress to exit the building so let's start then and look in detail at stage one which is the breach of the compartment that first compartment and we've got this time frame at 0-0 54 through to roughly 1:05 a.m. and at
00:29:54 through to roughly 1:05 a.m. and at section 3.1 of your report you've explained that you have conducted a simple modeling analysis what you described is a simple first principles elimination analysis of the fire
00:30:07 elimination analysis of the fire scenario in the compartment of origin it's that correct yes and you say that you've done this to bound the actual fire scenario within the kitchen more precisely can you explain what you mean
00:30:19 precisely can you explain what you mean by bound the actual fire scenario yes I think one of the things that is always very important to try to establish is that is if this event was outside the
00:30:30 that is if this event was outside the expected conditions that the building was designed for so if you are in in in a housing complex there are certain fire
00:30:41 a housing complex there are certain fire events that we accept as being events that are a regular occurrence what I call in my report an event of probability of one now people sometimes
00:30:53 probability of one now people sometimes believe that fire is a rare event and actually fires are not rare events fires occur very regularly what happens is that generally we have put so many provisions to try to protect us from
00:31:05 provisions to try to protect us from fire that what becomes a rare event is an event of magnitude that is sufficient to actually affect people or affect the building in a significant way so we have all these provisions and we designed
00:31:16 all these provisions and we designed these provisions to be able to cope with certain scenarios and those scenarios are considered to be the the common scenarios so the first thing that I was trying to establish is given the
00:31:28 trying to establish is given the evidence that we have and the actual nature of the evidence that we have that is quite coarse and this is quite common you know to every construction of a fire that you are working from debris so it's very difficult to get very detailed
00:31:40 very difficult to get very detailed information of everything that was happening in in in this so what we're aiming at is to try to look and see if the fires that created
00:31:53 look and see if the fires that created the situation we're of a nature that was extraordinary now by doing this very small bounding analysis which is we took the worst possible fire growth the slowest
00:32:04 possible fire growth the slowest possible fire growth and we applied it into the kitchen now the kitchen has a very small floor plan so effectively it's very rapidly filled up with smoke now for a fire to burn you need fuel and
00:32:17 now for a fire to burn you need fuel and you need oxygen so either lack of either of the two of them will actually stop the fire now if the fire gets strong enough then what happens is that the
00:32:28 enough then what happens is that the temperature of the smoke is so hot that the fire follows this process that is called flashover so effectively everything within the compartment ignites and and effectively the fire flashes over so what we had
00:32:41 the fire flashes over so what we had observed was that in the particular kitchen of Grenville tower the fire had never reached flashover so effectively what happened was at some point during
00:32:52 what happened was at some point during the growth of the fire the fire either was lacking fuel or he was lacking oxygen in such a way that it could not get to temperatures that were high enough to bring the room to flashover
00:33:03 enough to bring the room to flashover just ruling there what would you have expected to see in a flashover event that we didn't see in the kitchen of flat 16 so in in a flashover event every combustible material would have ignited
00:33:14 combustible material would have ignited because there is enough heat coming from the smoke to bring them to ignition so what you will get is effectively the full of destruction of all the components now you you can see for
00:33:25 components now you you can see for example in in Granville there's appliances for example which the paint remains undamaged so the fact that the pain remains undamaged that means that the fire did not reach flashover
00:33:36 that the fire did not reach flashover because the paint would have blistered and ignited so so effectively there's sufficient evidence within the space of elements that were in sufficient proximity that actually were not ignited
00:33:50 proximity that actually were not ignited by the fire which basically meant that there was no attainment you know flashover so given that we we have that evidence that is our key piece of evidence and we can go back and
00:34:02 piece of evidence and we can go back and try to then put as much fuel as we can and as small as fuel as we can given the the typical fuels that you have in there
00:34:13 the typical fuels that you have in there and see when it stops having enough oxygen effectively the smoke has descended to the floor and the oxygen is prevented from reaching the fire and therefore the fire cannot continue to
00:34:25 therefore the fire cannot continue to increase not because the fuel is not there but because the oxygen is not getting there and and by doing that we can ascertain that the fire that
00:34:36 can ascertain that the fire that actually was occurring in that space you know was somewhere between 60 and 300 kilowatts so I'm gonna come to that and say in your simple modeling that you've
00:34:47 say in your simple modeling that you've done in the main body of your reports just just to be clear what the parameters are for that simple model you've assumed that all windows and doors to the kitchen were closed and you've plotted different fire scenarios
00:34:59 you've plotted different fire scenarios that the size of the fire and its heat release rate we see that reference HRR heat release rate can you just explain what a heat release rate is yes so the heat release rate is the actual
00:35:10 so the heat release rate is the actual energy that is being released by the fire and as you said you've looked at fire growth and you've classified the fire as either slow medium fast or ultra
00:35:23 fire as either slow medium fast or ultra fast are those general classifications that are routinely used in fire modeling yes those are classifications are used mostly for fire for design and therefore they are the classic classifications
00:35:35 they are the classic classifications that we will use to test our design so is what we normally will use as a reference to try to bound the fire so a slow fire will be as as low as possible and an ultra fast as fast as possible
00:35:47 and an ultra fast as fast as possible are you team extreme extremes and is it right that your simple model also assumes that the fire is in the middle of the room well the the kind of model that we're doing it doesn't make any
00:35:59 that we're doing it doesn't make any difference where the fire is it basically treats the problem in a way such that it doesn't really matter you know where where you put the fire
00:36:11 where you put the fire the reason for that is that in a small compartment of that nature the impact of the fire will effectively affect the entire compartment almost simultaneously so it really doesn't matter where you
00:36:22 so it really doesn't matter where you put the fire yeah let's just go to one of your figures which help illustrate this can we go to your figure six now we've got a new reference for this document because it didn't appear right as clearly as we'd like in your in your
00:36:35 as clearly as we'd like in your in your report can we go to JT OS six zeros three please on the screen and can we
00:36:48 three please on the screen and can we zoom in on the top diagram please there just to be clear unfortunately in the PDF of your report that we released the smoke layer the gray smoke layer wasn't
00:36:59 smoke layer the gray smoke layer wasn't very clear so can you just explain what this basic model is showing yes so basically that that shows a little bit of a schematic of the model that that we
00:37:12 of a schematic of the model that that we presented and basically what it shows is an upper smoke layer in gray which will be basically a no more genius layer that represents the smoke and then in the bottom you have the air so the fire acts
00:37:24 bottom you have the air so the fire acts as a pump so it basically takes fresh air and then sends smoke you know to the top and that is called a two zone model and it's a very is the most simple representation that we have as a tool as
00:37:37 representation that we have as a tool as a regularly used to offer fire and if we now go to figure seven which if we can pull up
00:37:45 pull up JT OS six zeros one at page 39
00:38:00 and if we can zoom in on the graph at the top please bigger seven now this explains the
00:38:12 bigger seven now this explains the results of your simple modeling some basic terms is that correct can you just talk us through what we see here yes so basically what you get is the temperature of the smoke on the vertical
00:38:23 temperature of the smoke on the vertical axis and you get the time on the horizontal axis the red curve shows the evolution of the temperature of the smoke as a function of time so as you see because that is the ultra fast fire
00:38:35 see because that is the ultra fast fire the temperature will grow faster now by the time it reaches in this particular example I need to clarify that we run this model multiple times and under different conditions and so in this
00:38:46 different conditions and so in this particular example the fire will the smoke will reach the floor and the fire will stop growing at a temperature of about 230 degrees and in the other
00:38:59 about 230 degrees and in the other extreme you know will be the the case of the of the slow-growth fire and what you can see is the temperatures are growing much much slower and and the smoke layer will touch the floor and the fire will
00:39:11 will touch the floor and the fire will stop growing at that point when the temperatures reached slightly above a hundred degrees so in this very simple model and we've got a peak heat release
00:39:23 model and we've got a peak heat release relay rate before smoke filled the kitchen during the ultra-fast fire of approximately 300 kilowatts which corresponds to a hot layer of approximately 220 degrees is that right yes yeah and in contrast with the slow
00:39:37 yes yeah and in contrast with the slow fire growth that results in a peak heat release rate of approximately 60 kilowatts and a hot layer temperature of approximately 110 degrees centigrade and
00:39:50 approximately 110 degrees centigrade and so you've put your fire in the size range 60 to 300 kilowatts in terms of heat release rate on your simple modeling yes is that a small or a large
00:40:02 modeling yes is that a small or a large fire so a 60 kilowatt fire will be no bigger than a wastepaper basket a 300 kilowatt fire will be about half a chair so in both cases those will be
00:40:16 chair so in both cases those will be fires that we will expect to be below our typical design values so these are the kinds of fires that you would expect we will regularly have in a housing
00:40:29 we will regularly have in a housing building and therefore we the building has to respond appropriately to this fires
00:40:35 fires now you say on page 39 of your report that you've used a computation zone modeling tool which enables you to look at different fire scenarios in your analysis is that right yes and that's a
00:40:48 analysis is that right yes and that's a computer modeling tool developed in the USA is that correct yes it's a computer model developed by the National Institute of Standards and Technology and it's called C fast C fast yep and you say that this enabled you for
00:41:00 you say that this enabled you for example to model the fire including with an open kitchen door yes and you say that the results of that show that if the door was open then the smoke layer will exit the kitchen allowing the fire
00:41:12 will exit the kitchen allowing the fire to grow because of the oxygen resulting in higher temperatures and a flashover is that correct yes and is it right that the heat release rate necessary to deliver that flashover was around a thousand
00:41:24 flashover was around a thousand kilowatts yes will be approximately a thousand kilowatts and what you said about that very basic modeling as it confirms that the kitchen door was probably closed during the early stages of the fire as that yes yep
00:41:36 of the fire as that yes yep now just turning into Appendix B of your revised report can you confirm that in that appendix you've now provided some more detail of
00:41:47 you've now provided some more detail of the additional modeling work that you have done yes and is it right that you've expanded Appendix B and your most recent report served in October compared with what we saw in May yes and in
00:41:58 with what we saw in May yes and in general can you just explain in very general terms what you've sought to do in Appendix B yes I think one of the very important aspects of oven analysis
00:42:09 very important aspects of oven analysis of this nature is to be able to use the tool that is appropriate for the precision of the input elements that we have so we have some information from the scene we have some information from videos and and on the basis of that we
00:42:21 videos and and on the basis of that we have to use a model that has a consistent level of precision if we use a model that is more precise effectively what we're doing is giving a false sense of precision so we
00:42:32 giving a false sense of precision so we have to stick to a model that is of adequate or comparable level of precision to the information that we have so the simple model is that now what I do is to gain confidence on my
00:42:43 what I do is to gain confidence on my simple model then what I do is I use more sophisticated tools to inform me and run a whole bunch of other difference in areas all different characteristics try to play with
00:42:54 characteristics try to play with different variables that are enabled by a more sophisticated model just to make sure that answers that I provided with my simple model are correct so effectively this whole exercise of
00:43:05 effectively this whole exercise of Appendix B is a mechanism to gain confidence on the validity of the simple model and you've explained that you've done two different forms of modeling you've done the computations own
00:43:16 you've done the computations own modeling a cephas modeling you just took its route and you've also done something called computational fluid dynamics CFD modeling using a simulator can you just
00:43:27 modeling using a simulator can you just explain the difference between the two and what that is yes so the simple model that I use effectively uses two layers so it has a hot layer and a cold layer and it has no openings so effectively
00:43:39 and it has no openings so effectively you're just filling a box the sea first uses the same two layers but it allows to open and door open and close doors and windows so that you can allow flows
00:43:50 and windows so that you can allow flows through the doors and the windows so it is the same model conceptually but it allows you to have that possibility of taking smoke out and getting more fresh
00:44:01 taking smoke out and getting more fresh air in now while the computation of fluid dynamics model we it was developed by the same organization the National Institutes of Standards and Technology and it's called the fire dynamics simulator and effectively that what it
00:44:13 simulator and effectively that what it does it breaks the room into slightly little cubes so instead of having two big layers what you have is thousands of little cubes and you're basically modeling every little cube so you can
00:44:25 modeling every little cube so you can resolve in every position of the room what the temperature is going to be and and and basically the heat release rate and the flows and all the details so it's just simply a higher spatial
00:44:37 so it's just simply a higher spatial resolution so you can see what is happening in every point it's what we see in Appendix B the same as a sensitivity analysis it's beyond a sensitivity analysis because a
00:44:48 sensitivity analysis because a sensitivity analysis normally what it is is you take the input parameters that you put in and you varied them through a certain percentage just to make sure that your inputs aren't correct here
00:44:59 that your inputs aren't correct here we're trying to test also the physics by using a much more sophisticated sophisticated physics with the same inputs we're trying to make sure that actually the simple model is delivering
00:45:10 actually the simple model is delivering the right answers to the questions that we want to answer so let's just start with the computations own modeling that you've carried out you've explained in
00:45:21 you've carried out you've explained in appendix B that 2-zone model variations have been used for this more specific analysis first trying to model the assumed ventilation conditions based on the availab available evidence for
00:45:33 the availab available evidence for example kitchen door closed main window partially open and then secondly exploring other scenarios for example kitchen door open or closed or other windows open now before we discuss the
00:45:47 windows open now before we discuss the results of those models I just want to remind ourselves what the kitchen window looked like in flats extinct so I think it's helpful to remind ourselves of that can we go to one of the figures in dr. Lane's report that's B la s6 zeros ate
00:46:03 Lane's report that's B la s6 zeros ate at page 23 thank you so I think this is the kitchen window I believe it think it's in fact 13 on the opposite side this is can you confirm this is
00:46:16 this is can you confirm this is effectively the same window that we had in flat 16 yes and we see on the top right and a kitchen extractor fan with a surrounding unit the surrounding panel
00:46:28 surrounding unit the surrounding panel yes and then a large window on the left can you just confirm how that window could open so that window could open tilted inwards or open completely so
00:46:41 tilted inwards or open completely so he's swinging in or tilting in yeah and how about the little window underneath the kitchen extractor fan I believe it could only swing open so when you talk about looking at different modeling different scenarios
00:46:53 different modeling different scenarios of different windows open we're talking about these windows here exactly thank you
00:46:58 you now in terms of your modeling for scenario one which is the assumed ventilation conditions based on the existing evidence which is kitchen door closed large window partially open what
00:47:10 closed large window partially open what you've said is that you're your more sophisticated modeling shows that the heat release rate is in the range a hundred and ten to 360 kilowatts is that right yes and you say that compares well
00:47:22 right yes and you say that compares well with your simple model of of 60 to 300 kilowatts yes and in scenario two you say that the extra ventilation from the open door means a flashover scenario with a peak heat with heat release rate
00:47:34 with a peak heat with heat release rate of 1.5 megawatts is that correct yes now turning then to the computational fluid dynamics you just talked about these tiny little pieces of the jigsaw in the
00:47:46 tiny little pieces of the jigsaw in the box you've explained the results in in appendix B is it right that you've modeled the whole flat say for I think the second bedroom in the living room where it was a scene that these doors
00:47:58 where it was a scene that these doors were closed yes the figure 82 of my report which showed the model that we conducted
00:48:23 yes so if we go to JT figure-eight t2
00:48:34 yes so if we go to JT figure-eight t2 yes JT OS six zeros one so you will see one if you just wait for it to come up on the screen yeah and if we can zoom in
00:48:47 on the screen yeah and if we can zoom in on figure eight to two thank you so we can see on the right hand side that we are modeling the kitchen and all the rooms adjacent to the kitchen under the assumption that the partition is closed
00:49:01 assumption that the partition is closed and basically the smoke can leave the corridor and and enter only the bedroom in in the back and you've looked at the
00:49:13 in in the back and you've looked at the fire being located both on the floor and behind the fridge is that right yes can you just explain why you've done that the the dynamics of the fire are
00:49:25 that the the dynamics of the fire are very different if you have a fire that is on the floor then if you have one that is progressing behind an obstacle when you have a fire that is progressing behind an obstacle you will restrain the amount of air that
00:49:36 you will restrain the amount of air that can get into the fire so the flames will be longer because the fuel requires to get air from higher points to be able to be fully consumed well if you put it in the middle the flames will be shorter
00:49:48 the middle the flames will be shorter because you have air coming from all directions so you have to model both extremes and in in the simple model we only model the one in the middle because we were looking for the smaller possible
00:50:01 we were looking for the smaller possible fire because we were bounding you know the the condition so but in here we tried both just to make sure that we covered both potential scenarios and you say that you've modeled several
00:50:13 say that you've modeled several ventilation conditions in terms of the windows being open or shut in terms of the fire size for the fridge is it right that you've used results from some of the standalone tests that were carried
00:50:25 the standalone tests that were carried out by the BRE for the Metropolitan Police to estimate the potential heat release rate for the fridge yes so what happened as I understand it is
00:50:36 so what happened as I understand it is that the Metropolitan Police did some testing setting fridges on fire similar to those in flat 16 to see what heat Willie's relate that if they got is that correct yes can we just look at the results in graph
00:50:50 can we just look at the results in graph form from that if we go to figure 57 which is on page 144 of your report that's JT os6 zeros one page 144 and if
00:51:01 that's JT os6 zeros one page 144 and if we can zoom in there we go now what you said in your report is that the tests that were carried out which are represented here showed an initial peak
00:51:13 represented here showed an initial peak heat release rate of 400 kilowatts after seven minutes from the start of the standalone fridge test it then reduces to between 75 and 100 kilowatts before
00:51:26 to between 75 and 100 kilowatts before much later after about 32 minutes it peaks in the range of of a megawatt to 1.6 megawatts is that correct and that's
00:51:39 1.6 megawatts is that correct and that's effectively what we see depicted in that this graph here is that right so you can see that initial peak of 400 after after seven minutes but then our diminishing profile yes you say in your report that
00:51:53 profile yes you say in your report that these results are relatively consistent with the 60 to 300 kilowatt heat release rate range that you use for your simple model can you just explain that yes so the the tests are conducted by bre were
00:52:06 the the tests are conducted by bre were conducted under hood so you're basically allowing for all the oxygen that is necessary to reach the fire so this will be the maximum burning capacity of of the refrigerator without considering the
00:52:17 the refrigerator without considering the fact that oxygen might not get there like will happen in in a compartment so if if you look at the time line of about seven minutes until reaching 400 that is
00:52:29 seven minutes until reaching 400 that is fairly consistent with somewhere in between a slow and an ultra fast so it falls more or less in between the the range of values that we we work with now
00:52:41 range of values that we we work with now we observed also that the smoke layer descended in five minutes so effectively you will not reach to 400 kilowatts you will probably stop a little bit earlier because the smoke would have gone down and and
00:52:54 smoke would have gone down and and that's more or less what results show that effectively the fire stops growing because there's not enough air being able to feed you know the the the fire so in many ways using this as an input
00:53:08 so in many ways using this as an input is quite effective in trying to compare it with the simple model to show that effectively all the numbers are within the same ranges that we were operating
00:53:19 the same ranges that we were operating so that explains why you haven't gone back in your main report and adjusted your range of 60 to 300 to make it 60 to 400 absolutely I think again I go back
00:53:30 400 absolutely I think again I go back you know to the fact that you know we need to use the the right tool for the right problem so I do not want to with my report make anybody think that we
00:53:42 my report make anybody think that we have more precision than the precision that the simple model has so turning them to the results of your CFD model you say that the results from that model for a fire located in the back of the
00:53:54 for a fire located in the back of the fridge and with the large window tilted apron small window open but the door closed show that temperature magnitudes both by the window and by the door are when that are within
00:54:07 and by the door are when that are within the bounds of the predictions in the simple model is that correct that's correct and you've also run the same analysis but with a higher heat release
00:54:20 analysis but with a higher heat release rate just to check the figures yes at 400 to 500 kilowatts that right yes and you say again that for a fire located in the back of the fridge and with the
00:54:31 the back of the fridge and with the large window open small window open but the door closed the model managed to maintain the 400 kilowatt level but it didn't maintain the 500 kilowatt level can you just explain that yes so this
00:54:44 can you just explain that yes so this type of model because it's modeling things in a lot more detail it allows you to see really how much energy is being released and so it's taking into account how much air is meeting with the
00:54:56 account how much air is meeting with the fuel and how much you really is releasing so I can input energy and but I can measure also the output so effectively what this model does is whatever can not burn then it's
00:55:07 does is whatever can not burn then it's left as unburned smoke that just goes away and I can actually account for that so effectively with the model I can tell them no matter how much energy I put in only four hundred burns and I can put a
00:55:20 only four hundred burns and I can put a thousand I can put five hundred and it will immediately go back down and only four hundred will burn so effective it verifies that you are oxygen starved so you cannot burn more because you don't
00:55:31 you cannot burn more because you don't have enough air getting into the into the fire yep now you've also said in your appendix B that your sixty to 300 kilowatt simple model gave a good
00:55:42 kilowatt simple model gave a good estimate of average compartment temperatures but that only the CFD model can establish something called the spatial distribution yes he just explains what spatial distribution is yeah because in the CFD we are modeling
00:55:55 yeah because in the CFD we are modeling the small little cubes that fill up the entire compartment each cube will have a temperature so I can know exactly what the temperature is in that point so
00:56:06 the temperature is in that point so spatially in all the directions I can know exactly what the temperature is in the other models I'm assuming that the hot layer the smoke is only one temperature and the cold layer is only
00:56:17 temperature and the cold layer is only one temperature so I only have two numbers and I don't have the spatial distribution in the compartment and you've also said that your CFD model delivers more excited senyu ated
00:56:28 delivers more excited senyu ated temperatures accentuated temperatures can you just explain what you mean by accentuated temperatures yes so I think the easiest way to describe it is to look at all
00:56:39 look at all bigger 91 I think figure 91 yes yes so if we go JT OS six zeros one that paid one four nine yes can you just explain
00:56:52 one four nine yes can you just explain it by reference to this figure yes so as you can see in the dotted line represents a simple model and and effectively gives you the same
00:57:04 effectively gives you the same temperature all along the height because the whole smoke layer has the same temperature now the the CFD was the temperatures are slightly lower at the bottom and slightly hotter at the
00:57:15 the bottom and slightly hotter at the top and and therefore gives you the distribution with height of the temperature now one of the things that I need to clarify in there is that while it shows this accent where temperatures
00:57:27 it shows this accent where temperatures and it shows that is obviously going to be hotter at the top and colder at the bottom we cannot rely on those numbers so those numbers are beyond the precision of the information that we
00:57:39 precision of the information that we have so effectively the fact that the red curve shows that you are at 300 degrees might not necessarily be correct at the top you probably don't have 300
00:57:50 at the top you probably don't have 300 degrees you might have a little bit lower and and those things we will never be able to ascertain because the precision of the information that we're inputting into the model is not good enough so being able to say that is 260
00:58:03 enough so being able to say that is 260 250 is about as precise as we can be and yes we can say is plus minus 50 degrees and that will be perfectly fine but we cannot claim that the precision of the
00:58:14 cannot claim that the precision of the field curve is actually correct now within the CFD modeling that you've carried out you've also looked at variability by fire location as we
00:58:25 variability by fire location as we discussed before both at floor level and at the back of the fridge feyza is that correct yes and you've said that I think you've mentioned this before that a floor fire produces what you call more scatter of the data again can you just
00:58:37 scatter of the data again can you just explain what that means yes what what happens when you put a fire in in the floor is that the way in which the hot gases go up and they bring the cold
00:58:48 gases go up and they bring the cold gases in creates a situation by which the flames flock to it you're going to have the hot gases going up then they bring cold air and then the flame shrinks because everything burns
00:58:59 flame shrinks because everything burns and then the whole gases go up again so you have flames that go like this pulsating that creates data points are going to change when the flames are up then the temperature goes up when the flames are down the temperature goes
00:59:10 flames are down the temperature goes down well when you have a vertical fire and is burning as a wall everything is pushing up so effectively it's much more stable and then what you get is fairly consistent temperatures are all the
00:59:22 consistent temperatures are all the different that the and Heights so does it follow from from that that you accept that a fire located in a corner or against a wall but it will behave differently from a fire in
00:59:33 will behave differently from a fire in the middle of the room oh yes there will behave differently nevertheless are the the more you confine the fire so if you're behind something or you're in a corner effectively what you get is a
00:59:45 corner effectively what you get is a taller flame so it's a scenario that is already considered when you consider the smallest fire because remember we're bounding all we're doing is trying to find what are the fires that effectively
00:59:57 find what are the fires that effectively could do what they did in your simple analysis that you did in your main report it was based on a calculation from Google dry drysdale which was based
01:00:09 from Google dry drysdale which was based on a fire in an open space do you agree that other aspects of that drysdale paper deal with fires closer to a wall or in a corner yes so basically if you
01:00:21 or in a corner yes so basically if you look at a Google dry sills book you will find that he will produce different equations for fires in a wall fires around a corner but in all those cases the flame will be taller so effectively
01:00:34 the flame will be taller so effectively it will be already included in my pounding analysis I'm just setting the boundary so all if I did all those refinements I will find points are already included in my two limits that
01:00:48 already included in my two limits that was my next question does your modeling take account of that yes because effectively you are looking at the smallest possible and the biggest possible so everything is already all the in-betweens there are more precise
01:01:00 the in-betweens there are more precise are already included so you don't accept that your simple models should have referred to those other Drysdale calculations no no I mean it's a you know you could do it just as a further validation to show that that they fall
01:01:13 validation to show that that they fall in between but the CFD model already does all that so effectively if I'm already running the see of the model there is really no point in using again simple calculations for a situation that
01:01:25 simple calculations for a situation that I have already calculated and you've also looked at variability in ventilation in the kitchen with different windows open and Claire that includes the large window in the
01:01:37 that includes the large window in the open tilt position and the small window open is that correct yes and you've said that this produces a peak heat release rate of about 400 kilowatts which can be
01:01:48 rate of about 400 kilowatts which can be sustained yes can we just look at what you say in your report about this can we go to its on page 1 5 - JT OS 6 zeroes 1
01:01:59 go to its on page 1 5 - JT OS 6 zeroes 1 can we zoom in on 9 3 4 3 1 2 3 4 3 8 so there you say results presented in
01:02:11 there you say results presented in Figure 88 indicate that for the large window in the tilted position and the small window for the open a peak heat release rate of approximately 400 kilowatts can be sustained this means that a larger fire will result in a
01:02:22 that a larger fire will result in a higher overall compartment temperatures as shown on Figure 89 as there's more air available to support combustion again does that mean that there's any difficulty with your simple model of 60
01:02:34 difficulty with your simple model of 60 to 300 kilowatts no or all that it means is that the model says that if I put 4 hunt if I open the window the heat
01:02:45 hunt if I open the window the heat release rate will increase a little bit now the model says there is 400 kilowatts but that level of precision is not grounded so all we can say is the temperatures that I gave are
01:02:57 temperatures that I gave are approximately right but they could be potentially slightly bigger if if the window was open do you think it makes much difference whether it's 300 kilowatts or four hundred kilowatts well
01:03:09 kilowatts or four hundred kilowatts well it does make a difference but it when you say it makes much difference I think you have to ask that question in the context it makes much difference for what and I think that's that's the
01:03:22 what and I think that's that's the important question or so so in in some cases it will make a difference and then at that point I will have to say this model is not sufficient to do that but for other things it doesn't make any
01:03:33 for other things it doesn't make any difference because we are way outside the ranges for example so and as you go on to say on the same page
01:03:44 on to say on the same page in the next paragraph we've got it here on the screen models were run to analyze the difference in thermal profiles created by the opening of the small kitchen window in addition to the the
01:03:57 kitchen window in addition to the the large tilted kitchen window the results shown in Figure 95 indicate that there's little difference between the two with the lower ventilation resulting in only slightly higher temperatures
01:04:08 slightly higher temperatures attributable to the lower heat with heat losses from the compartment you were just explaining can we just look at that in Figure 95 and it will help to look at that that's JT OS 6 zeros 1 at page 1 5
01:04:22 that that's JT OS 6 zeros 1 at page 1 5 3 now here we basically this is showing between the the continuous lines and the
01:04:33 between the the continuous lines and the dotted lines the difference between whether the small window is open or closed is that correct yes so in case one the small window is closed but in
01:04:44 one the small window is closed but in case G the small windows open and can you just explain why you're saying this shows that there's little difference between those two scenarios so basically
01:04:55 between those two scenarios so basically given the coarseness of the inputs are going to this model you will consider all those lines to be the same and the way you will normally represent that is that will be an average plus an error of
01:05:07 that will be an average plus an error of about 10 to 15 degrees at both sides and so there's really not much of a significant difference other than a slight trend upwards but effectively given the inputs that we're putting I
01:05:19 given the inputs that we're putting I could not ascertain that that even that difference is actually that real so I would normally what I will do in a plot of that nature is average everything give a single plot and put an error bar
01:05:31 give a single plot and put an error bar of plus minus 10 degrees so just testing that and what about potential gaps around the doors so there's the sliding door to the kitchen and then there's
01:05:44 door to the kitchen and then there's also the kitchen doors itself is it possible that the doors would not have provided a complete seal and could that have made a difference it would have been a very very minor difference I mean generally leaks will be considered as
01:05:57 generally leaks will be considered as being a much much smaller flow rate than open window I mean clearly the one thing that does make a big difference is an open door and and and that has to be taken into
01:06:09 and and and that has to be taken into account but leakages are lower in the pecking order than an open window an open window will be a much thing much more so if an open window can change
01:06:20 more so if an open window can change things by 10 or 15 degrees I would imagine that leakages will not change it by one or two degrees and what about evidence from witnesses of drafts around the windows and from under the doors
01:06:31 the windows and from under the doors post refurbishment again would you think that that could change the results in your modelling no the again it will fall way within the category of noise and
01:06:44 way within the category of noise and what if the doors were not fully shut could that affect your modeling when you say not fully shut I mean if you're talking about 5% it's going to be a very very small gap and therefore again it
01:06:56 very small gap and therefore again it will make no difference but if you're talking about 20 30 percent then of course as you start opening the door then you're making a very significant and that's when you get to flashover
01:07:07 and that's when you get to flashover what about if the extractor fan was in the on mode and sucking out of the kitchen again could that make a difference well that again it will make a slight difference now if
01:07:19 it will make a slight difference now if you look at the typical flow rates of an extractor fan in general they're very small compared to the types of flow rates that you will get by smoke production or by egress of smoke out of
01:07:31 production or by egress of smoke out of the door so imagine what you see when you have a fire and you open a window you see an enormous amount of smoke coming out so that is clearly much much more than what a fan can can extract so
01:07:44 more than what a fan can can extract so of course all these things will make a slight difference but it will not be a significant difference would you agree that if you did allow for some additional ventilation such as around the doors and for the possibility that
01:07:56 the doors and for the possibility that the fire was not positioned in the center of the room but was against a wall in a corner that there might be local areas within the smoke layer for example at ceiling level where the fire could have reached approximately five
01:08:09 could have reached approximately five 50 degrees C would you accept that yes but can you explain why you've not taken that account in your modeling or have you taken that no we we have taken into
01:08:20 you taken that no we we have taken into account so basically we've made a clear distinction between heating by means of the smoke and heating by means of flame impingement so what you're talking about of hot spots localized heating areas is
01:08:33 of hot spots localized heating areas is effectively the flame in itself reaching that location and creating a hotter area within the smoke layer so the conclusion that we came up with is that the
01:08:45 that we came up with is that the temperatures that the smoke layer can reach cannot reach the typical ignition temperatures of most of these materials you know but the flames if they actually touch any of these components will
01:08:58 touch any of these components will actually reach those temperatures now we did a detailed analysis of that I'm coming to that is that about spilled please dispute is coming to that next
01:09:10 please dispute is coming to that next yeah before we get to that can you just explain why you used an average smoke layer temperature in your modeling yes because you you have to differentiate two things one is the smoke and one is
01:09:21 two things one is the smoke and one is the flame impingement so I wanted to separate both so if the smoke gets hot enough that it can ignite the components that basically means any component with your room could have ignited when it
01:09:34 your room could have ignited when it enters the small player now if the smoke layer cannot reach those temperatures that basically means that only the air the components that were in reach of the flames could have ignited so that allows
01:09:47 flames could have ignited so that allows me to establish how far the fire can be before he can not touch any combustible material so I'm separating the two things to make sure that I establish
01:09:58 things to make sure that I establish what is igniting what is it also right that you used a steady state fire in your CFD modeling as opposed to a growing fire yes and why have you done
01:10:11 growing fire yes and why have you done that because what we were testing with the CFD was effectively if there was enough oxygen to burn so there was no point in increasing the fire you just put it at the maximum value and see if
01:10:22 put it at the maximum value and see if you have been of oxygen to burn so it many times you use different modeling strategies depending on what you're testing and because in this case what we were testing is do we have enough oxygen then
01:10:33 testing is do we have enough oxygen then I want to fix the fire at the maximum and see if I actually have enough oxygen or the fire starts going down and its own because it doesn't have enough oxygen to burn so let's turn we're
01:10:44 oxygen to burn so let's turn we're nearly finished with the modeling but let's turn to the the external spill plume temperatures so you've done some modeling which assists in terms of what you refer to as these external spill
01:10:56 you refer to as these external spill plume temperatures and those are temperatures if the fire had vented out of the kitchen window is that correct yes but that's different to what I was talking about which is the flame impingement yes can you just explain the
01:11:09 impingement yes can you just explain the difference no no there's three things so there's when you have the the compartment yep okay you're going to produce a smoke layer so the smoke has a certain temperature within the smoke
01:11:20 certain temperature within the smoke there will be the fire and the fire can penetrate the smoke sometimes and get hotter in a certain region so there's a whole section of my report when I discuss this what I call the ceiling jet
01:11:32 discuss this what I call the ceiling jet temperatures so is effectively how far the flames can reach it's not the hot smoke temperature it is the flame itself touching and then the third one is what
01:11:43 touching and then the third one is what is happening to the outside and that's the spilled plume so you have a compartment that has hot smoke and the hot hot smoke will come out of the compartment mix with cold air and I will create a spill plume
01:11:59 now on the external spilled food temperatures analysis you say that this shows that smoke temperature would only reach this is smoke temperature it would
01:12:10 reach this is smoke temperature it would only reach temperatures capable of igniting the ACP toilet cladding if there was a large fire size with ventilation able to support it and thus under post flashover conditions is that correct yes and in general you've said
01:12:24 correct yes and in general you've said that this more sophisticated modeling confirms your confidence in the simple model is that correct yes do you think it's likely that you'd like to do more modeling at phase two I I do think that
01:12:36 modeling at phase two I I do think that the modeling will only become necessary as a function of more detailed testing so there is a need if if there is a need to refine what are the conduct side
01:12:48 to refine what are the conduct side conditions that led to ignition of the external system you know then tests will have to be done before modeling because you have to produce the right input data so that you actually get as it is
01:13:02 so that you actually get as it is justifiable to do a more precise model yep now I'm coming on to look at the role of the uPVC windows surrounds and that section of your report I think you were just talking about yes but before we leave this this modeling topic and I
01:13:16 we leave this this modeling topic and I just have a question about Table seven of your report can we just go to that that's jto s60 is one at page 140 now in
01:13:29 that's jto s60 is one at page 140 now in that table you've summarized some of the results from your zone modeling and in the fourth substantive line you've got a smoke filling time of 50 seconds for an ultra-fast fire with a corresponding
01:13:41 ultra-fast fire with a corresponding peak heat release rate of some three hundred and sixty kilowatts is that right yes we look in the fourth line down and the last of the ones in this scenario one is it right that this does
01:13:54 scenario one is it right that this does not use the standard heat release rate calculation from an ultra fast fire which would result in a figure have 470 kilowatts yeah so there's a confusion on on what those 475 is so the
01:14:08 on what those 475 is so the when we use an input we utilize a standard what is called an alpha t squared v so effectively we plug in a time and we get a heat release rate but
01:14:20 time and we get a heat release rate but that is the input as a fuel that we're putting in there what this model does it calculates how much it's burning so what happens is that I am inputting 475 but
01:14:32 happens is that I am inputting 475 but at some point the model stops me because it says I don't have enough air and it stops me at 360 and as you can see for all the cases when I try to push it in all the cases it would pretty much stop
01:14:43 all the cases it would pretty much stop at the same place because that's the amount of air that is available so you can see in the first in the far right column you will see 350 355 360 360
01:14:54 column you will see 350 355 360 360 because that's where it tells you this is as much air as I have now when I open the door now I have as much air as 1550 and then I can get much more so so we can now confuse the input with the
01:15:06 can now confuse the input with the output so what is being presented there is the output that incorporates fuel and oxygen well the number that you quoted is the input but I cannot burn all that fuel because I don't have enough air so
01:15:20 fuel because I don't have enough air so let's turn now to the section of your report where you've looked at the role of the uPVC windows surrounds when looking at the breaching of the compartment you focus quite heavily on
01:15:31 compartment you focus quite heavily on the role of the uPVC around the windows in general can you just explain why you've done that yes because the the uPVC serves as a cover for a whole array
01:15:43 uPVC serves as a cover for a whole array of other materials that potentially could burn now uPVC is a material that from a flammability perspective is a very robust material is a material that
01:15:54 very robust material is a material that is very difficult to burn so in principle it could potentially be an adequate protection layer you know for these materials nevertheless the uPVC has a
01:16:07 nevertheless the uPVC has a particularity which is that it loses its mechanical strength at very low temperatures so effectively can actually fall off and so this is a reason why I thought very important to focus on the
01:16:20 thought very important to focus on the uPVC
01:16:21 uPVC you've explained in your report that it has a melting range of between 75 and 105 degrees C yes that correct and it rapidly loses stiffness at 60 degrees
01:16:33 rapidly loses stiffness at 60 degrees Celsius yes and it loses 80% by 80 degrees and a hundred percent by 90 degrees yes can we just look at table one of your
01:16:44 can we just look at table one of your report that's J TOS six zeroes one at page 37 can I just ask you Williams kind of gets to know it will behave like
01:17:01 kind of gets to know it will behave like gum so it does flow but it's very very viscous so it is more like gum so in
01:17:12 viscous so it is more like gum so in this table you've given various material properties of a number of materials that are important in terms of that the kitchen and can you just explain here what we
01:17:24 and can you just explain here what we see for the the uPVC in the bottom two lines yes so what you see for the uPVC are two characteristics one is a significant temperature and the second
01:17:36 significant temperature and the second one is the melting temperature and you can see that the melting temperature is so this is of the order of a hundred degrees you know while the ignition temperature is almost 400 degrees and
01:17:49 temperature is almost 400 degrees and while we're here what we see on the top line we see polyethylene that's the material that was inside the ACM panels yes that correct and you put that there
01:18:01 yes that correct and you put that there that has an ignition temperature of 377 degrees C and that's just the polyethylene if that right just not related to the aluminium will come later to the door panels and then we have PIR
01:18:14 to the door panels and then we have PIR which is effectively insulation yes in the second column and you've got that with an ignition temperature of 306 to 377 degrees C is that correct yes now in
01:18:26 377 degrees C is that correct yes now in terms of the UPV C you've talked about the fact that it has this elastic modulus which is of important I think what you were just describing can we just look at that let's look at figure 9 of your report
01:18:38 figure 9 of your report that's JT OS 6 zeros one at page 41 can
01:18:49 that's JT OS 6 zeros one at page 41 can you just describe for us what we see here and what the different the red and the blue lines are we've got blue is the modulus I think yep can you just explain what that is and also what the red line
01:19:00 what that is and also what the red line is showing yes so this is a test conducted by Professor Bisbee and basically shows you what is the the the module elastic modulus for uPVC at
01:19:12 module elastic modulus for uPVC at ambient which is 2.5 times 10 to the 9 and and you can see that as you start increasing the temperature
01:19:21 sorry it was ambient temperature is about yeah a little bit above to 2 times 10 to the 9 so as you start increasing the temperature what happens is that the value starts dropping so that's the blue
01:19:32 value starts dropping so that's the blue line so you get a decaying value that eventually hits zero so in other words he has no strength by the time he gets to about 8090 degrees and by a hundred
01:19:45 to about 8090 degrees and by a hundred clearly has nothing left so that will be the blue line and what the red line is it just shows you the rate at which that happens so what you can see is that at the beginning there's very little change
01:19:56 the beginning there's very little change so you can see it's flat very little change and then eventually it starts changing drastically and that happens at about sixty degrees so what what you're looking for on the red line is when it starts going up because that's telling
01:20:08 starts going up because that's telling you when it starts to change what you're looking from the blue line is when it ends because that tells you when it doesn't have any more strength so between 60 and 100 degrees you effectively are going from having almost
01:20:20 effectively are going from having almost its full strength to having no strength and you said in your report that most fires originating from fuels typical of a domestic kitchen will have the capacity to significantly damaged the
01:20:31 capacity to significantly damaged the uPVC is that right absolutely because if if we go back to the original discussion that we were having we established that we needed a fire of the size of a frying pan to be able to
01:20:44 pan to be able to to bring the smoke layer to the floor and that was the limits in which we were operating so this particular fire could not be bigger than a frying pan and and
01:20:55 not be bigger than a frying pan and and so then if you look at the smoke layer temperature the smoke layer temperature is around at the most 200 degrees so he cannot ignite anything but nevertheless is a hundred degrees above the
01:21:07 is a hundred degrees above the temperature that you need to basically take the PVC down in other words it loses all these mechanical properties now we did a detailed heat transfer calculation actually a very conservative one and we showed we had plenty of time
01:21:19 one and we showed we had plenty of time to heat the uPVC to the point where would have lost all this mechanical integrity so this is very important because again it separates and this is a reason behind the strategy that we
01:21:31 reason behind the strategy that we follow for modeling so it separates the smoke temperature from the flame temperatures so the smoke can not ignite anything but it can actually mechanically fail the uPVC to ignite
01:21:44 mechanically fail the uPVC to ignite things we need a flame and you've said in your report that the uPVC would have reached temperatures with a total lock loss of mechanical strength in approximately five to eleven minutes is
01:21:56 approximately five to eleven minutes is that right yes and you also say that the kitchen is sufficiently small that it doesn't matter where in the room the fire is too cause that total loss of mechanical strength exactly so with the
01:22:09 mechanical strength exactly so with the CFD and all the other validations are we did we showed that effectively the very simple model that doesn't take into account spatial resolution in other words you can place it anywhere you want will effectively be sufficient to be
01:22:22 will effectively be sufficient to be able to establish that you've noted in your report that the uPVC is held in place by an adhesive a kind of glue which you also say is vulnerable to heating and you say the ability to
01:22:36 heating and you say the ability to secure the uPVC at elevated temperatures is considered negligible and we we just look at that if we go to figure 55 of your report that's JT OS six zeroes wonõt zero zero
01:22:48 that's JT OS six zeroes wonõt zero zero 42
01:22:50 42 so it's because this what what we're seeing here is underneath the uPVC surround is that correct yes and can you
01:23:01 surround is that correct yes and can you just do attention to the adhesive is it the bottom label there yes so it's the bottom label and you can see the the mark of the of the adhesive so adhesive is a polymer and it will actually behave
01:23:12 is a polymer and it will actually behave in a very similar way as a uPVC it will lose to always mechanical integrity by the time it gets to about 6070 degrees so effectively both the adhesive and the PVC will have no mechanical strength so
01:23:25 PVC will have no mechanical strength so the adhesive has no capacity to keep the uPVC in place and the weight of the uPVC is much more than what the new PVC can hold itself what we can see under the
01:23:37 hold itself what we can see under the PIR foam insulation which was all the way around the windows is that correct yes top bottom left right yep and what
01:23:48 yes top bottom left right yep and what is your view about this arrangement in terms of any potential path of fire spread out of the window well effectively the the smoke even though is temperature is very low is capable with
01:23:59 temperature is very low is capable with a big margin of safety you know to mechanically fail the uPVC so it opens a direct path for any flame to actually impinge on any of the combustible
01:24:10 impinge on any of the combustible materials on the inside just on this topic can we just look at some of the photos that you've used in your report to illustrate the failure of the uPVC that we saw at groennfell tower can we
01:24:23 that we saw at groennfell tower can we go to JT OS 6 zeros one at page 43 to start with so let's just come here to
01:24:35 start with so let's just come here to steaming in the top one for the moment
01:24:39 so you've said in your report that the ferries are usually around the head and the jam can you explain what you mean by the head and the jam by reference to these photographs so you can see the
01:24:50 these photographs so you can see the piece of uPVC hanging in there and you see where it came from so effectively this will rip off downwards you know falling all the way to the bottom that's kind of what I
01:25:02 to the bottom that's kind of what I meant yeah and can you explain you also use the word fall-off in this context is that just not it falls it's fault fault off so it basically first starts the forming and then eventually it falls off and you see it more clearly Indy India
01:25:14 and you see it more clearly Indy India in the next photograph mr. chairman I'm now going to turn to a different topic did you want to chosen it's very good I don't know if you can it's finished
01:25:26 don't know if you can it's finished these photographs so yes let's go to the one at the bottom of the page so you can see at the top how its fold off and I believe there's actually one on the next page as well if we can go to that yes
01:25:38 page as well if we can go to that yes you can see it on the side and then in this case and also on the top
01:25:50 so I think that's a convenient moment for a break would it be a good idea yes
01:25:57 I'm gonna ask you I think not to talk to anyone about for evidence while you are in room and then to go with the actual she'll look after you will come back at half-past eleven thank you very much
01:26:08 half-past eleven thank you very much together
01:26:21 all right apostle Evan please
01:39:23 right
01:39:45 - carry on yes thank you thank you yes thank you so now we can turn to the topic of the breakout of the fire from flat 16 and the method of ignition of
01:39:57 flat 16 and the method of ignition of the facade materials I'm going to give a trigger warning at this point because in about five to ten minutes I'm going to be sharing a video of the early stages
01:40:08 be sharing a video of the early stages of the fire at ground floor tower going up the east face from flat 16 this contains images and audio that some may find distressing I will also be taking professor Joe arrow to a number of
01:40:20 professor Joe arrow to a number of stills and photographs of the fire in this section of my questioning so I will give another warning when I get to that video but I wanted to give it now in case an element so we prepared thank you
01:40:32 case an element so we prepared thank you that's very helpful now in your section 3.5 of your report and first of all just to be clear you have not addressed caused an origin of the fire in your report which is dealt with by other
01:40:44 report which is dealt with by other inquiry experts is that correct yes I've taken the information from Professor McCadden
01:40:50 McCadden and professor Bisbee on that matter thank you have you considered the different hypotheses which have been posited by Professor Bisbee in terms of the method of ignition of the cladding
01:41:02 the method of ignition of the cladding materials on the facade yes in his latest report professor Bisbee discusses two particular hypotheses first what is now called hypothesis b1 which is
01:41:15 called hypothesis b1 which is essentially the impingement of flaming and hot gases through an open window whether that be through the extract panel or via the extract fan itself and
01:41:26 panel or via the extract fan itself and then subsequent ignition of the external ACM panels immediately above the kitchen window is that correct yes and he's also discussed what's now called hypothesis
01:41:37 discussed what's now called hypothesis b2 which is the ignition by flame of the of exposed flammable materials in the window surround and the external cladding system being penetrated by fire
01:41:48 cladding system being penetrated by fire fire allowing flame spread back into the back of the cladding cavity is that correct yes you agree that these are the two possible routes of ignition out and into
01:42:01 possible routes of ignition out and into the cladding yes do you think there are any other plausible candidates for that
01:42:07 dead they're clearly the two most probable causes so I just want to start by discussing hypothesis be one the
01:42:18 by discussing hypothesis be one the venting through the window opening and up into the panels above the window so I think as we discussed just before the break does it remain your beer that the smoke itself is not going to be hot
01:42:31 smoke itself is not going to be hot enough for the smoke that's venting through the window opening to ignite the cladding yes you say that the maximum temperature of the smoke layer is around 220 degrees Celsius even with an
01:42:42 220 degrees Celsius even with an ultra-fast fire is that correct yes so ignition of the materials even surrounding the window specifically the PIR insulation which is behind the uPVC
01:42:53 PIR insulation which is behind the uPVC that requires 306 degrees Celsius is that right yes now you've calculated that direct ignition via direct flame or plume impingement through the window
01:43:05 plume impingement through the window would require fire of around 830 kilowatts to ignite the ACP through the window is that correct yes can you just explain for the term and how you've
01:43:16 explain for the term and how you've calculated that yep so basically if we provide enough ventilation to allow the temperature of the flames to reach those
01:43:27 temperature of the flames to reach those those those temperatures you can establish what is a heat release rate that will deliver the necessary temperature so that you can ignite the cladding from the outside and the one
01:43:39 cladding from the outside and the one thing that that is very different about both hypotheses and maybe this is a time to clarify that is when we have a compartment fire the compartment is
01:43:51 compartment fire the compartment is always going to be hotter than the plume outside so from a physical perspective a path that ignites from the inside is a more more probable cause of ignition
01:44:04 more more probable cause of ignition because
01:44:05 because temperatures are always going to be higher in the inside than in the outside now professor Bisbee comes from a different angle which is also perfectly possible which is once something ignites
01:44:16 possible which is once something ignites that something can create a flame and that flame can be the one that results in the ignition of the subsequent materials now he's coming from the observation so he's looking at different
01:44:27 observation so he's looking at different images and he's basically looking at the different flames are moving in different directions and he is observing that there is a high probability that a flame could have been pinched you know on the
01:44:39 could have been pinched you know on the external cladding so the two options and the way that we are given to the two options and the reason why I didn't feel there was any need for me to clarify any further in my report is because we are
01:44:52 further in my report is because we are coming from different angles and I believe that determine is to consider both in the sense that one comes from a purely physical analysis of the problem that shows that the hotter part and the
01:45:04 that shows that the hotter part and the closest to a flame will be from the inside but the other one is more a probabilistic one is what ignited first and if there is a sequence of ignitions that resulted in a flame that could have
01:45:15 that resulted in a flame that could have perfectly be the case of igniting on the outside but there comes more from observations of images and observations of evidence yeah it might be helpful at this point to look at your table three
01:45:26 this point to look at your table three that's JT OS six zeros one at page 50
01:45:36 if we can zoom in on the table at the top of the page can you just talk us through just in basic terms what this
01:45:47 through just in basic terms what this table is showing us in terms of fire size and distance and these three materials yeah so basically what what you see in in the table is depending on
01:45:59 you see in in the table is depending on the location of the material and its ignition characteristics we looked into having a flame and maybe maybe we should look at the diagram first
01:46:33 Oh beauty go 13 BB yes so if we go to JT of6 zeros one at 0-0 47 page 47
01:46:51 and if we can zoom in on Figure 13 at the bottom yes so basically those are the two potential options so you can
01:47:02 the two potential options so you can have a fire that is unobstructed that directly impinges on a target and that target could be the PIR or the uPVC or the cladding so we know what the
01:47:15 the cladding so we know what the position of these components is so we can establish what the distance is between the fire and the target so on the basis of that I can establish how big of a fire do I need so that the
01:47:26 big of a fire do I need so that the flame at the position of the target has sufficient temperature to ignite okay and if there's an obstacle then the flames will have to go to the ceiling then to progress along the ceiling and
01:47:40 then to progress along the ceiling and effectively hit the target so given that the smoke can not ignite it has to be direct impingement from the flame so what we looked into was given the position of the fire how big of a fire
01:47:52 position of the fire how big of a fire we had to have to be able to ignite the targets and that's what you have on the table and you just talked about the phenomenon of a ceiling Jets that might have shared behind an object so the fire
01:48:04 have shared behind an object so the fire goes up behind the object and then across the ceiling and out towards the window how likely do you think that might have been here well if the if the fire was established behind any obstacle
01:48:16 fire was established behind any obstacle that would have had to be the case because effectively he had to go through the obstacle before it reaches a target so the only way that that could have happened is going up hitting the ceiling and then propagating across the ceiling
01:48:28 and then propagating across the ceiling towards the target so it would be highly probable can I just ask you to consider it slightly different hypothesis which is that the fire is breaks out behind an
01:48:39 is that the fire is breaks out behind an obstacle but to the side of the target so in other words it doesn't have to go over the obstacle to get to the tongue and it might go down it will be bounded
01:48:50 and it might go down it will be bounded by even by the two of them so this is the worst-case scenario and the other one is the best-case scenario yeah so so you will be somewhere in between and so that's what we're giving the to range so this helps explain what we see in
01:49:03 so this helps explain what we see in your table 3 correct do you want to just go back to that night yes if we just go back to table 3 which is on page 50
01:49:21 so if you can now just talk us through for each of the elements what you're seeing so so we know how big a fire can be now because we've done the analysis
01:49:32 be now because we've done the analysis so if we take that size of a fire then the distance that you see there is how far do I need to move the fire away from the target before it cannot reach the
01:49:43 the target before it cannot reach the ignition temperature so and that's where we see the figure of 830 kilowatts that's where you see the maximum
01:49:56 that's where you see the maximum distance yep the final column yeah but I put to you the smallest fire eight hundred and thirty kilowatts yes do you night the polyethylene yes at the top I
01:50:09 night the polyethylene yes at the top I don't window exactly and you say that's a flashover fire so you think that's unlikely yes in terms of direct flame impingement through an open window is it therefore
01:50:20 through an open window is it therefore relevant that the flames would have fed out into the open atmosphere outside the the flat yes it would have had to ignite something in between because the flame
01:50:31 something in between because the flame would have been had to be placed closer to the opening to be able to be smaller and still reach the ignition temperatures of the cladding and does
01:50:42 temperatures of the cladding and does the flame get cooled in the process of coming out of an open window and is that relevant to the analysis of whether or not that's a likely method of impingement yes so the the moment the
01:50:53 impingement yes so the the moment the flame exits the compartment there's going to be fresh air and that's going to cool the temperatures of the flame so it's going to it is always going to be the case that the spill flame is going
01:51:06 the case that the spill flame is going to be colder than the interior compartment it cannot be the opposite so so yeah so that that will definitely influence the analysis now but again I want to make this point again that there
01:51:20 want to make this point again that there are in this particular type of scenarios because we're talking about flames that can impinge on numerous things there can be a sequence of ignitions so one thing can ignite another one in
01:51:31 so one thing can ignite another one in Canada another one so and those things you can only ascertain by looking into what the visual evidence that you have so I think when comparing my conclusions
01:51:44 so I think when comparing my conclusions with Professor bismuth conclusions we have to make sure that we understand that I did not do the detailed analysis of the images that's what he did and and he didn't do the detailed
01:51:55 and and he didn't do the detailed analysis of the fire dynamics which is what I did and the two things complement each other can we just look for a moment about what the method of impingement might have been for the acp panels above
01:52:08 might have been for the acp panels above the window can we look at a picture of what we see above the window that can we go to figure 40 of Professor bisby's report that's lby yes six zeros one at
01:52:20 report that's lby yes six zeros one at page 68 yes now this is a good photograph which shows you what you see we now just to make clear the ACM
01:52:32 we now just to make clear the ACM material on the column has been removed here to the left of the picture but to the right we're looking directly up from
01:52:43 the right we're looking directly up from the window to the ACM cassettes that were immediately a bit above is that correct yes and we see there that the way the cassettes were fabricated is there was a 90 degree return and then a
01:52:54 there was a 90 degree return and then a kind of level yes underneath the window immediately underneath above the extractor fan is that correct can we
01:53:06 extractor fan is that correct can we also look at another picture that's a picture from dr. lanes report that's BL a s five zeros 10 at page 26 figure
01:53:18 a s five zeros 10 at page 26 figure 10.26 this is a another photograph of the window this is to the right hand side of the window and we can see those
01:53:30 side of the window and we can see those cassettes above and she's put a ring in there which come to in a moment but just looking at these photos what do you think the mechanism could have been for igniting
01:53:42 mechanism could have been for igniting those ACM cassettes above the window if the flames had vented out through an open window well I mean you need to ignite the polyethylene that has a
01:53:53 ignite the polyethylene that has a specific temperature that you need to attain and not only that the polyethylene is a thin film that is in between two aluminum plates the aluminum plates have very high thermal
01:54:04 plates have very high thermal conductivity so they take a lot of energy away from the polyethylene so normally these type of materials are actually quite difficult to ignite because what happens is that the heat
01:54:16 because what happens is that the heat that you apply goes away through the polyethylene or through the aluminum and the polyethylene tends to melt instead of igniting so it requires a
01:54:27 instead of igniting so it requires a significant amount of heat to be able to ignite these panels now the mechanism would have been that eventually either through melting or through splitting you would have had a surface of the
01:54:38 would have had a surface of the polyethylene that is exposed a flame will have creeped in there and that would have ignited the the material are there any exposed edges of polyethylene above the window I would imagine that
01:54:52 above the window I would imagine that there would be dr. Lane has some I think marked here on the right-hand side does that affect the analysis in terms of whether or not there are well if there will be no exposed edges it will be even
01:55:04 will be no exposed edges it will be even more difficult to ignite because you have to breach the encapsulation of the material and so all those details will have some impact on the way it ignites
01:55:15 have some impact on the way it ignites but one that it would be very very difficult to predict if this had been the mechanism of fire spread would you have expected a time delay given the factors you were just talking about when
01:55:26 factors you were just talking about when compared with other possible routes not necessarily can we just look at the thermal imaging from flat 16 which
01:55:39 thermal imaging from flat 16 which indicates that the fire may have entered from the window and the corner if we go again within dr. lanes report to be la s6 zeros at page 43 can we go
01:55:52 to be la s6 zeros at page 43 can we go to figure 9.3 7 so in the image at the top we have still from the thermal
01:56:03 top we have still from the thermal imaging that was taken is that correct yes does this image help at all in your view about what the route of escape may have been through the window not from my
01:56:16 have been through the window not from my perspective because it is too late so 114 I believe is that a thermal image camera footage and and at that point you
01:56:28 camera footage and and at that point you would have been already at least about 10 minutes into the event and and as you saw from all the other diagrams that is already very late in in the whole process now that doesn't mean that that
01:56:41 process now that doesn't mean that that could have not been the moment in which or the area in which it it it breached all that means is that in fairing that back from an image that is was taken and
01:56:52 back from an image that is was taken and 114 it's very difficult because it's so late in time that a lot of things would have happened in between do you infer anything from the thermal imaging about which side of the window would have been
01:57:03 which side of the window would have been getting the most heat in terms of temperatures inside the compartment again I mean clearly at that point it is clear that those are the areas that seem to be the hottest which areas the areas
01:57:17 to be the hottest which areas the areas are in yellow yeah and but as you can see still the temperatures are 150 degrees so clearly there is a concentration of heat in there but it is more the smoke layer type of heat now
01:57:29 more the smoke layer type of heat now one of the things that that many times thermal imaging cameras mislead us is the different materials have different emissivities so while the camera might think is reading more heat it might
01:57:41 think is reading more heat it might actually be reading less heat because it's just the material that is emitting more energy so I I wouldn't make too much out of that image other than the fact that there seems to be a slight
01:57:52 fact that there seems to be a slight concentration of heat in now you have concluded in your report that you think the most likely route of ignition of the facade is by flame of exposed flammable materials in the
01:58:04 exposed flammable materials in the windows surrounds is that correct yes does that remain your view despite reading professor Bisbee's report that that remains I say that remains my view from a physical perspective I think that
01:58:17 from a physical perspective I think that there is a case but I do not discard by any means you know what the visual evidence might might show because clearly as I say you can have a random
01:58:29 clearly as I say you can have a random sequence of ignitions I can actually lead to an external ignition so I cannot discard that as a possibility yeah and just to be clear can you just crystallize summarize why you think that's the most likely route
01:58:40 that's the most likely route fundamentally because the fire dynamics will tell you that the highest temperatures and the closest proximity to the flames is going to be in the compartment anything outside the compartment is going to be colder and
01:58:51 compartment is going to be colder and further unless you find a path of ignition after ignition that brings you there and that you can only tell by a detailed analysis of of images
01:59:02 detailed analysis of of images can we just be clear on what you think the most likely path is so we've talked about the melting and deforming of the uPVC it should be by the smoke layer itself without any direct frame
01:59:13 itself without any direct frame impingement and then what's the next thing that you think is most likely to have igniters that's impossible to say because all the materials in there will be will have ignition temperatures are
01:59:24 be will have ignition temperatures are lower than the ignition tender then the temperatures that the flame could provide so effectively you create as soon as as the flame reaches a certain size you will create a condition by
01:59:37 size you will create a condition by which any of this materials could ignite what materials are we talking about here let's just be clear what the candidates are we've got we talked before by reference to the photograph of immediately behind the uPVC we have the
01:59:48 immediately behind the uPVC we have the insulation it's a small layer of insulation that we have top bottom left and right is that correct that's PIR insulation yes around the window and then we also have an EDP M membrane on
02:00:01 then we also have an EDP M membrane on the
02:00:02 the side do you think those two are both candidates for and then so is the uPVC itself of course yes and they're from
02:00:13 itself of course yes and they're from there if those materials had ignited around the window sides let's take the column side so we've got the insulation we have the edpm membrane what happens then in terms of the column so then you
02:00:26 then in terms of the column so then you will get flames into a cavity and and effectively you are affecting the ACM panel you're affecting everything so what follows after will be just the progression of the fire through the
02:00:38 progression of the fire through the space and it could come out as easy as it went in so so in principle the sequence that follows after is again almost impossible to detail step by step
02:00:50 almost impossible to detail step by step but but all the different components as you could see in the in the previous photograph that you show they're also much in proximity that there is no question that there will be a sequence
02:01:01 question that there will be a sequence of ignitions of all of them so you think all of those will have ignited as part of the path yes out and it's right isn't if there were no cavity barriers around
02:01:12 if there were no cavity barriers around the windows I don't believe something and you've calculated that a fire with characteristics similar to that of a kitchen fire if placed within 3 meters of the window is capable of igniting
02:01:24 of the window is capable of igniting those combustible materials adjacent to the window is that correct absolutely yes
02:01:29 yes and for example you've said in your report that a fire at floor level of just 20 kilowatts is capable of igniting materials at windowsill level I the lower parts of the level yes and again
02:01:41 lower parts of the level yes and again what materials are we talking about them uh it could be basically we took as a reference the ignition temperatures of all of them so it could have ignited any of them and as you say you've also
02:01:53 of them and as you say you've also looked at fires behind an obstacle because of the fact that it may have been behind the fridge yes where the two bounding so the fire that is unobstructed is the smallest possible
02:02:05 unobstructed is the smallest possible fire and the other extreme will be the one that is fully confined behind an obstacle and in terms of that fire we were just discussing behind an obstacle sealing jet across the ceiling you've noted in your report that there was a
02:02:17 noted in your report that there was a strip of pearl board kind of legacy stripper of pearl board above the window on the flat side of the window before you got to the uPVC surround yes is that
02:02:28 you got to the uPVC surround yes is that something that you remain interested in yes because obviously that will be the one that will be in closest proximity you know to a flame so it will be the first one to be affected so you think it's possible that the ceiling jet may
02:02:41 it's possible that the ceiling jet may have impinged on that first and then onto the uPVC or the insulation yes and do you think that's something that should be the subject of further
02:02:52 should be the subject of further consideration and testing at phase two I mean I think that that clearly it is important to try to have as many pieces
02:03:03 important to try to have as many pieces of the puzzle as possible nevertheless the importance to the overall outcome of what was the the first thing to catch on fire is probably
02:03:17 first thing to catch on fire is probably not that significant and it's right isn't it that the different materials around the window would have had different thermal inertia x' that's right and that's the speed at which they
02:03:29 right and that's the speed at which they flame speed at which they pyrolyze and release combustible gases it's a speed at which they can absorb energy towards ignition and if something has a low thermal inertia does that mean it's
02:03:41 thermal inertia does that mean it's first to ignite compared to something with a material of a high thermal inertia yes a material with low thermal inertia will ignite much faster and is it right that the PIR insulation would
02:03:52 it right that the PIR insulation would have had the lowest thermal inertia of any of those materials that we were just discussing yes and is it right that the polyethylene would have had the highest thermal inertia yes do those thermal
02:04:05 thermal inertia yes do those thermal inertia values assist in working out which is likely to have been the root of ignition not clearly they they just give
02:04:16 ignition not clearly they they just give you an estimate of what could have gone for
02:04:20 for but this numbers are only valid in the sense that they had to be under exactly the same conditions so if you have a flame impinging on the polyethylene but
02:04:31 flame impinging on the polyethylene but 10 centimeters away from the PIR the polyethylene will ignite faster than the PIR so the way in which the fire evolves and how it interacts with these materials is really the dominant
02:04:44 materials is really the dominant function I mean what we're talking about here is a is a very small fire being capable of igniting any of the things that's the ultimate question now what
02:04:55 that's the ultimate question now what the sequence is and all the details is extremely difficult because while they are related to all these material properties they're much more related to where the flame was in relationship to
02:05:06 where the flame was in relationship to the material again just to test this a little bit more what about the the aluminium skins that we have on different materials you've talked previously when we looked at the ACM
02:05:18 previously when we looked at the ACM cassettes that they had an aluminium skin may well have been relevant in terms of whether it was first to ignite what about the PIR and the foil that is on the the PIR the the foil on the PIR
02:05:32 on the the PIR the the foil on the PIR and inasmuch as the aluminum skin are going to have an impact in trying to slow down ignition that's that's clear the the aluminum being thicker the
02:05:43 the the aluminum being thicker the aluminum skin of the ACM being thicker obviously has a bigger impact so it is actually quite difficult to a Titan ACM panel and and but all these things again
02:05:54 panel and and but all these things again you know they do have an impact so obviously expose PIR will be more susceptible to ignition than P are covered by an aluminum film and just to
02:06:05 covered by an aluminum film and just to help me with this and is the purpose of the because the very thin skin the PIR is its function to dissipate the heat or to exclude the oxygen award its
02:06:18 heat or to exclude the oxygen award its function is to actually is not to dissipate the heat in this case although it does have a reflective so part of the heat gets reflected out now its function is mostly to separate the fuel from the
02:06:29 is mostly to separate the fuel from the oxidizer so that delays the whole process of ignition because once the material reaches the point where it starts evaporating then it still has to
02:06:40 starts evaporating then it still has to reach the oxygen before it ignites and the barrier cells to block that transfer thank you do you think that the exposed sides of the insulation in the columns
02:06:53 sides of the insulation in the columns so they had a foil face that they had exposed sides might be significant in this context well they are going to change the outcome and in in the sense
02:07:04 change the outcome and in in the sense that the exposed sides will ignite faster than the areas are not exposed but in this context I think given as I say the proximity of all these materials the complexity of the cavity and the
02:07:18 the complexity of the cavity and the nature of the fire event it's extremely difficult you know to figure out to what extent that would have mattered or not yeah can we just look at a picture of that just to orientate ourselves on that
02:07:29 that just to orientate ourselves on that so if we go to figure eight point three seven and dr. lanes report that's BL AF six zeros eight at page 35 so this is a
02:07:40 six zeros eight at page 35 so this is a picture where we can see the column insulation which was a hundred millimeters with the foreskin with the ACM column panels have been taken off so
02:07:53 ACM column panels have been taken off so we see it inside and we can see the exposed edge there is that what you were just talking about yes and you're saying therefore that may have paid a slight different in terms of if it's got into
02:08:04 different in terms of if it's got into the column you've got an exposed edge or potentially exposed edge there yes but again you know going back to the point that I was making you'll see also other materials involved a very intricate
02:08:16 materials involved a very intricate geometry
02:08:16 geometry you know if from from an idealized perspective a designer will be able to model performance so I would like to be able to create some
02:08:27 like to be able to create some calculations that allow me to tell you what the performance is of the system here we have designed and built a system that we've made it so intricate and
02:08:38 that we've made it so intricate and complex that we have no capacity to be able to predict performance so when we are discussing these little details we have to put that into context that effectively this is such a complex system that being able to say this is
02:08:51 system that being able to say this is how it went and this is a direction and it jump from here to here is a complete impossibility because the system is way too complex can we also look at figure
02:09:02 too complex can we also look at figure 10.10 of doctor lanes report that's B la s five zeros ten yes so here what we're seeing is we're looking at the column
02:09:15 seeing is we're looking at the column that's faced on the right we're looking at some of the column cassettes that were sorry the column panels that were the ACM panels on on the columns
02:09:27 the ACM panels on on the columns covering those columns and we can see that she's highlighted some exposed PE cause where it's been cut elimination to those columns again do you think that
02:09:38 those columns again do you think that that could have been significant in terms of the route of fire spread of that 16 again you know all those elements are are potentially significant
02:09:51 elements are are potentially significant they could potentially have an influence you know but once again I mean look at the complexity of the system being able to predict to what extent it mattered to
02:10:03 to predict to what extent it mattered to me is completely overwhelmed by the fact that you have a very small fire in the interior that can actually have the capacity to ignite any of these components that at the end remains to me
02:10:14 components that at the end remains to me the the bottom line the details are very very difficult to articulate in a separate way I now want to turn to the visual evidence which is you say
02:10:25 visual evidence which is you say professor Bisbee has considered in a lot of detail and I'm about to play professor Bisbee's video so I just want to repeat
02:10:32 to repeat the trigger warning at this point we're now going to be showing a video of the early stages of the fire when full tower up the East face this contains images and audio that some may find distressing
02:10:44 and audio that some may find distressing and I'm then going to be asking you about a number of stills that we see in relation to that visual evidence I'm going to just play the first part of the video approximately eight minutes and
02:10:55 video approximately eight minutes and we're going to look at the time period between 105 and 117 in this video we're going to stop it there so if I can now so we just pause for a minute because well I can't see anyone making to leave
02:11:08 well I can't see anyone making to leave this room but there might be people
02:11:26 all right should we go on then yes so if I can now play that video
02:11:52 [Music]
02:12:00 but
02:12:14 [Applause]
02:12:26 and this bio so
02:12:33 I'll call overhead or graveyard shift but I've seen the ends like the Luiza that is what Nozawa jockey is smoked
02:12:46 that is what Nozawa jockey is smoked I'll be pissed if that was my order V for top of sideways my state
02:13:00 not to
02:13:02 ends
02:13:06 [Applause] [Music]
02:13:26 [Music]
02:13:53 laughing dog
02:14:03 this wheeler [Applause]
02:14:17 [Music]
02:14:23 quite a special chakra
02:14:31 [Music]
02:14:36 Sipho case the house guys don't make fires kids parents keep kids away yeah fire game
02:14:58 if without the evil omvana
02:15:21 my god [Music]
02:15:35 if not yeah [Applause] [Music]
02:16:17 people above it must be spoken here
02:16:40 watch on the floor what
02:16:49 [Applause]
02:16:56 I think what gets in there well most people guess in the head behind
02:17:14 the warning go
02:17:47 the bosses
02:18:05 [Applause]
02:18:26 [Music]
02:18:42 [Music]
02:19:33 I've shown that now because that passage is going to be relevant to a number of topics that were going to come to in a moment
02:19:41 moment [Music]
02:19:42 [Music] now that visual evidence has been addressed as you say in professor bisby's report can we just turn up what professor Bisbee has said about it in particular if we look at his report lby
02:19:56 particular if we look at his report lby is six zeros one at page one four five paragraph six nine two to start with [Music]
02:20:21 if we could just zoom in on that's that's great yep so there he said since I submitted my initial phase one expert report additional video evidence of the early
02:20:32 additional video evidence of the early fire spread to the cladding taken from outside the tower has become available this shows that beginning at approximately 1:00 11:45 molten material is burning on the upper surface eyes
02:20:44 is burning on the upper surface eyes sill of the spandrel rain screen cassettes immediately below the kitchen window of flat 16 this is coincident with external flaming venting through
02:20:55 with external flaming venting through the hole created by the failure and movement of the extract fan and infill panel it is considered likely that this burning material is melted PE filler
02:21:06 burning material is melted PE filler from the ACM cassettes located directly above the window it should be noted that this material could also be XPS core material from the window infill panel housing the extract fan however I
02:21:18 housing the extract fan however I consider this less likely now just pausing there can we look before I ask you some questions about this at figure 65 of Professor bisby's report which is the still which he's referring to there
02:21:31 the still which he's referring to there that's at Elba lb YS six zeros one at page one to two figure 65
02:21:45 and if we can zoom in on 65 at the bottom so professor Bisbee appears to be highlighting in particular at this point that we have molten material burning
02:22:02 that we have molten material burning immediately below the kitchen window is that what we can see there in this photograph it's burning on on the edge of the kitchen window yep I would agree with her and what conclusions would you
02:22:15 with her and what conclusions would you draw from the presence of that burning material in that bottom left-hand corner of the window that clearly the ACM is already involved at that point in the
02:22:26 already involved at that point in the fire and do you think it likely that that burning material is melted PE filler from the ACM cassettes located directly above the window most likely and does that affect your view that the
02:22:41 and does that affect your view that the most likely route of ignition is by flame of exposed flammable materials in the window surrounds not necessarily I think you have to keep in mind that we're talking about 1/12 so if we take
02:22:55 we're talking about 1/12 so if we take the moment in which the fire was noticed by the the detector we are ready about 17 minutes into the fire now fires have
02:23:08 17 minutes into the fire now fires have before they start the period of growth they sometimes have a very long incubation period where they might be just simply simmering in there but they have the capacity depending on their
02:23:20 have the capacity depending on their location to activate the detector so the detector could have detected the fire at a very early stage we have given us maybe five six ten minutes of incubation before the growth started you know in
02:23:33 before the growth started you know in that case then that conclusion will be probably most appropriate but if the incubation period would have been very short then all the major events would
02:23:44 short then all the major events would have happened in the first 10 minutes so effectively that would have been too late and most likely would have ignited from the inside before so there's a lot of uncertainty on the way in which the
02:23:55 of uncertainty on the way in which the fire actually evolves at the beginning and the
02:23:57 and the we have an alarm doesn't necessarily tell us what was the stage of the fire and how long it would take it before it starts affecting things and in a similar manner the images is what we're seeing
02:24:09 manner the images is what we're seeing from the outside so we have no capacity to see what is happening behind so I think this is a very important piece of evidence that shows you that there is significant involvement of the external
02:24:21 significant involvement of the external cladding in the fire at this point but it is not necessarily conclusive that that is the only way in which the fire could have ignited you know because it
02:24:33 could have ignited you know because it really depends on the way the fire revolves and that's something we will probably never know and when you talk to moment ago about we know we had the alarm are you talking about the smoke alarm going off in flat 16 if we look at
02:24:46 alarm going off in flat 16 if we look at that picture that's on the screen at the moment would it be right to understand that the whole of the area surrounding the window is now involved in the fire
02:24:57 the window is now involved in the fire potentially although not necessarily cameras saturate very rapidly and then there's a smoke reflection and numerous different things so at that distance it will be quite hard to pinpoint exactly
02:25:09 will be quite hard to pinpoint exactly what sectors are actually burning but because of the demarcation lines it is it is quite clear that there is a significant event going on in there thank you yes and if we can just finish
02:25:24 thank you yes and if we can just finish off what Professor Bisbee says then if we can go back to lb ys6 series one at page 145 and look at paragraph six nine
02:25:35 page 145 and look at paragraph six nine three so there he says if the external cladding was first ignited and sustained burning due to heat from flames venting from the from the kitchen window of flat
02:25:47 from the from the kitchen window of flat 16 I buy an external fire plume see drysdale one would expect to observe the earliest evidence of dripping burning a CMP
02:25:56 CMP filler originating from the location directly above the fan mounting an inward swinging kitchen window that was located directly beneath the extract fan panel the dripping PE would most likely
02:26:08 panel the dripping PE would most likely originated from directly above the extract fan panel however as already noted the available visual evidence presented in this section suggests that dripping burning PE spears to have first been observed falling from the base of
02:26:20 been observed falling from the base of the window as at its southernmost edge so would you agree with professor Bisbee and what he's saying in that paragraph about you would have expected the dripping and melting ACM had it been as
02:26:33 dripping and melting ACM had it been as a result of the flaming through the extract panel to have been dripping and melting at the top of the window not at the bottom left-hand corner of it yeah I couldn't disagree with that which
02:26:44 couldn't disagree with that which doesn't mean that our dripping could have not been happening inside that we couldn't see so so in in in many ways I mean this is a difference you know between you know putting some physical arguments and and putting evidence from
02:26:57 arguments and and putting evidence from images so we need to contrast because that's really what we have but I think the the points are being made are fundamentally correct and they stem from visual imaging and and it's information
02:27:08 visual imaging and and it's information that is extremely valuable that should complement you know the analysis from the inside but it's very difficult to put a sequence of events and say which one comes first because what you're
02:27:19 one comes first because what you're saying is you wouldn't see it well it's come round the inside picture because it may have gone inside the column and been burning there before we actually see it visually on the outside exactly can I take you back to just
02:27:31 exactly can I take you back to just another image this is an earlier image at 105 from mr. cabanas mobile phone if you go in your report to JT OS 6 zeros one at page 56 line 5 8
02:27:44 to JT OS 6 zeros one at page 56 line 5 8 4 1 5 8 2
02:27:49 [Music]
02:27:58 and if we can focus in on that image there
02:28:07 so this is a screenshot taken from the video recovered for mr. Capades mobile phone at timestamp 105 57 do you agree that this image appears to show flames
02:28:19 that this image appears to show flames around the extractor fan and the window of kitchen of the kitchen of flat 16 and a visible fire plume behind the window yes and is it possible that our fire
02:28:33 yes and is it possible that our fire located by the wall or in the corner of frat 16 would have produced an adhered fire plume well first I guess we need to define the concept of water right here
02:28:45 define the concept of water right here so so there's when when you have a fire there's two types of compartment fires the the types of fires were you have the smoke layer that dominates the problem
02:28:57 smoke layer that dominates the problem in other words what you get is gases that fill the compartment but there is no great motion going on in those cases the smoke will just simply spill and it
02:29:08 the smoke will just simply spill and it will be adhered to the wall so effectively you have smoke just literally touching the walls and moving up now many times for example when you have a door open and you have some ventilation what you get is a flow so
02:29:21 ventilation what you get is a flow so the fire acts like a pump and it pushes the smoke out in which case you get a disattached smoke you know plume because the pollute the smoke is pushed away by the flow that gets created in the
02:29:33 the flow that gets created in the compartment so in this particular case given the fact that the door was closed and given the fact that most of the openings were closed it is very unlikely that you had high velocities inside the
02:29:45 that you had high velocities inside the compartment so it will be most likely that you have a nadir fire plume in other words you will have the smoke touching the surface moving and so
02:29:58 touching the surface moving and so effectively at at this point you do have ignition that has happened of a component that is partially in partially out and how that happened is very
02:30:10 out and how that happened is very difficult to define now the again the interesting thing is that this is 10 minutes
02:30:17 minutes from the moment of the smoke alarm so we already have 10 minutes of gap happening happening in there so as a symptom that the fire is emerging out of the
02:30:29 the fire is emerging out of the compartment is a very clear symptom but it's hard to relate to anything else beyond that so do you think this has any light on whether there might have been
02:30:40 light on whether there might have been direct flame impingement from an adhered fire plume on the external wall materials at the head of the windows I think what's been suggested it comes out of the window where the extract fans
02:30:51 of the window where the extract fans gone and sticks to the surface of the ACM connect cassette that we looked at before that's immediately above the window and ignites it that way do you think that visual evidence helps on that
02:31:02 think that visual evidence helps on that well basically what you have is a flame now that particular flame will result in a heat flux that is applied to all that section and effectively it is true that the flame will impinge now this in size
02:31:16 the flame will impinge now this in size is a fairly small flame and it isn't raining a lot of air so the question here will be does that flame have enough heat to be able to ignite the cassette
02:31:29 heat to be able to ignite the cassette and and that question is one that that we have not resolved and I do think that probably if that path is going to be followed then that needs to be tested because effectively it is not about
02:31:40 because effectively it is not about having a flame is having a flame that is sufficiently strong to provide sufficient heat flux to be able to ignite the cassette and just to be clear I think you and professor Bisbee have
02:31:51 I think you and professor Bisbee have excluded the idea that the flame could have started in the extract fan and produced sufficient heat to then ignite the panels above is that correct yes so basically we if you do a simple analysis
02:32:03 basically we if you do a simple analysis of the size of that flame by the time you get to the cassette even if it's adhered
02:32:09 adhered the heat flux will have already decayed enough that is quite unlikely that that's what what is the the the only source of ignition now if other things are burning around then it's a slightly different story you
02:32:22 then it's a slightly different story you know but because you're supporting with an extra flame an already existing amount of heat but uh but just the by itself doesn't have the capacity to produce enough heat to be able to do
02:32:34 produce enough heat to be able to do that yep just a few more questions on this topic and I've been asked to put to you that there was firefighter evidence from firefighter Brown that when he was leaning out of the kitchen window and
02:32:45 leaning out of the kitchen window and trying to squirt the hose back at the fire and that he could see flames traveling within the cavity now that's certainly after 120 is that of any
02:32:57 certainly after 120 is that of any assistance at all in terms of this question of break out from the compartment well the the only information that that provides is the fact that that the uPVC was gone because
02:33:09 fact that that the uPVC was gone because he could actually see through and and the fact that there was flames in the cavity that tells you that the fire had already progressed into the cavity so if anything the conclusion that you can make is at that point the fire service
02:33:22 make is at that point the fire service knew that the fire was in the cavity but does it help us at all his evidence about break out from the compartment it's too late it's too late in time yeah
02:33:49 so finally on this topic I've asked you before about the possibility that with with additional ventilation in that room in that kitchen for example around the doors and if the fire was not in the
02:34:01 doors and if the fire was not in the center of the room but at the in a corner or against a wall whether there could have been local areas within the smoke layer where temperatures could have been higher and might have melted
02:34:12 have been higher and might have melted for example the following elements the window frame in its fixings is that possible
02:34:18 possible of course I mean it doesn't need the extra ventilation or it doesn't need the flames to be in any particular position effectively what you have is a fire
02:34:29 effectively what you have is a fire flame and if the flame for whatever reason is tilted in the in a certain direction it might be impinging on many of the objects that are there and and
02:34:40 of the objects that are there and and could potentially heat them up quite significantly so you're talking about direct flame impingement potentially could have melted the window flame and its fixings what about weakening the the plastic
02:34:52 what about weakening the the plastic thermal disruptor that held the two part window together everything everything is possible and the the XPS core of the the
02:35:03 possible and the the XPS core of the the window infill panels which are to the to the left of the kitchen window same I mean I think yep and melting of the components between the ends of the
02:35:14 components between the ends of the window assemblies in the original structure DISA made of aluminum I presume and so the melting temperatures are about 600 and so you have to have
02:35:26 are about 600 and so you have to have you know for melting of aluminum you have to be able to demonstrate what kind of size of a fire you will be able to need to get to those temperatures but effectively if you put it close enough
02:35:38 effectively if you put it close enough you will be able to get to those temperatures
02:35:44 I'm now going to turn to some connected but different topics compartment ation do you agree that a high degree of complementation around each flat
02:35:56 complementation around each flat enclosing every service riser the stairs the lobby's is the first layer in the layer of safety moving the basis of fire safety guidance in high-rise buildings the compartment ation is the one layer
02:36:11 the compartment ation is the one layer that not only gives you protection but gives you robustness to the strategy is very difficult to break a compartment ation so it is an incredibly it's not the first layer of protection it is a
02:36:23 the first layer of protection it is a very important layer of protection because is the only one that really brings robustness in into the system the other ones can all fail and and there's
02:36:34 other ones can all fail and and there's no recovery from them so if the smoke detector doesn't work the smoke detector does not work well if the compartment ation gets a crack you may get a little bit of a leak but you still get a significant amount of protection so the
02:36:45 significant amount of protection so the compartment ation in itself provides that component of robustness that no other layer of protection provides so you agree that that's the critical feature in the design of high-rise buildings for this type of high-rise
02:36:57 buildings for this type of high-rise buildings yes it is a critical feature and is it your evidence that in the event of any fire starting near a window at Granville Tower there was a disproportionately high probability of
02:37:09 disproportionately high probability of fire spread into the cladding system absolutely
02:37:17 and you've said in your report that based on your analyses that the size of the fire that could reach the uPVC and ignite the combustible materials around the window are within a range that can be considered a feasible event within a
02:37:30 be considered a feasible event within a residential kitchen is that correct beyond that I think it will be an event that will happen inevitably in a kitchen in a residential house so it has a probability what I call probability of
02:37:41 probability what I call probability of one yes I have to ask you about that when you say it's got a probability of one precisely what do you mean by that you mean it's inevitable a fire of a frying pan is going to happen in a
02:37:53 frying pan is going to happen in a kitchen within the life of the building and when we design for example for compartment ation we design for a post flashover fire so we accept that
02:38:05 flashover fire so we accept that everything smaller than that is very highly probable so we have to design our compartment ation to withstand a post flashover fire so so yes I mean this is
02:38:16 flashover fire so so yes I mean this is an inevitable it's perfectly foreseeable event and you will say say that because a fire of this nature can be expected the building is required to respond appropriately precisely what do you mean by that what I said at the beginning was
02:38:29 by that what I said at the beginning was that fires are very common events but fires that create significant damage are rare events and we design buildings to make that happen so we produce all these
02:38:41 make that happen so we produce all these layers of safety to try to make sure that we turn a very high probability event into a very rare event so the building is required to respond to deliver that so that a fire of this
02:38:52 deliver that so that a fire of this nature doesn't progress beyond a kitchen and I want to just focus for a moment before we leave stage one on on the end of stage one of breach of the
02:39:03 of stage one of breach of the compartment of origin do you agree that in principle there is a defined point in time at which complementation is breached yes so there is a I mean it
02:39:16 breached yes so there is a I mean it obviously is very hard to pinpoint exactly you know when that point is but by 105 you already see dripping or burning
02:39:26 burning polyethylene so it is clear that at that point there is external propagation happening somewhere in in in there so so that already in itself gives you a clear
02:39:40 that already in itself gives you a clear idea that the fire is progressing in a manner that is unexpected because it is not a flame being projected outside and not igniting anything or project or propagating into
02:39:52 anything or project or propagating into other spaces it is a flame that has barely come outside but it is already creeping into the external components of the building so that that's your evidence about the time when
02:40:03 evidence about the time when complementation has failed that's an estimate of time that I put at the end of my stage one which is 105 to 108 or 105 well 105 to 108 and a slightly
02:40:16 105 well 105 to 108 and a slightly different question what time do you think complementation had visibly failed or is it the same answer well it has clearly failed by 108 109 and there's
02:40:27 clearly failed by 108 109 and there's evidence of failure by 105 so between those two times you have an evolution of the images as you saw from the video an
02:40:38 the images as you saw from the video an evolution of the images that by the time you end the minute 108 it is very clear that you have external components burning by the time you are in 105 you
02:40:51 burning by the time you are in 105 you have the first evidence so you have that range of time where where it becomes absolutely clear that there is external burning and do you think that is the
02:41:04 burning and do you think that is the point that firefighters ought to have realized that complementation had been breached I mean that's a very difficult question to answer because it is how do you interpret the images now clearly
02:41:17 you interpret the images now clearly firefighters are used to see flame projections because a post flashover fire will normally break the window and you have a flame projecting to the outside being able to identify that that
02:41:29 outside being able to identify that that flame is not a flame projection but it is actually a flame that is creeping into the
02:41:35 into the into the building requires a level of training that enables them to understand a complex structural system and that's a there's a very different question now obviously by the time you get to 111 you
02:41:46 obviously by the time you get to 111 you know then it is fairly obvious pieces are beginning to fall down so by 111 you can say it is clear that something is burning on the outside but uh but the interpretation is the hard part is how
02:41:58 interpretation is the hard part is how you interpret what you are seeing the stage that computations breathe is your evidence that ignition of other components of the facade and the
02:42:09 components of the facade and the external flame spread is inevitable in this situation yes and you also say that the assumption underlying the stay-put policy or approach is no vertical flame
02:42:21 policy or approach is no vertical flame spread is that correct yes so is it right that once the compartments been breached and you have ignition of the facade it is going to be undermining and invalidating of the stay-put it
02:42:34 invalidating of the stay-put it invalidates by definition the statehood policy because it's based on a required boxing of the fire into one compartment and is it your view at that point that once that's breached compartment ations
02:42:46 once that's breached compartment ations breached egress or or rescue rather than stay put is a preferred option it is my my opinion that that will be the case so
02:42:58 my opinion that that will be the case so I now want to turn to stage two of your analysis now you have stage two as covering the fire ascending to the top of the East elevation and the Associated
02:43:10 of the East elevation and the Associated vertical fire spread and that's between approximately 105 a.m. and 1:30 a.m. is that correct yes and I want to consider first the importance of this vertical fire spread now you say in your report that the
02:43:22 now you say in your report that the flame spreads rapidly from level four to the architectural roof detail in approximately twelve to fifteen minutes from the establishment of flames on the facade is that condition and you also
02:43:34 facade is that condition and you also say that in general vertical flame spread is much faster than horizontal flame spread and this was the case at ground floor towers that rise yes now we heard something about this when professor Bisbee gave his present
02:43:46 professor Bisbee gave his present back Eugene but can you just explain again in very simple terms why vertical frame spread is expected to be so much faster yeah III think I think here is really important to understand the
02:43:57 really important to understand the physics behind it because when we're talking about a fire we're thinking about fuel burning with air and and producing energy and and that is the
02:44:08 producing energy and and that is the concept of a fire if it's in a box the the energy will be used to heat up that box and the energy is accumulating in the case of flame spread it is extremely important to understand where the energy
02:44:19 important to understand where the energy goes because depending on where the energy goes you have a capacity to continue to spread the fire because if you think about it is the energy that you're producing that is heating up the
02:44:30 you're producing that is heating up the other material until it makes it ignite and allows the flame to spread so the flame is going to be jumping up as we provide energy and we heat the material and we allow that material to ignite so
02:44:42 and we allow that material to ignite so if I'm in a vertical wall and I'm producing energy here the energy is going to go up so it's going to start heating up all this area so effectively all the energy that I'm producing is
02:44:54 all the energy that I'm producing is being delivered to the material step by step so effectively I'm not losing energy all the energy is going to where it's supposed to go so it is heating up the material very rapidly and allowing
02:45:05 the material very rapidly and allowing it to ignite and allowing the flame to spread now if I'm trying to spread down which is what we call a post spread then I'm producing the energy here the energy
02:45:17 I'm producing the energy here the energy is mostly going up and only a minut fraction is going down because all the coal the gases are going up not so effectively what you're getting is very weak spread because you have very little
02:45:28 weak spread because you have very little energy heating up the material and bringing it to ignition if you spread laterally in that case what you have is the heat is going up and you're trying
02:45:39 the heat is going up and you're trying to heat on the side now obviously the flames are sometimes going to tilt so you're going to get a slightly better condition but still you are going against the flow because the flow is coming here and bringing the heat up so
02:45:52 coming here and bringing the heat up so because all the heat is going in the direction of spread vertical spread is going to be significantly faster than downward spread or lateral spread both cases are
02:46:04 spread or lateral spread both cases are what we call a post frame spread well this is what we call forward spread now the final nuance to this is that if I don't have enough energy then it will not spread well with vertical I will
02:46:17 not spread well with vertical I will always have enough energy because all the energy is going there is just take longer so if this is a weaker fire it will take slightly longer but eventually it will get there but here because I'm
02:46:28 it will get there but here because I'm fighting against cold air I might not have enough energy so it actually will not spread so in the case of a post spread you might get a condition where he actually just doesn't even spread at all well in the case of vertical spread
02:46:40 all well in the case of vertical spread it will most likely go all the way up here now you say that this is all very well traversed in the available literature including in Drysdale who has this it vertical spread it 10 times
02:46:52 this it vertical spread it 10 times faster is that then horizontal flame spread I don't remember exactly how the 10 times faster but I will imagine it would be the latter oh yeah the horizontal things but and and you said
02:47:05 horizontal things but and and you said that whilst there's not much reliable data on the characteristics of other international fire events the most common scenario is flame spread rapidly upwards with very limited laterals flame
02:47:17 upwards with very limited laterals flame spread is that right yes because the the third factor is the available fuel that you have so if you don't have the capacity to spread fast enough laterally
02:47:28 capacity to spread fast enough laterally by the time you've burned out all the material then you stop having the energy supply and then it stops burning so depending on what is the amount of fuel that you have you have a longer time to
02:47:40 that you have you have a longer time to assess the spread so if you have if you don't have very much fuel which is normally the case in this particular type of installations then you will not be able to spread horizontally or
02:47:52 be able to spread horizontally or downwards you've given some examples of what you were just talking about can we go to those it figures 21 that's JT Oh air six zeros one at page 59
02:48:04 air six zeros one at page 59 so we've given us three examples here the torch building in Dubai the LaCrosse building fire in Melbourne and the address building in Dubai can you just
02:48:15 address building in Dubai can you just very briefly talk us through each of those by reference to this concept of vertical flames spread much rapid and less horizontal flames yep the the the
02:48:27 less horizontal flames yep the the the most clear ones are the top two so to be the torch and the lacrosse building so as you can see in the torch building you have very large fire that propagates upwards and on the right-hand figure you
02:48:38 upwards and on the right-hand figure you will see in the left corner this is unfortunately a different angle of the but in the left corner you will see the damaged area of the building and you can see it's a very narrow strip that has propagated all the way from the bottom
02:48:50 propagated all the way from the bottom to the top in the case of the lacrosse building you have a fire that starts in the balcony in an air conditioning unit and it spreads over the cladding all the way to the top but it as you can see
02:49:01 way to the top but it as you can see from the right picture there's only one row of apartments that gets affected and it never spreads laterally in the case of the address is slightly more complicated because there is a bit of
02:49:13 complicated because there is a bit of lateral flame spread in the case of the address because as you can see was a windy day so the wind is carrying the flames to the one side but uh but the rate at which it propagated vertically
02:49:24 rate at which it propagated vertically was easily 10 times much more than 10 times greater than the lateral spread so and and eventually this fire dies on its own before it actually manages to to go
02:49:37 own before it actually manages to to go more than two and a half apartments yeah so you said that the available footage from these incidents indicates that once flames spread to the top they proceeded to decay and eventually extinguish
02:49:49 to decay and eventually extinguish there's no is that right and you've actually quantified the flame spread rates and those other international fires compared with ground floor can we just look at that that's figure 23 at page 61 of your report
02:50:05 so can you just explain to us here we seem to have lots of different fires at the bottom and then what do we see in in the graph yeah so so what what you see
02:50:16 the graph yeah so so what what you see in in the in the horizontal axis is the different events from the and rebuilding in 1972 all the way to the Granville Tower and then you get an average
02:50:27 Tower and then you get an average vertical external flame spread now given that the quality of the images is not always consistent what we opted to do here was just take a few data points
02:50:40 here was just take a few data points that we could actually see and then just take an average knowing that normally the flame spread starts slower and then it starts speeding up so it accelerates at the end but we didn't include that
02:50:51 at the end but we didn't include that that's why we have the error bars in there to show that at the maximum value for example the case of the water club at the maximum value was 25 but the minimum value was 5 so it gives you a
02:51:03 minimum value was 5 so it gives you a sense of the range but the average value is the one that that is important so as you can see Grenfell falls in the category of the fires that actually
02:51:14 category of the fires that actually spread slower yes so we have Granville on the bottom right hand here and it's placed amongst some of the slowest flames with an average speed of about 4
02:51:27 flames with an average speed of about 4 meters per second so it meters per minute and as opposed to the extreme case of the address for example where you have about 22 meters per minute you
02:51:39 you have about 22 meters per minute you said in your report that the expected heat fluxes on an external wall can be of a magnitude of a hundred and 20 kilowatts per meter squared is that correct yes can you just explain very
02:51:51 correct yes can you just explain very briefly how you've calculated that you've referred to the hour Garhwal global research technical report is it right that you've taken that as an extrapolation from that yeah so
02:52:02 extrapolation from that yeah so effectively if you look at the data that you have on internal compartment fires you will find that internally you can get above 200 kilowatts
02:52:13 get above 200 kilowatts per meter square so inside the compartment you're gonna have about you know 200 now then once that heat starts coming out it starts decay and it drops so this report by Agarwal effectively
02:52:28 so this report by Agarwal effectively tries to use that information to create a test and in their test they try to create a profile of how this heat flux is going to decay so it's going to go
02:52:39 is going to decay so it's going to go from this originally more than 200 inside and start dropping until he goes to about five or something lower than that so they produce a curve that stops
02:52:51 that so they produce a curve that stops at about fifteen centimeters from the edge or from the bottom and that 15 centimeters these are about a hundred and twelve kilowatts so basically I just filled it up and put above 120 because I
02:53:04 filled it up and put above 120 because I know it has to go from about 200 you know to 110 in that corner or that little little part and I want to discuss some of the architectural elements that
02:53:15 some of the architectural elements that might impact on the rate of vertical flame spread you've explained in your report that there's a complex interrelationship between a number of different elements of these kind of systems in terms of the impact on flames
02:53:27 systems in terms of the impact on flames on vertical flame spread is that correct yes and that you've got effectively multiple processes interacting with one another yes can we focus for a moment on the the ACM panels themselves can we go
02:53:40 the the ACM panels themselves can we go to the text of your report that's JT OS six zeros one at page 60
02:53:50 lines one six four nine and one six five one
02:54:01 if we can just read that so you say there the politic polyethylene info was placed between two aluminium plates that were melt in the range 580 to 650
02:54:13 were melt in the range 580 to 650 degrees C thus in the presence of a significant flame the aluminium would have represented no protection to the polyethylene flames are typically between 600 and 800 degrees C there's a
02:54:25 between 600 and 800 degrees C there's a hotter than the melting temperature of the aluminium is that correct yes so you've explained in your report that the high thermal conductivity of the
02:54:37 high thermal conductivity of the aluminium is resulting in a heat transfer to the polyethylene infill is that correct and also a wave away from it as well yeah yep and the significance
02:54:49 it as well yeah yep and the significance of the away from it that you can potentially melt it and produce a gap that splits the two panel faces exactly we're just going to come today's and the splitting in a moment in fact let's go
02:55:02 splitting in a moment in fact let's go to that let's look at for your figure 26 again that there's a new reference to that because the version in your report is not very clear that's jto s60 3 and
02:55:13 is not very clear that's jto s60 3 and it's the bottom diagram so here as I understand it you've attempted to explain what processes are occurring
02:55:27 explain what processes are occurring when we get vertical flame spread with an ACM panel where you have aluminium on the outside and then the polyethylene on the inside is that correct
02:55:38 the inside is that correct yes and you talked a moment ago about that this the splitting you've got a little diagram there can you just explain that and the significance of it yeah would you mind if I actually stand
02:55:49 yeah would you mind if I actually stand up and so to me this is where the great complexity of the system stands in the sense that you have multiple layers so
02:56:01 sense that you have multiple layers so you have to concrete structure in here you have a material that is a charring material that eventually is going to consume itself you have a gap between the two of them and then you have a composite system that has two layers of
02:56:14 composite system that has two layers of plus the polyethylene in the middle this polyethylene is going to melt as it heats up now the rate at which it heats up in the aluminum is going to result in altering the rate at which is going to
02:56:25 altering the rate at which is going to melt so how this material is going to start falling off is going to depend on how fast the heat goes through the aluminum now how fast the heat goes to the aluminum depends if you have a fire
02:56:36 the aluminum depends if you have a fire inside or you have a fire outside it depends on the wind that you have it depends on the width of the cavity and it depends on how the insulation is burning so effectively you have all this
02:56:47 burning so effectively you have all this system of incredible complexity all interacting with each other to try to give you the final outcome and eventually the system is so complex in nature that is almost impossible to
02:56:58 nature that is almost impossible to predict what it is is true behavior so when you we were talking a moment about these complex systems with multiple processes interacting that's what you're
02:57:09 processes interacting that's what you're trying to show in this diagram is that right absolutely so this diagram basically gives you a schematic that is actually quite simplified of all the different processes that you can
02:57:20 different processes that you can actually have all interacting with each other in one of these particular systems one of the things you say in your report is that the aluminium provides no protection to the polyethylene inside can you explain precisely why that is
02:57:32 can you explain precisely why that is yes so if you have a flame here and that is a very significant flame that has already been established that flame is going to have heat fluxes that are quite significant and can bring the aluminum
02:57:44 significant and can bring the aluminum far above its melting temperature so you might have dripping of the aluminum not only that you're gonna have melting of the polyethylene which results in splitting so you will have the two of
02:57:55 splitting so you will have the two of them separating so the flames are going to creep inside so the aluminum cannot be seen once the flame is established as a protection to the to the polyethylene it is just simply a barrier that is
02:58:06 it is just simply a barrier that is going to disappear and very rapidly once you have a flame that is established and you've also highlighted in your report the important role of these open vertical
02:58:16 vertical these open vertical columns and you've said that the acceleration of vertical fire spread can be explained in part by these channels producing chimney effects
02:58:28 these channels producing chimney effects is that because flames elongates possibly up to five to ten times in a concealed space is that right well what what happens is that depending on the size of this gap if this gap is too
02:58:39 size of this gap if this gap is too narrow is going to block the oxygen and the flame is going to try to creep outside so in that case it will not spread now as I start increasing this what you create is a chimney effect and
02:58:50 what you create is a chimney effect and this flow becomes very dominant so you get a flow that is going in that direction and it's carrying the fuel away so it's elongating the flame and allowing it to spread much faster and
02:59:03 allowing it to spread much faster and you say that the width of the cavity is playing a fundamental role in terms of determining the flame spreads absolutely so if you make the width of the cavity very very small you might end up choking
02:59:14 very very small you might end up choking the fire because the air cannot get in but as you start opening it up you might accelerate it but as everybody knows if you make a chimney too big then it doesn't draw the air so in that case you
02:59:25 doesn't draw the air so in that case you will start decaying again so it's a very sensitive parameter that can have a huge impact on the outcome but it's difficult to know if it's going to be beneficial or detrimental because it also depends on all the other interplay because for
02:59:37 on all the other interplay because for example if this material burns very vigorously he's going to have a huge impact on the temperature in here and the nature of the chimney yeah we're gonna come to that material a minute when you say this material you were pointing there I think to the PIR
02:59:49 pointing there I think to the PIR insulation is that right yeah we'll come to that just in a moment have you specifically considered the width of the clarity's created by both the columns and the spandrels at groennfell tower in
03:00:01 and the spandrels at groennfell tower in terms of its impact on vertical flame spreads no I don't think I have the capacity to be able to consider that in a quantitative way and establish how that width is going to determine a flame
03:00:13 that width is going to determine a flame spread but do you think that in general terms the the presence of that cavity would have promoted vertical flame spread not necessarily I do not have a clear opinion of it
03:00:24 clear opinion of it I think clearly will have influenced the nature of the flame spread but I'm not a hundred percent sure if it's going to be detrimental positive but the cavity clearly has an
03:00:35 positive but the cavity clearly has an effect and does it have an effect we're gonna talk about this in a minute combined with the PIR insulation if you've got a cavity where the insulation is on fire or flaming does the fact you
03:00:47 is on fire or flaming does the fact you have a cavity there potentially again grow in importance absolutely well I think the if you have a cavity in here and you have a material here you're
03:00:59 and you have a material here you're going to hit an exchange of heat between this two so not only the PIR is going to support burning within the cavity but actually the cavity and the burning in
03:01:11 actually the cavity and the burning in the cavity is going to support the burning of the PIR prr requires a fairly significant heat flux to continue to burn so if I was to remove everything and eliminate the cavity it is very likely that the PIR will extinguish but
03:01:24 likely that the PIR will extinguish but if I put all this ensemble and I have this exchange of heat between all the surfaces and the flow and the burning in between the cavity I can sustain the burning of the PIR so all these things are playing with each other in this in
03:01:37 are playing with each other in this in the system at a level of complexity that is incredibly difficult to come up with a prediction of what leads to what
03:01:48 just before we will come on in a moment and we may have to do it after the break to look at the PR PIR in a bit more detail you've referred in your report to
03:01:59 detail you've referred in your report to other complex geometries of the system that might affect the rate of fire spread would you agree that angular geometry including for example wing
03:02:10 geometry including for example wing walls or re-entrant corners might have played a role so take for example a column corners where we have an angle of I think 135 degrees as between the
03:02:21 I think 135 degrees as between the column and then the face of the spandrels it would have most definitely played a role I think the most difficult question to answer is would it actually help the spread or the turret or spread
03:02:32 help the spread or the turret or spread and that's a question that I will be have no capability to answer how could it have deterred the spread because it can it can if you look at the other geometry it is all about how the heat is
03:02:45 geometry it is all about how the heat is being exchanged so if I have something for example that has an angle like this then the way in which the heat is being transferred from one surface to the other one is actually far so even this
03:02:57 other one is actually far so even this might have not ignite if it's sufficiently far this might have not ignited in which case of represents a barrel but if I slightly move it and I put it close enough and then it ignites then the two of them are exchanging heat
03:03:09 then the two of them are exchanging heat with each other in which case it will become much faster so so it really depends on the detailed characters and many times unfortunately will be even coupled to the conditions of the day if
03:03:21 coupled to the conditions of the day if it was a windy day maybe 130 degrees would have not been enough you know well you will need 1/4 you know to stop the spreading so all these things are we we
03:03:32 spreading so all these things are we we can we can really do not ignore the level of complexity of what we're talking about this is really not a very simple system it's an incredibly complex system and as we discussed before the
03:03:44 system and as we discussed before the presence of films or skins or coatings on material they have the potential to affect the vertical flame spread absolutely and in films are combustible
03:03:55 absolutely and in films are combustible are what we call thermally thin materials like paper so for example a log of wood is thermally thick and a log of wood will have a very very hard time burning
03:04:06 will have a very very hard time burning on its own because it's a big bulk material so if I take the log of wood out of the chimney it will extinguish well a piece of paper which has the same composition as a log
03:04:19 which has the same composition as a log of wood because it's very thin it will burn very easily so thin films when they're combustible will have a significant impact on spreading claims just to round this off then I think this
03:04:32 just to round this off then I think this helps us explain can we just go to what you said at lines 91 to 95 of your report that's JT OS six zeroes one at page four if we can highlight in on 91
03:04:49 page four if we can highlight in on 91 to 95
03:04:56 there you say details of the cladding will have an impact on flame spread rates although in the case of grim fault our upward flame spread rates are not uniquely fast a comparison with other
03:05:08 uniquely fast a comparison with other international events shows that upward flame spread for the Grenville Tower is among the slowest it is therefore possible to ascertain that detailing of the facade system as opposed to its material composition has only a minor
03:05:20 material composition has only a minor impact on the evolution of this fire can you just explain for us why you say that taking that last sentence I mean we when we designed this type of facades we introduced all sorts of different
03:05:32 introduced all sorts of different components that are intended to slow potential flames / to protect like for example the thin film in front of the PIR and and the cavity barriers and and
03:05:47 PIR and and the cavity barriers and and so forth so we put all these components in principle to try to reduce the rate of spread now if you compare the spread of Granville Tower with with most of
03:05:58 of Granville Tower with with most of other international events and you see that actually the spread rate is not among the fastest is actually on the lower end you can tell that all these things more or less worked okay to try
03:06:11 things more or less worked okay to try to slow the spread but effectively they didn't solve the main problem you know which is the fact that we had a combination of materials that could sustain the problem so I could have put many other of these little Corrections
03:06:24 many other of these little Corrections and probably would have not made even any improvement and some of the faults that you might find in some of the the components might have not been responsible for any worse behavior what
03:06:38 responsible for any worse behavior what we can see is that given the type of materials that we have we are more or less at the baseline of the type of spread that we're going to have so you're saying this the important thing
03:06:51 you're saying this the important thing is the material composition of those materials
03:06:54 materials yeah yeah so I think that is an appropriate have a good point naming yeah yes well time we had a break for some lunch professor so we'll stop now we'll come back and resume it two
03:07:06 now we'll come back and resume it two o'clock and again I'm going to ask you not to talk to anyone about for evidence while you're
03:07:24 right 2 o'clock please