Professor David Purser's toxicology evidence on how toxic smoke caused deaths and incapacitation at Grenfell Tower
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00:00:00 Good morning, everyone.
00:00:29 Welcome to today's hearing. Today we're going to hear evidence from Professor David Purser,
00:00:34 the expert toxicologist instructed by the inquiry. Yes, Mr. Chairman.
00:00:39 Yes, Mr. Chairman. Good morning to you. Good morning, members of the panel. Before I call
00:00:44 Professor Purser, I just want to mention this. He is a toxicologist. He has analysed the
00:00:51 relevant evidence which relates to the deceased on the night at Grenfell Tower. You'll recall
00:00:58 that he provided a phase one report. He's now provided a report for this phase, his
00:01:02 phase two report. His evidence does contain descriptions of facts and matters about the
00:01:08 deceased's last movements and the immediate causes of death, which many will find distressing.
00:01:14 I wanted to raise that at this stage so that those who are following these proceedings,
00:01:18 both in person here in the hearing room and on the live stream, are aware of the contents
00:01:23 of his evidence in general terms, and then they can choose whether or not they listen
00:01:28 and follow or not. Yes.
00:01:29 So this is a trigger warning. Thank you very much.
00:01:32 Can I now call Professor Purser, please? Thank you.
00:01:48 Good morning, Professor Purser. Welcome back to the inquiry. I understand you're going
00:01:52 to take the oath. Yes.
00:01:53 So there should be a testament there. Would you take it in your right hand and read the
00:01:57 words on the screen, please? I swear by Almighty God that the evidence I shall give shall be
00:02:02 the truth, the whole truth and nothing but the truth.
00:02:05 Thank you very much indeed. Now please sit down and make yourself comfortable.
00:02:10 Thank you. Yes. Yes, Mr Millett.
00:02:17 Thank you, Mr Chairman. Professor Purser, good morning.
00:02:19 Good morning. You are Professor David Purser, CBE.
00:02:22 That's correct. And can I ask you please, before we start
00:02:26 your evidence, please, that when giving evidence, if you could keep your voice up so that the
00:02:31 person who sits to your immediate right there typing away can get down everything on the
00:02:35 transcript clearly. Also, please don't shake your head or nod your head. You have to say
00:02:40 no or yes, as the case may be. We'll take breaks in a normal way at about 11.15 or 11.20
00:02:47 during this morning and at an equivalent midway point during this afternoon. And finally,
00:02:54 if there's anything in the questions that I'm asking you which are unclear or you would
00:02:57 like me to repeat or put a different way or there's parts of your report that you'd like
00:03:02 me to show you, then we can do that. I understand, yes.
00:03:06 All right. Should there be a screen display?
00:03:09 Oh, here it is. The screen's in front of you, yes.
00:03:11 Yeah. You should have... Everything that I'm going
00:03:14 to show you will appear on the screen in front of you. And we can take it as quickly
00:03:18 or as slowly as you like. Now, first, can you confirm that you provided a preliminary
00:03:23 phase one report to the inquiry dated the 5th of November 2018?
00:03:27 Yes. And can you confirm that that report, and
00:03:29 I'll just give the reference, DAPR 501, 601, sorry, that that report was the subject of
00:03:37 your evidence at phase one of this inquiry? It was, yes.
00:03:40 And that you were asked questions about that on day 84 of the phase one hearings, yes?
00:03:45 Yes. And the transcript reference for that, if
00:03:48 we need it, is INQ3015183. Now, you've now provided a final report entitled your phase
00:03:55 two report, I think, haven't you? Yes, I have.
00:03:57 And is it right? That's now in three parts, and I'll just read those into the record.
00:04:02 Yeah. Sections one to four are at DAPR 605. Section
00:04:09 five is at DAPR 5011. And section six is at DAPR 606.
00:04:17 Yes. Yes. Now, I'm going to ask you some detailed
00:04:21 questions about that shortly, but is it right to say that your phase two work builds upon
00:04:27 the preliminary conclusions you reached in your phase one report?
00:04:30 Yes, it's a continuation, basically. Yes. Now, can we go then to DAPR 605?
00:04:39 And go to page 17. And you can see there a summary of your instructions
00:04:47 at paragraph two. Paragraph one and two. Paragraph one says, I've been asked to provide reports
00:04:55 for the purposes of phases one and two of the inquiry, which address the following issues.
00:04:59 One, the production of toxic gases in domestic fires and the consequences of inhaling toxic
00:05:05 gases in such circumstances, both physiological and behavioural. Two, the toxicity when exposed
00:05:11 to fire of certain materials which were present at Grenfell Tower. Three, any recommendations
00:05:17 arising from points one to two above, including as to any further testing which ought to be
00:05:22 carried out which is relevant to these issues. And then at paragraph two, you say, I was
00:05:30 asked to provide a report for phase one, and you explain what that was. And there. Can
00:05:38 you confirm that you have updated and expanded on your preliminary conclusions where necessary
00:05:43 in this phase two report? Yes, I have, yes.
00:05:45 And is it also right that, as you say at paragraph four here, if you look down at that towards
00:05:51 the foot of your screen, now in the middle of your screen, that you've addressed, quotes,
00:05:55 how each of the 71 persons who died were prevented from escaping, how they were overcome
00:06:00 and the causes of their deaths. That's what you've done in essence.
00:06:03 Yes, I wanted to address each individual named person.
00:06:06 Yes. Now, just to explain, is it right that the number 71 is the number of persons who
00:06:13 died on or about the night of the 14th of June 2017 and did not include Pilly Burton
00:06:20 who died some months later? That's correct.
00:06:22 Right. And if we turn to the bottom of page three, please, in this document, if we go
00:06:26 back to page three, we can see a signature on the report dated 10th of May 2022. Is that
00:06:32 your signature? It is indeed, yes.
00:06:34 And have you read this report recently? Yes.
00:06:37 And can you confirm that the statements of fact that you've made in it are true to the
00:06:41 best of your knowledge and belief? Yes, they are, yes.
00:06:43 And can you also confirm that the opinions that you've expressed in this report represent
00:06:48 your true and professionally held opinions? They do, yes.
00:06:52 And can you also confirm that you have provided this report in the same way as you would have
00:06:56 done to a court? Yes.
00:06:58 Thank you. Now, you've also provided two further documents to the inquiry recently which have
00:07:02 been disclosed to court participants. I'm going to show you those and ask you about
00:07:08 them. The first is DAPR 5012. If we could please have that. That is entitled, summary
00:07:17 of approximate fire arrival and occupant flat exit times and outcomes from detailed
00:07:22 accounts in section six, floor by floor analysis. First, can you confirm that you prepared this
00:07:28 document? I did, yes.
00:07:29 And this is a document which serves, does it, as an aid memoir for your analysis and
00:07:34 your conclusions in the phase two report? Exactly. I thought it would be helpful as
00:07:38 a, if you like, a quick reference to what was happening on each floor each time.
00:07:45 Thank you. We could refer to if necessary.
00:07:47 Can you explain in short terms what it shows?
00:07:49 Yes. So, as you can see there, you've got each floor there and the document is set out
00:07:56 in six pages. Each page is for one column of flats. So, the page you put up is all the
00:08:04 flats, it refers to all the flats six on the east side of the tower from the 23rd floor
00:08:10 down to the fourth. There's an approximate estimate of the time that the fire arrived
00:08:16 outside each of those flats, approximate time that the occupants left the flat if they did
00:08:23 so and then the final column is just a brief summary for me of who was in those flats.
00:08:32 Where they're outlined in red, those are people who died during the incident. The others,
00:08:40 those evacuated successfully. So, just a quick reference guide really. The detailed behind
00:08:48 all this is in section six of my report. Yes, thank you. Can you confirm that there's
00:08:52 nothing new in that document and that it is simply a summary of the data, the more detailed
00:08:58 data found in your report? Yes.
00:09:00 Thank you. Again, the statements of facts set out in this document are true to the best
00:09:04 of your knowledge of me. They are, yes.
00:09:06 The second document is at DAPR 5013, please. That is entitled summary table of toxicity
00:09:15 endpoints in each 23rd floor flat. Did you prepare this document as well?
00:09:22 I did, yes. What does it show?
00:09:23 If you just scroll down to the table. Yes, can we go to the foot of it?
00:09:29 So this was something I did prepare initially a while ago, but I felt it was quite important
00:09:35 to demonstrate the issue of what was the latest time that occupants of different flats around
00:09:46 the tower, i-flat six to flat one at each level, the latest time they could have left
00:09:54 their flat and still succeeded or had a good chance of succeeding in descending the stair
00:10:00 without being overcome in the stair on the way down. So it's a kind of last time that
00:10:04 you might reasonably be expected to have self-evacuated had you had the opportunity to do so.
00:10:13 And this is, I prepared this originally just for the top floor. I started the top and worked
00:10:18 down because most of the deaths were at the top of the tower. And these times, they're very
00:10:25 approximate, but they give a picture, if you like, of that situation. Caveat is that as you go down
00:10:32 the tower, there's a slight lag in the way the fire went round the tower. So these times would
00:10:39 be increased by a few minutes on the lower floors. But they're quite close to these times for the
00:10:45 upper half of the tower. We can come back to this in discussion later if necessary.
00:10:51 Yes, thank you. Can you also confirm that there's nothing new in this document and that it's simply
00:10:56 a summary of the data contained elsewhere in your report?
00:10:58 Yes, it's a summary of the data in the report, yes.
00:11:01 And again, it would follow that you can confirm that the statements of fact set out in it are true
00:11:05 to the best of your knowledge and belief?
00:11:07 Yes.
00:11:07 And similarly, the opinions expressed in it are your properly and professionally held opinions?
00:11:13 They are, yes.
00:11:14 Now, can we then turn to your qualifications and expertise? You've set your background and expertise
00:11:20 relevant to the matters we are investigating here at this inquiry. At Appendix D, can we go to that,
00:11:27 please? That's DAPR 6-0 is 10. 5-0 is 10. 5-0 is 10. There it is. And I'm not going to go through all
00:11:39 that today with you. First, can you confirm that you have reviewed and updated this CV?
00:11:43 I have, yes.
00:11:44 The purposes of this report.
00:11:45 Sorry, yes, I have, yes.
00:11:46 And just picking out some key points. First, you have a PhD in neurophysiology from the
00:11:51 University of Birmingham.
00:11:52 Yes.
00:11:53 And a diploma RC path in 1984 from the Royal College of Pathologists.
00:11:57 Yes.
00:11:58 And I think, as you say in your second report, which we'll come back to, you're a diplomat member
00:12:02 of the Royal College of Pathologists.
00:12:04 Yes.
00:12:06 That's correct.
00:12:07 Yes. And was that from 1984 or was that more recently?
00:12:11 No, that's continuous from 1984.
00:12:13 Right. And what does diplomat member of the RCP mean?
00:12:17 Well, there's a qualification that's usually obtained by clinical medical pathologists.
00:12:25 They become members MRC path. I'm not an MRC path. But the College of Pathologists offered
00:12:32 the opportunity for toxicologists to obtain a diploma in toxicology, which I took in 1984.
00:12:40 And then you become a member of the college. But I want to make it clear, I'm not an MRC path.
00:12:46 Right. Thank you. Do your specialisms that you've listed in your CV include the medical effects
00:12:54 of inhalation of toxic smoke and gases on the body, the human body?
00:12:58 They do. As far as a toxicologist would normally deal with these matters, or a physiologist, yes.
00:13:04 Yes. And you currently act, I think, as a consultant in relation to toxicology,
00:13:08 environmental hazards and human behaviour in emergencies, combustion chemistry and hazard
00:13:14 modelling. Those are the areas where I'm active, yes.
00:13:18 Yes. And you're currently a visiting professor at the University of Central Lancashire.
00:13:22 That's correct. In the Centre for Fire and
00:13:25 Hazards Science, I think. Yes.
00:13:28 If we go to the foot of page two of this document, we can see there in summary that
00:13:33 for 17 years or so between 1974 and 1991, you were in the Department of Inhalation Toxicology
00:13:41 at the Huntingdon Research Centre, where you conducted and directed research in environmental
00:13:45 and inhalation toxicology, yes? That's correct, yes.
00:13:49 Did that work include research into the effect of fire products on the nervous system,
00:13:53 the lung function and behaviour in order to evaluate the mechanisms whereby fire products
00:13:58 causing incapacitation and death? Yes, it did.
00:14:02 Yes. And if we look a little bit above that, we can see that from 1991 to 2006,
00:14:08 you worked for the building research establishment, the BRE, Fire Research Station, now BRE Limited,
00:14:14 where you continue to work on the toxicological and behavioural aspects of human fire exposures.
00:14:19 Is that right? Yes, that's correct.
00:14:21 That related to occupant behaviour in relation to means of escape, chemical yields of toxic smoke
00:14:27 and evaluation of fire hazard development. Is that right?
00:14:30 Yes, those are the areas of research I was conducting.
00:14:33 Yes. And on page three, if we go to that, please, you identify yourself as a member of a number of
00:14:38 institutions, including the Royal College of Pathologists, the British Association for Lung
00:14:44 Research to 2017 and the International Association of Fire Safety Science to 2018. Yes.
00:14:51 Yes, and you were awarded a CBE for services to fire safety in the 2015 New Year's Honours List.
00:14:57 I was, yes. Yes. And in 2013, the Institute of
00:15:01 Fire Engineers awarded you the David Rabash Medal for outstanding contribution to the advancement
00:15:07 of knowledge in fire behaviour. Yes? They did. I'm not a member of the
00:15:11 Institute of Fire Engineers, but they did. I can't be that honour, yes.
00:15:14 And if we go to page four, you say you were a member of a number of British and International
00:15:18 Standards Committees. Yes, I'm still a member of some of those, yes.
00:15:22 And they include, I think you've set them out, a hazard to life from fires.
00:15:28 Yes, that still continues. I'm a member of that still.
00:15:31 Fire Safety Engineering Means of Escape. Yes.
00:15:33 And the National Association of Fire, of Statement Fire Marshals Scientific Advisory Group.
00:15:40 That's now more or less wound up, but I was a member of that for a number of years, yes.
00:15:44 And I think you've also been a member of various Department of Health Expert Committees.
00:15:48 As you've set out? In the past, yes.
00:15:49 In the past. And you've lectured widely on toxicology, combustion chemistry and fire safety
00:15:55 at universities nationally and internationally, I think.
00:15:57 Yes. And at page five, you say that you've also
00:16:01 worked as a legal expert, page five. You've worked as a legal expert in a number of different
00:16:09 fora nationally and internationally on the subjects of fire toxicity and human behaviour.
00:16:15 Yes, these were various cases that came up over the years.
00:16:19 And also on page five, we can see that one of those appointments was as expert to the
00:16:25 Departement de Savoie in Chambéry, France, the Tribunal de Grande Instance de Bonneville,
00:16:30 Procès de la Castrofe du Tunnel du Mont Blanc in 2004 to 2006.
00:16:35 Yes. Yes.
00:16:36 And on page six, you've authored and presented a total, I think, of 152, we've counted,
00:16:41 I think, 152 publications and conference presentations between 1969 and 2018.
00:16:48 Yes. And one can scroll down
00:16:51 at some length to see what they are, if one wants to. Yes?
00:16:55 Yes. Yes.
00:16:56 Now, can I then go to your phase two work and start with some general principles?
00:17:03 And we'll pick up some specific instances later in your evidence.
00:17:07 The easiest place to start, I think, would be your contents page on page 13 of DAPR 605.
00:17:16 So DAPR 605, page 13, please.
00:17:20 And we can see there that the report, which is a very long and complex document, to be fair,
00:17:25 is helpfully arranged in the following sections.
00:17:29 You've got the summary of contents here, and then you've got introduction,
00:17:33 then methodology is section two.
00:17:37 And if we turn the page, please, we have section, or the very foot of the page, section three,
00:17:43 which is the results of analysis of fire and toxic smoke spread and effects on exposed occupants.
00:17:50 It's the foot of page 13. And then if you turn the page, please, to section four,
00:17:56 four, analysis of toxicology results. And then over the page again,
00:18:07 section five is the extent to which different materials are likely to have contributed to the
00:18:13 effects of toxic smoke on the tower occupants. And then section six, underneath that, floor by
00:18:20 floor analysis of causes of incapacitation and death at Grenfell Tower. Yes?
00:18:27 Yes.
00:18:27 And then a number of appendices. Appendix A is timings and reported smoke conditions in the stair.
00:18:34 Appendix B is analysis of fire spread across the tower.
00:18:38 And then we don't need to turn the page, but Appendix C is common terms and abbreviations,
00:18:42 and then the CV, which I've shown you.
00:18:45 Now, I want to start by asking you to take us through these sections and explain first the
00:18:49 purpose of each one and secondly how they link together. And so to begin at the beginning,
00:18:54 as it were, how was the work that you conducted during this phase of the inquiry different
00:18:59 from the work that you undertook at phase one in very broad terms?
00:19:04 It's more a question of depth. So for phase one, I was asked to do two sort of things, really. One
00:19:17 was to talk in general about fires, and I talk about various past experiments and cases we've
00:19:24 done, how people are overcome in fires. I talked a lot about the toxicology of fires, effects of
00:19:30 heat in fires, this sort of thing. And then the other thing I addressed in phase one was, if you
00:19:35 like, a preliminary general outline of what I felt had happened in terms of exposure to toxic smoke
00:19:42 at Grenfell Tower. I was just reviewing my summary of that report before we came today,
00:19:50 and I feel it's still very much valid and stands up against what I've done in part two.
00:19:57 The main thing I wanted to do, and I felt needed to be done in part two, as I said, was to address
00:20:04 in detail what had happened to each individual person who died in the fire. And in order to do
00:20:10 that, I carried out two sort of approaches. So for one approach, I found it helpful to understand
00:20:21 what had happened, to, as it were, step back and look at the tower as a system, the occupants and
00:20:27 the tower and the fire, everything was in it, step back and look at it as a system. And I found that
00:20:34 very helpful because, as I think we've already indicated to some extent, for example, if you look
00:20:42 at what happened in one flat six on one floor, you'll find that the same sort of things, same
00:20:49 sort of conditions were occurring in all the flats six almost at the same time, and then very
00:20:55 similarly in flats one all the way around. So to understand what happened, because our information
00:21:00 tends to be somewhat patchy, some flats we have good information, some somewhat less so,
00:21:06 I found my understanding was certainly assisted by looking at them as a group.
00:21:12 Similarly, when you're thinking of what's going on in the lobbies, which is a crucial part of this,
00:21:19 then on each floor the lobbies are, to understand what's happening in lobbies, you need to look at
00:21:25 what all the people in all the flats on that floor are doing, and by looking at the lobbies
00:21:29 as a set, it also helped me to understand how things were unfolding. Obviously the stair is
00:21:35 common to everybody, so what happens in the stair with time is so important in the outcomes of this
00:21:41 incident. I was looking at the stair. Another, so in a way I'm pooling the data to get, to prove my
00:21:47 understanding. Another way I pulled the data is with respect to the toxicology and pathology results.
00:21:56 Now unfortunately as you're aware, many of the persons who died in flats at Grenfell,
00:22:02 their bodies were essentially reduced to ashes, and so the amount of information that we're left
00:22:10 with for toxicology pathology is rather limited. I think Electra Forensics did a wonderful job in
00:22:18 locating the bodies in the various flats, and I've made great use of their work, but fortunately
00:22:26 we have a small number of cases where sufficient tissues were obtained from the flats to get some
00:22:34 blood toxicology data and some pathology data, and by inference and looking at the other people in
00:22:40 the same flats or in similar flats on different floors, I think this is giving us a good understanding
00:22:47 of how things worked out. Similarly, I am very grateful to 21 persons who gave me permission,
00:22:57 who are survivors, who gave me permission to look at their hospital data, and by pooling that data
00:23:05 I feel I've learned a lot about the conditions, particularly in stair and the flats for those who
00:23:10 survived, which also affected those who died. So by looking at it as a pooled data set, that was very
00:23:16 helpful to me. Also, by pooling that data I was able to preserve the anonymity of those persons
00:23:24 and just look at them as a group. So that's all this sort of looking at things as a pooled sets,
00:23:31 and then in part six of my report, that's where I go floor by floor in detail looking at the analysis
00:23:38 for each flat, particularly those where people died, and how they were individually affected.
00:23:44 So that's the overall approach that I've used. Yes, thank you very much. And in the most general
00:23:49 of terms, if you can do this, and it may not be possible, are you able to summarise extremely
00:23:55 pithily what you found as a result of having done that work? Yes, I'll try to. So I think it's
00:24:05 helpful to look through it in a sequence. So the first thing that's happened obviously is that we
00:24:11 have the fire going rapidly up the east side of the tower outside basically the kitchens of each
00:24:17 flat six. And as the fire arrived at each level going up, it very quickly broke through into those
00:24:25 flats. And the occupants of those flats became aware very quickly that there was something wrong. In
00:24:31 fact, many of them were aware before the fire actually got to their flats. And the key actions
00:24:39 they took was they were obviously, they went to the kitchen, they saw the flames outside, they saw
00:24:44 the flames start to break through in the smoke filling their flats. They were immediately very
00:24:49 highly motivated to evacuate. And I've read the individual witness statements and some of the
00:24:57 evidence in some detail and studied it. And I have to say at this point, all those witness statements
00:25:03 that I've spent a lot of time looking at were very, very helpful to me in understanding what
00:25:08 happened. So I'm very grateful to those witnesses for making all those statements. And what it showed
00:25:16 is that they rushed very quickly. Some of them ran out without only partially dressed. They went maybe
00:25:21 grab a phone and a passport and the children as it were. And all occupants of flat six
00:25:29 evacuated the flats within a very few minutes, very, very quickly. And they then went out into
00:25:36 the lobbies at an early stage in the fire when the lobbies were still substantially clear of smoke.
00:25:42 And then most of them then entered the stair and the stair was clear of smoke. So they were able
00:25:47 then to move down the stair or between floors within the building. And many of them evacuated
00:25:52 the tower at that time. Sadly, some of them, as we know, took refuge in other flats higher up the
00:25:57 building. But the key point about those flat six occupants was they were highly motivated by the
00:26:04 smoke and fire coming into their flats to immediately evacuate. And they were able to do so
00:26:10 because the lobbies were clear and the stair was clear at that time. And that then contrasts
00:26:17 with what happened next because within a few minutes of them doing that, the lobbies on most
00:26:23 floors became filled with dense smoke. And those occupants, some occupants of other flats had
00:26:29 already left during this early phase. But once that happened, I feel it strongly inhibited those
00:26:36 who'd remained in their flats from attempting to escape. So the filling of the lobbies within a
00:26:43 couple of minutes of the fire arriving outside each flat on each flat six on each floor,
00:26:49 the filling of the lobbies was a key event which then inhibited occupants from escaping,
00:26:55 led to many of them remaining in their flats and ultimately led to their
00:26:59 becoming overcome by asphyxia gases and dying in their flats. So this was a key event. Now
00:27:07 some occupants, even after the lobbies filled with smoke during this early stage,
00:27:15 were highly motivated to escape and were succeeded in crossing the smoke filled lobbies,
00:27:22 finding the stair had some smoke but really not very much. They were then able to descend and
00:27:28 escape in safety. And the whole thing sort of goes in periods of time. So you've got this sort of
00:27:37 period of time before about 125 to 130 odd when on different floors the lobbies were really clear,
00:27:47 so people were able to move around and escape relatively easily in quotes. Then you have a
00:27:54 period when the lobbies are filling with smoke, some people are still coming out, about 50, more
00:27:59 than 50 people succeeded in crossing that smoke and coming down the stair through reasonable
00:28:05 conditions at that time. We can go into detail later if you wish. And at the end of that period,
00:28:11 which takes us up to about 141, something like that. Now the last couple of people who came down
00:28:20 from a high floor in the tower was Petra Duoliver and her companion. And they crossed the lobby
00:28:28 with some difficulty leaving at about 136 on the floor they evacuated from. With some difficulty
00:28:34 they managed to make it to the stair but they were then able to descend in safety. Then we have a
00:28:42 period of about half an hour or more when nobody comes down. And I believe what's happening then
00:28:48 is that those people who were still in the tower had remained in their flats, so they were sort of
00:28:56 staying put as it were. And that was partly influenced by the fact that their flats at that
00:29:03 time were relatively clear of smoke for most of those flats, but they were inhibited from leaving
00:29:09 by the smoke in the lobbies. And if I may, I would suggest it's a little bit like the way to look at
00:29:16 this from the point of view of effects of irritant smoke is it's partly physiological and it's partly
00:29:23 behavioral. So it's a little bit like, imagine a pair of scales and there are weights going into
00:29:32 either pan, do I go or do I stay? I feel very sorry for these occupants who were trapped in these flats
00:29:40 because those who left early, after early cues that there was a fire outside, noises of fire
00:29:48 engines, people bringing them up, a bit of smoke, smell maybe, a bit of odour, they made this decision to leave
00:29:55 at an early stage. They opened the door to the lobby, found the conditions clear, so they had,
00:30:03 if you like, weights in the side of the pan that is saying I think we should go or we should go and
00:30:08 investigate. And they had no obstacles from doing that, so they were able to perform that task with
00:30:13 relative confidence. Once the lobbies filled with smoke, then they had a strong incentive not to
00:30:22 enter that lobby and they needed a very big push factor to make them do it. Do you understand how
00:30:27 I'm looking at these various influences on people? So it's a combination of behavioral and physiological
00:30:34 effects. So those people that remained in their flats were able to do so initially because their
00:30:40 flats were relatively clear of smoke, but over the next hour or so, depending on which flat you were in,
00:30:47 the fire, external fire, moves around the building and comes to each flat in turn, first to flats one,
00:30:55 then to flats two and flats five, then to flats four and then to flats three, eventually at about
00:31:01 half past three, four o'clock. And as the exterior fire came around the outside of these flats,
00:31:07 the occupants were then faced with this difficult decision again. Now they had a very urgent
00:31:14 situation because they had a large fire coming around the outside and penetrating from the
00:31:18 outside of their flats and they also had the dense smoke in the lobbies. And so we have a second wave,
00:31:25 if you like, of occupants who attempted and many of whom succeeded in evacuating at that time.
00:31:32 Now from my analysis of the conditions and the timing of this, I spent a lot of effort
00:31:37 into trying to establish the exact timelines for these events, exactly what people were exposed
00:31:44 to at different times and how they were affected. And my overall conclusion from this is that
00:31:50 those occupants who remained in their flats until the exterior fire arrived, if they left their flat
00:32:00 and attempted to cross the lobby and enter the stair as soon as or within a few minutes of the
00:32:06 arrival of the exterior fire, the exposure that they'd had to some toxic smoke fire leakage from
00:32:13 the lobby up to that point was of relatively minor. In other words, they hadn't accumulated
00:32:19 a large dose of asphyxians up to that time. So if they were able to cross the dense, the lobbies
00:32:26 were extremely hazardous, filled with very dense smoke and high concentrations of asphyxian gases.
00:32:32 So if you, for example, were in a flat three and you wanted to get across to the stair, you only had
00:32:38 a very short distance to cross and although the conditions in the lobby were really bad,
00:32:43 you had a good chance even of holding your breath for the short period of time to cross to the stair.
00:32:49 Once you got into the stair, there was a lot of smoke in the stair, but from my analysis,
00:32:54 the concentrations were moderate, which meant that it was possible to walk down the stair and spend
00:33:01 up to about 15 minutes walking down the stair, breathing asphyxian gases on the way down. Conditions
00:33:07 weren't very unpleasant, but by the time a person got to the bottom of the stair, the dose they'd
00:33:14 accumulated was on the cusp, on the threshold of an incapacitating dose of carbon monoxide.
00:33:20 So if you had acquired a limited dose, as I believe these occupants had, up to the time you left the
00:33:27 flat and you crossed the lobby efficiently, you had a good chance of succeeding in walking down
00:33:34 and escaping the, walking out the tower. And that continued up to about, the last person to do this
00:33:40 was at about four o'clock from a high level of the tower and then some, a couple of others came out
00:33:46 later from lower levels of the tower. So this shows that the conditions in the stair, in the stair,
00:33:55 remained survivable, if you like, and negotiable for a long period of time during the incident.
00:34:02 And if people were encouraged to leave before they were overcome in their flats, they had a good
00:34:09 chance of being able to make it out alive. Now then you have a group of people who attempted to
00:34:16 leave their flats but collapsed almost immediately in the lobby or on the first flight of the stair
00:34:23 when they got into the stair or perhaps after a couple of floors. And when I analyse the situation
00:34:29 for that group, that cohort if you like, what I find is that those were mostly people who remained
00:34:38 too long, they remained longer in their flats. Now what happened with each flat was that obviously
00:34:44 you've got multiple rooms in a flat and the fire is moving around slowly in a sideways manner.
00:34:52 So depending on which flat you're in, it starts to come to one room in your flat. So for example,
00:34:57 if you were in a flat one, the first room affected by the fire coming from flat six is the living
00:35:03 room. Now that meant that the occupants of that flat, those flats, flats one for example, were able
00:35:10 to shelter in the bedroom, the next room along. If they closed the interior doors, they were able to
00:35:15 remain in there for some time even though there was fire coming past the living room next door.
00:35:23 And then eventually the fire moved past their last refuge in whichever flat they were in.
00:35:30 Once the fire came externally outside there and broke through the window in their room of
00:35:37 refuge there where they were sheltering, then conditions deteriorated very rapidly.
00:35:43 And occupants who tried to evacuate then had acquired too much of a dose of asphyxia before
00:35:50 they tried to leave and that's why they collapsed so quickly in the lobby or the stair.
00:35:58 I have a couple more points if I may continue. So those who died immediately in the lobby or
00:36:08 almost immediately after entering the stair, often that's because they they'd remained in the last
00:36:15 refuge room if you like of their flat. Too long in a sense, they got too big a dose before they
00:36:22 tried to set out and in a couple of cases I think they more or less just stepped out the door and
00:36:26 immediately collapsed. So they only just made it out before they would have collapsed in the flat.
00:36:31 Those who remained in the flats were then rapidly overcome and asphyxiated
00:36:37 by asphyxiating gases, mostly carbon monoxide. And from my analysis of the pathology and
00:36:44 toxicology data we have, all those occupants for whom we have blood data show very very high doses
00:36:55 of carbon monoxide in their blood, well above the lethal threshold limit. So I am convinced that they
00:37:03 died from smoke exposure inhalation of asphyxian gases, not from burns, although their bodies were
00:37:11 subsequently burned in the fire, many of them. So that's the people who died in the flats.
00:37:18 And yes, the other point I wanted to make was the lobbies. The lobbies were from the accounts of
00:37:27 people who tried to cross the lobbies and I'm talking mainly here about from about two o'clock
00:37:32 or 2 30 up to about four o'clock. The condition, the smoke in those lobbies was incredibly dense
00:37:39 and by my understanding of the composition of the smoke that means that the concentrations of asphyxian
00:37:47 gases, carbon monoxide and to somewhat lesser extent hydrogen cyanide were very high levels,
00:37:53 capable of causing collapse if inhaled after three or four minutes. Very high levels indeed.
00:38:01 Now if, as I said, if you were in a flat one, a flat two or a flat three, the distance you had to
00:38:09 travel in order to get from the front door of your flat to the stair door was really quite short
00:38:15 and so most people who attempted to do so were able to do that without really
00:38:19 being exposed to these extreme conditions for very long in the lobby.
00:38:24 Where I found a problem arising was for occupants of flats five and flats four because they had a
00:38:31 more complicated and tortuous, not particularly longer but a bit longer, but it was mainly the
00:38:36 complexity of the route and I've read a number of accounts of surviving witnesses who became
00:38:45 disorientated and confused in those lobbies. A couple of them went into the into the rubbish
00:38:51 chute door by accident, others tried to open the cupboard that had recently been installed
00:38:57 and so they were having great difficulty finding their way to where the stair door was. Some of
00:39:03 them had to go back and try a couple of times before they succeeded in doing this. So they were
00:39:08 in danger of inhaling of exposure to these extreme conditions in the lobby. Now in most cases they
00:39:15 managed to negotiate and did this but there were a couple of examples where I think people succumbed
00:39:24 because they were exposed to those conditions and if I think I should mention it at this point,
00:39:31 I think the Belcardi family are one where we should explore this area of the lobby.
00:39:37 The second which is a clear example in a way is the three persons who died on the 10th floor
00:39:44 because they arrived in the lift to the 10th floor having had virtually in my opinion no exposure
00:39:51 to anything up to that point and yet having stepped out of the lift they were unable to
00:39:57 cross that short distance to the stair to carry on down the stair and their bodies,
00:40:03 one body was found just outside the lift, the other two were found in the little
00:40:08 blind corridor that led to flat one and I think they became disorientated, well they did, they
00:40:13 became disorientated in that lobby and therefore inhaled that lobby smoke for a few minutes. Now
00:40:21 it has to be only a few minutes because say it had been 20 minutes, surely you would have found
00:40:26 your way to that stair door, they had to have been overcome within a very short period of time
00:40:33 and this is about 1.25, this is just after the fire has come up past that floor so
00:40:40 this tells me that the conditions in terms of asphyxia and gas concentrations certainly on the
00:40:46 11th lobby and I believe by inference on most of the other lobbies up the tower and not all of them
00:40:52 but most of them were really extreme at this time and that's why we've got those particular cases.
00:40:59 Just finally to round this off from the analysis I've done looking at particularly at the survivors
00:41:06 and the those who for the hospital data I had the conditions in the stair were never as bad as that,
00:41:14 the conditions in the stair were of moderate concentrations of smoke and asphyxia and gases
00:41:19 so although they were very hazardous as I say it was possible to inhale that those conditions
00:41:26 in that stair for maybe 15 minutes without being overcome if you were an adult slightly more
00:41:32 hazardous for children. I think that that more or less covers my points I wanted to raise this time.
00:41:38 Thank you. Yes thank you very much Professor. Now before we turn to some detailed aspects of your
00:41:44 approach and your methodology I just want to highlight with you if I can the principal caveats
00:41:50 in the light of which your approach and your analysis and conclusions should be viewed.
00:41:54 First it's right to think that it wasn't possible to measure exact concentrations during the fire
00:42:01 and all your analysis is based I think on estimations on the available evidence.
00:42:05 That's correct yes. And they're not exact measurements but approximations do the
00:42:10 best you can. That's correct yes. And you've used I think a squiggle to show the times that you've
00:42:16 I understand it's called a tilde. A tilde it's in my notes and I wasn't sure whether that was
00:42:19 the type of graphical error or not but a tilde right to show that the the times that you've
00:42:24 given are approximations. Yes. Yes and when you provided a time of death as approximately
00:42:30 or with a tilde how broad was the estimated time range? Yes I had some difficulties with this because
00:42:37 I think it might be an opportunity to explain. May I use the flip chart? Yes you find it helpful
00:42:42 to yes. We're talking mainly here about carbon monoxide as the main cause of incapacitation
00:42:52 and death in these occupants. So I'm just going to draw in and I'll come back and
00:42:58 I'm just going to draw in and I'll come back and
00:43:30 I'm not the next Banksy I'm sorry.
00:43:37 If we think of somebody who's exposed to is this a good position carbon monoxide at say a thousand
00:43:45 parts per million concentration which is about half what there was I believe in the stair.
00:43:54 Say there's somebody who's walking down a corridor for example the Mont Blanc tunnels I've you alluded
00:43:59 to earlier and analyze that or down the stair at Grenfell and if we assume for a moment that the
00:44:05 concentration of gas they're inhaling is constant all the time they're walking down
00:44:12 and on the right hand axis here I'm looking at the percentage of carboxyhemoglobin in their blood
00:44:22 and just if we assume that they start off with a clean sheet that they haven't had any exposure
00:44:28 every time they inhale this smoke containing this toxic gas then each lung full of carbon monoxide
00:44:38 then combines with the hemoglobin in your blood to form carboxyhemoglobin COHB and of the 100 percent
00:44:48 of hemoglobin in your blood an increasing proportion becomes converted to carboxyhemoglobin
00:44:54 which means the bit left over to carry oxygen to your brain and your tissues is reduced in proportion
00:45:00 not only is it reduced in proportion but the carboxyhemoglobin inhibits the release of the
00:45:06 oxygen that is carried to the tissue so it's a very serious effect on oxygen supply to the body
00:45:13 so what effect does this have well initially so it's so you've got a steady increase
00:45:19 so let's say you go up to 10 percent carboxyhemoglobin what will that do to you?
00:45:30 Well the answer is virtually nothing you would be totally unaware that you're inhaling it
00:45:35 and it would have no effect upon you whatsoever a heavy smoker can get up to 10 percent carboxyhemoglobin
00:45:41 without showing any symptoms at all the problem arises if you're actively walking along
00:45:47 when the percentage rises to about 30 percent so for a person and this is based on experiments
00:45:54 partly on experiments that I carried out myself at 30 percent you're liable to get a sudden change
00:46:02 from being normal walking around good if you're on the phone you're making good contact and
00:46:09 agreement with people you suddenly become dizzy then you collapse you go to a sort of physiological
00:46:14 cliff it's quite dramatic you collapse down and you're now unconscious and more or less in a coma
00:46:21 and that's at 30 percent as soon as that happens your breathing drops considerably so
00:46:29 if you were walking down the stair you might be breathing 20 liters of air a minute
00:46:37 if you are once as soon as you collapse and you're unconscious that could drop to about
00:46:43 five liters a minute so of course the effect this have is that then the rate of uptake
00:46:49 of the gases you're inhaling is slowed down so the increase in the level in the blood
00:46:58 is still carried on increasing but at a slower rate the other problem we have with Grenfell is
00:47:04 that depending on where you were the concentration you're inhaling might also be changing
00:47:09 but we can make pretty good estimate up to this point of collapse and that's very important of
00:47:15 course in the Grenfell context context because if you're anywhere in the tower and you haven't
00:47:20 collapsed then you still have the ability to move around and possibly escape once you're unconscious
00:47:26 you're going to just stay there unless somebody gets you and carries you out immediately
00:47:31 you're you're going to stay there and carry on inhaling and eventually die as we know many people
00:47:36 did so so we've got to the 30% what then happens is you then have this slower slow continued uptake
00:47:45 until you get to about 50% and I've got some slides to show you there if we want to of data
00:47:50 on this 50% carboxyhemoglobin half your hemoglobin converted to carboxyhemoglobin
00:47:57 is more or less the threshold for lethality and what that means is if you're alive and you reach
00:48:04 50% if you are rescued at that point and treated and given oxygen to breathe your your probability
00:48:14 of recovery is very poor so then if you if you've got 40% in your blood and you're rescued unconscious
00:48:23 and treated you you should wake up within a few minutes and within a half an hour or so all that
00:48:30 CO is taken from your body you should make a good recovery and there's a good chance you have no
00:48:35 subsequent effects from an acute exposure like a grand fall make a good recovery once you've got
00:48:41 to about 50% you're very unlikely to survive you're going to most likely suffer brain death
00:48:48 and and never and never be able to recover I mean but of course it depends a bit on the individual
00:48:55 but that's the general point so 50% carboxyhemoglobin is a very important
00:49:02 end point for us to bear in mind now what happens next so let's say the subject has got to 50% but
00:49:11 they're still alive so they're lying down they're in a coma they're totally unaware of what's going
00:49:17 on they're breathing very slowly and the breathing is slowing continuously at a rate depending upon
00:49:25 the individual person and this process continues with the concentration in their blood continuing
00:49:31 to increase until their heart circulation and their breathing cease at that point they die
00:49:41 and the concentration of carboxyhemoglobin above it is like it's frozen at that point
00:49:47 and if if we recover pathology samples that that is the level that we will then measure and it's
00:49:53 very stable in the cadaver in the blood of a autopsy so so 50% is the threshold if you like
00:50:03 the point of no return for most people but the amount that you find in if you if you recover
00:50:09 a sample from that person it can be anything between 50 and even in up to 90% at death so a
00:50:17 person who's got 90% in their blood at the point of death and there were a couple of examples at
00:50:23 Grenfell it meant they must have been technically alive in order and continuing to breathe
00:50:30 until they reached that point very very slowly with their respiration gradually failing
00:50:35 so it's very difficult for me to calculate if you like that time because of the variability
00:50:42 in the amount they're breathing and possibly in the gases they're inhaling but I can give a very
00:50:48 approximate window if I've got that data if I know they died at 90% I know they must have lived
00:50:55 for a long time before they died but even though they reached that high level they would not have
00:51:03 been it was not survivable so had they been rescued removed at that time and treated there's
00:51:11 really no chance that they would have survived so 50% is more important in that context yes thank
00:51:18 you now the other another level that's mentioned earlier and I think we also need to be very
00:51:23 interested in is the highest level that they could reasonably achieve while in various locations in
00:51:31 the tower and still have the headroom if you like to be able to take up more and not reach a
00:51:39 collapsing dose by the time they evacuated so I think that's why this succession of endpoints
00:51:44 need looking at and in some way the final one it just tells us the point of which they actually
00:51:52 that's the system the vital systems packed up if you might stop working but it doesn't really
00:51:58 relate to whether or not they could have survived sorry does that help yes it does thank you very
00:52:03 much just one just very final point if we don't have a couple hemoglobin data for that particular
00:52:10 individual who died we don't know whether they died at 50 or 90 so I have to give the range
00:52:19 that could be either of those extremes but professor would we be right in understanding
00:52:25 maybe this puts it a little crudely that 30% you become unconscious and comatose
00:52:34 and at 50% you're likely to die yes there's another caveat on that though if you're if you're
00:52:41 in a flat and you're just sort of sitting around or walking around the flat in a or as we are in
00:52:47 the court here now then the threshold at which you become unconscious is for round about 40%
00:52:54 carboxy hemoglobin when you get up and start walking actively as down the stair then you're
00:53:00 obviously need more energy more metabolic input to your breathing and so you succumb at a lower
00:53:08 dose when you're being physically active and in fact what what has been observed quite a lot in
00:53:14 fire deaths is somebody who was maybe in bed in a house with a house fire I remember a particular
00:53:20 case where two children were in bunk beds and they they achieved quite high blood levels
00:53:27 um but they were found in the act of trying to get up and get out of the beds
00:53:32 so the very physical act of moving was enough to make them collapse at that point
00:53:38 thank you
00:53:41 yes thank you um just in relation then to further caveats I think we can take these
00:53:47 sorry quite quickly no it's very no it's very helpful to have that presentation professor
00:53:51 it really is I just want to go back to the caveats yes just for a moment um it's right
00:53:55 that your information came from a wide range of sources and included witness statements from
00:53:59 occupants and firefighters yes yes yes the 999 or some of the 999 called transcripts yes
00:54:07 photographs and analysis of external fire spread yes and other experts reports such as those of
00:54:13 dr lame professor bisby and professor terraria yes yes and of course I relied very heavily on the
00:54:20 chairman's phase one report appendix for the times of leaving the tower for each person and is it
00:54:25 right that well as a substantial amount of evidence about a particular deceased your findings have
00:54:31 taken into account that evidence yes yes and it's right I think also as you've said that in some
00:54:36 cases there was very limited information available about particular individuals and is it right that
00:54:42 in that situation your your analysis has been limited by those constraints that's correct yes
00:54:48 now I just want to examine some methodology with you just identifying where it is in the
00:54:55 in the report section two largely the paragraph 10 of your of your phase two report in page 18
00:55:03 we don't need to go to it I don't think at dapr six areas five page 18 you've described the
00:55:08 essential principles of the production of toxic smoke during a fire and in summary is it right
00:55:15 I'm just going to put these propositions to you is it right first that burning materials produce
00:55:19 a wide range of toxic products yes and some toxic products are produced from most materials yes
00:55:27 and is it right that the type of toxic product produced from a material will depend upon the
00:55:31 extent of the elemental and organic composition of the particular material yes and they divided
00:55:37 I think gases and particulates yes yes that's correct and I think is it right both can be
00:55:43 irritants yes so all basically all materials when they burn have a high carbon content
00:55:50 and when that carbon when those carbon in the fuel is burned it turns to a range of products
00:55:57 and one set that we're very interested in is the carbon particles which are the actual smoke
00:56:04 and soot particles which have obviously affected vision but a proportion is is released as
00:56:13 partly combusted organic problem materials substances some of which can be very highly
00:56:19 irritant powerful chemical irritants which are often associated with these particles
00:56:25 so that's one category that we need to consider very carefully another source of these irritants
00:56:32 is acid gases and these acid gases only occur if the relevant elements are present in the fuel
00:56:40 and the most important one is chlorine so many many substances have a certain amount of chlorine
00:56:46 in the organic added to the organic matrix of the material when these are burned produces
00:56:52 hydrogen chloride acid gas which is a strong irritant so those are the irritants and then we
00:56:57 have the asphyxiant gases and really it's a very short list and the most important of carbon oxide
00:57:03 hydrogen cyanide carbon oxide from all materials that burn because they all contain carbon
00:57:07 hydrogen cyanide only if they have nitrogen in the organic structure of the material yes thank
00:57:13 you now we're going to come back later to your analysis of the three main fuel packages at
00:57:17 granville tower and their relative contributions to the production of toxic gases in that incident
00:57:25 in your report you've referred to some common terms which inform your analysis and your work
00:57:29 and you've explained those in more detail in the phase one report but could you just explain to us
00:57:34 what what a fractional effective dose is yes that's one of those terms i have to go back to the
00:57:53 and if you need your phase one report i can show it to you
00:57:57 uh well i'm just going to i'm just going to try and explain the principle of it right
00:58:02 so if we think of carbon monoxide again one way of expressing a dose of carbon monoxide
00:58:10 that would incapacitate you is in terms of the amount of the amount available to inhale so if
00:58:18 for example we had um
00:58:22 about
00:58:26 three at 3,500 parts per million and we inhaled that for 10 minutes then you could express the
00:58:37 dose inhaled as 35,000 ppm dot minutes so it's so it's the concentration multiplied by the time
00:58:49 is an expression of dose available so um if we were in any particular fire
00:58:58 with time as i showed you earlier the person would inhaled a certain dose up to that time
00:59:04 and the FED fraction effective dose is a way of expressing that in a sort of normalized form
00:59:12 so what we do is very simply we have a fraction and the denominator of that fraction is 35,000
00:59:21 which is the dose required to cause incapacitation and the numerator is the dose obtained up to that
00:59:29 period of time in the actual event so let's say you're you it's a thousand ppm for 10 minutes
00:59:37 then you've had 10,000 ppm minutes divide that by 35 that gives you the FED as a fraction up to that
00:59:45 point of time so we sum these fractions throughout the fire until the fraction becomes one till that
00:59:52 this equals that and we say well at that point the person will collapse so FED1 is the fractional
01:00:00 dose predicted to cause incapacitation now that's for a single gas but of course we have multiple
01:00:06 gases and so we have to have some way of dealing with the combination and this also provides us
01:00:12 with a way of doing that so we do a similar a similar calculation for the fractional dose
01:00:18 of hydrogen cyanide for example and from the top three multiple studies that we've made
01:00:23 some complications in this but we treat them as essentially additive so what we would say is at
01:00:30 a certain point in time if the FED the fractional dose inhaled of carbon monoxide is 0.5 and if the
01:00:38 fractional dose inhaled of hydrogen cyanide is also 0.5, 0.5 plus 0.5 equals one we've now reached a
01:00:45 time during this exposure when we predict that person would be overcome that's the essence of it
01:00:52 Does that is that yes it does just to be clear on this
01:00:57 was there any significance there in your demonstration there of 35 000 parts yes yes well per million per
01:01:03 minute so that I prefer to for carbon monoxide I feel it's more useful to express the fraction in
01:01:15 terms of the calculated cup oxyhemoglobin because we can then relate it to the data that we have
01:01:20 so another way of expressing this is to say
01:01:25 I should have done this before 30% cup oxyhemoglobin is the dose of carbon monoxide in the blood
01:01:33 which would become overcome so if you calculate with expressions that we've got the dose
01:01:40 achieved so let's say you've got 15 after a certain percent cup oxyhemoglobin after a certain point
01:01:47 time then you've got half of a dose for incapacitation so that's another way of coming
01:01:53 at it now in international standards we we've used both these methods depending on the application
01:02:01 and 35 000 is the figure in the international the ISO standard from the committee that I
01:02:06 serve on sometimes so 30 right I see so 35 000 35 000 ppm minutes of carbon monoxide
01:02:15 represents approximately the dose available to be inhaled that could overcome you before
01:02:22 before in capacity point of incapacitation thank you expressing it as calculated cup
01:02:28 oxyhemoglobin is a more accurate way of doing it it also is more useful to us because
01:02:34 we can then compare our findings with actual blood measurements made on survivors and
01:02:39 photographers yes um now um I want to ask you some questions about the calculations to estimate
01:02:45 exposure to and the effects of irritant smoke is it right that to estimate the extent of exposure
01:02:52 and the effect of irritant smoke you've relied on first there are a number of things but first
01:02:57 the results of a bre study of materials toxicity
01:03:03 sorry I want to just explain briefly if I may so over the years I've done a lot of toxicology
01:03:09 experiments and studied human data on irritancy of various individual chemical irritants so there's
01:03:15 a big literature out there from industrial hazards and things on for example if a person
01:03:21 is exposed to hydrogen chloride at about 300 parts per million what would it do to you
01:03:29 and we have some information from accidents and things on this so if you know what gases are there
01:03:35 you can make some sort of estimate of what it would do to somebody if they inhaled it
01:03:40 and by looking at the as we've discussed at the composition and the data I obtained when I burnt
01:03:48 these materials in tests at bre of the gases that come off from these materials I can confidently
01:03:54 say that all the materials involved the various fuel packages that we're going to discuss in a
01:03:59 minute at Grenfell would have contained considerable quantities of organic and inorganic irritant gases
01:04:07 so that's on the supply side if you problem if you like yeah but to to determine what effect those
01:04:14 are actually going to have on an exposed person is somewhat more uncertain so we have methods of
01:04:21 doing it but I feel we have a much better method for Grenfell because we have a wealth of witness
01:04:32 statements on on this so for Grenfell I've relied for the severity if you like of the
01:04:39 irritancy that people experienced on what they said they experienced because I felt that was much
01:04:44 more first hand yes now I just want to see if I can identify the report that you refer to
01:04:49 there's a 2003 a march 2003 bre study which you refer to in this context and I just want to see if
01:04:57 if if we've identified it correctly can we please go to dap six zeros two sorry seven zeros two dap
01:05:05 seven zeros two and have that up this is a report that you prepared for Anthony Bird on the 26th of
01:05:12 March 2003 the potential for including fire chemistry and toxicity in fire safety engineering
01:05:19 you see that yes and is that the report that you're referring to right so as the 2003 report yes
01:05:25 but that that report is results of two furnace experiments and measuring the yields and
01:05:32 concentrations of these various gases produced when you burnt that set of materials and so that's
01:05:37 the data set that I've relied on for just about all the work I've done for Grenfell yes I see thank
01:05:42 you very much and I think it was prepared by you and Jenny it was indeed yes your who's in the court
01:05:49 over there very much just to make sure I'm on the board yeah very good um the second thing I think
01:05:54 you relied on is this right was the tests carried out by Professor Steck and a stack on the elemental
01:06:00 composition of smoke particulates and and toxic gas yields from samples taken from Grenfell tower
01:06:06 itself yes so just very briefly obviously the work we did some years ago at BRE was on a generic
01:06:14 set of materials they were very some of whom which were the same polymers the same general materials
01:06:20 as they are in Grenfell particularly the poly isocyanurate the poly vinyl chloride polyethylene
01:06:29 and the polystyrene so we tested those were included in what we did at BRE but they weren't
01:06:35 actual samples obviously from Grenfell tower and so we felt it was important that
01:06:42 samples from the actual tower tested and the chairman supported this research so
01:06:47 Professor Steck carried out that research so that work was done mainly on these sort of
01:06:51 structural materials um on samples the materials actually recovered from the tower
01:06:59 does that cover the point sorry um yes it does thank you very much um
01:07:03 um and uh third the third category of documents you relied on was an assessment of witness
01:07:09 descriptions of conditions and medical records i think which indicate the extent of smoke
01:07:14 obscuration and the severity of smoke irritancy yes yes now let's then turn to the the assessment
01:07:21 of exposure concentrations and effects and i just want to ask you about your calculations
01:07:26 yes um you've explained uh in um your um the first part of your report page 37
01:07:34 uh at section 2.6 let's just go to that dapr at six zeros five page 37
01:07:42 um
01:07:50 yes section 2.6 and you say uh this this section is entitled using smoke density and visibility
01:07:58 as a first approximation to estimate exposure concentrations and time to incapacitation from
01:08:03 the effects of asphyxiant gases yes um you you've explained here in this section uh how you've
01:08:10 estimated exposure concentrations and time to incapacitation on the basis of smoke density
01:08:15 and visibility now in summary and just correct me if i'm wrong about this is it right that
01:08:20 when a fuel material burns it produces certain yields of particulates carbon monoxide and
01:08:26 hydrogen cyanide yes and and while the actual concentrations vary as they're diluted by the air
01:08:34 is it right that the ratios of smoke particulates carbon monoxide and hydrogen cyanide each remain
01:08:41 constant yes right approximately and you mean the relative concentration yes yes and i think is it
01:08:47 right that you then took the elemental compositions the yields and the concentration data from the
01:08:52 materials used by or used for the bre experiment yes you and and your wife carried out jenny carried
01:08:59 out to derive the fuel mixture from the three main fuel packages at grenfell that's correct
01:09:04 and was that let's just take them off exterior cladding yes yes the window surrounds yes and
01:09:11 then the mixed flat contents exterior cladding and insulation and insulation right for the
01:09:16 exterior cladding system yes yes that's right yes the window surround and then the mixed flat
01:09:21 yes yes excuse me yeah yes and and you then use those to estimate the ratios of those materials
01:09:30 yes at grenfell yes yes um now let's go please to page 41 of this document this is taken from your
01:09:38 phase one report figure one and here it is and it's entitled concentrations of carbon monoxide
01:09:44 and hydrogen cyanide at different smoke visibilities for a mixed fuel set from phase one report figure 19
01:09:51 and am i right that this shows the estimated concentration of carbon monoxide and hydrogen
01:09:57 cyanide ppm in relation to the visibility reflected in meters under both well ventilated
01:10:05 and under ventilated conditions yes yes yes now have you assumed here the ratio 27 to one
01:10:13 for carbon monoxide and hydrogen cyanide as you've calculated elsewhere now this is some other ratio
01:10:18 sorry yeah this this example here was for a particular set of fuels for fuel package
01:10:27 mixed fuel package uh that i worked on some years ago um there was it's not dissimilar from the sort
01:10:36 of packages we have at grenfell but it wasn't just this this particular diagram and the data
01:10:41 and it was specifically tailored to grenfell but they illustrate the import very important point
01:10:46 that as i said the ratios of smoke and hence visibility uh and asphyxia and gases within that
01:10:54 smoke are are linked the ratios are constant so for this particular fuel package which is i would
01:11:00 say fairly typical of what we'd expect to see at grenfell anyway um there's a very important point
01:11:05 here which is that if for example you can see for five meters at the right hand corner of that graph
01:11:12 it means that the concentrations of these asphyxia gases carbon monoxide and cyanide that
01:11:18 you're inhaling are extremely low such that you could breathe them for some hours without really
01:11:24 suffering any ill effects but as soon as the visibility gets down to for example one meter
01:11:31 then you're starting to get quite serious concentrations of these gases that could cause
01:11:37 incapacitation after some minutes of exposed minutes of exposure so there's a as a proxy for
01:11:46 a very approximate estimation of the amount of carbon monoxide and cyanide that people in
01:11:52 grenfell were inhaling at any particular time if i can have an approximate idea of how seriously
01:12:00 dense the smoke was that they were exposed at that time i can make an estimate of that in in
01:12:06 within these broad ranges and what i'm looking for is are we are we operating in a range where
01:12:12 these concentration are are effectively harmless that you could be exposed for some hours without
01:12:16 really suffering are they in this kind of middle range where where you might be able to perform
01:12:22 for example come down spend 15 minutes walking down a stair and just about make it down or are
01:12:29 we in the realm as i believe we were in the lobby of the 10th floor where a few two or three minutes
01:12:36 or five minutes exposure will have you unconscious so i think it gives us a take on that now
01:12:42 uh this is with one particular fuel package for grenfell phase two i've refined the data sets
01:12:50 to reflect as far as i can the specific grenfell fuel packages so the numbers that i've used for
01:12:58 the phase two work are a recalculation of this sort of picture but more targeted at grenfell
01:13:05 now in the graph that we can see here my question is really directed at the ratios
01:13:12 of carbon monoxide to hydrogen cyanide yes so they remain constant at 27 to one throughout the
01:13:18 graph well i'm not sure what the ratio was approximately that in here but what i'm saying
01:13:23 is that for for my examination of the grenfell fuel mixes i found that the ratios in the
01:13:32 cladding and insulation when the when the from the work that we've done we believe that
01:13:40 essentially all the polyethylene was burnt away very quickly in the fire at any one point
01:13:47 on the exterior of the tower and from the residues left behind approximately half the mass
01:13:54 of the uh celotex insulation was burned away which means that approximately equal masses about 50
01:14:03 plus 50 mass ratio of those two fuel were burned and from my data from our bre tests on the yields
01:14:13 and compositions of these materials i was able to arrive at an approximate ratio of carbon
01:14:20 oxide to cyanide i would expect to find in the smoke from that burning cladding and insulation mix
01:14:27 and i arrived at a figure of around about 26 27 to one and that's important because it means that
01:14:36 anybody breathing that smoke or whatever concentration the toxics is going to be
01:14:41 dominated by the carbon monoxide components but that there's going to be significant contribution
01:14:47 from hydrogen cyanide so both are important but it's dominated very much by carbon monoxide
01:14:53 i then did an analysis and it has to be very approximate for what i'd expect to find is the
01:14:59 fuel load of individual materials in an individual in an individual flat so the way i went about this
01:15:08 was i on the internet i found a local authority website of advice for removal people about what
01:15:18 items you'd expect to find in typical uh flat or house and in terms of how many beds and what weight
01:15:25 they were how many cupboards etc etc so i was able to come up with a kind of fire load contents package
01:15:34 for a flat and then i related that to the composition of those materials to as far as i
01:15:40 could to the materials we've studied in our date in our bre experiment to work out the elemental
01:15:47 approximate elemental composition in terms of carbon nitrogen hydrogen uh chlorine for flat
01:15:54 contents and the yields more more importantly the yields and yield ratios of gases that we'd
01:15:59 expect from a typical total involvement this is the total involvement a fully involved compartment
01:16:06 fire of an entire flat and the important conclusion i came to was that the nitrogen content is about
01:16:16 three percent by mass of both the fuel package one that burning on the outside of the tower and the
01:16:22 contents and therefore that the ratios of co to cyanide from any part of the contents burning at
01:16:31 any time are going to be similar to the ratios that we would get from the outside burning materials
01:16:38 and therefore the the toxicity in that sense is going to be very similar and also for the smoke
01:16:44 as well yeah thank you that's right that's very helpful sorry no no that's very helpful
01:16:49 we may see a little bit of that in the next uh in the next figure mr chairman i know the time but
01:16:55 there are one or two further questions on this very topic i'd like to finish off if we can
01:16:58 yes sorry if that's all right with the professor um professor can we then turn down a page please to
01:17:03 page 42 to look at figure two and that's uh entitled to calculated time to collapse from asphyxia
01:17:12 at different smoke visibilities from phase one report figure 18 yes so that is for the fuel
01:17:17 package we've just been looking at not specifically for grentle but very similar kind of people that
01:17:22 was really my question is that's the same mix is it of carbon monoxide and hydrogen that's the mix
01:17:26 that i use for the illustration i put into my phase one report it's not specifically tailored
01:17:32 to grentle but it's similar similar ratios so taken together these two figures figures one and
01:17:38 two is this right show how you've calculated the time to collapse from asphyxia based on the
01:17:43 in meters there are illustration of the method yes yeah exactly so it's a rough estimate where
01:17:48 visibility is less than one meter it will take roughly 20 to 25 minutes to collapse yes yes i
01:17:54 see and when it's less than half a meter it will take less than 10 minutes yes yes i see thank you
01:17:59 mr chairman is that a convenient moment yes yes thank you very much well professor as you were
01:18:05 told earlier we're going to have a break during the morning we'll take it now uh so we'll stop
01:18:09 there we'll resume please at 25 to 12 and um as i'm sure you know i think i said this to you on
01:18:15 previous occasions while you're out of the room please don't talk to anyone about your evidence
01:18:20 or anything i understand yes all right thank you very much would you give me the usher please
01:18:23 thank you
01:18:36 thank you very much mr millet 25 to 12 please
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01:34:51 would you ask professor perser to come back in please
01:34:59 yes
01:35:09 all right professor you ready to carry on yes thank you very much yes yes thank you mr chairman um
01:35:14 professor can i please show you then next in the same document page 48 d apr six zeros five 48
01:35:22 page 48 table seven and at the foot of the at the top of the screen there's a table entitled calculated
01:35:30 approximate co and hcn concentrations as a function of visibility through smoke from flat contents
01:35:36 and exterior cladding and insulation and you've set out there the visibility the smoke density
01:35:41 the flat contents divided between carbon monoxide and hydrogen cyanide and the cladding plus
01:35:48 insulation and the splits there as well um does it right that that shows you
01:35:53 essentially what it shows you um as you described it yes yes that's right and this is this is
01:35:58 specifically for those those grenfell sets of data yes and just just to pick a point up in the footnote
01:36:06 uh you've used it says includes 100 percent p e cladding and 50 percent p i r insulation yes and
01:36:12 that's i think an assumption that has that underlies all of your work right no well actually
01:36:19 that was um a very crude estimate based on my visits to the tower in 2018 or whatever it was
01:36:26 um that about half the insulation burned away um but obviously all of the cladding was gone
01:36:32 but subsequent to that uh professor steck's team have done an amazing and very detailed survey of
01:36:38 the tower to measure with some precision how much of that insulation has been burned away
01:36:44 and not only did they look at the um what remained on the tower now because one of the problems is
01:36:50 that things have changed a bit over the years they used the drone footage to validate the what's there
01:36:58 now with what appeared immediately after the fire in fact you can see on the drone footage the fire
01:37:02 is still burning to some extent so we have a pretty good picture of how much of that insulation is
01:37:08 was burned away and how much now remains now then can we go to um the next table down same page table
01:37:17 eight uh which runs over to um page 49 here is the table estimated volume concentration ratios
01:37:25 for mixed flak contents compared with those from cladding and insulation under two ventilation
01:37:29 conditions yes and can you explain how you came to your findings the relative concentrations of
01:37:35 carbon monoxide and hydrogen cyanide are similar regardless of the origin whether from exterior
01:37:41 materials or flat contents yes okay by reference to this table i did refer to this a bit before
01:37:46 we broke yeah so basically if we take the cladding and insulation because it's simpler in the sense
01:37:51 that there's only two materials involved um i looked at firstly the elemental compositions of
01:37:59 those fuels so polyethylene is almost is entirely very pure polymer really it's just carbon and
01:38:07 hydrogen so it's a very high carbon content um but nothing else carbon hydrogen only whereas
01:38:14 polyisothiomerate has ratios of well has elements of carbon oxygen nitrogen and chlorine in it
01:38:24 and we measure those for our bre work and then professor steck has remeasured them for the actual
01:38:30 Grenfell materials so those are the elemental compositions but uh more perhaps more or as
01:38:36 important than that is what happens when you actually burn these materials so all these
01:38:40 materials were burned in our bre uh work at the on the tube furnace to measure the yields and
01:38:48 concentrations of these gases and the relative and hence we can look at the relative concentrations
01:38:53 of smoke co and cyanide when we burn these under control conditions and that for the cladding and
01:39:00 insulation that work has been repeated by professor steck on actual rental materials for the flat
01:39:06 interior contents that relies more on the general materials that we studied at the time of the bre
01:39:12 work and from that work as i've said we found that uh there were these certain ratios involved
01:39:20 and um what i've used those ratios for all my fed calculations that i've carried out
01:39:28 for estimating the effects on occupants of flats lobbies and the stair and essentially the the
01:39:35 ratios so from what we were saying this morning earlier if you know the concentration of one of
01:39:43 these elements one of these items you can calculate the concentrations of all the others by
01:39:49 these set of ratios yes thank you yes i see and if we then turn to the next page paragraph 176
01:40:01 uh and this is at the foot of the page underneath the heading method for estimation of exposure
01:40:08 concentrations and effects on occupants of that's lobbies and stair and the first is from witness
01:40:13 evidence you say at 176 there um from the descriptions of dense irritant smoke in the
01:40:20 lobbies and based on the general fire conditions i estimate that with almost zero visibility in
01:40:25 the lobbies the concentrations of co are likely to have been high in the approximately 5000 to
01:40:31 10 000 parts per million co range with hcn in the approximately 190 to 380 ppm range based on the
01:40:39 ratios between smoke density and gas concentration shown in table 8 that's correct that that's the
01:40:44 position and then smoke density at that concentration is this right would cause collapse or could cause
01:40:49 collapse within three to five minutes for any person in the lobby so inhaling those asphyxia
01:40:54 gases that that amount of carbon dioxide that amount of cyanide for three or four minutes
01:40:59 would cause you to collapse yes yes three three to four minutes well it depends on where you are
01:41:05 on that range and obviously it's quite a wide range because one of the problems is if you can see
01:41:11 five meters uh and then it goes down to two meters you're conscious of that difference
01:41:17 the difference between able to see 10 centimeters and five is you can't really judge so all we can
01:41:23 say is it's very high yes i see now can we please go then to page 50 the next page and the next
01:41:29 paragraph where you say this this is paragraph 177 you say the main exposure to asphyxia gases
01:41:36 for the majority of occupants escaping down the stair having left their flats before or very soon
01:41:41 after the arrival of the exterior fire occurred while they were descending the stair or over
01:41:46 periods of approximately five to 12 minutes depending on which floor they descended from
01:41:51 and their descent speed yes based on the descriptions of the smoke conditions and the
01:41:55 fact that most of these occupants were able to descend and walk from the tower the average co
01:42:01 concentrations in the stair during these descents were at moderate concentrations in the range
01:42:06 approximately 1000 to 2000 ppm co and approximately the 35 to 75 ppm hcn this first
01:42:15 approximation estimate of the stair conditions is based on the descriptions of the smoke conditions
01:42:19 by descending occupants evacuating or evacuating occupants described very dense smoke in the
01:42:25 lobbies with no visibility the majority of those evacuating successfully after approximately 2 am
01:42:32 also described severe smoke conditions in the stair with also with very poor visibility
01:42:37 some occupants could see nothing in the stair but others reported being able to see lights in the
01:42:42 stair or their knees or a person in front of them others described the visibility improving at lower
01:42:48 floor levels below approximately the 10th floor c appendix a based on these accounts on the
01:42:54 developing conditions and the flat and that occupants succeeded in walking down i've made
01:42:58 a preliminary estimate that this indicates visibility approximately in the 0.4 to one meter range so
01:43:05 moderate conditions of asphyxia gases averaged over the stair column shown in table seven enabling
01:43:11 them sufficient time to descend without inhaling a dose causing collapse as indicated by figures
01:43:16 one and two now first can you explain how you estimated visibility
01:43:24 at between 0.4 meters and one meter in the stairs
01:43:32 so obviously this is very i mean the word approximately should perhaps be in heavy type
01:43:36 it is a very very approximately this is the first approximation i'm making it so all i'm asking
01:43:41 myself is how bad was that smoke was it not too bad at all really quite bad or
01:43:49 or is there any chink of light if you like in there and so simply based upon what these
01:43:56 witnesses are saying i'm estimating we are we're operating in this approximate range it's
01:44:02 it's pretty bad you almost can't see it in fact you can't really see ahead of you
01:44:07 but because smoke tends to be layered even in a stair and some witnesses did actually refer to
01:44:12 this sometimes they could see their knees or their feet or you know the stair rail so that to me
01:44:21 it means we're operating in approximately this range of visibility and the variables in that
01:44:26 range would be you've got to take into account the differentials in concentrations in the smoke
01:44:32 layer where you are on the staircase and the time yes yes um now how long using that range
01:44:41 1000 to 2000 how long would it would it take on your estimate to cause collapse yeah so one uh
01:44:50 sorry i should just add assuming you start from a base of no carbon monoxide or hydrogen cyanide
01:44:56 uptake yeah i think it was a more of a worked example later on but i mean we're talking very
01:45:01 approximately especially if we went back to that other figure a thousand parts per million you can
01:45:08 walk through for about half an hour
01:45:12 and what was it you said 2000 would be about half that time that's very very approximate
01:45:16 and of course it varies a bit on the individual and what they're doing
01:45:21 that's walking that's walking yes right and static static um
01:45:28 um the ratio is 40 percent to 30 percent oh hang on a minute static is quite a bit longer
01:45:35 because you're breathing less yes so your uptake is about half that so sort of roughly twice as
01:45:42 twice as long right so you could you could before in capacitation spend an hour in the stairs and
01:45:51 or between an hour and between 30 minutes and an hour depending on where you were on the range
01:45:56 might be helpful to go back to that diagram with the smoke density
01:46:02 yeah there's something like that yes so we can go back to table eight the table seven i think page 47
01:46:10 page 48 page 48 let's go to that table seven at the top is that the one no i meant the figure with
01:46:16 the um curved graph on it oh
01:46:22 well perhaps we can do that shortly um can we get then go to page 50 of your report and look at
01:46:27 paragraphs 178 um and there um you derive more accurate estimations of exposure and uptake of
01:46:36 asphyxia gases and effects on carbon monoxide and you cover that i think in some 10 paragraphs
01:46:42 between 178 and 188 um and you've done that i think through an analysis of individual experiences
01:46:48 is that right yes so here here um looking at the condition of the people uh when they got to the
01:46:56 bottom of the tower so for example uh one of the first uh two people i looked at was um namey
01:47:06 namey lee and lydia liao and they both walked down from the 22nd floor it took them we have a
01:47:15 fairly accurate understanding of when they entered the tower entered the stair just after they
01:47:20 finished a 999 call so they're one of the few examples where we have some actual objective
01:47:26 time data uh and we know the time they left the bottom of the stair and so i estimate they took
01:47:32 it took them 11 and a half minutes to walk down and so all the time they're walking down they're
01:47:38 inhaling carbon monoxide and a little bit of cyanide so um the state they're in the condition
01:47:46 they're in when they reach the bottom of the stair gives me an indication of how much they've inhaled
01:47:51 now what from the witness statements uh namey said uh i think she was uh she met some firefighters
01:47:59 um very close to the bottom of the tower the lower floors and she felt that she would have been able
01:48:05 to continue um walked out unaided but they insisted on helping her whereas her companion
01:48:13 had sort of semi-collapsed more or less collapsed and had to be carried out so you can see they were
01:48:17 both on this cusp of collapse um which means that they were at about 30 percent coboxa hemoglobin
01:48:25 so knowing that they were at 30 percent coboxa hemoglobin and knowing how long they were exposed
01:48:30 i can calculate what the concentration of co they were exposed to was with some reasonable accuracy
01:48:36 plus or minus about 20 percent uncertainty yes now um we'll come to i think to that worked example
01:48:42 shortly but that's that's that's very helpful indeed as an introduction can i just explore
01:48:46 with you the indicators that you've used to inform the more accurate estimates that you do in these
01:48:52 paragraphs from individuals can we go first please to page 145 in this report or this part
01:49:00 of your report page 145 table 18 and that's entitled blood carboxyhemoglobin ranges with
01:49:07 effects of increasing severity on unexposed subjects and likely associated extent of post
01:49:12 exposure lung injury resulting from inhalation of irritant smoke soot particulates and just to
01:49:18 summarize that am i right that it goes like this if you start at the bottom of the table
01:49:24 roughly 20 to 25 percent are occupants who are alert and active with no signs of dizziness
01:49:30 weakness or impending collapse and they had accumulated blood concentrations of carboxyhemoglobin
01:49:35 of less than 20 to 25 percent so i can't see where you're reading that from it's the last entry in
01:49:42 in the table minor signs even in active subjects yes yes yes and then moving up i'm just i'm just
01:49:49 walking you through this um and then the next one up is occupants who are able to walk but
01:49:55 reported symptoms of dizziness weakness or collapse especially where one person is able to walk
01:50:00 while a companion collapses and requires assistance to evacuate those people had accumulated a blood
01:50:06 concentration of carboxyhemoglobin in the range of approximately 25 to 35 percent
01:50:14 so you're reading from the text but you're looking at the table is that what you're i'm i'm summarizing
01:50:19 the yeah so essentially if you're in that range around about 25 to 35 percent that's the sort of
01:50:25 concentration where we're seeing people collapse if they're active physically active yes yes and
01:50:30 then the next one up 40 to 45 percent is an increasing incidence of collapse loss of
01:50:35 consciousness in resting subjects yes yes and and the lung injury effects are also identified
01:50:41 yes and that 45 to 50 roughly percent you've got collapsed coma and death yes and then above 45
01:50:49 percent to 90 percent unconscious and comatose until death decreasing breathing so this i think
01:50:55 summarizes um what you told us before um at what level of blood concentration of carboxyhemoglobin
01:51:03 would an individual be likely to lose consciousness i think you told us earlier it was 30 percent
01:51:08 so 30 percent for somebody who is walking quite actively along and about 40 percent for somebody
01:51:14 who is sitting at rest yes or or just walking slowly around a flat yes and you gave us the the
01:51:21 lethal threshold here really which is which is about 45 percent well depending yes i mean
01:51:28 i would normally say 50 but it's in 45 50 you start to get i mean i have got a diagram to show
01:51:34 this from actual data but the survival the survivability very quickly if you look at
01:51:43 survivability against dose it sort of does that where this is about 45 to 50 percent there's a
01:51:50 huge drop off these are people who've been rescued and survive these are people who who have been
01:51:57 rescued alive but then to go on to die and and the survivability percentage drops precipitously
01:52:05 in this middle range here right now where an individual is known from the evidence that you've
01:52:11 studied to have had limited exposure to asphyxiate gases in the flat before they left the flat
01:52:18 is it the case that any accumulated exposure to carbon monoxide can be attributed to uptake in
01:52:23 this lobby and the stair yes so the way to think of it is that it's a continuous process
01:52:28 as soon as you start to be exposed to carbon monoxide inhale it you're building up a dose
01:52:33 in your body as i mentioned earlier and for the gremfield occupants that starts with them in the
01:52:38 flats now one of the sorry if i may just say one of the important aspects of the gremfield instant
01:52:44 was that after the lobby's filled with smoke some people were then trapped in their flats for up to
01:52:50 two hours and during that period they nearly all well they all except one i can think of i think
01:52:57 reported smoke leakage around their front doors flat entrance doors into their flats from the
01:53:03 lobby so this very bad lobby smoke is leaking into the flats all right and so i was at pains to try to
01:53:13 understand and estimate how serious was that exposure during that period before the external
01:53:19 fires come around to their flat my conclusion after having looked at all these data is that
01:53:25 they were able to limit their exposure quite successfully by sheltering in various rooms
01:53:30 opening windows on excuse me on sides of the tower away from the fire so that the dose they
01:53:37 accumulated while in the flat was actually quite low but it's all building up and then they go into
01:53:43 the lobby if they hold their breath they don't take any in but if they inhale any of that bad
01:53:47 lobby smoke then they get a bit more of a spike but it's such a short period it's probably quite
01:53:52 trivial if they efficiently get across the lobby and then the major exposure continues as they
01:53:57 descend the stair so it's the cumulative total by the time they've reached the bottom of the stair
01:54:02 that we need to consider and where that's been acquired so one can break it up i think but is
01:54:08 it right also that it follows from what you said that where an individual is known to have had some
01:54:13 or perhaps significant smoke exposure before evacuating their flats then the difference
01:54:19 between their calculated uptake in the stair and the total uptake is this right is going to represent
01:54:26 the difference in the extent of their exposure well in the flat before entering the stair let
01:54:30 me just clarify that because it's quite important so basically by looking at lots of quite a lot of
01:54:35 different people and doing these calculations i was able to establish that the concentration
01:54:40 the average concentration which is important figure in the stair during this period and we're
01:54:44 talking mainly about the period between about 2 30 and 4 o'clock 50 odd people who came down during
01:54:50 that period so during that period the concentration of carbon monoxide in the stair was of a moderate
01:54:56 level and by looking at the lots of a number of individuals i was able to home in on a figure
01:55:05 of 1800 parts per million as my best estimate of the average concentration of carbon monoxide
01:55:10 in the stair during that period right now that concentration means that you by the time you if
01:55:16 you walk from an upper floor you're going to be at sort of 20 odd percent cup oxyhemoglobin just
01:55:24 acquired in the stair by the time you reach the bottom if you walk from the upper floor
01:55:30 just acquired in the stair by the time you reach the bottom if you've reached 30 at the time you
01:55:36 reach the bottom then the difference is 10 where did you get that 10 you had to get it while you
01:55:41 were in the flat does that does that clear yes yeah so i look by look by being very looking very
01:55:49 closely at the acquired dose in the stair which in itself was important i was also able to deduce
01:55:55 what the pre-exposure was in the flat up to that time and in doing that did you did you take
01:56:01 account of uptake in the lobby yes now for some of these calculations i assumed that they took a few
01:56:10 breaths in the lobby during this transition period as they crossed the lobby and um as i've said i
01:56:18 think the concentration in the lobby were really high but because it's still anywhere only talking
01:56:23 about a couple of breaths or 10 20 seconds at the most the the spot the amount of dosing
01:56:31 acquired during this period in the lobby is very very small in the context of the entire exposure
01:56:38 so if you came out of say a flat three again and you went straight across holding your breath and
01:56:44 got into the stair door into the stair then you've inhaled nothing in the lobby if however you took
01:56:51 a few involuntary breaths while crossing the lobby even though the conditions are really bad
01:56:57 because that period is so short it doesn't significantly add to your dose if however for
01:57:03 some reason you become disorientated and stay there for a few minutes then it's very serious
01:57:08 another point i would make is that there's a reflex physiological response to inhaling smoke
01:57:15 which is that you get involuntary breath holding for a few seconds it's a it's a very physiological
01:57:21 reflex so if you walked out into the lobby and took a breath you'd hold your breath you can't
01:57:28 not do that but you can only do that for a short period of time but it would be long enough for
01:57:31 you to get across the lobby if you were taking a direct simple movement and holding your breath
01:57:37 would that have a physiological effect well anybody can hold their breath for a few seconds and
01:57:46 not collapse if you like yeah no so i don't understand the question but if you've heard if
01:57:51 you're holding your breath is there therefore less less oxygen in your system yes but you you've got
01:57:56 we can all you know dive or hold our breath for maybe a minute so that's that's not a problem
01:58:01 that's not a problem that's not that's not for not for a few seconds so was it also the case that you
01:58:07 took into account the variability presented by the fact that people coming out of flats on different
01:58:12 levels would have to travel down the stairs for a greater or lesser distance yes i like that showed
01:58:17 up when i looked at like this hospital data yes yeah i see and let's then turn to the applied
01:58:23 example if we go please to page 51 i'm so sorry before we do that i can actually can i take you
01:58:29 back please to page 42 you wanted to be shown the graph um on page 42 i think in relation to my
01:58:36 question about about distances yes so can you repeat the question um well i think my question
01:58:45 was whether or not you um can you tell from can you tell from this chart uh how much um
01:58:56 we have to look at the previous two charts well let's look at the previous the one before that
01:59:00 yes let's go back a page to the top of we really need them on the same page which i've got
01:59:05 they're not um page 41 figure seven
01:59:11 sorry figure one
01:59:19 if you go to page six of the document i prepared before we of my graph and things they're both on
01:59:27 the same page so we can see them right well all right so don't worry so so what i'm saying is that
01:59:33 if you um if you're exposed to well i did do some calculations on on people walking down the stair
01:59:43 and at uh eight at about 2000 ppm you could i think i can i haven't got the figures in my head
01:59:54 but you could walk for about 15 minutes now i think the question you were asking me was if you
01:59:59 were sitting would you be able to go longer and you certainly would and because you are breathing
02:00:09 about twice as much when you're walking as when you're sitting it should double the time before
02:00:15 you would collapse approximately yeah thank you does that cover i mean i'd have to do some
02:00:19 calculations that was the question really address it that was the question and that's that that's
02:00:22 the answer that's very helpful there can i then turn please to page 51 of this document paragraph
02:00:27 189 and following and this picks up on something you mentioned a few minutes ago your evidence
02:00:34 here you've explained your methodology through an applied example yes and i think this is right
02:00:41 there are two individuals who you used um who successfully evacuated from flat 193
02:00:48 on floor 22 they entered the stair at 310 left the tower at 321 so it took 11 minutes
02:00:56 to descend the stair from floor 22 yes and i think you've then estimated their exposure in
02:01:01 three scenarios yes and you've set those out yes in sections 331 332 and 333 of your report yes
02:01:10 yes we could scroll through that and that the assumptions in each scenario are let's have them
02:01:15 up and the scenario one top of page 52
02:01:21 is assumed free from exposure in the flat scenario two is inclusion of exposure which
02:01:29 is a foot of page 53 yes inclusion exposure in the flat and lobby in addition to the stair and then
02:01:37 um three assumptions um so scenario three uh i think you find um on page um top of page 57
02:01:47 i included the other gases is the other gases the other is fixing gases and you provided a
02:01:52 figure for each scenario and i just want to take each in turn if you get back please to 50 page 52
02:01:58 and look at figure three shall i just talk you through this yeah i was going to ask you just
02:02:04 to do that so this is an ex this is a this is a if you like well quasi theoretical example it does
02:02:10 represent these two individuals who actually did perform this task and it uses their actual exposure
02:02:16 time but for this particular scenario as you can see from the beginning of that that graph the dots
02:02:22 along the bottom are at zero so i've assumed which wasn't actually the case but i've assumed for this
02:02:27 post of this worked example they had no exposure up to the time they left the flat so so they're
02:02:34 in completely smoke-free flat and then they step out into the lobby they cross the lobby taking
02:02:41 perhaps a couple of breaths but the effects of that are trivial as i explained and then they
02:02:45 enter the stair and over 11 and a half minutes they walk down the stair and that's their main
02:02:49 exposure and when the time they get to the bottom of the stair they've reached about 30 percent
02:02:55 kuboxy hemoglobin they're in a state of near collapse one's collapsed and one hasn't in reality
02:03:01 so from my co uptake calculation methods i can calculate what carboxy hemoglobin they would have
02:03:13 acquired if the average concentration during that descent was at various levels this is completely
02:03:19 arbitrary i just put a figure into my spreadsheet and i calculate their uptake for that particular
02:03:25 scenario and let's say i've guessed very accurately that they would be inhaling 2100 ppm of carbon
02:03:34 monoxide so when i run that through the analysis that then equates to the exactly correct if you
02:03:42 were a dose of 30 percent at the time they get to the tower so i would say if they had no exposure
02:03:49 before entering the stair and they still got to 30 percent at the bottom then the average
02:03:54 concentration would have to be somewhere around 2100 parts per million in the stair if we repeat
02:04:01 the calculation for a some a similar but somewhat higher figure of 2600 then we predict that they
02:04:10 would have got to 40 percent carboxy hemoglobin and would have in fact collapsed quite a few floors
02:04:16 up in the tower before when they were at 30 about two-thirds the way down which they didn't do so
02:04:22 that can't be correct similarly if we look at the pink curve which is for 1600 ppm then they only
02:04:31 get to 20 percent by the time they exit the tower and they would have been uninjured unaffected so
02:04:36 we know it can't have been as low as 1600 so i think this gives you two things it shows you the
02:04:43 method i'm using but it also gives you some indication of that is really quite accurate
02:04:48 you know that we can't we're not going to double or treble these gas concentrations it's got to
02:04:53 be somewhere in this range for it to be true now this is assuming no prior exposure then the next
02:04:58 example i deal with the flat but yes now let's go to that which i think is uh scenario two page 54
02:05:06 is that that's what you're yes yes if you blow that up a bit now as i've said uh by looking at
02:05:16 a number of these cases and in fact in at least one of them uh the occupants um isn't i've forgotten
02:05:24 the name now but but is it Burton one of these occupants he he stated in his witness evidence
02:05:31 that their flat was totally clear of smoke up to the time they left i think it's Pilar's husband
02:05:39 i'm thinking of Nicholas Burton yeah Nicholas Burton so Nicholas Burton uh said that their flat
02:05:45 wasn't penetrated by smoke up to the time they left so his only exposure was in the stair and
02:05:52 yet by the time they reached the bottom they were in this kind of almost collapse condition so by
02:05:57 looking at a number of examples like this i've honed in on the actual figure average figure
02:06:03 for the co in the stair as as 1800 parts per million all right so in this worked example i
02:06:10 have in front of you now this shows the uh concentration profile i've used for
02:06:19 li and lao um taking into account their exposure in in the flat now i just need to explain what
02:06:27 this shows so the right hand side of that the end of that chart uh if we look at the um
02:06:37 co concentration there where that where the label says two escaping in the stair that's the little
02:06:42 just say people can follow this that's the little black bar in the middle yeah so that this this
02:06:47 is represents the concentration with time of carbon monoxide that i've used for this analysis
02:06:53 right and so as you can see i've set that at 1800 ppm and and that covers the time period the 11
02:07:02 and a half minutes during which they were actually descending the stair and from a number of people
02:07:09 i've estimated that they were exposed to 1800 ppm while descending the stair in reality in that case
02:07:17 um and um before that they had a very short exposure to a very high concentration in the
02:07:24 lobby which is why the black chart those those figures go right up the top of the graph but it's
02:07:28 very short so the dose they've inhaled is very small and before that we've got the concentrations
02:07:35 of smoke and gases that i've estimated very approximately that they could have been exposed
02:07:40 to while they were in the flat and you can notice see that they were in the flat for
02:07:45 how long from well one about half past one to nearly three o'clock you know for a long
02:07:50 period of time they were in that flat and um they were exposed to an increasing
02:07:57 what we don't know the exact shape of that profile of increasing but it would have been
02:08:00 a gradual increasing profile of smoke and gases the smoke this is shown in terms of visibility so
02:08:08 the red graph is coming down because the heart the lower the visibility the higher the concentration
02:08:13 of smoke so it goes in the opposite direction to the curves for gas concentrations i hope that's
02:08:18 not too confusing and that's the that's just to be clear that's the move the red is the visibility
02:08:23 yeah so the red is the visibility that's coming down because there's more smoke yes and in fact
02:08:27 yes i've got sorry i've got the pink is the optical density per meter which is the smoke
02:08:31 concentration yes that's right so you've got smoke concentration cyanide concentration and
02:08:36 carbon monoxide concentration now those are arrived at by me just putting in
02:08:43 rough estimate numbers into my spreadsheet based upon their description of the conditions at that
02:08:49 time and by putting in that curve and running it right the way through the analysis i end up with
02:08:55 a calculation which we'll look at in a minute but i end up in a calculation of the dose they've
02:09:01 acquired from all those gases breathing all those gases by the time they reach the bottom of the
02:09:06 stair now these concentrations are constrained by the dose they eventually reach so if i put in a
02:09:14 profile like this and calculate the outcome and i find that it predicts they count they count they
02:09:20 collapse at the top of the stair then obviously i put too much smoke and gases in the flat so i
02:09:25 have to rerun with a lower curve if on the other hand they haven't acquired enough then i need to
02:09:32 do more so it's a kind of a iterative process i use to arrive at these numbers yes i see so
02:09:37 perhaps if we go on to the next graph it yeah that's fine think of five page 56 please
02:09:45 so this then from that that gas profile i've just showed you this is their calculated fed
02:09:51 uptake and this is just i've just plotted the carboxyhemoglobin on this chart so this is
02:09:57 predicting the carboxyhemoglobin in their blood with time from the time they first took refuge
02:10:03 in flat 193 up to the time they walk out the bottom of the tower or stagger out the bottom
02:10:11 of the tower perhaps the better way of putting it so the sharply rising part is the bit they've
02:10:19 acquired in the stair which is constrained by all the other people i've analyzed on this figure of
02:10:24 1800 ppm the bit before that is the dose they must have acquired it while in the flat in order for us
02:10:32 to arrive at 30 at the bottom and by constraining it by that outcome and i feel this is quite robust
02:10:40 quite strong it means that and to some extent a surprising result to me that they cannot have
02:10:48 inhaled more than about nine or ten percent carboxyhemoglobin over that entire period they
02:10:54 were sheltering in that flat from the smoke that had been leaking in from the lobby so they were
02:10:59 able by taking various precautionary measures to avoid a serious exposure now i'll just briefly
02:11:07 will say you know why this is very significant because when i when i worked for the rose park
02:11:12 inquiry in scotland rose park care home fire and we reproduced the actual incident there one of the
02:11:19 features of that incident was that there was a a very large fire in a corridor which filled the
02:11:25 corridor with about 10 000 parts million of carbon monoxide very similar to what i believe was in
02:11:32 the lobbies at grenfell and there were a number of people who were in their rooms behind closed
02:11:38 doors in enclosed rooms the occupants during that incident so they were in a similar situation they
02:11:45 were in juxtaposition to this very high concentrations in the lobby but they were in the closed bedrooms
02:11:52 and they were there for up to 50 minutes before they were rescued and those occupants when they
02:11:58 were rescued were comatose and in fact subsequently died so even though they were not in the same
02:12:05 compartment the same room as the fire over that period of time sufficient smoke and
02:12:10 asphyxia gases had leaked into their room about one to two thousand ppm concentration
02:12:16 over a period of an hour or so to result in them ultimately dying so it could quite easily have
02:12:22 been the case that something very similar could have happened at grenfell but it didn't and this
02:12:27 is a my calculation demonstrating that fact does it also give you an indication of the last or
02:12:35 a point in time at which one could exit the flat on that floor at that time and survive
02:12:41 yes so i think it does show in fact quite that um but the time they left just just after about
02:12:48 perhaps within right just go back to that particular case then so uh no naomi and lydia
02:12:57 were in the flat with it was a tucare family wasn't it and um they um said in the in their
02:13:06 witness statement that uh that there was smoke in the flat building up over that period up to some
02:13:12 extent and then as it got closer to the point that they left at about 3 10 so quite late levers
02:13:19 from from that very high floor um they saw that the fire was coming around hadn't quite reached
02:13:27 the external fire was juxtaposed to their flat um let me think we're on uh we're in a flat three
02:13:35 oh i was gonna have a diagram wasn't i what happened to the diagram of grenfell floor plan
02:13:39 i was promised uh we can find that for you professor sure um if we go to uh page 13 of
02:13:49 my we can have it up we can have it up but let's just show it on the screen blar
02:13:55 six zeros nine page 12
02:14:06 seven zeros nine page 12 sorry
02:14:11 um blar seven zeros nine page 12
02:14:20 um
02:14:24 yes we want floors um four to 23 want that bit blown up
02:14:33 right so we are in um we're in a flat three aren't we just to say this is from barbara lane's
02:14:39 barber lane's report yeah but it's just a general floor plan yeah so so that's right so i'm just
02:14:46 trying to worry forgive me i'm just trying to orientate myself here so so in this particular
02:14:51 case the spread of fire was a first to first reach that flat was coming along the south side
02:15:01 of the tower wasn't it yes so the first room to be affected was the first bedroom in this particular
02:15:10 flat or this column of flats so what uh day me and uh lydia saw was that the fire was about to
02:15:20 come past the pillar in the middle there and was starting to was just about to attack that bedroom
02:15:26 when they evacuated um and so the first room in that flat to be affected by the fire would be that
02:15:33 bedroom what they actually so the the others were all sheltering i think in the living room so they
02:15:38 were able to avoid initially that exposure but um what lydia uh and naomi said or naomi i think
02:15:47 and i'm thinking of her statement was that by this time the hallway of that flat was filled with very
02:15:54 very dense smoke and they after their final 999 call just before three uh about 304 um 309 they
02:16:06 went to the bathroom to try to wet towels to cover their faces and had quite some difficulty
02:16:13 negotiating to cross that hallway because of the density of the smoke and they spent a few i don't
02:16:19 know maybe 20 seconds or so getting these wet towels and then they prepared it took one last
02:16:25 breath that's right they they said we took one last breath from the only window this would have
02:16:30 been a west facing window in the living room where they could still get fresh air they took
02:16:36 a final breath of fresh air and then they plunged through the smoke in the hallway of the flat
02:16:42 across the lobby and made it to the stair so you can see that the conditions were quite there was
02:16:48 quite a lot of bad conditions in that in certain places at least in that flat at that time and yet
02:16:53 my calculations show that by sheltering in that living room and having access to an open windows
02:16:59 on the clear side they were able to minimize their exposure up to that point in time so so that
02:17:06 unlike the occupants at um roth park they were in quite a good condition to be able to still
02:17:15 walk all the way down the stair yes thank you can we then go back to your report uh da pr
02:17:20 605 page 57 57 and go to paragraph 219 and there uh you have scenario three inclusion of other
02:17:32 asphyxian gases in the analysis and at figure six a little lower down the screen if we can have a
02:17:37 look at that scroll down to figure six this is the full fed analysis the flat the flat 193 case
02:17:45 and you there set it out taking into account all asphyxian gases in in addition to or including
02:17:51 carbon monoxide could you just talk us through that slide please let me just
02:18:06 yeah so this is for the yeah sorry i'm this is the my head around this again
02:18:11 yeah so this is uh so this is just the third in the set isn't it that's right
02:18:14 yeah sorry so this is still just for naomie and lydia um but this time i've i've included the full
02:18:20 analysis which includes the um uptake of hydrogen cyanide which you can see is the blue curve there
02:18:29 and um what else i got the oh yes right so that as i mentioned earlier the fractional effective
02:18:37 dose calculation that we use for a mixed gas set uh includes individual terms for each individual
02:18:45 gas and the sum terms assuming simple additivity for the fractions of the two various gases i think
02:18:54 i explained that earlier so in this curve here i've got the fractional effective dose for
02:19:00 carbon monoxide on its own that's the red curve i've got the summed fractional effective dose
02:19:10 for cyanide alone that's the blue curve and then i've got the fed in sum which is the black curve
02:19:18 which is for the two those two gases added together and also includes some consideration
02:19:24 of the influence of carbon dioxide on their breathing and also of our reductions in oxygen
02:19:31 from the fire which in this case is trivial so it doesn't really affect the calculation
02:19:36 and what this illustrates is that um they were overcome essentially by carbon monoxide that's
02:19:45 the biggest term in this analysis but you can see that based upon the ratios that we talked about
02:19:51 earlier i have estimated that there would certainly have been some contribution from
02:19:56 hydrogen cyanide from these burning materials and just to remind you uh to the extent that that may
02:20:03 have come from the cladding insulation the only material in the insulation producing cyanide is
02:20:10 the insulation the pir selotex insulation is a source of cyanide but to the extent that the
02:20:19 uh this some of this smoke may be derived from burning flat contents we're talking about things
02:20:25 like upholstered furniture which also have a high nitrogen content so it just illustrates here that
02:20:31 the dominant gas here that's causing incapacitation is carbon monoxide when i later went on to look at
02:20:38 the hospital data the doses of carboxyhemoglobin that people are acquiring and being affected by
02:20:45 is almost exactly what you'd expect to see from carbon monoxide alone so the influence of cyanide
02:20:53 is relatively minor in my opinion in this case you say it's relatively minor but you also say it was
02:20:59 significant yes and you say that in paragraph 225 in the next page all right explain the
02:21:05 explain how it is significant if you can yeah okay
02:21:08 okay
02:21:13 it's there it's having an effect and we shouldn't ignore it now i might be getting into some
02:21:19 complexities here there there's a quite a difference between the way people are affected
02:21:25 by cyanide and carbon monoxide they're both asphyxiant gases it's possible that they have
02:21:32 a fractionally additive effect although there's still some uncertainty about that
02:21:38 but one of the key features and i've got a figure that i might look it up in a minute i've got a
02:21:44 figure that i prepared that illustrates it is that if you're exposed to a low concentration of
02:21:56 carbon monoxide and a very low concentration of cyanide the cyanide has almost no effect so for
02:22:05 example if i expose you to less than a hundred parts per million of cyanide then you can function
02:22:16 inhaling that gas for about 30 minutes at 100 ppm but if i double that to 200 ppm you're going to be
02:22:24 unconscious within three minutes so the effects of cyanide are partly dose related but partly
02:22:32 concentration related now because we're dealing here because of the ratio that i established
02:22:39 earlier and because we're dealing here with moderate concentrations of carbon monoxide it
02:22:43 means that the concentrations of cyanide are low enough that it doesn't have it's not really
02:22:52 driving the outcome but it is contributing to some extent however and this is where
02:23:02 i suspect it may have had more influence on the occupants of the 10th lobby
02:23:07 because we're here whereas here we're talking about 1800 ppm of co in the lobby we might be
02:23:14 talking about 10 000 ppm of co and the cyanide is going up proportionally and at those ratios
02:23:21 and those concentrations cyanide becomes a more significant actor in collapse not so much in cause
02:23:29 of death but in cause of collapse and quite a lot of my work has been directed at looking at the
02:23:34 relative influences of cyanide and co in fires and from from fires containing relatively high
02:23:42 concentrations of cyanide like furniture upholstered furniture fires funny enough they're not funny
02:23:48 enough that there has been in the last two days a press report of a prison fire and i think it was
02:23:55 ecuador or somewhere where the prisoners set fire to their mattresses which are high nitrogen content
02:24:02 materials and i think about 48 deaths it's happened the last couple of days so under certain
02:24:07 circumstances cyanide can be a very important driver of outcome but in this particular case
02:24:13 because of the ratios i i believe it's it's having a it's there but it's having a relatively
02:24:19 limited effect can you just explain why when it comes to floor 10 the lobby on floor 10 you say
02:24:25 the cyanide is going up proportionately there i need to try and find this excuse me man well we
02:24:32 may be i may be able to help you with that is it d a p r six zeros three page 24
02:24:38 four that's the one thank you thank you very much yes so this was these are the results of some
02:24:47 experiments i conducted at huntington so this shows the relationship between between exposure
02:24:55 concentration and time of consciousness for exposed subjects these were in fact primates
02:25:05 and the blue curve is for carbon monoxide and the little table there shows you the relationship
02:25:13 between inhaled concentration and time to incapacitation and ct product which is the
02:25:21 exposure dose to concentration so you can see that for these small animals the concentration
02:25:29 concentration of dose the dose of carbon monoxide at which they collapsed became unconscious was
02:25:38 about 27,000 parts per million minutes ct for the first figure there so but a thousand ppmc
02:25:47 carbon monoxide the concentration was a thousand and after 26.6 minutes the subjects became
02:25:54 unconscious and multiply those two figures together gives you 22.660 and it's just under
02:26:01 27,000 and then when the experiment was repeated at 2,000 4,000 and 8,000 ppm the calculated dose
02:26:12 at which they collapsed was always the same as you can see there it's a constant it's just under
02:26:16 27,000 ppm minutes so that's for carbon monoxide so dose and time they're absolutely
02:26:24 and concentration are equivalent if you were exposed to half twice the amount for half the
02:26:29 time it has exactly the same effect as half the amount for twice the time sorry i have a gun
02:26:34 so i see and do these do these two lines the red and the blue lines do they interact yes so that's
02:26:40 so that's the blue one is the co but in contrast to that if you look at the cyanide curve it doesn't
02:26:44 follow that pattern and and if you look at the little table on the top right i've calculated
02:26:52 the two figures together so if i exposed to 87 ppm of cyanide then i've got 30 minutes before
02:27:04 i collapse and you multiply those two figures together you get 2610 but if i exposed to 300 ppm
02:27:12 i collapse after 0.9 of a minute giving a figure of 270 so it's 10 times more toxic if you like
02:27:20 when it's at that higher concentration yes but i mean would you have i'm trying this slightly
02:27:25 differently yes if you were to eliminate the carbon monoxide from this therefore take the
02:27:29 blue line out altogether would the would the line for hcn still look the same oh yes so these are
02:27:35 independent they're not they're not so these were different experiments one one set of expenses on
02:27:40 co1 was i just plotted them on the same chart that's very helpful yeah sorry now can we then
02:27:46 go back to your report please at d apr six zeros five page 58 and this is your your calculation
02:27:55 now part four pages paragraphs 229 to 233 where you've got the forward calculation of carbon
02:28:02 monoxide uptake for flat occupants and is it right that that you were able to use a number of markers
02:28:09 to inform your analysis for individuals in different locations yes yes and did that include
02:28:14 and just run through the the pointers here that is this right that where some occupants in a flat
02:28:19 successfully escaped and others were unable to you were able to measure the exposure and the
02:28:23 uptake for all individuals in the flat as similar up until the time that the individuals successfully
02:28:29 escaped yes yes and where you have 999 transcripts available for those individuals or
02:28:35 or those present you've relied on the condition of the individual to estimate their level of
02:28:40 asphyxiant intoxication yes so for example if an individual is semi-conscious then they're
02:28:46 estimated to have had an accumulated dose of about 40 percent carboxy yeah yes and for individuals
02:28:53 who fell from the tower their blood carboxy hemoglobin was fixed i think at the time they fell
02:28:59 yes so this is very sad but actually it gives an exact point in time and an exact dose
02:29:06 yes at that point of time and you were able to use those levels i think to calculate their exposure
02:29:10 and the exposure of those who were left in the flat at that time yes yes and for those individuals
02:29:15 who died in the flats i think you've used their post-mortem blood carboxy hemoglobin levels
02:29:21 where that where they were available yeah yeah to estimate their exposure in the flat yes and then
02:29:26 correlated obviously with any 999 core transcripts yes thank you now you've also explained on the
02:29:32 next page in section four that you've applied the washout method to evacuating occupants from
02:29:39 the tower now let's see if we can just have a bit more clarity on that for those who've never heard
02:29:45 of the expression the washout method you've described it at paragraph 234 page 59 overview
02:29:54 of method are you able to summarise that for us and just explain it yes so basically so if you've
02:30:00 inhaled a certain dose of carbon oxide after point in time anywhere and then you take it out of that
02:30:07 exposure and you're exposed to air as soon as you're exposed to air every every breath you exhale
02:30:13 contains some carbon oxide that you're excreting from your body you're washing it out of your
02:30:19 blood by breathing it out and so the concentration remaining attached to your hemoglobin the carboxy
02:30:25 hemoglobin decays with time longer as you breathe it gradually gets washed out until it's all gone
02:30:33 now the rate at which it's washed out depends upon the partial pressure of oxygen you're inhaling
02:30:39 because it's the oxygen that's driving it off your blood and so we express this in terms of
02:30:46 the half life the time it takes to get rid of half of the dose that's in your body at any point in time
02:30:53 and so the half life of carbon monoxide in the blood of a person breathing air is very long it's
02:31:00 about four and a half hours so if you walk out of a tower with 30 in your blood it's going to take
02:31:06 four and a half hours for you to get down to 15 left okay long time but if somebody gives you
02:31:14 oxygen to breathe from a face mask when you walk out the tower which is 100 oxygen then the half
02:31:22 life is about 74 minutes just not just over an hour varies a little bit with individuals and
02:31:30 i've obtained that that figure from published studies on you know the literature and if you
02:31:36 look at the literature you get various estimates this was one recent publication looking at quite
02:31:43 a large number of individuals and and they're all fairly close but that's that's the figure i've
02:31:48 i've used so 74 minutes half life for somebody breathing oxygen from a face mask
02:31:55 and if we look at figure eight on page 63 of the same part of your report there is a set of carbon
02:32:05 monoxide washout curves for four persons evacuating from flat 183 would it be helpful just to look at
02:32:12 there was a couple of diagrams i put in just illustrating the basic calculation first
02:32:19 we can do that is i think that's a page 60 i think we go to that
02:32:24 so this was this was just to illustrate what i've just said really so the upper the upper example
02:32:29 this is sort of semi-theoretical but is based on actual data so imagine there's somebody in the
02:32:35 tower they walk out and they've got 30 percent carboxyhemoglobin in their blood they stand
02:32:40 outside for for 20 minutes before anybody gives them oxygen so that's a little red bit at the top
02:32:45 of the curve and they're washing out the co but very slowly they're then given oxygen to breathe
02:32:50 and this curve then becomes steep after about 70 minutes they arrive at hospital and somebody takes
02:32:56 a blood sample and that's the red first red diamond on the curve and then various samples
02:33:01 are all taken at intervals so i can i can fit a curve to those samples this is what i've actually
02:33:06 done for these actual hospital figures and then i can back extrapolate that curve to the time
02:33:13 they were first given oxygen if i know what that is so in this particular case suppose i know that
02:33:20 they started at 20 minutes then i can calculate that they had about 28 29 percent carboxyhemoglobin
02:33:27 at the time they started breathing oxygen right now the lower curve is exactly the same thing
02:33:33 but in this case i've made a different assumption so i've assumed that they came out of the tower
02:33:39 they were from a lower floor they were they had about 20 percent carboxyemal they weren't
02:33:45 semi unconscious or anything so they weren't given any oxygen but eventually they they didn't they
02:33:50 looked unwell so they were taken to hospital when they got to hospital the same blood sample was
02:33:55 taken and they were started on oxygen so now my back extrapolation goes along that that blue curve
02:34:01 because they were all the time before they got to hospital they were only breathing air and that
02:34:07 means that they could only have had about 20 percent carboxy globin at the time they walked out the
02:34:11 tower so that's just to illustrate the approach so i see so if we can do you want to move on to the
02:34:17 next lot uh yes sorry no that's very that's very helpful the next lot lot is at figure eight on
02:34:23 you were just going to ask me about yeah page 63 and i think right so this is for a set of actual
02:34:29 grenville occupants yes from flat 183 yes and i've anonymized them so i i can't remember who
02:34:36 they were but um basically this uh for this for these individuals i i have a number of blood
02:34:46 measurements taken at hospital which is shown by the enlarged dots on those graphs so those
02:34:52 are actual readings and from those readings i've fitted curves to their individual washouts
02:35:01 for those for those for those set of individuals and so it gives you some idea of the variability
02:35:08 of this method now the dashed line in there is the average 74 half minute half life curve
02:35:18 you can see that little dashed line so you can see that some of the some of the occupants
02:35:24 in the tape in the legend i put the calculated half lives for these ones right so so the dotted
02:35:30 line is the the published data set curve factor that's the 74 74 yes um but 183 this individual
02:35:41 183 you see their washout was um to fitted to their actual data shows a slightly more rapid
02:35:48 half life of just under an hour 58 59.8 minutes so um back calculating their figure it gives a
02:35:56 figure of about 35 percent when they left the tower or when they were first given oxygen and um also
02:36:06 183b also had a quite a rapid out um washout time you'll notice that she had quite a high
02:36:15 figure at the time she left the tower that per individual was a heavy smoker if you smoke
02:36:20 cigarettes you get quite a bit of carbon oxide in your blood even before you you're in the fire so
02:36:26 i think that's why her figure is a bit higher but the green curve was actually for a child
02:36:34 if i remember rightly or a young person uh and you can see it's quite a shallow they've got quite a
02:36:40 long half life a longer half life and that person was asthmatic and when they got to hospital they
02:36:46 were in some distress and the hospital tried to put them on a ventilator put them in an induced
02:36:53 coma put them on a ventilator and the hospital records show that they had great difficulty
02:36:59 ventilating this person because of their bronchoconstriction and they had to use this
02:37:04 particular uh special method of ventilation called cpap which is a sort of pulsed uh air
02:37:11 method and and by doing that they were able to overcome this problem and ventilate this person
02:37:17 so that they made a good recovery but uh i think this curve shows that it is picking up the fact
02:37:24 that this person had was in an asthmatic state and that's partly why the washout curve is shallower
02:37:29 than it was for the other individuals so get some idea of the individual variation yes um then let's
02:37:35 turn then on that topic to individual characteristics and the effect of particular characteristics of
02:37:42 the individual on the rate of uptake of asphyxiates and let's let's start with children but um when i
02:37:48 ask these questions and you answer them please don't name any of the children you can avoid it
02:37:53 um now you've you've explained i think that the rate of uptake of asphyxian gases by infants and
02:37:59 young children is about twice the rate of that of an adult which would then hasten the time to
02:38:04 collapse and death yes yes and you've given us a number of examples first it does the increased
02:38:11 rate of uptake for children apply equally between those who are sheltering in flats
02:38:17 and those who are descending the stairs
02:38:22 in a word yes um let me just just go through that so it's a basically
02:38:28 for all animals from mice to elephants the amount of air you breathe each minute depends on the
02:38:34 ratio of your body surface area to volume ratio so the bigger you are the less you need to breathe
02:38:41 per unit body weight and that applies equally to humans so the smaller the child the more it
02:38:48 breathes per minute per unit body weight and i mean in theory i could do more accurate calculations
02:38:54 of this but because of the all the unknowns were involved here it didn't seem appropriate
02:39:00 but on as an approximation a small child is going to who's sitting in a flat this is your
02:39:09 question sorry breathing carbon oxide their uptake rate will be approximately twice that
02:39:17 of an adult sitting next to them when they walk and this is quite important when they walk down
02:39:24 the stair both will increase by a factor of two or so so an adult sitting in a flat is breathing
02:39:31 10 liters a minute eight to ten meters a minute we are we're all doing that here now if we start
02:39:36 to walk down a stair fairly vigorously that doubles to 20 or so so and the same would apply
02:39:43 to the child from their double whatever they started at right if however the child was carried
02:39:51 so it was say it was an infant and was carried down then of course they continue to breathe at
02:39:55 their resting rate because they're not exercising and therefore a small child say a three or four
02:40:01 year old child who is walking down the stair through the smoke is at much greater risk than
02:40:06 the same child were they being carried say by a firefighter or a parent yes that's very helpful
02:40:13 and and is it likely in all cases where infants or young children were sheltering in flats
02:40:20 with their parents that they would have lost consciousness and died before their parents
02:40:25 yes i mean i think they certainly would have lost consciousness before the parents
02:40:29 and almost they would have died before the parents yes and what about young teenagers
02:40:33 slightly older children well it's it's in proportion so still sort of say a 12 year old
02:40:39 i would expect to see some some evidence for that as well but obviously it's in proportion
02:40:45 yes i mean also applies to adults so uh an adult with a heavy a large heavy body mass would go
02:40:55 for longer than one with a smaller body mass and let's then turn to the relevance of asthma
02:41:01 you've touched on that a moment ago yes can i just show you first an article
02:41:06 that you co-authored in 2016 that's a dap 703 page and i just want to show you page 27 let's
02:41:15 have a look at the first page first dap 703 it's it's entitled assessment of hazards to occupants
02:41:24 from smoke toxic gases and heat this is our chapter in the sfp handbook yes yeah yes it's
02:41:30 and indeed if we go to the foot of page one uh you can see um i think an indication of that
02:41:38 uh it's the copyright of the society of fire protection engineers 2016
02:41:44 uh and if we go please to page 27
02:41:47 if we look at the second paragraph down on the left hand column
02:41:57 in the penultimate paragraph break you say asthmatics and sufferers of other lung conditions
02:42:03 such as chronic bronchitis and reactive airways dysfunction syndrome are particularly susceptible
02:42:08 to bronchoconstriction on even brief exposure to very low concentrations of irritants with
02:42:14 distress severely reduced to rabic work capacity collapse and death resulting depending on the
02:42:20 sensitivity of the individual and the severity of the exposure it is the objective of fire safety
02:42:26 engineering to ensure that essentially all occupants including sensitive sub-populations
02:42:31 should be able to escape safely without experiencing or developing serious health effects
02:42:36 thus safe levels for exposure of the human population to fire effluent toxicants must be
02:42:42 significantly lower than those determined from experiments with uniformly healthy animal or even
02:42:47 human surrogates now um are you able to elaborate on how athma might have affected occupants
02:42:55 of the tower during the fire it's a very general question yeah right but focusing on how it might
02:43:02 have affected their prospects of escape with with pre-existing conditions yeah with yes with
02:43:10 okay mathematics and other lung conditions yes okay so we've got uh
02:43:14 it's quite a complicated question we've got various things two things happening here
02:43:19 one is the sensitivity to asphyxiance uh like carbon oxide as a gas yeah and the other is uh
02:43:27 the effects of uh irritants now this this material in this chapter here
02:43:37 derives from a lot of discussions that we've had over the years in the iso committee where we're
02:43:46 trying to produce standards in this area and nearly all the work that's been done both on
02:43:53 on animals and and human studies are based on otherwise sort of healthy individuals
02:43:59 and we are have been trying to come up with the sort of numbers we've been discussing up till now
02:44:05 on what sort of levels represent a danger of collapse for the average person and what might
02:44:12 be a reasonable safety margin to put on a design constraint which is partly what this chapter is
02:44:17 aimed at and um it becomes difficult because the objective data available for uh challenged
02:44:25 individuals is is rather limited and so there have been a lot of discussions on where this safety
02:44:31 level should be put and i'm trying to address here the principle of it and so what i'm saying
02:44:37 here is that i have some feeling for this because i'm a severe asthmatic myself is that uh
02:44:44 the irritants uh could precipitate an asthma attack the irritant smoke could be inhaled and
02:44:49 cause a severe bronchial constriction as in that example i showed you the green curve earlier
02:44:54 which could in itself lead to some degree of incapacitation collapse even if there's no
02:45:00 carbon monoxide present um so that's one issue that we have to think about the other is
02:45:08 susceptibility to carbon monoxide if you are asthmatic and you inhale a certain dose of carbon
02:45:14 monoxide would you be more susceptible now i would think all the risk is on the downside that you
02:45:21 probably would be but um for the rose park inquiry i had quite a lot of access to medical data for
02:45:29 those deceased in that case and i published a paper uh where i looked at the relationship
02:45:37 between carboxyhemoglobin at death and pre-existing health condition these weren't all elderly
02:45:45 persons as i am myself now uh who uh had quite a lot of pre-existing conditions
02:45:51 um what i found was a very clear relationship between the negative relationship between the
02:45:57 carboxyhemoglobin in the blood at death and pre-existing heart condition so if you had
02:46:03 severe heart or circulatory condition then at death you had a lower carboxyhemoglobin than one
02:46:11 person who had a healthy heart but when i did the same uh relationship for pre-existing lung disease
02:46:18 i i didn't find any significant relationship quite surprisingly so some of these individuals had
02:46:24 quite severe pre-existing respiratory disease and yet the carboxyhemoglobin at death was not
02:46:30 particularly different from those who did not have those conditions so it's quite a complicated area
02:46:36 but i think a precautionary principle would say that you would expect to be somewhat more sensitive
02:46:41 if you were pre-existing asthmatic or had some other condition right does that help yes just
02:46:47 just working this through then so when it comes to carbon monoxide as an asphyxiant
02:46:52 your opinion based on your research from race park was that when it came to lung
02:46:56 disorders it had no effect on limited effect if any yeah um what about hydrogen cyanide
02:47:04 hydrogen cyanide i i think that's your answer that is we don't have any data don't have any data
02:47:10 really no when it comes to irritants even in the absence of carbon monoxide um
02:47:18 um but my question is when going back to the green curve yes does the presence of an irritant
02:47:26 which constricts the airways and therefore can um slow the uptake slow the uptake yes i've thought
02:47:32 about this and um if it did anything we'd expect it to do so to some extent but
02:47:41 i would say was going to have a would make a minimal difference
02:47:44 um if we're breathing carbon oxide as a pure gas and one person is asthmatic and one person isn't
02:47:52 during that uptake phase i wouldn't really expect to see any difference if we're breathing smoke
02:47:58 and one is and with co in it and one is asthmatic one isn't then we might see some difference but
02:48:06 i don't think it would be a big factor right in the rate of uptake why would the rate of uptake
02:48:13 be different from the rate of washout in an asthmatic person
02:48:22 good question um
02:48:26 oh yes because well because they're not yeah so so right let me just recap this and think through
02:48:31 it if you're breathing the pure gas during the uptake phase and one is asthmatic and one isn't
02:48:39 i would expect no real difference but if you're if you're breathing the if you're breathing it with
02:48:48 smoke then there might be a difference um i'm not sure i've got the answer to this but
02:48:56 we do seem to be observing and that that person that's right sorry yes so if you had
02:49:03 essentially an asthma attack while you were inhaling this smoke and co then it might slow
02:49:09 it up i think and what we're seeing with that green curve is somebody who is washing out
02:49:15 during an asthma attack and it's the fact that in inverted commas they've got bronchoconstriction
02:49:21 which is impairing their their breathing and gas exchange outside the tower in that green curve
02:49:30 so by inference you might expect to see something similar phenomenon on the way up
02:49:37 if you if you were there to measure it yes thank you i'm striving a bit here it's a bit
02:49:42 you're getting a little bit outside my experience of what's actually happened in these cases
02:49:47 fair enough now coming back to the question of irritants uh is how is hcn hydrogen cyanide an
02:49:53 irritant an irritant as well as an effect as six not really no i mean i think some people can smell
02:49:58 it i can smell it some people can't it might have a very minor effect but it may if the one of the
02:50:05 reasons the difference i showed you earlier in those two curves and there is a big difference
02:50:10 and the reason for it is that carbon monoxide does not stimulate respiration so if you're
02:50:15 breathing sitting here breathing you breathe exactly the same whether or not there was
02:50:19 carbon monoxide in the room or not but cyanide is a very powerful respiratory stimulant and the
02:50:26 experiments i performed on this i found that if i exposed animals to say 150 plus million of
02:50:33 hydrogen cyanide then their breathing went up by a factor of three within a couple of minutes
02:50:41 right and so that greatly enhanced the rate of uptake and that's why they became unconscious so
02:50:46 quickly that's why there's a difference between that that's very sorry i should have mentioned
02:50:50 that no that's very interesting because when i asked you about the two curves the blue yeah
02:50:53 that's the reason for the difference yeah so does that tell us this that if you have
02:51:02 uh the proportions of hydrogen cyanide to carbon monoxide here that we had at grenfell yes uh the
02:51:11 uptake of carbon monoxide was greater because of the presence of hydrogen cyanide that it would
02:51:16 have been had hydrogen cyanide not been present right so if you're breathing uh hydrogen cyanide
02:51:22 at something of around 50 to 60 parts per million then the respiratory stimulus effect of that is
02:51:29 really quite mild so the effect it would have on co uptake would be quite minimal but if you're
02:51:37 inhaling cyanide at say 150 parts per million then you get this massive increase in breathing and as
02:51:45 you say if there's carbon monoxide is also present it would enhance that so if you have for example a
02:51:52 person who's at otherwise at rest breathing about 10 liters of air a minute and they start to inhale
02:51:58 150 ppm of hydrogen cyanide then within a couple of minutes they might be breathing 30 liters of
02:52:04 air a minute and so if they're breathing carbon monoxide as well you'll triple the rate of uptake
02:52:10 even though you're not walking or doing anything else it's and that may indeed be why we think we
02:52:16 are observing some degree of additivity between these two gases in terms of toxicity the additivity
02:52:22 may be as a result not of any particular systemic toxic effect which is quite complicated it may
02:52:29 simply be a reflection of the fact that the cyanide is stimulating breathing and therefore
02:52:34 the rate of uptake of the carbon monoxide but it's quite a complicated area yes i was going to ask
02:52:39 have you done any analysis on on your outcomes based on carbon monoxide subtracting the presence
02:52:52 of hydrogen cyanide well what i'm saying is that for the stair cases that we've examined
02:53:02 where we've got the back calculated hospital data the relationship between the condition they're in
02:53:09 and the carboxy hemoglobin estimates in their blood you can explain the outcomes for them in
02:53:16 pretty well entirely in terms of carbon monoxide the other thing i would say about the cyanide story
02:53:23 is that it's very in these certain circumstances it can be quite serious in terms of time to collapse
02:53:30 as soon as you do collapse your breathing drops right down so that effect no longer occurs
02:53:34 i've measured this so and and the uptake of cyanide tends to be some for that reason to
02:53:42 be somewhat self-limiting it's quite a complicated story so it what we're seeing is that it probably
02:53:51 does not contribute greatly to death it's its main seriousness of inhaled cyanide in fires is in this
02:54:00 rapid knockdown rapid collapse which then leaves you in in the situation where you continue to
02:54:05 inhale all these gases and then die sorry what was the question again well the question quite
02:54:13 answered have a question was whether or not you'd taken into account the stimuli oh yes sorry so
02:54:17 that was the point i was coming so i would say that for the stair occupants we could seem to be
02:54:22 able to explain all of all that we observe and for the flat occupants really in terms of carbon
02:54:28 monoxide perhaps with a minor contribution from the fact that so i was there for the lot for the
02:54:35 10th lobby i feel it may have for the reasons i've explained had a bit more of some more of
02:54:41 a significant contribution but still co is still a very important theme the major driver i think
02:54:47 right so would you say that the stimulus effect of car of hydrogen cyanide on on breathing was
02:54:55 essentially negligible when it came to calculating the uptake of carbon monoxide or did it have a
02:55:01 material effect i would say for the stair cases for the mod for the moderate levels of co and
02:55:07 therefore low levels of cyanide it had a limited effect plus also you've got to remember that in
02:55:12 the staircase they're walking anyways they're already exercising so it's getting quite complicated
02:55:17 for the as i say where the lobby
02:55:23 ones are concerned i think it may have had some some influence right and what about to some extent
02:55:28 taken to right and what about the flats themselves prior to the before before the time when the
02:55:35 flame front attacked the outside of the particular negligible yeah can i then just um the few minutes
02:55:41 before the the the break just turned to the question of the impact of physical impairment
02:55:46 impairments on the prospects of escape now you you i think confirmed that your
02:55:53 analysis of the potential for escape through the staircase would depend upon the occupants being
02:55:57 able to descend the stairs and to do so in a time period shorter than would be required to accumulate
02:56:03 the total threat to collapse yes 30 percent or so yes um if an occupant was impaired by a health
02:56:10 condition from coming down the stairs at all or impaired from descending within the window of time
02:56:15 before accumulating that incapacitating dose um will it follow that their prospects of escape were
02:56:22 negated or reduced yes it's quite complicated this isn't it because um from the examples that
02:56:27 i put in there and from my own experience of trying to run down the tower if you remember i
02:56:34 i'm i managed to i couldn't do it now i achieved nine seconds per floor when i did it in anger
02:56:43 um so if you're if you're coming down the tower in smoke free conditions as a as a reasonably fit
02:56:50 adult um you can obviously travel down at quite a speed um the the standard number that we use is
02:57:02 one meter per second coming down a stair linear travel um
02:57:10 if the stair is full of smoke then you slow down and you'll notice that although they
02:57:18 said that they they came they thought they traveled quite rapidly it i i calculated that
02:57:24 nae me and lidya were traveling at about 30 seconds per story compared to my nine so they were
02:57:32 about the third the speed and that fits in with what we know about travel in poor visibility
02:57:39 conditions in smoke has been some quite a bit of experimental work on this particularly in japan
02:57:44 um so um if you're traveling in dense smoke you're going to travel more slowly and i've allowed for
02:57:51 that uh so for each individual i've looked at i've looked for who survived i've looked quite
02:57:58 carefully at how they describe their descent in terms of some said they ran down some so they
02:58:05 came slowly so i've tried to allow for that so if you if you have a disability but you can still
02:58:11 walk and there were a number of examples of this in grenfell that one particular individual i
02:58:15 remember who was assisted by some another person to walk down then um if you're walking through
02:58:22 smoke uh you may not be traveling that much different speed than an able-bodied person
02:58:29 would because you're all equally slowed down by the dense smoke you with me if of course you aren't
02:58:35 able to come down at all then obviously you're forced to remain in your flat now there was one
02:58:42 particular case that struck me in reading through the grenfell witness statements
02:58:48 can i remember the name i'm afraid i can't of a couple where the uh the the lady was
02:58:57 uh quite severely disabled physically disabled and knowing that she would have no chance of coming
02:59:03 down the stair as soon as she became aware of the fire she immediately other with her companion got
02:59:09 in the lift and came down at a very early stage and therefore came down during smoke-free conditions
02:59:15 and survived so she had a game plan she had a plan b of how to get out if you like which was
02:59:22 extremely effective but dependent on the lift dependent on the lift yes yeah in her case yeah
02:59:28 yes and yes now working back a little then um what was the maximum level of coboxy hemoglobin blood
02:59:37 saturation that an average healthy individual could safely reach while in the flat in order
02:59:44 to exit the tower assuming 30 or less carbon monoxide uptake and assuming your reference
02:59:50 point of 1800 parts per million of carbon monoxide in the stair column yes so i'm uh so we're talking
02:59:57 really about this period after about half past two to four when we had these conditions so i would
03:00:04 say about you know about nine or ten percent pre pre-loading before you set off is about them
03:00:12 above that you're in trouble so for example uh in flat 205 um
03:00:21 nidhar mr nidhar fell from the tower with 20 percent in his blood at the time he fell
03:00:29 if he waited until that point and and then decided to walk down following his son and his wife
03:00:36 there's a good chance he would have not been able to walk all the way down but he would have
03:00:41 collapsed on the way down because he's pre-loaded 20 by the time he was halfway down the stair he
03:00:46 probably would have reached a point of collapse you understand the point i'm getting at exactly
03:00:51 yeah yes and i think the case you're referring to is mr mohammed san bernadon yes yes thank you
03:00:56 yes thank you thank you very much mr chairman is now a convenient
03:01:00 moment yes please thank you very much we'll stop there professor for some lunch we resume
03:01:05 at two o'clock please and again please don't talk to anyone about your evidence while you're out of
03:01:10 the room i understand all right thank you very much would you give the usher please okay
03:01:26 thank you very much two o'clock two o'clock please