Professor Christopher Johnson provides expert evidence on fireground communication systems, analyzing the design and operation of LFB's radio equipment at Grenfell Tower, including UHF radios, battery sets, intrinsic safety requirements, and communication failures.
00:22:47 good morning everyone welcome to today's hearing
00:22:50 hearing today we're going to hear evidence from professor
00:22:53 professor johnson who is one of the experts instructed by the inquiry yes yes mr chairman thank you good morning to you good morning members of the panel i now call professor christopher johnson
00:23:04 call professor christopher johnson please
00:23:14 good morning professor johnson good morning i understand you're going to take the oath i am there should be a testament on your right there would you take it in your right hand please and read the words on the screen i swear by
00:23:25 read the words on the screen i swear by almighty god that the evidence i shall give shall be the truth the whole truth and nothing but the truth thank you very much now please sit down make yourself comfortable oh
00:23:37 comfortable oh sorry we've got a hiccup that i'm afraid because
00:23:40 because this fun screen is the document screen is blank
00:23:44 is blank which
00:23:45 which i think you're switched on you've got to agree
00:23:50 this is what happens isn't it technology technology yes it's uh
00:23:56 it's uh it catches you out
00:24:01 i swear to all plugged in are you
00:24:18 ah just your life
00:24:27 the king has been a bit exuberant do you think
00:24:31 think sorry i didn't i didn't know
00:24:58 thank you very much felipe
00:25:02 all right i think we've solved it probably right mr miller i think we've sold it so on you go thank you very much mr chairman um good morning professor johnson good morning uh you've prepared
00:25:13 johnson good morning uh you've prepared a report for this inquiry entitled assessment of the design and operation of fairground communications systems available at grenfell tower on the night of the fire correct yes and it's dated the 27th of
00:25:26 correct yes and it's dated the 27th of november 2020. and let's have it on the screen cwj50119
00:25:32 please is that your report to the inquiry it is can you confirm that the facts and matters set out in it are true to the best of your knowledge and belief i can
00:25:45 best of your knowledge and belief i can have you provided a report in the same way that you would provide an expert's report to the cut to the court in this country i have does your report faithfully set out your opinions on matters which are relevant
00:25:57 opinions on matters which are relevant to this inquiry it does and have you read the report recently i have yes now if we can go please to page uh well section 174 sorry section
00:26:08 well section 174 sorry section 1.4 if we go to that please which we will find on page 14
00:26:21 you set out your disclosure of interests and a brief review of your background and we also find that i think in appendix a at page 278
00:26:32 appendix a at page 278 and i just want to draw some key points from your cv can i just run through some of the headlines with you and ask you to confirm or disagree or qualify as the case may be
00:26:45 disagree or qualify as the case may be am i right that you're currently a pro vice chancellor of the faculty of engineering and physical sciences at queen's university belfast i am and you've held that position since july 2020. i have
00:26:57 july 2020. i have and is it right that before that you were head of computing science at the university of glasgow between 2014 and 2020. i was is it right that you've also held previous positions in computing
00:27:08 held previous positions in computing science including at the university of glasgow between 1994 and 2014 yes yes and before that the university of york between 1991 and 1994. yes
00:27:21 between 1991 and 1994. yes and you hold i think is right amongst other qualifications a master of science in information processing i have yeah and a doctor of philosophy in computing science i do
00:27:32 science i do and as i understand it your default thesis explore the roles that human factors play in control systems is that is that a fair summary yes yes and is it right also that throughout your career you have researched and lectured on
00:27:43 you have researched and lectured on safety critical systems yes and also safety and communications projects
00:27:50 projects for major organizations including gchq the ministry of defense the united states navy and nasa yes and in relation to your work on communication systems is it right also
00:28:02 communication systems is it right also that you've previously advised on communications failures following major incidents such as the terrorist attacks of 9 11 and in london seven seven yes and i think it's right that in 2011 you
00:28:14 and i think it's right that in 2011 you were awarded a nasa fellowship i was and in 2019 you were appointed fellow of the royal society of edinburgh now can i thank you can i um
00:28:25 now can i thank you can i um look at the purpose of your report can we please go to page 15 and look at paragraph 2.1
00:28:34 you set out there under the heading methods findings and recommendations your instructions in general can you confirm for us please that the purpose of your report is to assess the design operation and
00:28:47 is to assess the design operation and efficacy of the communication systems adopted by the lfb at the grenfell tower fire i can confirm and in conducting that analysis is it right that you examined not only the technical and operational
00:28:58 technical and operational characteristics of the lfe's communications equipment but also the lfb's overarching communications systems yes
00:29:07 yes and in preparing your report i think it's right that you've had access to witness statements and documents provided to the inquiry i have and am i also right that you have in part at least proceeded on the footing
00:29:19 part at least proceeded on the footing of the findings in the chairman's phase one report yes very much so yes
00:29:25 yes uh and considered also matters and documents from your own expertise and professional experience and you've identified those clearly in the body of your report or in their footnotes yes yes
00:29:36 yes now during your evidence today what i i would like to do if i may is to ask you some explanatory questions about the main communications technology deployed by the lfb as at the night of the fire
00:29:48 by the lfb as at the night of the fire 14th of june 2017 and then we will look after that at the challenges or problems the high-rise firefighting can pose in respect of communications and and then we will turn later to the
00:30:00 and and then we will turn later to the way in which you suggest that those challenges can be overcome or mitigated i'm going to start then with the lfb's radio technology and its inherent limitations
00:30:11 limitations and within that the first topic i'd like to look at with you if i may is the subject of handheld radios first is it right that the the london fire brigades radios relied on two main
00:30:22 fire brigades radios relied on two main forms of radio communication technology first ultra high frequency or uhf technology which was analog and second airwave technology which was digital yes
00:30:34 airwave technology which was digital yes now we'll look at those and their differences in some more detail as we gave it for current purposes would it be accurate for me to summarize their different their different uses in the following way first uhf radio
00:30:46 following way first uhf radio was uh at the time of fire the radio relied on by the majority of firefighters on the incident ground yes whereas airwave radios were held by or at least possessed by senior officers
00:30:59 at least possessed by senior officers and where the means by which the incident ground would be able to communicate with the control room or other emergency responders yes yes and am i right that airwave was also known as the main scheme radio that's
00:31:12 known as the main scheme radio that's correct
00:31:13 correct now let's look at ultra high frequency or uhf radio in a little bit more detail now i think your report discusses two types of uhf radio device is this right
00:31:24 types of uhf radio device is this right the first is a handheld personal radio carried by all lfb firefighters which is like a walker talk a walkie-talkie yes and the second type of radio is that which formed part of the
00:31:36 radio is that which formed part of the lfe's breathing apparatus or ba uh now known as a barry said yes b-a-r-i-e
00:31:44 b-a-r-i-e that's that's correct yes now we'll come on to look at the differences between those in due course but just want to focus if i can on the uhf technology um now you've identified the fact that the uhf is an analog technology rather
00:31:56 the uhf is an analog technology rather than digital could you tell us in layman's terms if you can what the differences are between analog technology and digital um
00:32:06 um sound can be viewed as a waveform sinusoidal and analog
00:32:12 analog if you like samples that but with the digital approach it takes that that analog wave and breaks it into digital values of ones and zeros and then transmits it in
00:32:25 ones and zeros and then transmits it in a way that's analogous to how a computer would translate information it's first of all encoded into ones and zeros and then decoded into a sound that we can recognize uh
00:32:36 we can recognize uh in in
00:32:38 in in in
00:32:39 in normal normal hearing if you like and the translation into ones and zeros offers advantages in terms of in some ways in terms of encryption and in terms of
00:32:52 and in terms of integration with the internet protocol and so forth so however airwave as a technology itself was developed before many of the more recent advances in computational
00:33:03 recent advances in computational infrastructure and and so some of the possibilities of digital communication are not available in
00:33:11 in as they were deployed on the night of the fire for instance right now you i think explain that uhf radios operate in something called simplex mode yes
00:33:21 yes and you explain what simplex mode is when you describe the barrie radio set at sections seven point four point two and three
00:33:27 and three of your report can we just look at those please page one eight one
00:33:34 and on one eight one you see at seven point four point two you say only one party at the time can talk whilst while others listen until they hear an opportunity to transmit the limited power of these devices means
00:33:46 the limited power of these devices means that it is often impossible to cover an entire incident ground with simplex communications signal coverage weakens with distance and with obstructions between radios
00:33:57 between radios now we'll come to look at signal coverage shortly but for for the moment does simplex mode play any part in the power of a radio device um
00:34:08 um it does in the sense that if you're communicating between two handheld radios then there is a finite distance based on the power of the radio between which that communication signal will
00:34:19 which that communication signal will transmit
00:34:21 transmit other forms of communication as are illustrated in the dry ground below can have repeaters and other forms of technology that then extend that signal but it's not going from one handset to another handset we'll look
00:34:32 handset to another handset we'll look we'll look at that uh in a moment great uh
00:34:36 uh because it's um not on the screen but we'll look at this we'll look at the diagram but i think what you're telling us is this right is that if you're in simplex mode it may limit or the distance between
00:34:47 it may limit or the distance between handsets that can be used simplex mode is simply a form of communication which is one way in direction rather than obviously duplex which has two forms of
00:34:58 which has two forms of both one channel for transmit and another channel for receive so in some ways it's orthogonal to the power but in general the issue would be the power of hand-held to handheld communication
00:35:10 hand-held to handheld communication without any form of infrastructure to extend that signal would it be right to understand that simplex mode means that one person transmits while other people receive
00:35:23 while other people receive exactly and if someone who is listening wants to break in and transmit is he prevented from doing that or does he effectively cut off the first
00:35:34 he effectively cut off the first transmitter it depends on the situation but in normal circumstances they would potentially cut off the other transmitter by taking over the bandwidth or there would be a signal distortion
00:35:45 or there would be a signal distortion through that contention for the bandwidth right yes thank you and following that up what would happen uh
00:35:52 uh if two users tried to transmit messages at the same time the same thing it would it would effectively [Music]
00:35:59 [Music] cause interference between the two the two signals right and what would happen to the message of the person who was unable to transmit would he just get lost yes
00:36:10 would he just get lost yes and potentially also obscure the first responder as well right talking over is the phrase that people often use would the unsuccessful party so to speak uh have any way of knowing that their
00:36:21 uh have any way of knowing that their communication had failed
00:36:25 it would depend on
00:36:28 on so so normally people refer to things like radio discipline which is where somebody will say a message and then give a keyword typically something like over that then says i'm finished you can go next
00:36:38 go next so in the situation where somebody spoke over a person who was delivering a message that could arise if for instance they hadn't heard that the first person was already using that that channel for
00:36:49 was already using that that channel for example and felt that they could then the airways if you like were free for them to talk at that point would the um um well where radios allow more than one
00:37:00 um well where radios allow more than one party to transmit it to time i think that's is this right duplex mode duplex says uh in the circumstances that we see with these radios doesn't mean that more than one person can can speak any one time it
00:37:12 one person can can speak any one time it means that there will be one person speaking but another channel will be used to hear information coming back and so it may be possible for somebody to say something that is then heard but um it doesn't offer multi-party talking
00:37:26 um it doesn't offer multi-party talking because there's still only one channel for transmission so this is sometimes as the diagram below we'll show you is called half duplex yes well let's have that on the screen because i'm going to look at that now with you before i do can i just ask
00:37:38 now with you before i do can i just ask you this
00:37:39 you this is it possible to have or to find uh uhf radios that transmit in duplex mode
00:37:46 mode it is and do you know how long those have been available on the market i don't know that would be something let's look at the diagram at the bottom of page 181 where you've got figure 7.1 differences
00:37:58 where you've got figure 7.1 differences in simplex and half duplex and just in summary that's where the radius repeat so it transmits to a repeater in frequency a which i think is this right receives in
00:38:10 which i think is this right receives in a that transmits to each in b and the radios receive the signal from the repeater in frequency b yep yes and what are the advantages of half
00:38:22 and what are the advantages of half duplex mode in that it enables you to extend the the distance between the handheld walkie-talkies so you know as the name repeater suggests it repeats the message onwards to a
00:38:34 onwards to a recipient that may be distributed further
00:38:38 further and and it uh extends what in the report i've referred to as a signal localization effect uh yes and is it possible for uhf radios
00:38:49 uh yes and is it possible for uhf radios to use half duplex mode or does that require a radio repeater it requires a radio repeater in the in the architecture that we have here
00:39:00 the architecture that we have here now if you go to page 43 of your report please let's look at section 3.2.15 together you say that it's in the middle of the screen
00:39:11 screen a wide range of factors influence radio propagation shadowing occurs when an object blocks a signal attenuation when an object reduces the strength of a signal
00:39:22 reduces the strength of a signal reflection when a signal is propagated from an object and diffraction when the path of a signal is altered by an object i think it's also right that you go on
00:39:34 i think it's also right that you go on to say
00:39:35 to say that there are other factors as well such as the density and composition of surrounding materials including a building's construction yes yes meteorological factors including weather yes
00:39:46 weather yes uh and you cover that at 3.2.17 and the presence of fire itself yes yes and we'll look at some of those factors in more detail a little bit later but for the moment can we take it
00:39:58 later but for the moment can we take it from the list that you've set out there in your report that it's common for uhf radio messages to be degra either degraded or blocked entirely by any one of those factors yes depending on the environment yes
00:40:11 yes depending on the environment yes and what practical impact would the degradation or blocking of a signal have on the sender or the recipient of a radio message for
00:40:20 for for both parties it um creates the proper possibility that their message first of all may not be transmitted correctly to the recipient and the recipient may not hear that message
00:40:31 recipient may not hear that message clearly
00:40:32 clearly or in full um
00:40:36 degrades communication right and so for example um
00:40:42 um in the presence of fire what would it do to the sound of the transmitting voice again it could it could create interference and as i said in the report the actual
00:40:54 and as i said in the report the actual relationship between fire and the nature of that interference is not well understood it's widely accepted that there is an effect but to me it remains an area of significant
00:41:06 to me it remains an area of significant research that should really be conducted given the context of this inquiry and now if we go to page 96 of your report please let's look at section 5.1.3
00:41:21 you've referred to what we've just discussed i think as is this right signal localization yes yes
00:41:28 yes yes and at that paragraph uh you say in this context signal localization refers to the failure of low-powered radio signals to propagate beyond the immediate vicinity of the team
00:41:40 immediate vicinity of the team generating them this localization reduces the problems which might otherwise occur when signals from one team propagated to interfere with those of another now that am i right suggests that
00:41:52 now that am i right suggests that keeping radio signals at a relatively low power
00:41:56 low power might be an intentional strategy by organizations is that what you intend to say yes very much so right um then let's look on at page 142 please let's look there at section 6.6.5
00:42:12 you say and this is in the context of barry radios but you say signal localization could have helped communications by limiting propagation to small work groups so that everyone
00:42:23 to small work groups so that everyone hears the messages of their colleagues within their work group first does it does it follow from that using signal localization as an intentional strategy effectively amounts to relying on the
00:42:35 effectively amounts to relying on the fact that radio signals will only transmit so far and therefore will only be received by specific work groups yes and so perhaps by way of example in a
00:42:46 and so perhaps by way of example in a high-rise context would the idea be that radio messages of firefighters on the top floors of a building are unlikely to be received by the radios of firefighters at the base of the building
00:42:57 firefighters at the base of the building who are working on a separate task or perhaps by a low bridge head
00:43:02 i think that's the case but i don't think that that was thought through in many of the documents that i've seen in terms of what the effects of that would be to what we refer to as
00:43:13 would be to what we refer to as situation awareness across the whole of the fire ground do you mean by that that incident commanders didn't turn their minds to the fact that signal localization
00:43:25 signal localization meant that firefighters hired the building might not be able to hear people transmitting from low down in the building
00:43:35 i think that signal localization was intended to be effective within a small as a number of small working groups
00:43:48 but i think that the scale of the response
00:43:52 response created or created communication problems that had not been anticipated for the reasons that you described but also because the more powerful uhf radios that i'm sure will come on to discuss
00:44:04 sure will come on to discuss also suffered communication problems and they were intended to provide another way of linking um beyond the scope of the signal localization for the barrie sets if that if that makes sense yes it does turning
00:44:15 if that makes sense yes it does turning back to the question of working groups yes are you referring to here really the practice of dividing users up into small groups who are geographically proximate
00:44:27 geographically proximate yes yes yes so a work group would not work is this right because of signal localization if you were going to divide it into two and send half of it to the top of the
00:44:39 and send half of it to the top of the high-rise building and keep them keep the second half in the bottom the communi the extent or range of the communication would not be sufficient in many cases in that situation yes yes when you were preparing your report
00:44:51 yes when you were preparing your report did you see any evidence to indicate that the grenfell tower fire the lfb was intentionally trying to utilize signal localization in order to limit radio signals to particular groups
00:45:03 signals to particular groups of b18s
00:45:05 of b18s i think that the evidence i saw was that this was part of the pre-operational planning but that on the night of the fire at least in the early stages it it seemed that communications were effective within work groups but then as
00:45:17 effective within work groups but then as the as the night progressed um
00:45:22 um the it was not always the case that firefighters had barry radios um as they entered the building even when they were working in teams and so i thought some teams had no barry radios
00:45:33 teams had no barry radios and those initial working teams that may have been conceived in the early stages became
00:45:40 became more
00:45:42 more distributed communications became more difficult
00:45:45 difficult and
00:45:46 and the
00:45:49 it's in answer to your question fully there are more complex aspects which relate to the use of different channels between the ba teams channel channels and channel three which was used effectively in some cases between work
00:46:01 effectively in some cases between work groups on the night of the fire but the impression i got from the witness statements was that those those arrangements um
00:46:08 um became
00:46:10 became less sufficient during the course of the fire as communication problems increased and i think that contributed to as i said before loss of situational awareness that's noted by many of the
00:46:21 awareness that's noted by many of the witnesses
00:46:22 witnesses now at the beginning of that answer you referred
00:46:25 referred to
00:46:27 to pre-operational planning was that pre-operational planning for afr at grenfell tower or are you referring to some wider policy or planning arrangement um i i
00:46:38 arrangement um i i mean the wider policy in planning not things like the pre-site inspections and and the
00:46:45 and the ord entries for example so well for grenfell tower specifically or for other buildings throughout the i i think that the the planning was for general high-rise fires in the sense of
00:46:57 general high-rise fires in the sense of national guidance such as gr 3.2 and some other documents right so when you refer to the to the pre-ops planning are you talking about policy either at national law or at
00:47:08 policy either at national law or at brigade level yes yes yes now can we then please turn to page 53 can you just help me with this if i'm understanding your evidence correctly you're telling us that um
00:47:22 correctly you're telling us that um those who use um uhf analog systems must be aware that they have a limited range to put it in labels terms yes and that can be useful because it means you
00:47:34 that can be useful because it means you can confine the those who are taking part in the communications to a certain group within a certain geographical range yes and it becomes a problem if you're trying to
00:47:45 becomes a problem if you're trying to extend it beyond that geographical range exactly
00:47:48 exactly um
00:47:50 um is it possible to give us any indication of the sort of range within which those systems could be expected to work effectively
00:48:01 effectively in a high-rise building is it all too dependent on the structure of the building
00:48:07 building it's a it's a fantastic question and i wish i could give you a simple straightforward answer but the way i i feel about it having reviewed the evidence that's been provided to me by
00:48:18 evidence that's been provided to me by the inquiry is that
00:48:21 is that this there is an urgent need as i mentioned before for example the impact of fire on communication is not well understood and obviously has a tremendous effect in the context of this incident
00:48:33 and but i do i i feel that um there is strong opportunity in the aftermath of this fire to make a contribution and reduce the risks of
00:48:45 contribution and reduce the risks of future fires by developing methods that enable us to answer your question in a more satisfactory way than was done prior to this fire in other words i think there are it's not that it could not be done it's
00:48:58 it's not that it could not be done it's that it has not been done and i think if we if we applied our minds we would be able to come up with far better predictions to answer your question before a fire on a building by building basis that's helpful and i i i think i'm
00:49:11 basis that's helpful and i i i think i'm in danger now of anticipating mr bennett's life i'm gonna take the risk because
00:49:17 because you referred to the pre-planning stage and i just wonder whether in the material that you've seen you saw a conscious recognition
00:49:28 you saw a conscious recognition of
00:49:29 of the position that you've just described namely that you can use this system within a certain geographical area no doubt affected by the building and the fire and everything else but not if you get beyond it
00:49:42 else but not if you get beyond it did were people as far as you could see yeah aware of this problem yes a very specific example would be there's a continual reference throughout policy documents nationally and within the
00:49:53 documents nationally and within the brigade to blind spots within high-rise buildings and and that most commonly that are associated with methods of construction in in high rises so i think there's a general awareness
00:50:05 i think there's a general awareness i think there's one aspect that i would talk about which is that the the signal localization works well within working teams but as soon as you put more and more people into the same
00:50:17 put more and more people into the same location then that localization is eroded because too many people are trying to contend for the same channel and so there's it's not just the blind spots it's also the congestion which i
00:50:28 spots it's also the congestion which i feel
00:50:29 feel um it's that it's the combination of these
00:50:32 these different aspects the the construction creating blind spots that in that and the power that means that you can't communicate with the bridgehead further down the building and then the sheer number of users in a
00:50:43 then the sheer number of users in a defined locality so order in the report i've referred to this as a systemic kind of explanation where you take these these different factors which were all a problem on the night of the fire i think
00:50:54 problem on the night of the fire i think and and and and placed the fire fighters in a very difficult position is my view thank you very much that's helpful
00:51:03 helpful yes
00:51:04 yes um can we then look at page 53 please of your report and on that page you can see the heading which is uh i won't read out to you and
00:51:15 which is uh i won't read out to you and some key findings the paragraphs 4.1.2 and 4.1.3 you set out key findings there uh particularly about limitation of
00:51:27 uh particularly about limitation of power
00:51:28 power of output and signal localization helping reduce congestion and then at 4.1.4 you say this these benefits were lost in grenfell tower because so many teams were
00:51:40 tower because so many teams were deployed in close proximity that the channel became congested and interference occurred are you referring here to ba teams being deployed to the same floor or to upper and lower floors
00:51:52 or to upper and lower floors it's very difficult to be well
00:51:55 well certainly within the same floor that would be true but also because uh radio waves propagate in different directions in the ways that were described in in our previous answer um it could still occur between flaws as
00:52:08 um it could still occur between flaws as well if people were adjacent and trying to communicate with each other you could just
00:52:16 the the conflict between the communication would still occur in that situation too in other words if they if they're in too close to proximity and they try to communicate even though they're in different working groups
00:52:27 they're in different working groups their message will messages will conflict in the way that we described yes now
00:52:32 yes now building on that if um well accepts as a starting assumption that
00:52:38 that it's a likely scenario in a high-rise fire that you are going to have ba teams on different floors of a high-rise building
00:52:46 building would it be fair to say that the potential benefits of signal localization are unlikely to be realized in the context of fighting and fighting a fire in a high-rise building yes yes and i i would also say that some of
00:52:59 and i i would also say that some of these issues were revealed in previous incidents
00:53:02 incidents in
00:53:02 in that are described in the report such as 911 for example yes
00:53:09 yes can i then turn to barry sets and the concept of intrinsically safe can we go please to paragraph 44 sorry page 44 paragraph
00:53:21 sorry page 44 paragraph 3.3.3 of your report and um professor i apologize for jumping around but we're going to be doing that for much of the day thank you um now you you set out here an explanation
00:53:33 you set out here an explanation uh that the two types of uhf radio used by the lfb handheld radios and the battery sets operate at a different wattage
00:53:41 wattage i think it's right that the battery set operates at one watt whereas the handheld personal radios operate at four watts
00:53:48 watts yes yes and the handheld radios are the hx 480 and 481 yes yeah could you briefly outline what the what impact that power difference has on a radio's
00:53:59 that power difference has on a radio's signal strength in in
00:54:02 in in general terms the the higher the wattage the the greater the the uh the power of the of the handset to communicate and so in in terms of its practical
00:54:13 and so in in terms of its practical impact
00:54:14 impact uh where the signal strength is reduced would it be right to say that radio signals and messages would be unable to travel as far as those using stronger signals in general yes in general and the weaker signals might not
00:54:25 general and the weaker signals might not be able to penetrate through walls and floors particularly where they're made of concrete or steel yes and as a result is it right the radio messages simply may not reach their intended destinations yes
00:54:37 intended destinations yes now i write also in thinking that these problems may arise with all uhf radio signals but they're much more likely to arise where the signal strength is weaker yes that would be my interpretation now you you discuss the
00:54:50 interpretation now you you discuss the concept of intrinsic safety or is in your report could you explain again if you can in layman's terms what intrinsic safety is
00:54:59 safety is intrinsic safety is a term that is used to describe the suitability of a communication device in this case for use typically in an explosive or
00:55:11 use typically in an explosive or flammable environment and in general terms it relates to the possibility that that device might be the the cause of a fire or an extinction
00:55:22 the the cause of a fire or an extinction or a or an explosion um
00:55:27 so and there are different sorry i don't know how much detail you would like but there are different different categories depending on the the the nature of the substances and the home office specifies
00:55:38 and the home office specifies a particular level of intrinsic safety for use in particular sorts of flammable environments and i think you've set that out elsewhere in your report in a table yes
00:55:49 elsewhere in your report in a table yes you have we'll come to that um
00:55:51 um can we go to page 42 of your report and look at paragraphs 3.2.5
00:55:58 and you say there just above the table which we'll look at at the bottom of the screen but you say there at 3.2.5
00:56:08 3.2.5 a fire needs a fuel oxygen and an ignition source the power of the battery sets was deliberately limited to reduce the likelihood that the equipment might provide a fire's ignition source
00:56:19 provide a fire's ignition source yes
00:56:20 yes is that
00:56:22 is that is that power or perhaps what is limitation what makes a radio intrinsically safe it is possible to have higher powered radios that are also categorized as
00:56:33 radios that are also categorized as intrinsically safe but in general the higher the power then the the lower the level of intrinsic safety and so
00:56:43 and so by increasing the power of an intrinsically safe device it may not be suitable for use in all explosive or flammable environments um and the categorization i provided in the report provides an indication of
00:56:55 the report provides an indication of that yes
00:56:57 that yes and uh would it follow from what you've just
00:57:00 just explained to us that these intrinsically safe barrier sets with lower power at one what i think would have an increased chance of signal difficulty yes
00:57:11 difficulty yes and you go on i think to explain at 3.2.8 lower down your screen uh that it is possible to procure is radios that also offer higher levels of power and you've just made that point
00:57:22 power and you've just made that point just now
00:57:23 just now does it follow from that that there isn't a universal standard of intrinsic safety
00:57:29 safety it's more that there are standards for categorization of levels of intrinsic safety and the and the levels can be demonstrated through a series of tests for example that show a particular
00:57:41 tests for example that show a particular device meets that level of intrinsic safety
00:57:44 safety um but as it says in the report there's typically a trade-off in terms of the the power versus the level of intrinsic safety so
00:57:52 safety so again as i said a minute ago the more the higher the level of intrinsic safety that you are looking for
00:57:58 for then the more the more protection it offers you in an explosive environment and then in general the lower power it tends to be so these are all generalizations but that illustrates the trade-offs that are
00:58:09 that illustrates the trade-offs that are that are made um just just on that is it would the one the one what limitation or the power of the battery sets used by the lfb have been mandated by the lfb
00:58:20 been mandated by the lfb or would it come from a manufacturer or from tests the lfb could have procured higher powered intrinsically safe devices but they may not then have been
00:58:31 devices but they may not then have been suitable for all of the environments that the lfb may have encountered i have not been provided with the sort of analysis that would show
00:58:42 of analysis that would show what range they were planning for however i do notice that the home office further down in my report offers guidance on the on the level of intrinsic safety
00:58:54 intrinsic safety um
00:58:55 um it's not clear to me whether that was an explicit instruction to the lfb that one what should be the or the highest levels of intrinsic safety or what would be suitable for
00:59:06 suitable for the range of of tasks facing the lfb um
00:59:10 um so in general terms i can provide you with that
00:59:14 with that general response but the specific response as to what what process the lfb went through in terms of determining whether one what was appropriate for their
00:59:23 their for their operational needs is is more complex
00:59:26 complex and i again think that there should be an evidence-based approach that justifies the level of intrinsic safety that they determine suitable for their breathing apparatus
00:59:38 apparatus at the moment i believe that they are looking for a replacement which may be a more medium level quote unquote um and again i would like to know if that maps
00:59:49 if that maps across the range of of operational requirements that they might clearly be anticipated to have otherwise there may be a situation in which a higher level of intrinsic safety is
01:00:00 higher level of intrinsic safety is required
01:00:01 required but the replacement sets don't meet that or equally there may be no justified need for a higher for that medium level of intrinsic safety and a more powerful potentially system could be used so i
01:00:14 potentially system could be used so i think my feeling overall would be that that it would it would be beneficial in the future to see the evidence base that justifies this decision which does have an impact on communications in my view yes i see does it just look at the table
01:00:27 yes i see does it just look at the table which is slipping off the bottom of our screens at the moment which i think illustrates what professor johnson's really telling us and
01:00:34 and would it be right to understand just looking at this table that if you were working in an environment in group a you'd want a very low wattage radio
01:00:43 radio and if you were working in environment in group
01:00:46 in group g you might be able to use a rather higher wattage exactly and it just gives us some indication of the sort of range of atmospheres that might have to be considered right and i think also relevant to this is that some fire
01:00:58 also relevant to this is that some fire and rescue services um are not routinely providing intrinsically safe communication devices to their teams because they don't routinely encounter these sorts of environments
01:01:10 encounter these sorts of environments but yeah we'll just come to that later yeah just to finish the point off that the chairman has picked up if we can go over the page to page 43.
01:01:20 let's look together at 3.10 and 3.11. and indeed 3.12 just taking all those together there are as we can see there regulatory requirements
01:01:31 regulatory requirements published at the european level and by the home office and the hse about the use of uhf radios uh in in particular uh areas
01:01:43 areas yes yes uh now just coming back to the answer you gave a moment ago on what you've seen is it can you conclude that it's the
01:01:55 is it can you conclude that it's the case that the lfb's approach was not to map as you put it particular radio strength or intrinsic safety to particular environments but to use as i might put it a one size fits all one what approach
01:02:10 it a one size fits all one what approach yes and i think that that may be justified at the time of which they made the procurement but i think subsequently to that we can ask questions especially from the basis of the phase one report that's come out of
01:02:21 the phase one report that's come out of the inquiry whether or not that should be sustained into the future let's see that's my my feeling i see
01:02:28 i see we may come back to that um in general though how would you expect an organization deploying is intrinsically safe radios to set its level of intrinsic safety and i asked the question as at all
01:02:40 and i asked the question as at all before
01:02:41 before june 2017
01:02:45 i think
01:02:49 it's it's a very difficult question to ask in the sense that you're you're asking me to cast my mind back uh several years to that point but if i had ignoring the regulatory requirements
01:03:01 ignoring the regulatory requirements above if it had been my decision i would have tried to base it in exactly the same way that i'd described which to be as a safety engineer is a risk-based approach
01:03:09 approach however i feel that the the the regulatory requirements in this case probably predominated more than anything else rather than triggering a dialogue about what was an appropriate level of
01:03:20 about what was an appropriate level of intrinsic safety for the operational needs of a of an frs because i noticed for instance that in many cases breathing apparatus is used
01:03:31 many cases breathing apparatus is used in an environment where by definition there will be a flammable uh
01:03:36 uh environment whereas in many cases for a fire and rescue service the breathing apparatus is being used precisely because the flames are already present and the ignition source is already present
01:03:46 present and so the justification for intrinsic safety in that situation is reduced if that if that's clear yes would it follow from that that an organization which didn't uh set its wattage to the
01:03:59 which didn't uh set its wattage to the fire in front of it if i can put it very colloquially uh
01:04:04 uh was not um was adopting a one-size-fits-all and perhaps that would be inappropriate i think it's i think it's a complicated issue i think in the sense that there is a precautionary approach by setting a
01:04:15 a precautionary approach by setting a low level of a high level of intrinsic safety
01:04:18 safety you are safeguarding against a very wide range of environments but then you need to take measures to mitigate the communication failures that have been seen in many many previous incidents yes
01:04:30 incidents yes now if we go back a page please to 3.3.9
01:04:37 paragraph 3.3.9 on page 42.
01:04:44 so i'm sorry forward to page 44 paragraph 3.3.9 my mistake and you say at the foot of the page there most incidents in which battery sets are used do not involve flammable or explosive
01:04:56 do not involve flammable or explosive atmospheres and just focusing on a high-rise residential fire like the fire at grenfell tower would there be any benefits to using an intrinsically safe radio
01:05:10 i think that that would have to be an operational decision made at the time if if there was a concern for example over gas buildup and other and other another potential hazards within the environment
01:05:22 potential hazards within the environment but um
01:05:25 this in a sense would would ask me a question about what the policy would be if the barrie sets had a lower level of intrinsic safety than indeed they did on the night but the other the other the
01:05:36 the night but the other the other the converse part of this point is what i was saying before which is that if you go for a high level of intrinsic safety then you i think you have an obligation to consider the communications problems that we've described as being a consequence of the
01:05:48 described as being a consequence of the lower power yes i can see that they're certainly interlinked but yes you say it's an operational decision does it follow from that that in fact um where you've got no choice but to use a
01:05:59 where you've got no choice but to use a barry set with one what no no operational decision can be made because you haven't got anything else available well if we if we take a step back the personal radios that were also provided
01:06:11 personal radios that were also provided on the night with the higher power that we described previously at the 4 watts were used extensively during the fire and they should have been subject to a risk assessment prior to their use for
01:06:23 risk assessment prior to their use for the reasons that you suggest but i have seen no evidence to suggest that a risk assessment of the sort that i i advocated earlier was conducted and so the point that you're making is is a
01:06:35 so the point that you're making is is a correct reflection of what was the case on the night of the fire and not just a a theoretical abstract question to me yes
01:06:44 and i think you say that there might have been an operational justification for using uh a one watt level
01:06:54 level of intrinsic safety because of uh the potential for the presence of other ignition sources such as gas i i think so and but i i think that part
01:07:06 i i think so and but i i think that part of the problem i have as i read the the documents and the witness statements is that the lack of ability to communicate as you go further into a building provides no means then for you
01:07:17 building provides no means then for you to communicate your experience so somebody uh bridgehead for example making a decision that it's okay to use a 4 watt radio may lack the information about an
01:07:29 may lack the information about an explosive atmosphere further up the building so even when i say that there's a lack of a systemic argument about the safety of the communications on the fire ground i think as we go through today we'll see
01:07:40 i think as we go through today we'll see many situations where you can see that there are gaps within existing policy and that you know the policy says you should not use four watt radio until the risk assessment has been completed
01:07:52 risk assessment has been completed but that risk assessment has to be based on knowledge of people who may be using a one watt set who can't communicate with you and how do you ensure that you have a sufficient view to be able to do that risk assessment leaving aside the
01:08:03 that risk assessment leaving aside the fact that no risk assessment seems to have been done on the night of the fire do you know whether it was possible at the time to procure radios that could be switched into is mode in and out of is mode
01:08:15 into is mode in and out of is mode which could protect firefighters in the initial stages of an incident while the scoping out occurred i have seen radios of that sort but whether they would be suitable in this case i can't answer why why might they not be um i don't know
01:08:28 why might they not be um i don't know whether
01:08:29 whether there are any other what for example we described that there may be several different levels of intrinsic safety and i i
01:08:36 i i can't answer you that that kind of uh two-format radio would be sufficient to meet the highest levels of intrinsic safety without doing further checks can we go to page 55 of your report please
01:08:48 we go to page 55 of your report please and look at paragraph 4.2.6
01:08:55 and you say there that the nfb's policy on the use of the intel ht981is fireground radio states that higher powered personal radios should only be used by ba teams where battery sets are
01:09:07 used by ba teams where battery sets are unavailable and after a risk assessment has been conducted by a senior officer to determine that it is safe to use non-is communications can i
01:09:17 can i take you to lfb's policy 458 on the use of handheld incident ground radio that is at lfb 3013039
01:09:31 and it's what you refer to as footnote 88 which has just gone from the screen but it has been replaced by this policy as you can see reviewed as current as a 21st december 2015.
01:09:43 21st december 2015. and if we go to page two of that please and let's look at that page fourth bullet down under intel hx 480 81 incident ground radios it says this if dedicated battery sets are not
01:09:55 if dedicated battery sets are not available a minimum of a handheld radio must be carried intel 480 stroke 81 handheld radios are not intrinsically safe is must not be used in flammable or explosive
01:10:07 used in flammable or explosive atmospheres and should only be used where battery sets are unavailable the decision to use intel 480 stroke 81 handheld radios can only be made following a risk assessment carried out
01:10:18 following a risk assessment carried out at the incident so just looking at that is it right that it isn't in fact possible according to lfb policy uh for at least this policy for an incident commander to decide that
01:10:29 for an incident commander to decide that non-is radios should be deployed in circumstances where battery sets are available
01:10:34 available for example because they might provide better or stronger radio communication that would be my interpretation of that policy
01:10:42 policy and if we go on on the same page of your report page 55 we go back to that please look at
01:10:48 look at paragraph 4.2.7
01:10:52 you say that during the grenfell tower fire and in some previous incidents discussed in this section frs radio frs personnel used their uhf handheld radios instead of their battery sets
01:11:03 instead of their battery sets notwithstanding the fact that they'd not obtained approval from the ic incident commander and that the ic had not completed a risk assessment uh
01:11:14 uh now
01:11:16 now does that mean uh that when using their uhf radios in that way those
01:11:25 those firefighters or or other officers were exposed to the risk that intrinsically safe radios were designed to avoid yes
01:11:33 yes so an explosion for example yes can i just go back to a previous point that you that you made when you went to the lfb policy which as i said earlier on um it seems to have been the case but
01:11:45 it seems to have been the case but it is the case that in the intention was that in pairs of firefighters working with breathing apparatus only one
01:11:54 only one would potentially have a barrier set would have would have the the radio set however
01:12:01 however operational changes throughout the night meant that it wasn't always possible to ensure that these teams did have a barrier set and so the point that you were making with the reference to the policy
01:12:12 with the reference to the policy about the decision to use non-intrinsically safe radios if there was not a battery set available could have did occur on the night for some teams within the tower
01:12:24 although battery sets were available to some to some people now if we go to page 45 of your report
01:12:35 please um you can see that at section 3.3.11
01:12:45 page 45 uh you um pick up there are two bullet points there if you pick up the the second one sixth line down this is a quotation from the lfb's post
01:12:56 this is a quotation from the lfb's post grenfell tower fire review of its radio specification done in october 2019 yes and that suggests uh the ba teams were were doing what they were doing because of um and you say there's four
01:13:09 because of um and you say there's four lines up from the bottom of the bullet point
01:13:11 point due to experience with the poor signal propagation of ba radios confidence in the equipment is low therefore it is common practice for ba teams to enter smoke-filled environments fires
01:13:22 fires with their non-is4w fire ground radios on their tunics to improve communications
01:13:30 now that's what the nfb say am i right that your opinion is that the prospect of an incident commander conducting a risk assessment in the way the policy contemplates is
01:13:41 in the way the policy contemplates is problematic yes yes and is that because of your observation you make elsewhere that the nfb's policy doesn't explain how the outcome of a risk assessment can be conveyed to those who are already
01:13:52 conveyed to those who are already experiencing communications difficulties exactly
01:13:55 exactly so in simple terms would this be right that individuals who've lost radio signal have got no way of being told that they were permitted to use their higher powered handheld radios exactly
01:14:06 higher powered handheld radios exactly now if we go to page 55 again please and look at paragraph 4.2.8 could i just um add some one very quick sentence to my previous answer yes as
01:14:17 sentence to my previous answer yes as well when you're using the uhf handheld radios you may be on a different channel to those breathing apparatus colleagues and so those colleagues that didn't receive the command that they could use
01:14:29 receive the command that they could use their uhf radios will now not be able to communicate to those colleagues who are now using their handheld and so
01:14:36 and so as i said before there is a need to systematically analyze the reasons why all of these systems together provide an acceptably safe form of fire ground communication yes
01:14:49 now going to paragraph section section 4.2.8
01:14:54 4.2.8 on this page towards the bottom of your screen you say the nfb's policy does not explain how the outcome of any risk assessment is to be conveyed to teams who are already experiencing communication
01:15:05 communication communication failures which would trigger the risk assessment in the first place this illustrates the lack of a systematic approach to resilient communications and what do you mean by the lack of a systemic approach
01:15:17 the lack of a systemic approach to
01:15:19 to resilient communications exactly what we've just been through in terms of rehearsing situations that don't seem to have been covered by the policy
01:15:28 policy and in particular throughout my report i'm concerned about how do you recover communications once they have been lost and
01:15:36 and there's many reasons for that but one is that the the communication may have been lost for all of the reasons we we described
01:15:43 described but it may also have been lost because the firefighters were injured and in need of urgent assistance the lack of communication doesn't always imply that the communication medium is down it may mean that the firefighter
01:15:54 down it may mean that the firefighter has been overcome and so part of my of my care in this evidence is to is to make it clear that this is a safety issue
01:16:03 issue and not simply one about efficient firefighting both of the residents and for the firefighters
01:16:11 yes now can we go back to page 44 and look at paragraph 3.3.10
01:16:22 and this i think is is uh your introduction to some of the lfb's conclusions from the grenfell tower fire so far as communications are concerned and you say this other frs have moved
01:16:35 and you say this other frs have moved away from the use of is radios because of the communications concerns associated with low-powered higher-rated is devices but also because their ba teams routinely carry a range of other
01:16:47 teams routinely carry a range of other non-is equipment and you've got the passage we looked at and if we look at that in fact um a little bit lower down at page 45 you also say paragraph 3.3.12
01:17:02 you also say paragraph 3.3.12 after the part i've read to you this review also revisited the question of whether or not it's necessary for ba radios to meet is requirements and recommended introducing a higher powered
01:17:13 recommended introducing a higher powered 4 watt is specification for both ba and general fire ground radios
01:17:20 and
01:17:23 uh you will go on to say and i can i think to summarize this at 3.3.12 and 13 that the lfb's review of those matters resulted in the recommendation of the
01:17:34 resulted in the recommendation of the wattage of intrinsically safe radios generally be raised to 4 watts while the stock of lower wattage intrinsically safe radios be retained for more hazardous environments is that a fair summary yes
01:17:45 a fair summary yes right so the start of what you might have called the mapping exercise based on evidence yes and i think that then there would be a need for appropriate policy to make the decision when when they were to be
01:17:56 decision when when they were to be deployed yes now this may sound like a rather simplistic question but in your opinion how likely would it have been on the night that an increase from 1 watt to 4 watts would have alleviated if not
01:18:09 to 4 watts would have alleviated if not resolved the kinds of signal propagation problems
01:18:13 problems experienced at the grenfell tower fire i think on the night of the fire looking at the evidence many of the many of the firefighters resorted to using their personal radios anyway
01:18:24 using their personal radios anyway but i think the problem then is the issue for those who remained who are still using the breathing apparatus channel
01:18:31 channel and i think that that the the the attempt to maintain both forms of communication may have eroded situation awareness as people desperately tried to
01:18:42 awareness as people desperately tried to to form communication with their colleagues and the other point that i would would make here is not so much connected to power but it's connected to the physic physiological demands on the
01:18:54 the physic physiological demands on the firefighters and so before what personal radios that were being used with breathing apparatus if you could imagine that they are hand held and they're not connected to a a microphone inside the helmet and so
01:19:07 a microphone inside the helmet and so the officers are trying to hold the fire hold the radio while performing firefighting duties and rescue duties and so
01:19:16 and so the use of a four watt integrated radio within the breathing apparatus may have done some marginal improvement in terms of comparison with the handheld radios that
01:19:27 comparison with the handheld radios that the the personal radios that they carried
01:19:29 carried but its integration into the breathing apparatus i think would have helped tremendously if that had been coupled with
01:19:37 with a concern for the usability issues that many many of the firefighters suffered with the headsets anyway which is also covered in the report so yes yes thank you i'd like to turn next to
01:19:49 i'd like to turn next to leaky feeders and radio repeaters can we start by you're giving us please a layman's explanation of what that technology is and what it does so as we described with duplex
01:20:00 so as we described with duplex communication you can use a repeater to receive the radio waves from a handheld set and then re-broadcast it to another handheld set effectively extending the
01:20:11 handheld set effectively extending the the area of coverage now what that does as i described earlier is it reduces signal localization so if you've got you've got more and more people who can now access that channel
01:20:23 people who can now access that channel and so you have to wait potentially for longer to get your chance to talk so it extends the coverage but reduces the effect of signal localization and that's a single repeater
01:20:34 a single repeater now within a high rise or if you imagine perhaps a better example would be inside a tunnel um
01:20:41 um the repeaters have to be placed at a certain distance apart and then to boost the signal between those repeaters you can run a cable that effectively leaks signals
01:20:53 that effectively leaks signals and so anywhere along that cable you'll get better reception even if you're some distance away from the repeater i feel like the repeater amplifies the signal and the cable carries it um and it leaks
01:21:05 and it leaks normally the the decision for all of these the pieces of equipment that we see around us here is to shield them so they don't interfere with things but what a leaky feeder does is it transmits the communication so that anybody along
01:21:17 the communication so that anybody along the path of that cable will also be able to access it that's the that's the rough explanation the obvious as i said before downside is that it reduces signal localization more people
01:21:28 reduces signal localization more people have access to the communication channel and it doesn't reduce the problem of congestion so more people will be trying to talk on that same channel because they can be they can access it further apart distributed inside the
01:21:40 further apart distributed inside the building
01:21:43 building yes thank you now can we go to page 182 of your report and look at paragraph 7.5
01:21:53 7.5 you set out there a lengthy quotation from the witness statement of the lfb's dominic ellis who gives evidence there in his statement that certain radio channels
01:22:04 statement that certain radio channels for example channels 2 and 5 can only be used with a repeater now i think it's right isn't it that those are uhf channels yes yes uh and as we've seen you've explained
01:22:16 uh and as we've seen you've explained elsewhere uh on page 181 at paragraph
01:22:20 paragraph 7.4.7 that that is because the repeaters and leaky feeders enable the radios to transmit and receive half duplex frequencies yes
01:22:31 frequencies yes and just say we're absolutely clear is it right that the use of a half duplex frequency doesn't alter the fact that only one party can transmit a radio message at any one time yes right now is it right that where a leaky
01:22:43 now is it right that where a leaky feeder is used to access a half duplex channel
01:22:46 channel for example where channel 5 is in operation is that at the expense of a simplex channel like channel 6
01:22:54 channel 6 or can both channels operate simultaneously they can operate simultaneously but the person who is setting their radio has to choose the channel that it's on and so they won't they'll be allocated to one channel or
01:23:05 they'll be allocated to one channel or they'll select one channel at a time and so a big issue in terms of the processes that we've described earlier about deciding to go to a personal radio rather than a barry set
01:23:17 rather than a barry set would be that you'd have to bring the others in your team with you otherwise you would no longer be able to communicate with them right i see you would be on the wrong channel
01:23:26 channel so you'd have to get the information to them somehow that they needed to change channels yes
01:23:33 now um if we building on that a little bit go please to page 119 and 120 of your report starting at 119 we can see paragraph 5.8.5
01:23:45 we can see paragraph 5.8.5 uh
01:23:47 uh i'd like to show you the top of the screen first if we do that which is the um selected communications architecture which you get from policy number 466 in your figure 5.5 point c on that page
01:24:01 in your figure 5.5 point c on that page and you can see at a glance how that works it may be useful to come back to that in due course but if you look at 5.8.5 you say this
01:24:13 you say this pn 466 provides little guidance on the factors that should influence the decision to withdraw in the event of communications failures and then if you go over to page 120
01:24:28 your except which you have quoted ends with this
01:24:32 with this where a
01:24:33 where a radio leaky feeder is in use ba teams will be told to transmit on channel 5. now given that would it follow that a channel transition is an operational decision by the
01:24:44 is an operational decision by the incident commander rather than a necessary event yes
01:24:49 so it comes down to operational discretion yes and in addition to facilitating half duplex channels is it possible for leaky feeders and radio repeaters to enhance the signal of simplex channels
01:25:03 i i'm not sure about that but i i am restricting my comments here to the policy and the technical information provided for the tsr-2000s and associated equipment that
01:25:15 tsr-2000s and associated equipment that was used on the night of the fire right and in that case um they're to be used with the duplex channels as indicated in the evidence that was provided by the witness i see so so you say that actually policy
01:25:27 so so you say that actually policy doesn't
01:25:28 doesn't point you in the direction of using uh
01:25:32 uh um
01:25:32 um leaky leaky feeders and radio repeaters to enhance the signal of simplex channels i would have to check on that but it certainly that's not discussed at any point in in the information that i've i've had and uh available to me
01:25:44 i've i've had and uh available to me right
01:25:45 right now thus far we've been assuming we understand your point mr miller you're suggesting that um
01:25:51 um the equipment could be used to receive a particular signal and re-transmit that same civil boost if you like that same signal is that that's the point yes that's right yes is
01:26:03 that's the point yes that's right yes is that technically feasible do you know i
01:26:07 i i can't see any technical reason why but i also feel that the benefits of half duplex in extending the range are the reason why
01:26:18 extending the range are the reason why you would use them um so i would i would really have to look into that that's not something that arose during the preparation of my report where i was focusing more on the operational policy as was used on the
01:26:29 operational policy as was used on the night of the fire rather than what could technically have been done in other circumstances with that particular equipment i mean the reason i ask the question is that it's not clear
01:26:40 ask the question is that it's not clear to us at the moment whether it's physically possible um
01:26:44 um for leaky feeders and radio repeaters to work with simplex or whether they only work ever with half duplex or whether it's a matter of of programming
01:26:55 it's a matter of of programming do you know i i don't absolutely know but my feeling is that the benefits rely on the use of duplex communication to extend the range and and my intuition is that um trying
01:27:06 and and my intuition is that um trying to to use them with simplex doesn't provide the operational benefits that they're intended to provide in the first place but i would have to check that to be sure of my answer to you
01:27:17 answer to you now thank you yes now thus far we've been exploring the use of leaky feeders combined with radio repeaters to enhance radio signals and as you've highlighted in your report i think it's right that leaky feeders
01:27:29 i think it's right that leaky feeders can also be used uh in combination with telemetry repeaters to enhance telemetry signals is that right yes now when it comes to the installation of leaky feeders and repeaters
01:27:40 leaky feeders and repeaters you say in your report that they can either be fixed in buildings or tunnels yes um they can be portable to be deployed as needed at an incident yes
01:27:52 an incident yes or um they can be permanently installed on lfb appliances yes yes and just for your reference purposes this is all at section
01:27:59 section 7.2.7 on page 176. if we go to that page let's follow on from that if we go to that page page 176 and look at paragraph 7.2.4
01:28:11 and look at paragraph 7.2.4 you um you say there that leaky feeders have a limited range and their propagation is typically only effective within line of sight of the cable
01:28:22 cable yes
01:28:24 yes but does it follow from that that if leaky feeders are deployed or were deployed in the enclosed stairwell of a high-rise building such as that at grenfell tower they may well not be effective in enhancing
01:28:35 not be effective in enhancing propagation of radio signals beyond the walls of the enclosed stairwell yes and i i take from that that again i would strongly encourage some analysis
01:28:46 i would strongly encourage some analysis if this technology was to be continued to be relied on in any way in the future for studies to be done on realistic topographies of high-rise buildings to determine the extent to which your your
01:28:58 determine the extent to which your your question is true i think it is true um but i think there's a lack of empirical evidence to show exactly what that what that effect would be beyond the immediate
01:29:09 effect would be beyond the immediate stairwell
01:29:11 stairwell so does that mean that it as a matter of science the use of a leaky feeder at grenfell tower may well have not enhanced propagation of radio signals
01:29:23 enhanced propagation of radio signals into the communal lobbies or into flats and that's my feeling based on the evidence cited in my report from previous uh quote mixed unquote experience where
01:29:35 quote mixed unquote experience where they have been used in exercises such as osiris which is mentioned in i think it was
01:29:42 was russell square underground station but i've
01:29:46 i've found it very hard to find any evidence of the successful deployment of leaky feeders in high-rise buildings and to what extent does the same limitation that we've been discussing apply to fixed radio repeaters
01:29:57 fixed radio repeaters i think that they offer more opportunity and again there's evidence for for the use of those in for example the world trade center buildings again cited in my report and there was a but they don't offer a a
01:30:09 and there was a but they don't offer a a universal solution so as is cited in my report in in one area they clearly in one of the towers they clearly were of significant benefit but in another another area there was some confusion as
01:30:21 another area there was some confusion as to whether the system had been activated or not and so even though the system was activated the fire personnel and police personnel assumed that it wasn't available
01:30:33 are there differences in signal strength between portable repeaters and fixed repeaters i would imagine that there would be in normal circumstances by the additional provision of of mains electricity um but again
01:30:46 electricity um but again it may be that they they would have comparable strength if the if the electrical supply was compromised for instance through terrorist damage or a fire
01:30:55 fire and i think again a systemic approach would really run some of these scenarios based on previous experience to determine the sufficiency of either fixed or mobile because
01:31:06 fixed or mobile because as was noted during 7-7 some of the fixed installations were damaged by by the bomb
01:31:11 the bomb bought by the bombs and so people still at that point would need mobile repeaters to change to achieve the same communications outcomes
01:31:21 does a repeater propagate a signal at the same strength that receives it it can amplify it and make it stronger right
01:31:29 right but it it it's not the case that a repeater would wouldn't would never propagate a signal at level
01:31:36 at level or is it
01:31:37 or is it i can't envisage that but there may be scenarios in which that could occur but the the the i think the key point about your argument again is that um
01:31:48 i i feel that there was an insufficient risk assessment or evidence-based approach to actually work through some of the answers to this ques those questions so
01:32:00 questions so as you said earlier on i think there's a need for greater empirical experience to to
01:32:05 to i think
01:32:08 i think there was a reliance on these devices but without a questioning attitude to the evidence that showed that they would be sufficient in the case of a of a significant large-scale incident yes i see are leaky feeders and radio
01:32:21 see are leaky feeders and radio repeaters intrinsically safe no they're not
01:32:24 not not not as though we're available on the night of the fire right so would that mean that the logic which impelled the lfb to use a one watt barry set uh would also
01:32:37 uh would also um deflect them from using leaky leaky feeders and radio repeaters yes it seems to me
01:32:45 to me that some of the arguments associated with the deployment of leaky feeders and repeaters were not thought through in terms of intrinsic safety so you would need to have this is right you would need also to
01:32:56 this is right you would need also to have a a risk assessment some kind of risk assessment done by the incident command before deploying leaky feeders and radio repeaters and i and i i feel that many of the personnel on duty on the night were
01:33:07 personnel on duty on the night were unaware of some of these nuances
01:33:12 and that and the report i deal with some of the training issues about the deployment that have subsequently been been addressed i believe at least in part yes um mr chairman i've got about five or
01:33:24 um mr chairman i've got about five or ten minutes more with this topic before changing to a completely new topic would you rather finish the topic before we i would if that's convenient to you and to the witness well you don't mind going on a few minutes longer than usual i'm sure
01:33:35 a few minutes longer than usual i'm sure right thank you i'm going to park if i may the topic of uhf radios for the moment uh and and come back to look at that later but looking now at airwave or main scheme
01:33:46 main scheme uh is it right that airwave radio could be accessed either by a fixed radio fitted in lfe appliances or by using a handheld walkie-talkie type device yes and is it right that airwave radio was the way in which
01:33:58 airwave radio was the way in which officers at the incident ground could communicate with control yes and also with other emergency services yes and that wasn't i think possible with uhf
01:34:08 uhf no no now we've seen i think already um your we've heard your explanation of the differences between digital and analog
01:34:17 analog um
01:34:19 um and then moving on then to um some more detail can we go to page 218 of your report where you set out some evidence from phase one of the inquiry
01:34:31 phase one of the inquiry at paragraph 8.9.1 under the heading airwave coverage and you say this evidence in phase one of the inquiry indicated that airwave provided better coverage than the uhf personal radios
01:34:42 coverage than the uhf personal radios during the grenfell tower fire and then there's um some examination uh of uh
01:34:49 uh of uh a witness there uh namely uh brian o'keefe on day 19 which you foot noted over the page on page 450 at the footnote 450. um from a technical
01:35:01 footnote 450. um from a technical perspective are you able to explain why that might have been the case
01:35:06 yes i think it's an interesting set of questions i think um
01:35:11 um again there would be a need for a more evidence-based analysis i'm drawing that on the witnesses statements that many of them felt airwave radio would have assisted what they were doing better than the uhf but i also feel that that
01:35:23 than the uhf but i also feel that that argument may have been influenced by the fact that they didn't have the airwave and
01:35:28 and you know had they had it there's no guarantee that they would have achieved the effects that they anticipated um
01:35:34 um airwave can work in two different ways it can either work in direct mode or trunk mode in in direct mode it operates very much like uhf in other words you're communicating in a walkie-talkie style
01:35:46 communicating in a walkie-talkie style to another handset in trunk mode you go through base stations very much more like a cellular mobile phone and communicate with an infrastructure that can then go through cables depending on the on
01:35:58 go through cables depending on the on the on the you know on the on the architecture and so therefore the ability to communicate outside of the area is better supported by airwaves than it would be by uhf where you're you're
01:36:09 would be by uhf where you're you're effectively communicating within local groups on the scene the fire ground and do those benefits apply to any digital radio or are they specific to airwave as i mentioned before that the airwave devices could have been used like the
01:36:21 devices could have been used like the uhf radios in the walkie-talkie or direct mode but they weren't purposed for that for the operational use at least in
01:36:32 for the operational use at least in at the time of the fire what i really mean is the benefits that you've identified attributable to the airwave design per se or would they apply to or be attributed to any digital radio they
01:36:43 be attributed to any digital radio they wouldn't necessarily be applicable to all digital radios unless they had that trunk mode which connected back to an infrastructure it's the infrastructure that provides that out of out of fire ground communication capacity yes i see
01:36:57 now we've looked already at the possible ways in which uhf radio signals might suffer from degradation or blockage do those concerns apply to airway airwave radios yes they do
01:37:09 airwave radios yes they do do they apply to the same extent you can use greater degrees of signal processing on digital signals to recover the original message in the presence of interference
01:37:21 message in the presence of interference and so they in general tend to be slightly more resilient than analog uhf radios
01:37:26 radios however
01:37:27 however um
01:37:29 um i think it had been most people's experience with it with a digital radio at home that there comes a point when the total signal is lost whereas in uhf radio or analog radios you can sometimes make out
01:37:40 analog radios you can sometimes make out the signal even though it's extremely degraded
01:37:43 degraded so there's more of a in my experience more of a binary effect with digital radius and there is with ammo is it possible to enhance airwave signals using radio repeater and leaky feeder technology in the same way that it is in
01:37:54 technology in the same way that it is in some cases for uhf i would certainly believe so i've not seen leaky feeders used with this sort of technology but i i
01:38:03 i certainly believe repeaters would work very well yes can we go to please please to page 208 of your report and look at paragraph
01:38:12 paragraph 8.2.4 together yeah you say there
01:38:17 there uh the benefits of digital radio include the ability to maximize bandwidth through through the application of compression algorithms uh
01:38:27 uh could you just explain very briefly but in layman's terms if you can what that means
01:38:32 means um
01:38:34 um if you
01:38:35 if you were to access a video over the internet because of the amount of information that's required to cook to communicate the image and the sound together
01:38:46 the image and the sound together it's infeasible to transmit it in its real representation of zeros or ones and so algorithms are used to minimize the file size before it's sent across the internet
01:38:58 sent across the internet and
01:38:59 and the algorithms that do that um increase the efficiency of digital communication and um
01:39:07 and um so
01:39:07 so if you can you know if you if you look at your television recently you get 4k hd and that's possible because new forms of compression algorithm enable more and more quantity of data to be
01:39:19 more and more quantity of data to be transmitted on a relatively limited set of bandwidths and the same could be done
01:39:25 done for voice and for video using digital communication on the fire ground so there's greater flexibility and great greater ability to to offer multimedia contents
01:39:37 to offer multimedia contents right
01:39:37 right and at a paragraph 8.2.6 on the same page
01:39:42 page just about two-thirds of the way down your screen you say the digital format of these communications means that they can be routed over wired i.t networks as well as wireless infrastructures
01:39:54 well as wireless infrastructures is that the same thing as bandwidth maximization um
01:39:58 um it's more the case that
01:40:03 there are possibilities to use digital communication with the internet and with those forms of infrastructures which are well established for other forms of communication
01:40:16 and in the case of fire ground communication into the future we have to consider that the existing mobile telecommunications system and the existing infrastructure for
01:40:27 and the existing infrastructure for wider forms of telecommunication offer possibilities as backups to dedicated
01:40:35 dedicated service network communications and so forth so
01:40:39 forth so and
01:40:42 and even within the lfb's mobile digital terminal plans and so forth with the use of of 4g and then 5g applications as a way of routing this information
01:40:54 routing this information which of course with uhf you're communicating through radio signals from from
01:40:58 from handset to handset rather than using the possibility of wired infrastructure that exists for other reasons yes
01:41:06 given that uh um well let me ask you this is there a difference between broadband aggregation and the techniques that you've just been talking about i think broadband aggregation is one
01:41:18 i think broadband aggregation is one example
01:41:19 example what's an example of those wider possibilities given that that technology and i think you've referred to airway 4g max in your report yeah uh as one of those to exploit signal
01:41:30 as one of those to exploit signal strength yes from commercial operators given that that relies on commercial mobile operators what impact would that technology have on mobile phone users in the locality i think that's a that's a
01:41:42 the locality i think that's a that's a really excellent point and i think it's part of a much broader discussion both in the united kingdom and globally about what we can and can't do so
01:41:54 so for the for the chair um if we if we can use existing mobile infrastructure as a way of enhancing communication on the fire ground but as as the question
01:42:06 the fire ground but as as the question was suggesting that would have an impact on say fire survival guidance calls made by the public because any firefighter use of that infrastructure may limit the public's ability to to to access that
01:42:19 ability to to to access that within the uk we have different schemes that enable privileged access by fire and rescue services to the digital telephone networks but the consequences
01:42:30 telephone networks but the consequences of those of the scheme exists now is that it may turn off that system for the public which would be appropriate potentially in a counter-terrorism case but not necessarily or absolutely not in the case of a fire there are other
01:42:42 the case of a fire there are other schemes operated in the united states which are referenced in my report that still provide public access even though rescue services are given privileged access to that network
01:42:53 access to that network and to me that that is more flexible except in the case of a counter-terrorism scenario than the the uk's priority access schemes for existing telephone systems yes
01:43:05 existing telephone systems yes just finally i think you explained earlier that uhf radios only permit one party to transmit at any one given time and that others must wait for an opportunity to speak do airwave radios
01:43:17 opportunity to speak do airwave radios operate in the same way or differently it's much more flexible in terms of the digital uses of group communications but but
01:43:26 but the
01:43:27 the i come back to the point that i made before which is that although technically those kind of communications can be supported they're operationally not desirable because you you may effectively talk over a colleague trying
01:43:38 effectively talk over a colleague trying to relay an important message and so radio discipline is is as important in the operational use of airwave or the use of an airwave radio on the fire ground as it would be for any other
01:43:50 ground as it would be for any other communication yes thank you um thank you very much mr chairman is that a convenient moment for the break yes it's absolutely mr millet it is um and well as you know mr professor johnson we have a break during the
01:44:01 johnson we have a break during the morning and the afternoon sessions and we'll take our morning break now um we'll come back please at 20 to 12. and as with all the other witnesses i have to ask you please not to talk about
01:44:12 have to ask you please not to talk about your evidence to anyone while you're out of the room thank you all right thank you very much would you go to the usher
01:44:33 thank you 20 to 12.
02:02:27 would you ask professor johnson to come back in please okay
02:02:43 all right professor johnson ready to keep going yes thank you when you're ready thank you very much mr chairman mr professor uh i now want to turn to um the challenges posed by the firefighting context in in which
02:02:57 firefighting context in in which uh which which was posed by the fire on the night and start with congestion
02:03:03 first in the context of radio communications what do you mean by congestion congestion for me occurs when and as i've defined it in the report occurs when
02:03:14 occurs when people have important information to communicate but the channel is already being used by somebody else and therefore you have to delay your transmission in in deference to the other person completing
02:03:26 deference to the other person completing their transmission and not talking over them as we've described does it follow that in any large firefighting incident questions problems of congestion will arise
02:03:39 arise it
02:03:40 it i think
02:03:42 i think it does and i think that it should be anticipated and what practical impact does congestion have for radio users other than
02:03:53 than the obvious problems that you've identified already between speaker a and speaker b i think it's a
02:04:07 it introduces a myriad of problems beyond that that need to be thought through carefully in terms of the policies and practices of the organizations that make the communication during an emergency so a very specific example of when
02:04:19 so a very specific example of when congestion becomes particularly acute is where we have the blind spots if you like that are referred to in the national guidance and the for example the ba team can't
02:04:31 and the for example the ba team can't communicate for a period of time potentially finds out important information whether it be about a flammable atmosphere or whether it be about residents that need that need
02:04:42 about residents that need that need further assistance and because they can't communicate when they reach a place where the communication is restored for example by getting closer to colleagues they may be forced to wait and they'll have an
02:04:54 forced to wait and they'll have an increased amount of information to communicate to try and re-establish the situation awareness of their colleagues and so
02:05:01 and so the problems of congestion and interference that we'll describe i think in a second are exacerbated by the problems of lack of coverage right
02:05:11 right and you know at the heart of it may be that really important information is delayed waiting for less critical information to be to be communicated and the other point i would make as well is
02:05:22 the other point i would make as well is that these problems are exacerbated if you do not know that your message is being received by the intended recipient because you may then repeat your message to make absolutely sure that it's gone
02:05:33 to make absolutely sure that it's gone through even though you don't have the confidence that it's been received because you can't hear them you may be interfering or congesting the airwaves for other people now in section 6.5 i don't think we need
02:05:45 now in section 6.5 i don't think we need to turn it up but it's page 138 of your report you've i think explored the phase one evidence which tended to indicate that firefighters in the tower on the night were unable to transmit or hear anything on the uhf
02:05:57 to transmit or hear anything on the uhf radios
02:05:59 radios i i summarize your your your own observations on the evidence is it possible for congestion to block signals in this way or is that more likely to be the result of signal degradation or problems with
02:06:11 signal degradation or problems with radio propagation i think these are these are uh spectrum of issues that occur simultaneously and and so i mean conges as i described it before
02:06:22 conges as i described it before the
02:06:23 the the point-to-point communication between um
02:06:27 um barry sets within a group um it's typically one person is able to talk at any one time and so if that person is talking you you suffer from congestion because you have to wait for
02:06:38 congestion because you have to wait for that person to finish unless you want to talk over them within
02:06:43 within the half duplex setup that we described for repeaters and and leaky feeders that would still be the case with one person talking at any one time um does that does that answer your
02:06:54 um does that does that answer your question yes thank you now
02:06:56 now um uh
02:06:59 um uh can we go to page 46 of your report please and let's look together at section 3.5.4 you explain that having different radio channels for different aspects of an operation
02:07:11 operation can help reduce congestion um again it may sound like a simplistic question but can you just explain please why that why that is um as we saw in a previous diagram the
02:07:23 um as we saw in a previous diagram the intended architecture would be to have for example groups of co-workers using berry sets in one particular area of the building and then communicating with a colleague who
02:07:35 then communicating with a colleague who would then have their handheld more powerful radio to communicate for example to the bridgehead and there were other channels such as channel 3 that could be allocated to other work groups and that would not
02:07:46 other work groups and that would not interfere with the ba channel and that could be effective because the two groups are on different channels and therefore not interfering with each other because they can't hear each other while they well they work on potentially
02:07:58 while they well they work on potentially different tasks so in simple terms channels are effective at reducing congestion because they reduce the number of people wanting to transmit on any given channel yes
02:08:09 any given channel yes and what would happen if um somebody on one channel within one work group needed to communicate with somebody on another channel in a different work group they typically they would have to communicate with the coordinating officer as i
02:08:21 with the coordinating officer as i mentioned before who might be using their uhf radio depending on the context or they could change the channel off their radio but then that would that would remove them from contact with their colleagues and introduce new forms
02:08:32 their colleagues and introduce new forms of risk right so in theory you might have if you were a coordinator you might have to have both an airwave radio and a uhf radio i think yes i mean that but i think in in
02:08:43 in in practice we're really talking about the uhf they may have multiple uhf radios one which would be a personal radio one we could be communicating with the people on the on the ba radio or on channel three for instance but you'd
02:08:54 channel three for instance but you'd have to that coordinator wouldn't have to switch they couldn't use or they would have to change the channel on an individual radio exactly yes thank you now if we go to um the very foot of this page
02:09:07 the very foot of this page please
02:09:08 please you say at section 3.5.5 a list of the lfb's uhf channels and their uses is as follows and you've sat out at the foot of that page and onto page 47
02:09:20 of that page and onto page 47 the same list i think as in dominic ellis's witness statement which uh is already familiar to the panel
02:09:28 panel and to those who heard gary reason's evidence we looked at it with him and if we just put that up um briefly if we just scroll down to 47 page 47 and then on to page 48 we can
02:09:40 page 47 and then on to page 48 we can see the channels that are listed there that you've taken from the evidence and then if we go then to uh page 49
02:09:50 page 49 there's the diagram which we looked at earlier
02:09:53 earlier and that's a slightly different diagram but we can look at that um this is initial incident channel allocations which i think is taken from policy 488 lfbs policy 488 on incident communications
02:10:05 communications now rather than listing the available channels out aloud can i summarize them by reference to their usage perhaps and tell me if you disagree with anything i'm proposing
02:10:16 anything i'm proposing first incident command is this right that relied on channel one and you can see that from the pyramid based on the diagram or channel two as a backup with repeaters yes yes
02:10:27 backup with repeaters yes yes and then ba comms that happened on channel six or as a backup channel five uh with the use of repeaters you can see that from the ba cruise at the top of the diagram there running into the
02:10:38 the diagram there running into the burning house yes yes now although it's not on this diagram is it also right that there was a command unit for radio traffic which happened on
02:10:49 for radio traffic which happened on channel 10. i would have to check that i don't don't have the notes with me at the moment uh right um if we go to page 50 of your report the next page
02:11:03 look at figure 3.3 on that page this is channel 3 to reduce congestion on channels five and six detail there and i think we see there that channel
02:11:14 and i think we see there that channel three could be used for any other specific aspect or sector of an incident on the instruction of the incident commander or sector commander the case may be is that right yes yes and i think in later on in your report you say and
02:11:26 in later on in your report you say and just for our notes it's a page 149 section 6.8.9 that channel 3 was at times used to relay fsg fast survival guidance information at the
02:11:37 survival guidance information at the grenfell tower of fire yes it was now you've explained already how the power of a handset bears on its signal strength and the practical implications that might have for radio users
02:11:48 for radio users and you've explained in your report as we've seen that some of the lfb's uhf channels also impose limitations on the power of radio transmissions
02:12:00 transmissions yes yes yes now in the quotation that you've set out in your report um if we go to if we go to page 48 these back two pages um you
02:12:11 um you say
02:12:13 say uh oh we can see it it's not you but it's the quotation there that channel one
02:12:20 one is
02:12:22 is if you go to 3.5.6 at the top of the page
02:12:25 page channel one uh
02:12:27 uh is the only four watt channel and that most other channels operate at two watts except channel 6 which operates at 1 watt yes i'm summarizing but that's right isn't it yes
02:12:38 right isn't it yes what impact does a channel's transmitting power have on signal as as argued previously the higher the wattage in general the the the greater the distance the signal will travel and
02:12:50 the distance the signal will travel and the less signal localization there will be
02:12:53 be how does the transmitting power of a radio interact with the transmitting power of a channel a radio channel i think that the channel is purely an allocation of frequencies and so in general it shouldn't be that
02:13:04 and so in general it shouldn't be that the the power is determined more by the power of the handset rather than the channel itself although there may be there may be more detailed um issues that uh
02:13:13 that uh arise with frequency propagation but i don't think they're likely to be so important within this context i follow so just to use an example if a firefighter takes a handheld uhf radiator operating at 4 watts
02:13:25 radiator operating at 4 watts and uses that to send a message on channel 6 which is operating at 1 watt would that message be conveyed at 1 watt or at 4 watts i would believe it would be conveyed at 1 watt because that would be preset but
02:13:36 1 watt because that would be preset but i'm not 100 sure i think it would depend also on the devices that were being used right well sorry i'd just like to understand that please the the proposition is that the
02:13:48 the the proposition is that the radio operating at 4 watts transmits a message which is received albeit on channel 6 by a receiving station that is operating
02:13:59 by a receiving station that is operating at one watt i i would have assumed but i don't know much about this as you probably realized that the signal would be um sent at four watts
02:14:11 sent at four watts strength
02:14:12 strength and would be picked up by anyone within range of the 4 watt signal i think that it would be useful to have clarification of this from somebody within london fire brigade who understands how the handsets operate but my my
02:14:26 belief based on what i see in front of me is that the personal handheld radios operated routinely on all the channels at 4 watts and the ba equipment operated on the channel it was used at 1 watt
02:14:39 channel it was used at 1 watt so
02:14:41 so i would um i would be interested to know how the how the handsets attenuated the signal so in other words it looks it may well be that the handsets were designed designed to operate at a lower wattage
02:14:53 designed to operate at a lower wattage when assigned to those channels but i haven't seen any technical information on that to this point all right but uh are we right in understanding am i right
02:15:04 are we right in understanding am i right and understanding that when we talk about the wattage we're talking about the transmitting power yes not nothing to do with the receiver at all no nothing to do with the scene exactly and and similarly
02:15:15 and similarly nothing to do with the channel because the channel is a is simply a channel it's a method of allocation frequency it's not and doesn't determine
02:15:27 frequency it's not and doesn't determine power of transmission from this quote it looks to me as though the equipment is set so that the power of the transmission is reduced if it's set to a particular channel but as i said before this is the only quote that i've seen that makes that
02:15:39 that makes that makes that point well that's why i asked the question because it rather suggests that the channel has a transmitting power
02:15:47 power and you think you say that's not the case no i think that would be set within the device that would then transmit a lower power power if it was using those channels yes thank you sorry to intervene again but again
02:15:57 again i had understood that when we use the word channel we are actually just using a shorthand for frequency yes yes and each of these channels is a transmission at a different frequency yes that's
02:16:10 at a different frequency yes that's right that's right that's right well then help me when it says there is considerably lower power on channel six uh this is and this is a quotation from mr ellis's um witness statement but he's
02:16:22 mr ellis's um witness statement but he's i think quoting um from what he understands to be the home office regulation when he says there is considerably lower power on channel six the ba channel what does that mean
02:16:34 what does that mean i think
02:16:36 i think i i think this quotation needs further analysis
02:16:39 analysis i'm not comfortable
02:16:43 in the sense that i personally up until this point believed that the channels that were operating in other words that the devices were set as a particular wattage
02:16:55 devices were set as a particular wattage um and that the handheld radios operated on four watts irrespective of the channel
02:17:02 however that this quotation seems to be inconsistent with that with that belief and that it may be that the handheld radios that were capable of operating at 4 watts were in some way reduced to two watts if
02:17:14 were in some way reduced to two watts if a particular channel was selected i haven't seen that in any of the guidance right apart from this quotation coming back to your point about the channel six and the ba i mean that's
02:17:25 channel six and the ba i mean that's simply to say that the it's not it's not the channel that's that that's at that wattage it's the devices that operate on that frequency are only transmitting at one watt um as
02:17:37 are only transmitting at one watt um as we've suggested previously yes
02:17:41 yes i mean
02:17:44 i mean standing back and using your expertise as a as a an information technology scientist does it make sense to say that channel 6 has any power lower or higher than anything else not to me no
02:17:57 than anything else not to me no uh
02:17:58 uh now
02:18:00 now well would it follow from that that in fact
02:18:03 fact what is happening as you've seen it is that there are different channels signifying different frequencies and the lfb have made a decision as to what
02:18:14 as to what handsets or ba sets with different wattages will be allocated to each exactly thank you now um
02:18:21 um you
02:18:23 you um
02:18:27 yes but the same problem may may um
02:18:31 may um be identified elsewhere uh
02:18:35 uh perhaps you can help us with this can we go please to mr ellis's statement to the police this is at met triple zero seven seven eight three nine at page nine and let's look at the
02:18:46 at page nine and let's look at the second paragraph down uh
02:18:50 uh uh in light of what you've just told us i just
02:18:55 i just want to put this to you he says in that second paragraph this the reasons why the channels other than one and six are two what are somewhat difficult to explain this was the transmitting power of the
02:19:06 was the transmitting power of the channels of the maxon radio hx480 stroke one's predecessor and it is assumed that this was due to battery power as the higher the wattage the greater the draw on the battery the
02:19:18 greater the draw on the battery the reasons that the 480 stroke 81 used the same power outputs even though the batteries had improved was probably because it was not considered at the time that a greater output was required however lfp
02:19:30 output was required however lfp personnel who worked in this area have since retired as this was 12 years ago now um
02:19:38 are you eight first are you able to help us with whether the lfb would have been able to change the wattage of its channels
02:19:44 channels as is
02:19:45 as is suggested there
02:19:50 i i come back to the explanation offered by the chair which is which is my view too that the channels are simply allocations of frequency and that the and as you suggested yourself that the
02:20:01 and as you suggested yourself that the lfb made a decision of what power of devices would be available to transmit on those particular channels and that they're saying here that the decision to use at two watts on those
02:20:12 decision to use at two watts on those particular channels is for historical reasons based on the amount of battery power that it's that would otherwise have been needed to increase the wattage yes so it makes no sense to speak of transmitting power of the
02:20:24 speak of transmitting power of the channels
02:20:25 channels no not tommy radio no not to me now
02:20:30 now uh if we then go please to page 48 of your report
02:20:37 uh and look at paragraph
02:20:41 paragraph 3.5.8
02:20:46 um you can see there that you say the lfb had access underlined to channels four seven and eight at the time of the grenfell tower fire however they had not made it their practice to use these channels for additional capacity at the time of the
02:20:57 additional capacity at the time of the fire
02:21:01 and if we go on to 3.5.9 it says this opportunities were missed to increase the capacity and resilience of fire ground communications through the use of these channels which are now being used in particular channels four and seven
02:21:12 in particular channels four and seven and then you quote from mr ellis's statement again um uh could you explain to us briefly why you've reached that view opportunities were missed well
02:21:23 opportunities were missed well um
02:21:25 um if we take channel seven that was used for interoperability with um the police for example they they had just made the move
02:21:35 move operationally to airwave and weren't using uhf
02:21:38 using uhf um in the same way that they had been and so channel 7 was effectively vacant at that point because of the mps use of the use of airwave
02:21:50 and it had been freed for frs use
02:21:55 frs use but
02:21:56 but as as
02:21:59 as as argued previously well i think there's a there's a bigger context to all of this discussion if we if we look at the la canal house fire and the coroner's decision or coroner's recommendation that uh additional channels may have
02:22:11 that uh additional channels may have helped
02:22:12 helped in reducing congestion which is the context to this the statement i then make that additional channels may have helped reduce congestion is based on that argument from the from the coroner
02:22:24 argument from the from the coroner however later in the report i also make the
02:22:26 the the the balancing point that as i said before today that any change in channel for example where we were discussing channel 3 which is used in an ad hoc way sometimes for working groups
02:22:39 sometimes for working groups and the people moving to that channel would then no longer hear things on the other channels that they had previously been on and so there are opportunities to reduce congestion in the same way that the coroner had advised or
02:22:50 that the coroner had advised or recommended be considered in the aftermath of the previous tragedy um but then that would have created a greater need for coordination and coherency
02:23:01 coherency of communication on the fire ground yes
02:23:06 yes so
02:23:06 so can we summarize it that if did by using additional radio channels um in addition to those which were were used that would that might have had an adverse impact on the communications
02:23:18 adverse impact on the communications in the absence of somebody that he was able to coordinate and command i think an early decision should have been made to appoint a communications officer who would have been able to supported by appropriate
02:23:30 supported by appropriate policy and pre-incident training who would have been able to coordinate some of these decisions yes i see
02:23:38 yes i see um gary reason uh assistant commissioner reason told the inquiry that he thought channel 4 one of those three that you've identified was not used in the in this way because of
02:23:50 not used in the in this way because of the potential for interference with channel 6 the ba channel the default ba channel and and suggested that that was a feature of the radio spectrum which was set by a government department
02:24:01 government department and therefore something which the lfb could not overcome or mitigate in any way
02:24:05 way is that right i think it's entirely plausible and i've seen i've seen that evidence however
02:24:12 however i think that if
02:24:20 viewed in the light of what we know subsequently which of course makes it difficult to to to to know the force of the argument i think if people had gone back to the home office and made this point then the
02:24:31 home office and made this point then the channels could have been reallocated in a more
02:24:34 a more you know in a better way to maximize the the potential for the use of the different
02:24:39 different frequencies um but it from this perspective i i uh
02:24:46 uh it's it's very difficult for me to to without doing more empirical tests to actually know whether that assertion is true or not it's believable very you know very believable that you could have that kind of interference
02:24:57 that kind of interference um because two channels are an adjacent frequency spectrum right i mean are you aware of any ways of overcoming or mitigating that interference um
02:25:06 um by reallocating the channels so that they could be used i mean
02:25:15 i've i think that um
02:25:20 while that might be true for example of channel 4 then it may not also be true of channel seven and eight so the general point i think still holds that channels could have been used in different ways to support the operational requirements on the night of
02:25:32 operational requirements on the night of the fire
02:25:33 the fire but again
02:25:34 but again a proper safety assessment and a consideration of the transition between channels at key points in the fire and the coordination of that and communication of that i think is is
02:25:47 communication of that i think is is is essential and i i struggled in the existing evidence that i've seen to really know how that process was coordinated yes which is why i think the firefighters felt so
02:25:58 felt so it felt so unconnected if you like from other people in terms of the communication they received you said to paragraph 3.5.6 on the screen in front of you that proposals had been made within the
02:26:10 that proposals had been made within the lfb to consider a distinct channel dedicated for communications during high-rise incidents and you cite from the draft lfp powerpoint at lfb triple
02:26:21 the draft lfp powerpoint at lfb triple zero three zero one seven one from december 2014 uh and uh you um you
02:26:32 you which wasn't actioned i should add um
02:26:35 um and others may recall in fact a powerpoint which described this new channel which was explored in his evidence with mr reason uh and he said that he hadn't been made aware of that idea
02:26:46 aware of that idea um staying with the topic of additional radio channels you then i think go on to say at page 77
02:26:55 um if we look at section
02:26:59 section 4.13.1 there under the heading congestion and channel allocation the coroner that's the latino house coroner the coroner was concerned that some of the communications problems
02:27:10 some of the communications problems experienced by the barry cruz were due to congestion which might have been reduced by the provision of additional channels
02:27:16 channels her rule 43 letter therefore made the following recommendation to the lfb and you set it out there and um
02:27:24 and um you then i think go on at page 79 to set out the lfb's response to the coroner
02:27:31 coroner at paragraph 4.13.10
02:27:36 and over to page 80
02:27:40 which is where one finds it and uh if we go back to page 79
02:27:49 um you can see the lfp's most recent position on this issue
02:27:56 and the um uh the section it's a long passage and it starts at present the brigade has the capability to use multiple radio
02:28:07 the capability to use multiple radio channels
02:28:08 channels uh and uh if you pick it up uh at um
02:28:13 uh at um this third paragraph down in that it says the use of the it says the since the latino house fire the brigade has introduced a ba telemetry capability which has reduced the amount of ba radio
02:28:25 which has reduced the amount of ba radio communication which has required incidents this has been achieved through the use of new ba entry control boards which allow for a greater degree of automated monitoring and supervision of ba wearers the result that entry control officers
02:28:36 the result that entry control officers no longer need to check gauge readings with wearers by radio this new technology is therefore further increased capacity when using a single ba radio channel and reduce the risk of congestion in summary having carefully
02:28:48 congestion in summary having carefully considered the recommendation to brigade is firmly of the view that the risks associated with using more than one ba channel during an incident would outweigh the benefits that this operational practice would afford
02:29:02 now what is your understanding of the risks associated to crews ba or otherwise of using more than one radio channel at a significant incident well i think we've we've rehearsed them
02:29:14 well i think we've we've rehearsed them and it's already in a sense in the policy because of the possibility of moving to uhf communication um if ba sets were unavailable and as i said before some of the crews went in
02:29:26 said before some of the crews went in without without not be asex barry sets and some of the crews went in without battery sets so in that case you would automatically be changing channel yes as i understand it
02:29:36 i've been careful in the report not to try and present the panacea to these issues but to try and point out where i think
02:29:47 but to try and point out where i think the complexities and contradictions lie in the existing policy and i
02:29:53 and i i think that the coroner's point which possibly wasn't addressed here is that there is an issue of scale in the sense that having a single um channel for ba
02:30:05 having a single um channel for ba communication makes perfect sense while the number of people trying to use that channel is below a threshold but once it exceeds that threshold and those people are in a relatively confined space
02:30:16 are in a relatively confined space the channel can become ineffective because so many people are trying to use a scarce resource and also
02:30:24 and also as is frequent in the evidence that's been presented to the inquiry there's a tendency to rely on congestion rather than power and coverage yes and i and i feel that again
02:30:37 coverage yes and i and i feel that again as i mentioned before if if these lower powered radio systems are lack coverage then there's immediately a communications overhead when people try to come back into contact and relay all
02:30:50 to come back into contact and relay all of the information that they've received so it
02:30:53 so it i understand and i and i value the argument that's made here but there's a level of detail and complexity below it that i think needs to be explored in order to convince me
02:31:05 to be explored in order to convince me that it's safe in general for large-scale high-rise fires now what i read you was the brigade's response to the coroner's recommendations if we go to page 80 and
02:31:18 recommendations if we go to page 80 and look at 4.13.10 you say many of these same arguments about congestion have been reiterated in the aftermath of the grenfell tower fire and then
02:31:28 and then you
02:31:29 you can see in the second paragraph there you pick up the recommendation made by the coroner a consideration of in the second line whether it would be beneficial to consider the use of additional ba and personal radio channels at major
02:31:41 personal radio channels at major incidents
02:31:42 incidents and then it goes on to say the brigade concluded at that time that the risks associated with using more than one ba radio channel during an incident would outweigh the benefits that this operational practice would afford and
02:31:53 operational practice would afford and maintains a similar position at this time and you'll see footnote 155 links down if we can just scroll down please on page 80 to the bottom of the page
02:32:05 page to footnote 155 lfb grenfell tower improvement progress report at lfb triple zero six seven seven eight four so that's the brigade's position post grenfell
02:32:18 post grenfell um that conclusion is is the lfb's position post grenfell as well as pre-grenfell as we now see um what are your what are your views about that um
02:32:31 i i think that there is a greater need as i said this morning to go back and start examining from first principles the extent and reliability of radio coverage
02:32:42 extent and reliability of radio coverage uhf radio coverage in high-rise buildings
02:32:45 buildings i understand many of the arguments that have been made are valid but they don't address all of the complexities that arise in operational incidents
02:32:56 operational incidents and in particular i think
02:32:59 i think the previous incidents that i've noted in my report going back through 7 7 9 11 the
02:33:04 the uh you know the um king's cross etc whereas a huge amount of of
02:33:11 of of information has been gathered these these scenarios should be used to test these argue arguments um and i think again you know that the
02:33:23 the some of the questions that were asked to me about the construction of the buildings or the meteorology effect meteorological effects on the propagation of radio signals are areas that need to be researched
02:33:35 that need to be researched i mean not just for the sake of research but if people are to make an argument that this is a valid way of maintaining the safety of building occupants and the fire services then i think it needs to be based on evidence rather than on
02:33:46 be based on evidence rather than on assertion which often
02:33:48 often seems to me that that's really what's being used here given what you have seen in the evidence about the experience of communications on the far ground on the night of the grenfell tower fire
02:34:01 on the night of the grenfell tower fire do you consider that the conclusion that the lfb is maintaining a similar position at this time as cited here is justified
02:34:11 i would i would certainly my feeling is that it's not backed by sufficient evidence and i would i would question
02:34:22 and i would i would question it as a continued stance for an operation in the future that had the same characteristics as grenfell i i it may indeed be justified but i see i would like operational evidence and and
02:34:35 operational evidence and and evidence from drills and scientific experiments to give me any confidence that that could be upheld i mean i think what what's really important to me is that we've got two counter examples in
02:34:46 that we've got two counter examples in terms of what happened in latin latino hall and what happened in grenfell and so in order for this i i accept what they're saying but i would like to know what evidence they would base that on
02:34:58 would base that on so by counter examples do you mean cases
02:35:03 cases which would challenge the conclusion stated there yes i mean i think in both cases it's clear that the channels became congested and i and i i have said that what i've
02:35:16 and i and i i have said that what i've set out if you like what i believe the reasons for that to be partly to do with low power partly to do with the building construction but also to do and as acknowledged by lfb the number of firefighters deployed
02:35:28 number of firefighters deployed but that's not that that's i believe that we could conceive of many future incidents hopefully not but but future incidents in which similar problems might arise and we need a
02:35:40 problems might arise and we need a solution to simply say that people should be
02:35:44 should be more disciplined in their use of a radio to me
02:35:47 to me is not is not sufficient or not or not something that i would want people to place their lives on so how i feel about it can i ask you to go back a page please to page 79. let's
02:35:59 go back a page please to page 79. let's look at
02:36:00 look at a very
02:36:01 a very um a very slightly earlier passage at section 4.13.9
02:36:11 uh and you say the response ignored the fact that both channels five and six were intended to support ba crews depending on whether leaky feeders and radio repeaters were deployed and the firefighters might be using both at
02:36:22 the firefighters might be using both at the same time if the transition were not coordinated and then there's the passage i've read part of which i've read to you can i just ask you to explain what you mean when you say that the lfb's response ignored the potential use of
02:36:33 response ignored the potential use of channels five and six to support ba crews i think i've this is it's a refinement of the point that we made earlier on which is which is that you know
02:36:43 you know if you deploy these additional equip pieces of equipment to extend the range of the signals and people don't know that that's happened then especially because the reason you deployed them was that people
02:36:54 reason you deployed them was that people were not communicating how would they know then to transition to the new channel they would effectively be isolated and and when they did come back into range
02:37:05 range of their colleagues would not be able to communicate with them so it's again it's this issue of trying to trying to work through the nuances that that persuade me and other people that these are safe procedures yes
02:37:17 these are safe procedures yes and on the question of nuances let's just pick this up at page 150 of your report
02:37:23 report section 6.8.12 150 where you say there in order to move channel there must be an initial approval from the commanding officer and then coordination through
02:37:35 officer and then coordination through the designated communications officer otherwise some team members will not be made aware of the channel change and will therefore become isolated does that mean that in a nutshell um unless firefighters are told about the
02:37:47 unless firefighters are told about the move they may find themselves without any communications yes yes
02:37:51 yes yes now let's look then at lfb's policy 488 on internet communications um it's at lfb 50736
02:38:04 we saw it referred to in
02:38:08 in one of the diagrams and there it is reviewed as current 25th of may 2016. if we can go and if we can go please to page three halfway down the page you can see that uh section five of this
02:38:20 you can see that uh section five of this poly policy covers channel three uh
02:38:25 uh and if you look at 5.5
02:38:29 it says ensure that crews are aware that they must return to channel 1 following completion of the task now
02:38:37 now it says that in relation to that channel uh
02:38:42 uh it doesn't seem to be an instruction which is general looking at this policy um to what in extent uh if at all would that type of instruction alleviate your concerns
02:38:53 instruction alleviate your concerns about possible firefighter isolation
02:38:57 not at all i think that for the very very trivial example would be when is the task completed and how do you communicate that
02:39:13 i think the other examples i've cited of previous fires have illustrated that the the very real confusion that arises so
02:39:23 so for example there was one of the uh the hartfordshire fire and rescue service in reported where firefighters fatalities were sustained because the channels weren't adequately agreed at the start of the incident but i mean
02:39:34 of the incident but i mean here is
02:39:35 here is a is a another complexity in terms of coordinating right um i think in the in the under operational circumstances it might
02:39:46 under operational circumstances it might be very difficult to ensure that people did that at the same time and went back but you know i i think um there is a general problem i think which is how would you respond when you feel that communications have failed how do
02:39:58 that communications have failed how do you how do you re-establish communication not just with individuals but across the fire ground and you are you aware of any other ways in which the risk of isolation by moving channels could be mitigated
02:40:12 i i um
02:40:16 um i think there's again i've tried in the report to avoid saying this is how it could be solved but to point out that there is a need for a more sustained view and a sustained
02:40:27 more sustained view and a sustained argument about why existing provision or any future provision is safe and by exposing it to these arguments which are based on real experience for example with grenfell tower to really
02:40:38 example with grenfell tower to really see how these scenarios would be dealt with in detail in the recovery from a loss of communication there are plenty of ways in which we we could hypothesize that these things
02:40:49 we could hypothesize that these things could be dealt with but they need they also need to retain
02:40:54 retain a view of the digital fire ground in the future because i think many of the problems that arose here could be solved with with new forms of technology that are being experimented with in
02:41:06 that are being experimented with in other parts of the world but part of the problem here would be by relying on voice communication if you miss that voice communication you automatically use available bandwidth and saying what did you say what's what
02:41:17 and saying what did you say what's what channel are we on to kind of reconfirm that previous thing and i think it would some of this information would be better uh using data or a text-based system or something like that where people could
02:41:29 something like that where people could could get could get that information without commit without building up the the communication channel in other words voice communication is extremely inefficient at doing something like this
02:41:42 is there any role for radio operators in manually relaying messages across radio channels i say is there was there on the night as far as i'm aware individual um
02:41:53 as far as i'm aware individual um officers played that role but in a in a less formal role in a way was just purely fulfilling the operational duties that they had based on the diagrams that you saw previously
02:42:04 on the diagrams that you saw previously but but there are numerous examples of people repeating questions multiple times five or six times and not getting a reply or you know not knowing whether or not they've been heard at all
02:42:16 they've been heard at all i'd like to ask you a little bit more about congestion comparing uhf on the one on the one hand with airwave on the other can we look please at page 219 of your report at section 8.10
02:42:31 you say congestion remained a concern with airwave as the heading and then the subheading at 8.10.1 congestion was still an issue for airwave users on the night of the fire
02:42:43 airwave users on the night of the fire and if you go well
02:42:46 well as a preliminary question when it comes to the question of radio capacity and the problem about congestion is there any difference between a uhf radio and a digital airwave radio
02:42:57 digital airwave radio um
02:42:58 um as i mentioned before uhf in the simplex or peer-to-peer form between two handsets is highly constrained to one person communicating at any one time
02:43:10 person communicating at any one time that you can hear on the on that channel um with airwaves those limitations are are not there
02:43:19 but there are other forms of limitation which is that the these infrastructure that communicates the airwave signals has it has a capacity and so if large numbers of people are
02:43:31 and so if large numbers of people are communicating over a wide range of torque groups at some point that capacity is exceeded just because the infrastructure can't cope with it a bit like trying to get a a mobile telephone message on new year's
02:43:42 a mobile telephone message on new year's eve at midnight everyone i think has experienced that kind of delay whether the infrastructure is overloaded and even with more advanced architectures that's likely to be the case in something like grenfell tower
02:43:53 case in something like grenfell tower because
02:43:54 because so many people want to use the existing communications infrastructure in the case of airwaves with more dedicated systems that's not competing for public use but some of the issues of 4g and 5g i've mentioned before in that respect
02:44:07 i've mentioned before in that respect the other thing i would say as well is that
02:44:10 that there is a role for radio discipline in this and
02:44:14 this and as i've said later on in the report i think some of the airwave issues may simply have arisen because a small number of people were responsible for receiving the messages and they'd been communicating with others at the time of
02:44:25 communicating with others at the time of which people were trying to communicate with them so and as you say in your report at 8.10.2 on page 220 uh i don't think there's a need to go to it but you say airwave talk groups would be capable
02:44:36 say airwave talk groups would be capable of addressing the problem of congestion adequately yes could you just explain very briefly why you've come to that view well talk talk groups are analogous to channels in the sense it with airwave
02:44:49 to channels in the sense it with airwave and but much larger numbers can be set up because it's a digital medium and part of the hesitancy for london fire brigade using airwave in an operational context is that
02:45:02 context is that what they don't know that they question whether it would be efficient or reliable to set up a large number of talk groups on the scene of an incident to support all the different communication needs whereas with uhf you
02:45:14 communication needs whereas with uhf you have a very you know relatively small number of well-known channels and people should agree and understand on what they are the flexibility of airwaves if you like gives them more pause for thought would people create airwaves in an ad
02:45:25 would people create airwaves in an ad hoc way
02:45:27 hoc way and i understand that argument but i also would point to the metropolitan police service and the london ambulance service use of airwave and in the report i mentioned they have significant operational experience of
02:45:39 significant operational experience of setting up these talk groups to manage operational incidents um
02:45:44 um i hope that answers your question yes now um
02:45:49 now um yes
02:45:50 yes let's then look next at the impact of high-rise building materials on communications we'll come back to the use of airwave later uh can we go please first to page 56 of
02:46:01 uh can we go please first to page 56 of your report at section 4.3
02:46:05 and there you set out national guidance and reviews and some extracts from that at the time of the fire which i think confirmed that high-rise incidents may give rise to communications difficulties
02:46:16 difficulties yes yes so this was a no known as it were yes yes looking at gra 3.2 that you've set out at section 4.3.2 of your report in brief
02:46:29 at section 4.3.2 of your report in brief there
02:46:30 there you you can see that it says a high-rise incidence may create difficulties with lines of communication and radio reception the scene of operations may be a considerable distance from the access level and point
02:46:41 distance from the access level and point of command building construction may cause radio reception blind spots and affect radio based breathing apparatus telemetry systems uh now
02:46:53 uh if we go
02:46:56 if we go to
02:46:57 to um
02:46:58 um paragraph uh well let's go to a document nfb double zero one one zero six five four
02:47:06 four i will come back to the report in just a moment but i just want to show you an email internally within the lfb in february 2013 it's from jim a court
02:47:18 it's from jim a court to tim cut bill the 28th of february 2013 which we've seen with uh other witnesses particularly uh with ac gary reason and if you look at the third bullet
02:47:29 and if you look at the third bullet point down there it says this totally unobstructed lfb incident ground radios will transmit and receive clearly over a distance of more than 500 meters
02:47:41 more than 500 meters first do you have any view about whether that statement is accurate or not it seems very plausible to me so in theory is it right that uhf signals would be capable of traveling up a number of flaws in a high-rise
02:47:52 up a number of flaws in a high-rise block
02:47:53 block that's a different question so
02:47:56 so let's break it up but the distance of 500 meters which i think you said is reasonable would that be horizontal or could it be vertical it could be um it could be vertical but the question is
02:48:07 could be vertical but the question is totally unobstructed the caveat goes yes i see
02:48:11 i see uh
02:48:12 uh so
02:48:13 so uh
02:48:14 uh in the uh looking at lacking house which is of course the context in which this email was generated as you can see from the first paragraph uh the the weasel words there or the key
02:48:25 uh the the weasel words there or the key words perhaps are totally unobstructed in fact i think you're saying that that would never be the case with a high-rise building where you're seeking to transmit vertically yeah yes now let's go then back to your report
02:48:37 now let's go then back to your report at section 6.6.4 on page 142 page 142
02:48:42 page 142 and you say there
02:48:46 the barry communication system was in my view never designed to support incidents within a high-rise building where many users were in close proximity to each other and was some distance away from the bridgehead stroke ba communications
02:48:58 the bridgehead stroke ba communications operator see figure 5.5 c in previous section of my report which we looked at which provides an indication of the lfb's intended scale of battery usage
02:49:09 lfb's intended scale of battery usage now you mentioned the distance from the bridge head there how did that specifically influence the conclusion that you've reached i think that
02:49:23 the within that that point there are two issues one is the issue of congestion as we've described previously just the large numbers of people trying to communicate on the same channel
02:49:34 communicate on the same channel and then um the
02:49:37 the building material as you as you alluded to
02:49:41 to um
02:49:42 um creates problems of attenuation and signal loss um
02:49:47 um which
02:49:48 which combined with the lower powered signal strength of the barrier sets i think um you know
02:49:54 you know to me it's a
02:49:57 it's a situation where i would i think
02:50:01 i think the arguments that have been made for example in the coroner's court after la canal
02:50:07 canal about the
02:50:08 about the the use of repeaters and leaky feeders i think
02:50:13 i think those arguments are made in in in recognition of this argument which is that uh the longer the distance is between the bridgehead and and the and the ba crews
02:50:25 the ba crews um the more likely it is that communication will fail and that's because of a combination of distance
02:50:32 distance as a result of low wattage yes and obstruction yes before you even consider congestion yes and the impact of of things like
02:50:45 yes and the impact of of things like fire and any firefighting activities that generate large amounts of vapor for instance that we've mentioned before will attenuate the signal yes now in stating your conclusion here uh you've
02:50:56 stating your conclusion here uh you've referred to paragraph figure 5.5 c which i think you we saw earlier let's just go back to that if we may it's a page 119.
02:51:06 page 119. before we do can i just clarify one thing um do you remember a little early you were asked about the figure of 500 meters totally unobstructed for the range of what was described as an incident ground
02:51:19 what was described as an incident ground radio
02:51:20 radio we talking there about the handheld radios transmitting at four watts that's my interpretation of that statement yes right yeah do you have any idea of the range of a barrier set
02:51:32 idea of the range of a barrier set transmitting at one watt i this is part of the need for empirical evidence and if we come back as well to the to the series of questions that were made earlier this morning about battery
02:51:43 made earlier this morning about battery power i think that's germain here too so while while the transmission may be received at one point in the incident is that is that sustained through prolonged use for example
02:51:56 through prolonged use for example well that i can see but how about the range of the one what barry said i
02:52:02 i would anticipate it's significantly lower than the 500 meters but i i again would really welcome more empirical work on that and i haven't seen
02:52:11 seen that level of detail in the evidence presented so far to me all right thank you i'm sorry to interrupt you mr miller but it seemed to me a relevant question if we're talking about radios being used within the building yes where some were very and
02:52:23 building yes where some were very and some were not indeed yes indeed
02:52:27 indeed can i just comment on that as well because very very often what i see coming out um not just from this incident but from other incidents is a as a blank or a bold statement that the equipment functioned as intended
02:52:39 equipment functioned as intended and that to me doesn't give me that kind of level of granularity so when i say there needs to be better standards of investigation of incidents of this so i think those answers should should be
02:52:50 think those answers should should be asked for i think they're really important
02:52:53 important thank you
02:52:58 can we then look in in light of that particularly at figure 5.5 point c which you've referred to in paragraph 6.6.4 there on page 142 and 5.5 point c
02:53:10 6.6.4 there on page 142 and 5.5 point c is at page 119 we looked at it before briefly and you've entitled it selected communications architectures from pn uh
02:53:21 uh 466 which we looked at also yeah and you say that it provides little guidance on the factors that should influence a decision to withdraw in the event of communications failures but what i want
02:53:32 communications failures but what i want to ask you about is this what is it about that diagram that led you to the conclusion that barry sets were not designed for high-rising incidents high-rise incidents like grenfell tower i think there's an assumption that the
02:53:43 i think there's an assumption that the communications with the communication operators will be reliable and certainly the witness statements make it clear that many of the firefighters felt that those communication infrastructures
02:53:54 that those communication infrastructures were no longer sustained and therefore the information that the firefighters tried to relay as they went deeper into the tower no longer went back to the operations commander and then
02:54:05 and then by a consequence of that i think it's very difficult for the operations commander and for other key decision makers to retain a fully accurate position as to what was going on inside the tower
02:54:16 the tower there are too many people i think the scale this a part of what you were commenting to i think in the previous paragraph of my report is that it would be a useful exercise to compare
02:54:27 it would be a useful exercise to compare this with what actually was the scene and the scale of people involved during the night of the incident yeah um yes
02:54:35 yes now can we go back to page 56 of your report
02:54:39 report which we were looking at before
02:54:42 uh in the context of the contents of gra 3.2
02:54:49 3.2 and we looked at where it says as you've quoted the building construction may cause radio reception blind spots and effect radio based breathing apparatus telemetry systems you see that
02:55:01 you see that um with that in mind can we then turn to page 80 of your report and look at section 4.14
02:55:09 which is where you we find your discussion of the role of construction materials in more detail with particular reference to reports produced by the lfb following the latin house fire and if we look at page 81 specifically
02:55:22 and if we look at page 81 specifically paragraph 4.14.3 there's a long quotation there uh from
02:55:30 uh from appendix 63 which is the lack of report operational response of the lfb which is at lfb 3041759
02:55:42 and if you look at the third paragraph of that which is the one below the bullet points
02:55:48 um it it which starts when propagating radio waves if you look at the fifth line down it says this buildings which have a significant thickness sick of concrete or large
02:56:00 thickness sick of concrete or large amounts of metal used in their construction may significantly attenuate the signal concrete floors within buildings are often poured onto a metal pan which can completely block most radio signals some solid foam insulation
02:56:12 radio signals some solid foam insulation and some fiberglass insulation materials used in a building's exterior walls have foil backing which will reduce signals further energy efficient windows and metal window screens also form very
02:56:23 metal window screens also form very effective barriers to radio signals now first do you agree or do you disagree with what is what i've read out to you there definitely agree you agree are you aware of any other building materials which
02:56:35 of any other building materials which can impact will have an adverse effect on radio signals and their propagation exterior cladding exterior cladding that's quite a broad uh yes as i understand i'm not an expert
02:56:47 uh yes as i understand i'm not an expert on exterior cladding but i have to deal with that i have seen it mentioned in reports previously that has been a factor in radio propagation i can't tell you anything about the actual radio characteristics of of what was involved in granville but
02:57:00 of what was involved in granville but those that involve metal composites for example
02:57:03 example are often identified as affecting radio signals
02:57:07 signals involving metal well metal metal involved in their construction i don't know so would that be
02:57:14 be um the metal fixings and perhaps an aluminium rain or other metal rain screen out of skin i the kind of comments that i've seen have been pretty greenful and in this
02:57:26 have been pretty greenful and in this kind of level of detail so but again i i add that to my list of concerns about the measurement or pre-site inspections for radio signals within high-rise
02:57:37 for radio signals within high-rise buildings
02:57:38 buildings i think there are many individual variables that could contribute to an accurate assessment of the risk to communication created by the structure of the building
02:57:49 created by the structure of the building when you say um
02:57:53 um pre-site inspections do you mean um gathering of information under section seven seven two two d of the fra 2004 yeah you do um now this report as
02:58:04 2004 yeah you do um now this report as you can see mentioned could i sorry could i just pick up on that point because i think it's important i don't think that that should every every inspection should involve that but certainly over a particular height or occupancy
02:58:15 height or occupancy or or if a building was regarded as a high-risk prima facie then i don't think it would be disproportionate to ask more detailed questions that might affect communication
02:58:26 communication if i'm sorry to interrupt it i just feel that's an important point thank you absolutely i'm looking back at um the text here you can see that there's a reference to significant thickness or large amounts
02:58:38 large amounts um of these materials does it follow to the best of your understanding doing the best you can with this text that the thicker the layer of the material the more likely it will
02:58:48 will obstruct or degrade a radio signal i think
02:58:53 i think as
02:58:54 as as i mentioned before with 72d i i think that there is a need to base 72d on some empirical evidence about this again i think it's such an important issue and there's evidence of
02:59:05 issue and there's evidence of communication failures in so many large incidents previously that have not been collected consistently into a single corpus if you like the people could say this is a major problem because it was at lake and hall house it was in surety
02:59:18 at lake and hall house it was in surety tower as it was in so many previous incidents
02:59:21 incidents that it deserves an empirical basis on which to answer your question my my my
02:59:29 my my my my
02:59:31 my opinion
02:59:32 opinion um is that it would be
02:59:35 and when you say empirical evidence um do i take it do you mean tests on materials taken both alone and in in
02:59:45 and in in coordination with other materials making up for example a cladding system yes and also with the sensitivity to the construction techniques used by different buildings because with our
02:59:56 different buildings because with our with the estate even within a mile of here we'll see many different types of building with many different internal properties that would affect radio propagation and
03:00:07 and i i think given that many of those buildings also have ord entries that we may be discussed later on i think that for some of them that pose high risk it would be
03:00:18 that pose high risk it would be appropriate to do more detailed on-site testing to provide evidence of assertions about radio communications issues especially if intrinsically safe devices are to continue to be used
03:00:32 and would it follow in general terms
03:00:36 that an accumulation of materials for example a number of of concrete floors perhaps with a metal panel with rebar would also have an increasing impact on signal propagation
03:00:47 increasing impact on signal propagation yes yes
03:00:48 yes yes now let's look at the role of those problems we've identified thus far at grenfell itself and the post excuse me the post fire testing of those communication systems
03:00:59 testing of those communication systems um
03:01:00 um can we go please to page 141 of your report to start with and let's look together at section 6.6.1
03:01:10 and your conclusion i think there is that the communications problems experienced by the ba teams were caused by systemic interactions between when you set out three things
03:01:21 you set out three things one
03:01:22 one signal localization from lower powered is radios two the problems of limited signal propagation in high-rise concrete buildings as the teams moved to the upper floors and further away from entry
03:01:33 upper floors and further away from entry control and three congestion stroke interference between large numbers of firefighters in close proximity now looking at that would i be right to think that it's also your view that the
03:01:44 think that it's also your view that the lfb has incorrectly attributed the problems experienced on the night of the fire
03:01:50 fire solely or almost solely to congestion yes yes
03:01:54 yes yes and if we go to page 160 of your report please at section 6.14
03:02:05 you can see under the heading radio communications tests in grenfell tower post-incident tests in grenfell tower appear to have caused the lfb to focus on congestion stroke interference rather than the
03:02:17 stroke interference rather than the limited power of the is barry sets and there's a a text set out there
03:02:24 and uh if you
03:02:28 if you uh
03:02:30 uh look at the last paragraph in the text which is taken from the
03:02:36 the lfb grenfell tower improvement progress report page 38 as you can see from footnote 331 which is not on your screen but but don't don't worry about that it says the brigade has conducted
03:02:48 it says the brigade has conducted testing at grenfell tower since the fire which indicated that ba communications issues were predominantly caused by the volume of radio traffic but accepts that the tests confirmed some very limited
03:02:59 the tests confirmed some very limited signal propagation issues associated with channel 6 used for ba communications now i think you've examined haven't you the methodology behind those tests yes and you've examined their results too
03:03:12 and you've examined their results too and you set out those results in two tables in your report let's look at the first of those it's on page 161 if we turn the page at table 6.1 as we can see there
03:03:23 as we can see there and
03:03:24 and am i right in thinking that's the testing of the incident command uhf channels channels one and two yes yes and if we look at the table we can see from the top row that you've set out
03:03:35 from the top row that you've set out the test number condition which i think is the nature of the test conducted yes yes and then the result which as i understand it is taken directly from the nfb's documentation in
03:03:47 directly from the nfb's documentation in each case yes now let's look at each row in term first which is the first row of the table channel one um that was tested within the inner corner and atrium of grenfell tower and the messages were found to be
03:03:59 tower and the messages were found to be quotes clearly audible without signal loss
03:04:02 loss as we can see yes
03:04:06 yes and if you look at the second row as for messages sent on channel one from a radio placed in the same location as the first command unit cu-8 and received by other radios with within
03:04:17 and received by other radios with within the inner corner and atrium of grenfell tower those communications were described as possible yes yes yes um just pausing there were you able to infer anything about the quality of the
03:04:28 infer anything about the quality of the radio communication um from what you saw of these tests no and
03:04:33 and um you have the literal verbatim i think here from the original right
03:04:40 right but having studied the methodology and the then the results as stated could you tell anything about the quality of it no indication no and again in the report obviously i think that having a standard methodology and a more systematic
03:04:52 methodology and a more systematic approach that could be repeated built into building i think would help significantly in generalizing the insights from this fire if we look at the third row we could see that the same test was
03:05:04 we could see that the same test was repeated with a channel two using leaky feeders and radio repeaters uh and the messages were there described as being quotes clearly audible without signal loss yes
03:05:15 signal loss yes and in the fourth row channel one there are two twos i think because one is a repetition of the other but the fourth one being on number three channel one was tested with transmissions from the bridgehead locations
03:05:27 bridgehead locations which was uh floor zero two four and seven
03:05:30 seven of the tower to all higher floors and you can see that it was noted there that when the transmitting radio was at floor zero
03:05:38 zero there were various issues with transmission being received on floor 7 10 23 in the roof yes yes are you able to infer anything from the presence of those problems
03:05:50 those problems identified by the lfb here almost nothing right now you go on at page 162 if we can turn the page please to section 6.4 6.14.4
03:06:02 to note uh if you look at that paragraph there the nfb's testing results documents sorry document notes the findings from an additional test on uhf handheld radios
03:06:14 radios uh
03:06:15 uh uh with and i'm summarizing um the transmitting radio being established at floor 11
03:06:21 floor 11 and that test resulted i think in clear messages being received on all higher floors is that a fair summary yes yes um so that's uh table 6.1 let's look at table 6.2 a little bit lower down the
03:06:34 table 6.2 a little bit lower down the same page
03:06:35 same page there it is it's paragraph 6.14.6
03:06:40 and you've set out there the results of the testing of the barrie radio sets yes uh uh
03:06:46 yes uh uh first is it right that those radios were only tested inside the tower rather than outside the tower or the surrounding area as far as i know and looking at the first row of that table you can see the results for the testing of channel six
03:06:57 results for the testing of channel six as between the bridge head locations and all channel floors although i think the roof wasn't tested it again you can see that it's noted that where the transmitting radio is at floor zero
03:07:08 zero there were problems with transmissions being received on floors 13 and uh up to 16. yes and we have to pay 10 i think to page 163 for that we could just flip to page 163 and make that clear you can see
03:07:20 page 163 and make that clear you can see that floor 16 slight signal loss roof level not tested
03:07:27 now uh
03:07:30 as with channel 1 testing are you able to infer anything from the presence of those problems identified by the lfb there no
03:07:37 there no looking at the second row we can go back a page please to page 162 the foot of the page we can we can see um
03:07:47 um that uh
03:07:49 that uh i call it the second row it's actually it's it's called row three if you go back to page one six three
03:07:57 this is channel two yeah um
03:08:02 if you look at that that's again i think tests between the bridgehead locations and all the higher floors just as a clarification point channel two i think was a backup incident command channel rather than a ba channel
03:08:13 command channel rather than a ba channel specifically allocated yes yes yes yes now we looked earlier in your evidence um at the fact that channel 2 was set to 2 watts as we saw and required radio repeaters and leaky
03:08:25 and required radio repeaters and leaky feeders
03:08:26 feeders in the test we can see described here at row 3 channel two yes
03:08:34 yes it looks as if this repeater was deployed at the command unit's location rather than in the building yes um would it be right then to say that this test was seeking to replicate the impact of a fixed appliance repeater rather than the
03:08:46 fixed appliance repeater rather than the impact of a of portable repeaters that's my that's my interpretation of this yes now the results of channel 2 testing within the tower um say this channel 2 transmission and reception was intermittent when leaving
03:08:58 reception was intermittent when leaving the atrium and proceeding within the central stairwell of the building up until reaching floor three from floor three communication was possible from within flats but broken within the central stair core of the building
03:09:11 central stair core of the building are you able to infer anything from that finding
03:09:14 finding no
03:09:17 no and if we go on to page or back to page 160
03:09:21 160 and look at section 6.14.1 again
03:09:26 uh we looked at this a moment ago where we saw in the last paragraph in the quotation under that paragraph the view of the lfb uh that the communications problems on the night
03:09:37 communications problems on the night were predominantly caused by the volume of radio traffic having looked at what you've looked at and having now looked at the tests are you able to shed any light on why it is or how it is that the lfb was able to
03:09:48 or how it is that the lfb was able to come to that conclusion
03:09:53 i i think that they paid insufficient attention in reaching that conclusion to the caveats that were raised by their own people conducting the tests about the reliability of the
03:10:04 the tests about the reliability of the tests
03:10:05 tests and also by the evidence of commissioner dobson to the leckenhall hall fire
03:10:12 fire to the coroner in terms of the reliability of these kinds of tests yes well i think we'll come to that perhaps after the break at some stage but uh we will do but um
03:10:24 but uh we will do but um you're not able to tell and
03:10:27 and let me put something to you it's right i think that the lfb's tests had no introduced element of congestion no so they were demonstrating instances of poor reception at grenfell tower even in a congestion-free environment exactly
03:10:39 a congestion-free environment exactly right
03:10:42 now let's look at page 163 and continue with this that paragraph six point eighteen point six point fourteen point eight you say this however the lfb's post incident review of radio communications
03:10:54 incident review of radio communications had a number of important limitations and we can we can see those identified five-fold um first of all the lack of any communi any confirmation that meteorological
03:11:06 confirmation that meteorological conditions was similar to those on the night of the fire that's the first one second is uh is the deployment of radio repeaters as part of the tests when they weren't successfully deployed on the night
03:11:18 deployed on the night yes yes i'm so sorry to do this to you but when you nod if you would say yes oh i'm really sorry i'm so sorry i normally give witnesses a bit of training when they first come into the witness box and i felt afraid i
03:11:29 into the witness box and i felt afraid i failed to do that i apologize uh but if you no if you not or shake your head it doesn't go into the trend of course i apologize sorry it's quite all right it's my fault i'm still learning so
03:11:40 it's my fault i'm still learning so that's the second one the third i think is the difference um between the towers materials during the fire as compared with how the materials stood after the fire when the
03:11:52 materials stood after the fire when the testing took place yes yes the the fourth is the failure to replicate or account for any interference caused by other radio or or mobile telecommunication systems yes and
03:12:03 mobile telecommunication systems yes and i think the fifth one is the inability to replicate the effect of the fire itself
03:12:07 itself which would have an influence but we don't quite know how yet because science isn't sufficiently developed yes now to some extent those limitations are highlighted i think in documents accompanying the testing results and i
03:12:18 accompanying the testing results and i if you go to page 164 we'll see how you deal with that you say this at section 6.14.9
03:12:28 and you say
03:12:31 the nfp's reporting if it's pasted incident testing notes a number of caveats and restrictions associated with the methodology for post-incident tests are set up below particular attention should be paid to the second paragraph
03:12:44 should be paid to the second paragraph uh and in the second paragraph there's some underlining and it says the information uh
03:12:50 uh contained within this document and subsequent test results should not be read as taken and taken as a true and accurate reflection of how lfb radio communications performed during the incident and that underlining is in the
03:13:03 incident and that underlining is in the original document no that's my answer that's yours is it yes it says emphasis added in parentheses at the voice bottom right i think it's it's articulated in a different paragraph apologies um
03:13:14 in a different paragraph apologies um now um it goes on to say tests are being carried out at a time when the fabric of the building has significantly altered from that encountered at the outset of the original incident certain structural elements are no longer present and significant amounts of the building
03:13:26 significant amounts of the building covering an internal fabric and now missing all of which combined with the prevailing conditions both outside and inside the building together with the high number of users may have affected sick the ability of personnel to send
03:13:38 sick the ability of personnel to send and receive messages via incident ground radio systems and again this is a extract
03:13:46 extract from the post-incident testing methodology uh now in the light of the limitations that you've identified those five we saw a moment ago and this passage by the lfb
03:13:57 a moment ago and this passage by the lfb itself
03:13:58 itself how reliable do you consider the lfb's testing results to be purely indicative and not reliable in terms of the argument that's presented
03:14:07 presented and when you say purely indicative can you just explain what that means i think they provide an impression of what they found on a particular day that doesn't replicate in in almost every respect
03:14:19 replicate in in almost every respect what was actually experienced on the night of the fire now can we go back to page 82 of your report please
03:14:29 where you say this at section 4.14.4
03:14:35 you say the system the systematic analysis of interactions between building construction signal localization interference and congestion during the lack of house fire and the grenfell tower fire provides a more
03:14:47 grenfell tower fire provides a more convincing explanation of ba communications failure in high-rise concrete buildings rather than an explanation focusing narrowly on the number of ba crews committed now that conclusion is as you put it
03:14:59 now that conclusion is as you put it expressed as a more convincing explanation what is your opinion when considered on the balance of probabilities more likely than not i i strongly believe this
03:15:10 than not i i strongly believe this assertion rather than one that is purely based on congestion and i i would evidence that by the national gr 3.2 policy that says you have to be aware of blind spots in communication in
03:15:21 aware of blind spots in communication in high-rise buildings which is not not mentioned in the previous quote from the post-incident review and then what you've seen professor do you consider
03:15:33 you've seen professor do you consider the materials on grenfell tower uh
03:15:38 uh were more likely than not to have played a
03:15:42 a relevant part in signal propagation problems experienced on the night of the fire yes
03:15:46 fire yes yes
03:15:48 yes and so what is your overall view about the lfps conclusion that the communications problems on the night of the fire can be predominantly attributed to congestion or the number of radio messages being sent
03:15:59 of radio messages being sent i think it provides at the very best the partial explanation of the problems that were experienced and if any attempt is to make that to be a substantive argument then there needs to
03:16:10 substantive argument then there needs to be additional evidence provided um
03:16:14 um and you've seen none i've not seen any that would convince me that that alone was the explanation
03:16:26 and would that explain why uh
03:16:31 uh the failure by the lfb to mention congestion issues uh and focusing on well let me ask you this different way can we look at the um
03:16:42 this different way can we look at the um we look at the uh
03:16:45 uh lfbs 2019 review this is lfb double zero one zero five four six six that's the document your
03:16:56 that's the document your you've expressed a view about review of the specification for fire ground and breathing apparatus radios dated the 29th of october 2019 uh and and
03:17:08 uh and and if we then look at page 165 of your report
03:17:16 you say this at section 6.15.2
03:17:25 uh you uh you say uh in contrast lfb's review of its specification for fire ground and breathing apparatus radios dated october 2019 focuses exclusively on radio power
03:17:36 2019 focuses exclusively on radio power issues and does not mention the impact of congestion this is despite power issues having been largely disregarded by the lfb as a potential explanation for the communication problems
03:17:47 for the communication problems experienced on the night of the fire now can you just explain why that's significant i just felt that there was a a tension at the very best between
03:17:58 at the very best between a focus on congestion being an explanation for communication problems and yet the specification documents looking um on radio power
03:18:09 documents looking um on radio power issues rather than on congestion um
03:18:14 and have you seen anything to resolve that tension in every anything you've seen it remains a question in my mind as to what the balance is between those two issues and what going forward is the is the
03:18:26 the is the principal means of avoiding that this doesn't happen again
03:18:34 and if you look uh a little bit lower down the same page
03:18:38 page at section 6.15.4 on the screen and i should just point out this is under the general heading at 6 15 lessons learned you say neither of these responses
03:18:50 you say neither of these responses adopts the systemic view i have advocated throughout this report for the following reasons uh and when you say that the approach to its specification
03:19:01 its specification fails to adopt a systemic view could you just explain to us what you mean by that i think
03:19:07 i think that
03:19:11 as i've tried to argue that the the devices whether they're intrinsically safe or not and which channel allocations you use or not
03:19:21 not raise different issues in in different benefits in different ways and that the policies have to be tailored to the characteristics of the devices that are present and then the
03:19:32 devices that are present and then the difficult questions that arise from your choice of specification and need to be addressed and either through training for instance or in the case of the building
03:19:43 or in the case of the building construction through through more rigorous and methodological on-site inspections to prepare people for communication phases so if
03:19:51 if if you were to argue that an intrinsically safe device has significant benefits for the use of firefighting in high-rise buildings which is a reasonable argument
03:20:04 buildings which is a reasonable argument um you then need to deal with what mitigations would you put into place when large numbers of firefighters enter that building on the same channel and are working in close proximity
03:20:17 what would happen if you allow backup channels
03:20:20 channels or alternative channels as was the coroner's suggestion in the previous incident how do you then deal with firefighters potentially becoming isolated because they were on a previous channel rather than the one that you're
03:20:31 channel rather than the one that you're moving to and so forth so
03:20:35 so if all you do is focus on intrinsic safety
03:20:39 safety then i think and say these devices are safe because they're intrinsically safe and the only problems arise through users not not obeying radio discipline etc i think that that that shows a
03:20:51 i think that that that shows a huge misappreciation of the problems that were experienced by the firefighters on the night of this fire
03:20:58 professor thank you very much mr chairman is that a convenient moment yes thank you very much it is well professor johnson we will all get a break now so we can have some lunch we'll resume
03:21:09 we can have some lunch we'll resume please at two o'clock and as before please don't discuss your evidence or anything relating to it with anyone over the break okay all right thank you thank you very much would you give the usher then please
03:21:31 thank you very much two o'clock then please
03:21:59 you