Chapter 85: The expert evidence

¶85.1 In making our findings on the circumstances surrounding the deaths of those who lost their lives in the Grenfell Tower fire we have drawn heavily on the evidence of a number of eminent experts in a variety of fields. Their evidence may be conveniently described under the following headings: a.

The recovery and identification of the remains

¶of the deceased. b. The determination of the medical cause of death. c. The effects of the smoke and gases produced by the fire.

¶The recovery and identification of the remains

¶85.2 In respect of each deceased person the coroner, Professor Wilcox, issued an interim certificate of the fact of death pursuant to regulation 9 of the Coroners (Investigations) Regulations 2013. She was able to do so because she was satisfied in each case that the remains in question were those of the particular deceased. That resolves conclusively the doubts that at one time were aired about how many people died in the fire and who they were. However, we think it appropriate to describe in general terms the careful and painstaking process by which the remains of those who died were recovered and their identities confirmed. The procedure adopted followed the guidance contained in the Disaster Victim Identification (DVI) Guide published by Interpol in 2014, which set the standards for the identification of victims of disasters and was used in conjunction with protocols developed by the archaeologists and anthropologists working with police officers trained in identifying victims of disasters.³³ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/13}; Harrison {Day302/18:5}-{Day302/19:3}; {KHA00000001/3} page 3, paragraphs 9-12; Harrison {Day302/12:18}; {Day302/19:4}; {Day302/19:21} -{Day302/20:7}.

The recovery of human remains

¶85.3 The task of recovering the human remains was led by Dr Karl Harrison MSc PhD DSc, the lead forensic archaeologist. Dr Harrison had 20 years' experience as an expert forensic archaeologist, including working on police investigations.⁴⁴ Harrison {KHA00000001/1} page 1, paragraphs 1 - 4. Together with Dr Deborah Ryder PhD, he co-ordinated a team of 36 forensic archaeologists with expertise in the identification of human remains.⁵⁵ Harrison {KHA00000001/2} page 2, paragraphs 5, 6 and 8. Archaeologists were attached to teams instructed to search individual flats, each of which was treated as a closed fire scene to prevent the mixing of debris and to maximise the opportunity to identify any human remains.⁶⁶ Harrison {Day302/11:4}. Those search teams included DVI officers and licensed search officers (LSOs). It was the responsibility of the DVI officers to maintain the continuity of the evidential chain in order to minimise the possibility of a fragment of human remains being missed or wrongly attributed. The LSOs had a more general search function.⁷⁷ Harrison {Day302/15:8} -{Day302/17:1}.

¶85.4 Forensic archaeologists arrived at the tower on Friday 16 June 2017 and carried out their work over the next five months.⁸⁸ Harrison {KHA00000001/1} page 1, paragraph 5. They worked in different places at different times in response to the requirements of the police.⁹⁹ Harrison {Day302/9:23}. Dr Harrison divided the work of his team between June and December 2017 into three phases,¹⁰¹⁰ Harrison {KHA00000001/3} page 3, paragraph 7 and Table 1; Harrison {Day302/21:3}. the first two of which concentrated on those flats which were thought likely to contain human remains.¹¹¹¹ Harrison {Day302/22:2} {Day302/23:10}.

¶85.5 The first phase, which began on 16 June 2017 at a time when the team of archaeologists was smaller and the number of deceased was still unknown, had four elements. The first involved a visual assessment of the flats that were suspected to contain human remains. The search teams noted the significant volume of debris in those flats and assessed the challenges to the recovery and recording of human remains. The fragility of the remains that were visible led to a decision to search the debris in each flat in situ rather than remove it to another site. That avoided the risk of damaging the remains or mixing them up in circumstances where more than one person had died in a relatively small space.¹²¹² Harrison {KHA00000001/4} page 4, paragraph 15; {KHA00000001/5} page 5, paragraph 17; Harrison {Day302/23:13}-{Day302/27:24}.

¶85.6 The second element was the early development of search strategies. Given the extensive fire damage to the flats, with internal walls almost entirely destroyed, each flat to be searched was divided into sectors. It was decided at the outset that all spaces within the tower that had been destroyed by fire would be searched to the same extent.¹³¹³ Harrison {KHA00000001/5} page 5, paragraph 18; {KHA00000001/6} page 6, paragraph 20; Harrison {Day302/21:1}-{Day302/34:23}.

¶85.7 The third element took place on 15 and 16 June 2017 and before archaeologists had become involved in searching the tower's interior. Archaeologists assisted officers using victim recovery dogs to search the base of the tower and the area around it for human remains, since it was known at that stage that at least one person had fallen from the building.¹⁴¹⁴ Harrison {KHA00000001/6} page 6, paragraph 21; Harrison {Day302/34:25}-{Day302/37:9}. At that time the area remained under the control of the LFB and debris was still falling.

¶85.8 The fourth and final element of the initial phase also began on 16 June 2017. That was the recovery of visible remains from flats and bodies from the communal areas and the stairwell. That operation was undertaken at a time when the authorities were still responding to an emergency and the debris in the flats remained hot enough to present a risk of re-ignition. The structural integrity of the tower was also being assessed at that time, which required additional safety measures, including a limit on the number of people entering a flat at any one time. In the circumstances, emphasis was placed on the speed of recovery.¹⁵¹⁵ Harrison {KHA00000001/8} page 8, paragraph 23; {KHA00000001/9} page 9, paragraph 25; Harrison {Day302/37:10}-{Day302/41:3}.

¶85.9 The initial phase allowed areas of particular interest to be identified. They included flats where fragments of human remains might be found because people had been reported as missing or witnesses believed they had seen people at the windows, even if there was no obvious sign of remains.¹⁶¹⁶ Harrison {KHA00000001/9} page 9, paragraph 27. Acrow props were installed in flats to maintain structural stability. That made it necessary to move debris, which, wherever possible, was retained in the sector in which it had been found. If it was necessary to move debris out of a sector, it was not moved beyond the flat or lobby in which it had originated.¹⁷¹⁷ Harrison {KHA00000001/9} page 9, paragraph 28; Harrison {Day302/43:6} -{Day302/48:13}.

¶85.10 The second phase involved the careful excavation of debris to preserve any remains, which could then be lifted out. The debris was then left in situ. A record was made of the location of remains as well as of the position of any fixtures and fittings. Personal effects such as jewellery were recovered.¹⁸¹⁸ Harrison {KHA00000001/9} page 10, paragraph 29; {KHA00000001/12} page 12, paragraph 36; {Day302/50:21}-{Day302/53:25}.

¶85.11 The third phase began in August and continued until November 2017. It involved the comprehensive searching and sieving of the debris in all areas which had been subjected to burning to recover any other human remains, to identify and retain any material that might assist in understanding the spread of the fire and fire protection within flats and in identifying individuals, and to locate valuable or sentimental items, which could then be returned to the family.¹⁹¹⁹ Harrison {KHA00000001/12} page 12, paragraph 37; Harrison {Day302/62:3}.

¶85.12 The stairwell, part of the flats from floor 4 to floor 9 and all flats and lobbies from floor 10 to floor 23 were searched sector by sector. All debris in those areas of the tower was searched by hand by teams of DVI officers and LSOs led by a team leader and under the supervision of an archaeologist. Sieved material was bagged. The DVI officers and LSOs were given training in advance in recognising burnt bone, but the supervising archaeologist made a second check of any material that might be fragments of bone or tissue. In that way, any human remains as well as other items of potential significance, such as personal effects, medical implants or identification documents, were located and retained.²⁰²⁰ Harrison {KHA00000001/12} page 12, paragraph 37; {KHA00000001/17} page 17, paragraph 45; Harrison {Day302/55:2}-{Day302/57:24}; {Day302/59:5}; {Day302/62:13}-{Day302/57:24}; {Day302/64:17}.

¶85.13 A quality assurance process was adopted through the introduction in search areas of a foreign control object. There were no occasions on which a DVI or LSO team failed to find that object.²¹²¹ Harrison {KHA00000001/19} page 19, paragraphs 47-48; Harrison {Day302/72:1}-{Day302/73:23}. A system was put in place to ensure that all the debris had been searched and sieved and then retained in labelled bags. Each searched area went through two inspection stages. The second stage required an inspection panel comprising Dr Harrison or Dr Ryder as the lead archaeologist, the DVI co-ordinator, and the Scene Evidence and Recovery Manager to certify that all required steps had been taken.²²²² Harrison {KHA00000001/19} page 19, paragraph 49; {KHA00000001/20} page 20, paragraph 51; Harrison {Day302/68:21}-{Day302/71:15}; {Day302/78:1}-{Day302/80:25}.

¶85.14 Once a certificate had been issued, the bagged debris was removed from the tower so that no extraneous material was left in the flat.²³²³ Harrison {KHA00000001/20} page 20, paragraph 52.

¶85.15 In accordance with DVI protocols, when human remains were located, they were given a Unique Reference Number (URN) and placed in a sealed bag before being taken under secure conditions from the site of recovery to a holding area and then to the Westminster mortuary. The steps involved in this process were documented. A parallel system was followed in relation to items recovered from the building, such as identification documents and valuables, all of which were handed over to an exhibits officer.²⁴²⁴ Harrison {KHA00000001/39} page 39, paragraphs 87-91.

¶85.16 Following arrival at the mortuary, each bag was scanned and a preliminary assessment of the remains carried out.²⁵²⁵ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/68}; {GMK00000001/15-16}. Forensic pathologists conducted an initial post mortem examination, which was attended by forensic anthropologists when necessary.²⁶²⁶ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/16}.

¶85.17 Dr Gaille MacKinnon, BA MSc MCIfA FRAI (ChFA) was a director of Alecto Forensic Services Ltd with over 24 years' experience, including working on major terrorist incidents.²⁷²⁷ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/85-87}. She led the team of forensic anthropologists instructed to identify the human remains recovered from the tower.²⁸²⁸ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/20}.

¶85.18 Working with DVI-trained police officers, forensic pathologists and experts in DNA analysis, forensic odontology (a branch of forensic science that assists with identification of remains through the examination of dental records and dental remains) and fingerprints,²⁹²⁹ MacKinnon {Day298/65:22}‑{Day298/66:22-1}; {Day298/71:10-23}; MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/15}. the role of Dr MacKinnon's team was to construct a biological profile for each victim.³⁰³⁰ MacKinnon {Day298/63:9-14}. Following the initial post mortem examinations, they conducted a detailed anthropological examination of each of the 17 separate locations in the tower from which remains had been recovered, working on each flat or communal space separately.³¹³¹ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/16}.

¶85.19 The remains were carefully documented, mapped and reconstructed, if possible.³²³² MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/28}. An individual biological profile was constructed according to internationally recognised standards accepted in the wider scientific community.³³³³ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/34}. It included looking at age at death, sex, ancestry and any features or variations that differ from one person to another.³⁴³⁴ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {Day298/63:9-14}; MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/35}; {GMK00000001/37}.

¶85.20 The purpose of the anthropological examinations was to ensure that all human remains were attributed to the individual deceased to whom they belonged.³⁵³⁵ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/38}; {GMK00000001/41}. A particular challenge was the commingling of remains where a number of victims had died in the same location. That challenge was met by using standard operating procedures and by undertaking examinations of each flat or communal space individually.³⁶³⁶ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/21} Dr MacKinnon's team worked alongside experts in DNA analysis (which could be used to confirm identification)³⁷³⁷ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {Day298/82:22-25}; MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/23-24}. and odontology.³⁸³⁸ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/21-22}.

¶85.21 On completion of the forensic anthropology and odontology examinations for each deceased recovered from a particular flat or communal space, the human remains and documentation were reviewed in a procedure called "Anthropology Grand Rounds" involving Professor Wilcox, Detective Chief Inspector Andrew Chalmers (Deputy Senior Investigating Officer and Scene Senior Identification Manager), the Post Mortem Coordinator, Andrew Langley (Operational Forensic Manager (OFM), Metropolitan Police Service), and the lead anthropologists and odontologists.³⁹³⁹ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/42}.

¶85.22 Dr MacKinnon confirmed that, based on her examination and having regard to the rigour with which the recoveries and clearance of the flats had been undertaken, she was very confident that the remains of all the victims had been recovered and correctly identified.⁴⁰⁴⁰ MacKinnon {Day298/90:5-14}; {Day298/77:7-6}; {Day298/78:5-6}; {Day298/124:16-25}; {Day 298/125:4-10}.

¶85.23 The information reviewed during the Anthropology Grand Rounds procedure informed the deliberations of the Identification Commission, conducted under the direction of Professor Wilcox.⁴¹⁴¹ MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/18}. The identification of an individual deceased also drew upon other sources including comparative DNA and odontology.⁴²⁴² MacKinnon, Summary of the Forensic Anthropology Examination and Reporting Process {GMK00000001/22}. At the Identification Commission, Professor Wilcox reached a final decision on the identity of the deceased whose remains had been recovered from the tower.

The medical cause of death

¶85.24 We have already referred to the involvement of forensic pathologists. Dr Ashley Fegan‑Earl BSc (Hons) MB BS DMJ(Path) FRCPath FFFLM RCPathME led a team of 12 Home Office registered forensic pathologists who conducted post mortems on those who died in the fire and provided an opinion on the medical cause of death.⁴³⁴³ Fegan-Earl {AWF00000001/2} page 2; Fegan-Earl {Day298/19:17-21}-{Day298/27:16}.

¶85.25 Dr Fegan-Earl explained that although the work of experts in other disciplines could assist in determining the cause of death, it was for the pathologist, as the registered medical practitioner, to certify the medical cause of death.⁴⁴⁴⁴ Fegan-Earl {Day298/42:14}-{Day298/43:2}. The certification system uses a form which has two parts. The first gives the primary cause of death, which can be subdivided into two, Ia and Ib. For example, a doctor might record cardio-respiratory arrest as cause Ia and carbon monoxide poisoning as cause Ib, thereby indicating that cardio-respiratory arrest was due to carbon monoxide poisoning. Part II is used to record conditions that may have contributed to death, for example, heart disease.⁴⁵⁴⁵ Fegan-Earl {Day298/43:3-23}.

¶85.26 The destructive nature of the fire meant that a full post mortem was not possible in every case. Where a full post mortem could be conducted, a toxicology examination to ascertain whether there was carbon monoxide in the blood and an histology examination to ascertain whether there was soot in the airways was also undertaken, where possible. However, if a deceased's body had been subject to extensive heat damage, a full post mortem was not possible.⁴⁶⁴⁶ Fegan-Earl {AWF00000001/2} page 2; {AWF00000001/3} page 3; Fegan-Earl {Day298/25:11}-{Day298/40:25}.

¶85.27 The results of the post mortems were reviewed by other members of the team.⁴⁷⁴⁷ Fegan-Earl {Day298/28:8}. The medical cause of death for many of those who died as a result of the fire was recorded as "Inhalation of fire fumes", "Inhalation of the products of combustion" or "Consistent with the effects of fire". Dr Fegan-Earl explained that the first two were essentially the same and had been used where there was pathological evidence to show that the deceased had inhaled fire fumes.⁴⁸⁴⁸ Fegan-Earl {Day298/46:142}-{Day298/47:8}. The third formulation had been adopted where it had not been possible to conduct a full post mortem.⁴⁹⁴⁹ Fegan-Earl {AWF00000001/4-5} pages 4-5; Fegan-Earl {Day298/44:15}-{Day298/46:5}.

¶85.28 Dr Fegan-Earl agreed with Professor Purser's opinion that those who died in the tower had very probably been rendered unconscious by inhalation of poisonous gases, including carbon monoxide and hydrogen cyanide. One possible description of the cause of death, therefore, was inhalation of asphyxiant gases. In his opinion it was overwhelmingly likely that the deaths were the result of the inhalation of fire fumes rather than burning.⁵⁰⁵⁰ Fegan-Earl {AWF00000001/4} page 4; Fegan-Earl {Day 280/49:2}-{day298/51:3}. Nonetheless, while not disputing Professor Purser's opinion, Dr Fegan-Earl maintained that it was appropriate to use the expression "Consistent with the effects of fire" as the medical cause of death if it was not possible to confirm with certainty that the death was caused by inhalation of asphyxiant gases, although that conclusion might be strongly supported by scientific evidence and pathological experience.⁵¹⁵¹ Fegan-Earl {Day298/51:5}-{Day298/52:11}.

¶85.29 We have given careful consideration to the evidence of Dr Fegan-Earl and understand why he and his colleagues felt the need to show caution when ascertaining the medical cause of death. We keep in mind that it will be for the coroner to decide what to find as the cause of death in each case. However, as Dr Fegan-Earl acknowledged, we have the benefit of the evidence of a range of witnesses, including the expert evidence of Professor Purser. It is because of that additional evidence, and in particular the work done by Professor Purser, that we have reached the conclusion that, save for those who fell from the tower, we can safely find that death was due in each case to the inhalation of asphyxiant gases.

The analysis and conclusions of Professor Purser

¶85.30 Professor David Purser CBE BSc PhD DipRCPath was instructed to give expert evidence on toxicology. In broad terms, he considered the causes of the incapacitation and death of those who died in the tower,⁵²⁵² Purser, Phase 2 Report, Sections 1-4 {DAPR0000005}; Purser, Phase 2 Report, Section 5 {DAPR0000011}; Purser, Phase 2 Report, Section 6 {DAPR0000006}; Purser, Phase 2 Report, Appendix A {DAPR0000007}; Purser, Phase 2 Report, Appendix B {DAPR0000008}; Purser, Phase 2 Report, Appendix C {DAPR0000009}; Purser, Phase 2 Report, Appendix D {DAPR0000010}. building on the preliminary conclusions he had reached in the report he provided for Phase 1.⁵³⁵³ Purser {Day296/4:13-17}; {Day296/5:12-15}.

¶85.31 We found Professor Purser's evidence helpful and it has informed our findings about the individual deceased in the following chapters. Having considered his evidence, we regard him as a reliable expert on whose evidence we can rely in drawing conclusions about the circumstances of the individual deaths.

¶85.32 Professor Purser's expertise includes the physiological effects on the human body of the inhalation of toxic smoke and gases.⁵⁴⁵⁴ Purser {Day296/11:25}-{Day296/12:4}. At the time he gave evidence, he was a visiting professor in the Centre for Fire and Hazards Science at the University of Central Lancashire.⁵⁵⁵⁵ Purser {Day296/12:11-15}. His extensive experience is described in his report. He has wide practical experience of investigating the effects of major fires in this country and abroad, including taking part in an investigation by the French authorities into a fire inside the Mont Blanc tunnel.⁵⁶⁵⁶ Purser, Phase 2 Report, Appendix D {DAPR0000010/5]; Purser {Day296/15:2-13}.

¶85.33 In order to reach a conclusion on the cause of the incapacitation and death of each deceased,⁵⁷⁵⁷ Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/64-103}; Purser, Phase 2 Report, Appendix A {DAPR0000007}. Professor Purser examined the changing conditions in the flats, lobbies and stairs throughout the night of the fire, relying on medical records of survivors, transcripts of emergency calls, photographs of the exterior of the tower, the evidence of other experts and the chairman's findings in the Phase 1 report.⁵⁸⁵⁸ Purser {Day296/40:18}-{Day296/41:5}.

¶85.34 To estimate the exposure of an individual to irritant smoke and its effect Professor Purser estimated the fuel load and range of materials involved in the fire to calculate the average composition of the asphyxiant gases entering the tower. For that purpose he relied upon a study published by BRE in March 2003 entitled The potential for including fire chemistry and toxicity in fire safety engineering⁵⁹⁵⁹ {DAP00000002}. which contained the results of two experiments measuring yield and concentrations of various gases produced when certain products were burned.⁶⁰⁶⁰ Purser {Day296/47:3}-{Day296/49:7}. He also relied on tests carried out by Professor Anna Stec⁶¹⁶¹ Stec, Assessment of the toxicity and extent of penetration of smoke from combustible products on the Grenfell Tower Report {AASR0000010}. to determine the composition of smoke particulates and the yield of toxic gases obtained from burning samples taken from Grenfell Tower itself.⁶²⁶² Purser {Day296/49:15}-{Day296/50:8}. Professor Purser used descriptions given by witnesses of conditions in the tower and medical records of survivors to estimate the extent of smoke obscuration and irritancy.⁶³⁶³ Purser {Day296/50:11-16}.

¶85.35 The mechanism of death from exposure to asphyxiant gases is twofold: first, the carbon monoxide bonds with haemoglobin to form carboxyhaemoglobin.⁶⁴⁶⁴ Purser {Day296/168:22}-{Day296/169:5}. That prevents the haemoglobin from carrying oxygen⁶⁵⁶⁵ Purser {Day296/167:15-21}. which deprives the brain and heart of oxygen.⁶⁶⁶⁶ Purser {Day296/168:5-21}. Second, the carboxyhaemoglobin impairs the ability of the rest of the haemoglobin to deliver oxygen to tissues.⁶⁷⁶⁷ Purser {Day296/169:6-14}. Ultimately that causes a lack of oxygen to the heart and brain.⁶⁸⁶⁸ Purser {Day296/168:22}-{Day296:169:5}. Cyanide also prevents the tissues from metabolising.⁶⁹⁶⁹ Purser {Day296/169:10-15}. Both can cause hypoxia.⁷⁰⁷⁰ Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/107}. He agreed that in describing the cause of death, the effect of carbon monoxide in combination with hydrogen cyanide would appropriately be termed, "asphyxia from asphyxiant gases".⁷¹⁷¹ Purser {Day296/171:15-18}.

¶85.36 Professor Purser's study of conditions in the tower and information obtained from survivors added to the conclusions he drew from the toxicology and pathology reports on the deceased. The forensic data derived from those reports that record the concentration of carboxyhaemoglobin in the blood are important for measuring the toxicological effects of asphyxiant gases.⁷²⁷² Purser {Day296/164:17-20}.

¶85.37 Professor Purser's study enabled him to reach with some confidence a conclusion on the production of toxic gases in the tower, how those who died were overcome and the causes of their deaths. In most cases he was also able to provide an opinion about the time when death occurred.⁷³⁷³ For Professor Purser's range of time in each individual case, see Purser, Phase 2 Report, Section 6 {DAPR0000006}. His conclusions were necessarily approximate due to the number of factors involved,⁷⁴⁷⁴ Purser {Day296/33:6}-{Day296/39:5}. but we think that in each case they offer the most reliable estimate available.

¶85.38 Professor Purser reached a number of conclusions that are applicable to all the deceased and have informed the findings made in the following chapters. However, he accepted that they were subject to a number of qualifications. First, it was not possible to measure exact concentrations of smoke and toxic gases during the fire, so his conclusions were estimates based on the available evidence.⁷⁵⁷⁵ Purser {Day296/32:16-20}. Second, the concentration of carboxyhaemoglobin sufficient to cause incapacitation and ultimately death depends on the particular characteristics of the individual concerned.⁷⁶⁷⁶ Purser {Day296/34:19}-{Day296/35:18}; {Day296/164:10-20} and {Day296/39:13}-{Day296/40:9}. Third, if the amount of carboxyhaemoglobin in the blood of the deceased could not be measured, an estimate had to be made and it was not always possible to be confident about the level persisting at the time of death.⁷⁷⁷⁷ Purser {Day296/39:8-12}. Fourth, Professor Purser drew information from a wide range of sources, as mentioned above. Fifth, in some cases there was very sparse information available about the person in question, which limited the confidence that could be placed in his conclusion.⁷⁸⁷⁸ Purser {Day296/41:10-15}.

¶85.39 Moreover, the rate at which asphyxiant gases are absorbed depends on an individual's personal characteristics.⁷⁹⁷⁹ Purser {Day296/107:3-10}. Infants and children absorb gases at about twice the rate of adults, which hastens the time to collapse and death.⁸⁰⁸⁰ Purser {Day296/107:11-15}. If infants and young children were sheltering with their parents, it is likely that they lost consciousness and died before their parents.⁸¹⁸¹ Purser {Day296/109:2-9}. Respiratory conditions, such as asthma, also affect any response because they make people more susceptible to irritant particles in smoke⁸²⁸² Purser {Day296/112:5-11}. and those with the condition are generally more sensitive to their effect.⁸³⁸³ Purser {Day296/113:10-14}. If people were unable to leave their flats or descend the stairs, their prospects of escape were reduced.⁸⁴⁸⁴ Purser {Day296/120:19}-{Day296/122:23}.

¶85.40 Professor Purser identified three groups of material that contributed to the smoke within the tower: the external cladding and insulation and the window infill panels, the window surrounds and the contents of the flats.⁸⁵⁸⁵ Purser, Phase 2 Report, Section 5 {DAPR0000011/4}. During the early stages of the fire it is likely that the cladding, the window infill panels and the window surrounds were the main contributors to the smoke.⁸⁶⁸⁶ Purser {Day297/166:5}-{Day297/167:6}. The smoke from the fire on the outside of the building entered the tower⁸⁷⁸⁷ {DAPR0000015/2}; Phase 1 Report Volume IV paragraph 24.8. and the contents of the flats became involved in the fire at different times as it progressed.⁸⁸⁸⁸ Purser {Day297/168:24}-{Day297/170:17}. The contribution made by the different materials to the smoke varied.⁸⁹⁸⁹ {DAPR0000015/2}. We are satisfied that the cladding, insulation, window surrounds and window infill panels made a significant contribution⁹⁰⁹⁰ Purser, Phase 2 Report, Section 5 {DAPR0000011/5}; Purser {Day297/186:18-21}. but we are unable to say how much of a contribution each of them made at different times and in different places.

¶85.41 From the descriptions of dense, irritant smoke in the lobbies, the very limited visibility described by the witnesses and the general fire conditions, Professor Purser estimated that the concentration of carbon monoxide and hydrogen cyanide was likely to have been high and in the lobbies sufficient to cause a person to collapse within about three-to-five minutes of exposure.⁹¹⁹¹ Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/49}.

¶85.42 He estimated that moderate concentrations persisted in the stairs,⁹²⁹² Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/50}. which would have led to collapse (assuming no prior exposure) in approximately 15 to 30 minutes, if one were walking, or between 30 minutes and one hour, if static.⁹³⁹³ Purser {Day296/67:17}-{Day296/68:16}.

¶85.43 Having studied data collected from 21 survivors, Professor Purser concluded that their exposure to asphyxiant gases had occurred mainly during their descent of the stairs, rather than while they were sheltering in their flats.⁹⁴⁹⁴ Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/153}; Purser {Day296/214:17}-{Day296/215:4}. When considering the density of smoke in the stairs, and therefore the risk of inhaling a large enough dose to cause collapse while on the way down, Professor Purser drew a distinction between conditions up to about 01.49 and those thereafter.⁹⁵⁹⁵ Purser, Phase 2 Report {DAPR0000005/95} Sections 1-4; Purser {Day296/159:11-20}. Professor Purser relied on the accounts of Petra Doulova, floor 20, who exited the tower at 01:41:26 and Branislav Lukic, floor 11, who exited the tower at 01:49:09. Phase 1 Report Volume III Annex A. He considered that until about 01.49 it was still possible to descend the stairs without danger of collapse.⁹⁶⁹⁶ Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/96}. After that it was still possible to escape by the stairs, but was more hazardous due to the dense smoke and absence of visibility in both the lobbies and the stairs.⁹⁷⁹⁷ Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/96}.

¶85.44 Most of those who left the tower after 01.49 used cloths or towels to avoid inhaling smoke. The greatest danger was of collapse due to the inhalation of asphyxiant gases, which causes breathlessness, dizziness, light-headedness and weakness, followed by collapse and loss of consciousness.⁹⁸⁹⁸ Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/97}. Continued inhalation of those gases causes death from asphyxia.⁹⁹⁹⁹ Purser, Phase 2 Report, Sections 1-4 {DPAR0000005/97}.

¶85.45 Based on Professor Purser's evidence we find that:¹⁰⁰¹⁰⁰ Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/109}. a. Anyone whose blood contained between 20% and 40% carboxyhaemoglobin had

almost certainly inhaled enough smoke and carbon monoxide to be unconscious at the point of death, even if their remains showed signs of severe burns.¹⁰¹¹⁰¹ Purser {Day296/165:22}-{Day296/166:3}.

¶b. Anyone whose blood contained more than 40% carboxyhaemoglobin died from smoke inhalation and if serious burns were present, they were most likely to have occurred after death.¹⁰²¹⁰² Purser {Day296/166:4-9}.

¶c. A person whose blood contained less than 40% carboxyhaemoglobin but whose body showed no signs of burns probably died as a result of inhaling carbon monoxide and other toxic gases, such as hydrogen cyanide.¹⁰³¹⁰³ Purser {Day296/166:10-15}.

¶85.46 In the light of Professor Purser's evidence we think it likely that those who died in the tower after having left their flats inhaled most of the carbon monoxide that killed them while they were descending the stairs. The time it took them to do that was therefore a significant factor.¹⁰⁴¹⁰⁴ Purser {Day296/214:17}-{Day296/215:4}. If people left their flats before they were overcome, they had a good chance of being able to escape from the tower successfully.¹⁰⁵¹⁰⁵ Purser {Day296/27:4-9}. Those who did not survive the journey down the stairs had inhaled a significant amount of asphyxiant gases while in their flats and before entering the stairs.¹⁰⁶¹⁰⁶ Purser {Day296/217:23}-{Day296/218:1}. Those who remained in their flats until the fire arrived but were then able to escape successfully had probably not been exposed to a large amount of asphyxiant gases.¹⁰⁷¹⁰⁷ Purser {Day296/25:19}-{Day296/26:2}.

¶85.47 People were inhaling an increasing quantity of asphyxiant gases while they remained in their flats¹⁰⁸¹⁰⁸ Purser {Day296/218:2-5}. and the longer they did so, the greater the danger of their accumulating enough to cause collapse and death.¹⁰⁹¹⁰⁹ Purser {Day297/7:18}-{Day296/8:2}. However, in most cases they had inhaled a dose of asphyxiant gases sufficient to impede escape by the time the fire on the outside of the building reached the flats in which they were sheltering.¹¹⁰¹¹⁰ Purser {Day296/218:6-10}. The key distinction between those who survived and those who died is that those who survived left before the fire spread to the outside of their flats or the rooms in which they were sheltering.¹¹¹¹¹¹ Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/153}. In some individual cases, personal characteristics affected both their ability to escape and their vulnerability to asphyxiant gases.¹¹²¹¹² Purser {Day296/218:19-23}.

¶85.48 When the fire reached the outside of the rooms in which people were sheltering, conditions deteriorated very rapidly and they were exposed to a large amount of asphyxiant gases.¹¹³¹¹³ Purser {Day296/28:4-12}. When they then tried to evacuate, they had already accumulated a significant dose and collapsed quickly when exposed to further gases in the lobby or stairs.¹¹⁴¹¹⁴ Purser {Day296/28:15-22}. Those who remained in their flats and did not leave were rapidly overcome.¹¹⁵¹¹⁵ Purser {Day296/28:23-25}.

¶85.49 Almost all those who died in the tower had concentrations of carboxyhaemoglobin in their blood consistent with death from asphyxia rather than from heat or burns.¹¹⁶¹¹⁶ Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/124} figure 18. The two bodies with concentrations of less than 50% carboxyhaemoglobin that were recovered from the flats had heart disease which explained the lower result.¹¹⁷¹¹⁷ Purser {Day296/182:15-18}. For eight of those who died in the lobbies or stairs, all except one had very high carboxyhaemoglobin concentrations and did not have significant burns.¹¹⁸¹¹⁸ Purser {Day296/182:20}-{Day296/183:2}.

¶85.50 From those findings we conclude that all the deceased were comatose, and in most cases dead, before they were exposed to significant heat.¹¹⁹¹¹⁹ Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/138}; Purser {Day296/183:18}-{Day296/184:16}. The severe burning of bodies was likely to have occurred in all cases sometime after death when the fire entered the flats and consumed all the combustible contents.¹²⁰¹²⁰ Purser, Phase 2 Report, Sections 1-4 {DAPR0000005/139}; Purser {Day296/229:1-8}.

¶85.51 Professor Purser was unable to say whether any of those who died had inhaled enough hydrogen cyanide to make a significant contribution to incapacitation and death.¹²¹¹²¹ Purser {Day296/197:22}-{Day296/198:17}. He was of the opinion, which we accept, that it had made some contribution but that the dominant toxic gas causing incapacitation and death had been carbon monoxide.¹²²¹²² Purser {Day297/51:14-17}; {Day297/52:4-17}.