Chapter 110: The escape of fire from Flat 16

Chapter 110: The escape of fire from Flat 16

¶110.1 In Chapter 22 of the Phase 1 Report the Chairman considered the process by which the fire escaped from the kitchen of Flat 16 at Grenfell Tower and entered the external wall. Based on the evidence available at the time, he concluded that it had escaped in one or other of two ways: either by flames passing through the cavity around the column following the collapse of the uPVC window jambs, or by flames passing through the open window and impinging on the rainscreen panels directly above.^22122212 Phase 1 Report Volume IV paragraphs 22.36-22.39. Although the video evidence was more consistent with the former mechanism, the latter might also have played a significant role.^22132213 It should be noted that the reference to Professor Bisby's Hypothesis B2 in paragraph 22.39 of the Phase 1 Report Volume IV on page 538 is a typographical error which should actually refer to Professor Bisby's Hypothesis B1. Ultimately, however, that was of little significance, because in both cases it was the proximity of combustible materials to the interior of the compartment that allowed the fire to spread.^22142214 Phase 1 Report Volume IV paragraph 22.39.

¶110.2 In June 2019 the Metropolitan Police Service provided the chairman with a copy of a report dated 24 May 2019 by BRE of a large-scale reconstruction of the fire in Flat 16 that it had carried out and the conclusions it had drawn from it.^22152215 BRE Global Grenfell Tower Fire Investigation Reconstruction {MET00040237}. The reconstruction sought to reproduce as accurately as possible the configuration and contents of the flat immediately before the fire and two storeys of the external wall above. Based solely on the results of that reconstruction, BRE concluded that the fire had probably spread to the external wall through the extractor fan and the window infill panel in which it had been mounted, igniting the exposed edge of the polyethylene core of the panel above the window. The second most likely route was through the construction around the window.^22162216 BRE Global Grenfell Tower Fire Investigation Reconstruction {MET00040237/4} penultimate paragraph.

¶110.3 The chairman indicated in the Phase 1 report that once full information had become available from the reconstruction he would ask Professor Torero and Professor Bisby to prepare short supplemental reports explaining whether it caused them to alter or refine the views they had expressed during Phase 1. He also indicated that he was willing to receive submissions from core participants on the relevance of the reconstruction during Phase 2. In those circumstances, the findings made in Chapter 22 of the Phase 1 report remained provisional and subject to revision in this report.^22172217 Phase 1 Report Volume IV paragraph 22.42.

¶110.4 Professor Torero and Professor Bisby both considered the reconstruction report for the purposes of Phase 2^22182218 Torero, Phase 2 Report {JTOR00000006/163-169} paragraphs 13.1.10-13.1.43; Bisby, Phase 2 BRE Reconstruction Report {LBYP20000003}. and Professor Torero also dealt with it in the course of his oral evidence.^22192219 Torero {Day292/107:18}-{Day292/108:16}. He explained that even a large-scale test which attempted to reproduce the original construction and contents of Flat 16 as faithfully as possible could not accurately reproduce the evolution of the fire, since very minor changes in variable factors, including ventilation and fuel content, can result in very different outcomes.^22202220 Torero, Phase 2 Report {JTOR00000006/164} paragraph 13.1.16. He also analysed the fire created in the test and compared it with what is known about the evolution of the fire at Grenfell Tower, including the significant stages of its development. He concluded that the fire in the reconstruction was completely different from the fire that occurred in Flat 16 and that it was not possible to establish why its behaviour was so different.^22212221 Torero, Phase 2 Report {JTOR00000006/166} paragraph 13.1.31. In particular, the fire in the reconstruction had developed more quickly and had become hotter, with key events occurring at different times,^22222222 Torero, Phase 2 Report {JTOR00000006/167} paragraphs 13.1.33-13.1.34; Torero {Day292/107:18}-{Day292/108:16}. and had eventually reached flashover.^22232223 "Flashover" is a term used to describe the near simultaneous ignition of all combustible material within an enclosed area. As a result the materials around the window affected by the fire behaved differently during the reconstruction. That included the uPVC window surrounds, which are likely to have charred rather than deformed due to the sudden increase in temperature seen during the reconstruction. In those circumstances, the reconstruction represented a fire of a very different kind and did not cause him to change the opinions he had expressed in his previous evidence.^22242224 Torero, Phase 2 Report {JTOR00000006/167-169} paragraphs 13.1.35-13.1.43.

¶110.5 Professor Bisby was of the same view. He also emphasised that large-scale reconstructions are extraordinarily complex and that their outcomes are influenced by a range of factors that are difficult, if not impossible, to control. They include small differences in the type, amount and distribution of fuel within the compartment, the initial ventilation conditions, the creation of additional ventilation as a consequence of the fire (for example, through windows breaking) and the effects of wind. All those, and other, factors could alter drastically the progress of a fire.^22252225 Bisby, Phase 2 BRE Reconstruction Report {LBYP20000003/10} paragraph 58. As a result, a reconstruction could only demonstrate what could happen, not what did happen.^22262226 Bisby, Phase 2 BRE Reconstruction Report {LBYP20000003/11} paragraph 60.

¶110.6 Professor Bisby agreed with Professor Torero that BRE's large-scale reconstruction created a fire that was inconsistent with the available evidence of what had occurred in Flat 16.^22272227 Bisby, Phase 2 BRE Reconstruction Report {LBYP20000003/11} paragraphs 62-64. He also made it clear that only by conducting a detailed analysis of the sensitivity of the reconstruction to various different factors (which was not possible given the limited data available from the reconstruction) could any conclusions be drawn about the relevance of what had been observed in the reconstruction.^22282228 Bisby, Phase 2 BRE Reconstruction Report {LBYP20000003/11} paragraph 65. In those circumstances he concluded that the reconstruction did not provide any information that contradicted the evidence he had given during Phase 1 or cause him to alter his views.^22292229 Bisby, Phase 2 BRE Reconstruction Report {LBYP20000003/12} paragraph 75.

¶110.7 We accept the unchallenged evidence of Professor Torero and Professor Bisby that the fire created in the BRE reconstruction differed significantly from the fire that occurred in the kitchen of Flat 16. Since the reconstruction did not lead either of them to revise his original opinion, there is no reason for us to depart from the provisional conclusions reached by the chairman in Chapter 22 of the Phase 1 report. Accordingly, they now represent our final conclusions on the means by which the fire escaped from Flat 16.