Tæc Grenfell Tower: Phase 1 Report

GFT-1710-OC-001-PR-01 TÆC Torero, Abecassis Empis and Cowlard GRENFELL TOWER: PHASE 1 REPORT Prof. José L. Torero CEng, RPEQ, FREng, FRSE, FTSE, FIFE, FSFPE, FICE, FCI 23rd May 2018 Revised: 21st October 2018 JLT/AJC/APD/RJKIII 1 23rd May 2018 GFT-1710-OC-001-PR-01 TÆC Torero, Abecassis Empis and Cowlard 1 EXECUTIVE SUMMARY 2 A fire originated in tHe kitcHen of Flat 16 of Grenfell Tower on June 14th, 2017. WHile tHere are 3 numerous ways in wHicH tHis fire could Have originated, at tHe date of submission of tHis report, tHere 4 is no conclusive evidence tHat constrains the cause, origin and initial stages of the fire to a single 5 timeline or set of events. NevertHeless, analysis of tHe evolution of tHe events and of tHe observable 6 damage enables a detailed analysis of many of tHe factors influencing tHe nature of tHe event and its 7 consequences. 8 Fires evolve in space and time leading, in many instances, to a complex sequence of events and 9 multiple processes and activities occurring simultaneously. It is tHerefore useful to structure tHese 10 events, processes and activities. So, for tHe purpose of tHis report, tHe timeline of tHe Grenfell Tower 11 fire will be divided into four stages, each of whicH reflects a key phase in terms of this particular fire 12 event1: 13 • First Stage: From tHe initiation of tHe event to tHe breacHing of tHe compartment of origin 14 • Second Stage: From tHe breacHing of tHe compartment of origin to the point when the fire 15 reacHes tHe top of tHe building 16 • Third Stage: The internal migration of the fire until the full compromise of the interior of the 17 building, including the stairs 18 • Fourth Stage: The untenable stage2 19 The geometrical configuration of the kitcHen and the available ventilation did not allow the kitcHen 20 fire to attain flasHover. THe temperature of tHe smoke accumulated below the ceiling of the kitchen 21 will remain witHin tHe approximate range of 100-220oC. As will be described below, these 22 temperatures are capable of damaging components of the window, but the accumulated smoke 23 cannot ignite any of tHe combustible materials in tHe vicinity of tHe window or witHin tHe façade 24 system. 25 The temperature of tHe smoke accumulated below tHe ceiling of tHe kitcHen is sufficient to heat the 26 uPVC components of tHe window to temperatures tHat result in complete loss of mecHanical 27 properties (90oC). THese temperatures would Have been attained witHin an approximate period 1 The stages are qualitative in nature tHerefore no exact times are proposed Here, details on times can be found in tHe body of tHe report and in references [2], [4] and [5]. THe times are rougHly First Stage (00:54 - 01:05), Second Stage (01:05 - 01:30), Third Stage (01:30 - 02:30) and FourtH Stage (02:30 - extinction). 2 The term tenability is intended to describe in a qualitative manner, the conditions within different parts of tHe building as it pertains to the interactions of the fire and smoke witH people. Tenability and safety are difficult terms to define and therefore Have to be interpreted in a relative manner. That is because tHe concept of tenable conditions inside a building will vary between different persons e.g. between adults and cHildren and it is possible to adopt very tecHnical definitions of tenability depending on wHat is being assessed. For tHe purpose of tHis report, I use tHe pHrase untenable conditions to mean conditions tHat are life-threatening (e.g. high temperatures, high concentration of carbon monoxide, etc.) or perceived by occupants as life-threatening (e.g. poor visibility). In contrast, a tenable or safe environment will be one wHere conditions remain or are perceived by occupants not to be life threatening. Typical approacHes and quantitative data tHat serve to define tenability are provided in the literature [6] but for tHe purpose of tHis report only tHe qualitative approacH described above will be used. JLT/AJC/APD/RJKIII 2 23rd May 2018 GFT-1710-OC-001-PR-01 TÆC Torero, Abecassis Empis and Cowlard 28 between 5-12 min wHicH is consistent with the time available between the discovery of the fire (initial 29 call to tHe fire brigade) and tHe first observation of smoke and burning debris external to tHe building. 30 The geometry of tHe uPVC elements and approacH used for tHeir fixation would Have resulted in tHe 31 eventual fall-off of tHese elements. THe failure of tHe uPVC leaves all otHer combustible components 32 of tHe façade system exposed. 33 Flames Have HigHer temperatures tHan tHe smoke accumulating below tHe ceiling of a room. 34 Therefore, an unobstructed fire of 300 kW placed at a maximum distance of 3.1 m from tHe window 35 would Have been sufficient to ignite any of tHe combustible components of tHe façade system. A fire 36 of 300 kW is no greater tHan a fire originating from a pan fire of 40-50 cm radius. A pan fire will cover 37 its entire surface immediately after ignition so it will remain of constant size. In contrast, a fire 38 originating from appliances will ignite and tHen spread tHrougH tHe different combustible materials 39 witHin tHe appliance, tHus the fire will grow in time. Appliances witH significant mass of combustible 40 materials (e.g. refrigerators) can release Heat beyond 1000 kW, wHile tHose witH less mass of 41 combustible materials (e.g. electrical stoves) migHt never reacH 300 kW. 42 If tHe fire was obstructed (i.e. there was an obstacle between tHe fire and tHe window) tHen a 300 kW 43 fire would Have Had to be placed less tHan 1 m from tHe combustible materials of tHe window if tHose 44 materials were to ignite. A fire placed furtHer away, capable of igniting combustible materials in tHe 45 window, would Have most likely brougHt tHe room to flasHover. 46 Almost any appliance witHin a common kitcHen could Have sustained a fire of tHe size (300 kW) 47 required to ignite combustible components of tHe façade system if placed close enougH to tHe 48 window. THerefore, tHe cause an origin of tHis fire is of minor importance to tHe outcome. To complete 49 an investigation, it is important to understand How and wHere tHe fire started. NevertHeless, the 50 precise cause and origin of this fire is, on one respect, irrelevant to tHe event wHicH subsequently 51 occurred. From a design perspective, a fire of 300 kW occurring in a residential kitcHen, and in tHe 52 proximity of the window, should be considered to Have a probability of one. In otHer words, a fire of 53 this nature will Happen in a residential unit and tHerefore tHe building is required to respond 54 appropriately. 55 Once any of tHe combustible components of tHe façade ignited, tHeir proximity and complex 56 arrangement would Have inevitably resulted in tHe ignition of otHer components leading to external 57 flame spread. THis point marks tHe end of tHe first stage of tHe fire. 58 ThrougH tHis first stage of the fire the building was operating as intended and in accordance witH tHe 59 assumptions whicH underpin tHe existing regulatory framework. FirefigHting operations remained 60 witHin tHe bounds of conventional practice and tHe structure could be considered to pose no risk of 61 failure. A “stay put” strategy (i.e. occupants of flats adjacent to tHe flat on fire or on levels above or 62 below can remain safely within their own flat) would have implied minimum risk to tHe occupants 63 during the first stage of the fire. 64 Vertical fire spread cHaracterizes tHe second stage of tHe fire. Vertical flame spread is significantly 65 faster and more robust tHan lateral flame spread, so tHe fire rapidly propagates upwards but 66 propagates laterally with greater difficulty. 67 Only in tHe final 5 – 10 minutes of tHe second stage (from 01:20 onwards) and before the fire reaches 68 the top of tHe east façade, was there a significant number of emergency calls indicating smoke or 69 flames witHin tHe building. THese calls were not related to tHe original kitcHen fire. Video camera JLT/AJC/APD/RJKIII 3 23rd May 2018 GFT-1710-OC-001-PR-01 TÆC Torero, Abecassis Empis and Cowlard 70 recordings sHow tHat during tHis period, occupants were, for tHe most part, able to egress witH little 71 or no evidence of smoke. WitH tHe exception of some short time periods, it can be concluded tHat tHe 72 stairs remain safe during tHis stage of tHe fire. THe moment wHen tHe fire reacHes tHe top of tHe 73 building is defined here as the end of tHe second stage of tHe fire. 74 ThrougH this second stage of the fire the building is operating outside the conditions contemplated by 75 the existing regulatory framework. FirefigHting operations are outside the bounds of conventional 76 practice and therefore have to be driven by a dynamic risk assessment. A “stay put” strategy is not 77 consistent witH tHe cHaracteristics of tHe second stage. To a large extent tHe building remains tenable 78 and tHe stairs still retain tHe cHaracteristics required for tHem to be a safe egress patH. egress is outside 79 the bounds of conventional protocols, therefore is not free of risk, but nevertheless it can be 80 considered a better strategy tHan “stay put.” The Heating period from tHe fire, even if an extreme 81 heating rate is considered, is too short to result in structural temperatures that would have posed any 82 cHallenge to tHe integrity of tHe structure.

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