CTIF´s Dennis Davis on Grenfell Tower: Revisiting Residential Highrise Fire Safety
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Video: (Above) A slide show of the photos used in the presentation by Dennis Davis.
During the China (Shanghai) Fire & Emergency Expo 8-10 November 2017, CTIF Special Adviser Dennis Davis held a lecture on the Grenfell Tower fire. The in-depth paper behind the lecture about this tragic and complex event, which still shakes the UK, is now available on CTIF.org.
The fire occurred in Grenfell Tower, Kensington, North London, on the 14 June 2017 with London Fire Brigade recording a call at 00:54 and being in attendance 6 minutes later.
The 24 storey building (23 stories above ground) was public housing apartments with some other non-residential accommodation.
200+ firefighters with 40+ appliances attended and carried out multiple rescues of 60+ persons.
Conditions were described as extremely arduous with heavy smoke and heat restricting attempts to proceed upwards in the single staircase building.
By CTIF Special Adviser Dennis Davis
Erected in 1974 construction was of a typical solid concrete tower block design. UK Building Regulations do not require active (water sprinkler) fire suppression systems reliance being placed upon passive fire compartmentation and construction.
Grenfell Tower was extensively renovated in 2015-16 with the primary driver being improvement to poor insulation levels and air tightness of both the walls and the windows. The chosen strategy was to wrap the building inside an insulated envelope with protection of the insulation from the weather and physical damage.
The Grenfell Tower fire had followed an earlier one in London at Lakanal House where six people died. Both fires involved exterior cladding fire spread and after the earlier fire HM Coroner had directly raised this issue to help prevent other fires.
More recently there has been the Torch Building fire in Dubai and closer to here in China in Melbourne Australia a serious external fire occurred in the Lacrosse Building. Although neither lost lives it becomes apparent that the impact of fire spread on external cladding is certainly not something new or relates purely to the London fire.
The question raised is therefore “what might this mean to those of us involved in managing fires within the high-rise built environment”.
Many questions are now being asked by the public, the government and fire professionals and exploring what has happened may very well offer insights into future prevention.
In the UK a Judge has been appointed to lead a public enquiry and he has identified a number of issues which need to be explored. The issues cover 13 subjects such as:
1) the design, construction and composition;
2) modifications immediately prior to the fire;
3) modifications to the interior;
4) modifications to the exterior;
5) the fire safety measures in use at the time that the fire;
6) the effectiveness and duration of inspections;
7) governance and management arrangements;
8) how communications were maintained with the residents;
9) what fire advice was given to those residents between 2012 and 2017;
10) what response was made to any recommendations about fire safety;
11) consideration of the fire itself;
12) the response of the emergency services and finally;
13) the aftermath as there where there were many complaints around how the municipal authority responded. In all the Judges has tabled something around 180 detailed questions.
In addition and as a separate inquiry by a former leader within health and safety the regulatory arrangements surrounding the building’s construction controls are being considered. She is asking a series of questions about;
1) the overall legal requirements;
2) the roles and responsibilities of those involved;
3) the competences of key players;
4) the enforcement and sanction arrangements;
5) how tenants and residents voices were heard in the current system;
6) issues around quality assurance and testing materials;
7) the advantages and disadvantages of the current regulatory system; and a call for
8) international comparisons that may exist.
Quite apart from these two independent public and regulatory reviews there are also formal investigations being conducted by forensic scientists for the Metropolitan Police Service and London Fire Brigade, around the issues directly related to the fire, and a criminal investigation being conducted again by the Metropolitan Police regarding the fire and the surrounding circumstances.
In all therefore four significant enquiries are underway to try and learn the lessons of this tragic fire that has claimed perhaps 80 lives. The fire has multiple implications - not just for the built environment - but for the diverse matters like social housing policies and the concepts – like using fire safety engineering and performance based fire codes that operate globally.
Let's turn now to firefighting operations. Grenfell Tower was especially difficult to operate within because of the single stairway construction, used for evacuation and firefighting access. The fire strategy for firefighting and rescue operations was based on the provision that the compartment of each flat could sustain and contain a fire.
We are also all aware in the high-rise buildings there are important interactions between life and building safety that specifically affect evacuation.
Fundamental issues like managing duration, logistics, access and travel distances (for example from street to affected floor). These issues can be particularly difficult in legacy buildings where there are no active systems (such as automatic water sprinklers) or that lack fire detection and alarm, voice and communication systems or integrated control of ventilation and air conditioning.
All fire departments necessarily involve themselves in pre-incident planning discussing risk assessment, tactics in firefighting and use of building control systems whilst trying to recognise the likely fire dynamics to be encountered by rescuers.
Operations also depend on basic matters such as emergency vehicle access and water supplies with identification of good access points for firefighting, suitable elevators, protected shafts and compartment floors and walls that generally will enable them to have safe refuge as well as being used to contain fires within floors, if not within the apartment of origin.
Ventilation air handling equipment or in its absence natural ventilation creating stack effect fires are also part of this pre-planning process.
In new buildings such control systems are common and designed to meet fire requirements, for example, alarm and detection systems, compartmentation controls, air pressurisation of escape routes, structurally secure well protected vertical escape routes with internal linings that prevent fire spread, load-bearing elements that can sustain substantial fire loads, effective fire stopping and external walls that are non-combustible.
The London fire has for example highlighted the importance of a building’s external envelope in fire growth and spread.
The London fire also illustrated how multiple rescues can become a major consideration in both the duration and intensity of such an evacuation. The pressure and demands multiple rescues of around 60 persons highlights the extreme and traumatic stress rescues can place upon firefighters.
Another significant feature was the fire spread outside the originally affected 4th floor compartment where a fire in a refrigerator occurred. The external cladding system using a rain screen of aluminium composite material is now under detailed investigation.
It is speculated that this contributed to major and rapid fire spread. This is linked to high ambient air temperatures at the time in London, which meant the many windows were open, allowing the fire to move vertically and horizontally by re-entering the building floors above the original floor of origin.
This has laid bare the question around use of this type of material in high-rise buildings given. Under these particular circumstances, the structure and external envelope did not inhibit compartment spread as envisaged remembering there was also the absence of active suppression systems.
All these matters will of course be reviewed in the case of London but they are lessons which we must pay particular attention if the general approach has always been to protect residents in situ trying only to evacuate the affected floor and the one above and below.
This is not unusual for the UK where for many years guidance issued by local government for purpose-built blocks of flats was designed to assist those who had to manage these situations. It comes with the advice that, provided a full risk assessment had been undertaken, stay-put was appropriate.
Although there remains concern to many, and recently following the fire some local authorities have supported stay-put strategies by having wakeful all night watch keepers, many decisions as to whether to evacuate immediately, are now based on factors like if the buildings are single stairs or lack good stair lobby protection to inhibit fire, smoke and toxic gas spread.
The principle of defending the compartment has the advantage that not evacuating reduces the number of people using the stairs and avoids placing those less ambulant or physically restricted people at risk during evacuation.
It is being revisited. This reflects concern that delaying a decision as to whether an evacuation should be made is often left to late and this can be a life threatening decision. It also relies upon having a rapid containment of the fire by the Fire Department and each of the compartments must be well protected against spread from an affected compartment into, staircases and common areas.
Inspections conducted throughout the UK post the fire have identified many compartmentation weaknesses often introduced inadvertently by residents, like replacing their apartment fire resistant door with one they find more aesthetically pleasing. Other concerns found were internal increases in fire loading, wall linings and decorative internal ceiling linings that increase fire growth, damaged internal walls and opened the compartment to the external envelope the building.
In the UK as in many countries as part of energy-saving strategies and sustainability in the built environment insulation panels have been fitted to externally clad many older buildings with the thermal cladding requiring some form of rain screen and installations subsequently tested on similar panels indicate test failures. Other issues relating to external fire spread on high-rise buildings such as wind strength and direction can also directly impact upon fire phenomenon and spread.
A further operational concern with internal firefighting is that arising from electrical and data cables which are now used extensively and in legacy buildings are often surface mounted using plastic conduits for trunking. In the UK there have been deaths of firefighters were this common conduit has failed and the cables released creating high levels of risk of entanglement or electrocution.
It is worth noting that in the UK generally active sprinkler systems are not prevalent both because of the previous adoption of passive protection using compartmentation and the general level of cost. Thus unlike many other countries suppression systems are not used and in building control practice it is not a requirement to retrofit alarm and communication systems. Phased evacuation in older buildings is therefore currently a manual affair although following the fire many local authorities with residential high-rise towers are now installing internal sprinkler systems.
In more complex buildings of course fire engineering systems provide an intrinsic level of safety. Fire engineering does rely often on interactions between building systems and again in a serious fire this can rapidly become damaged.
In high-rise residential buildings as London as shown the consequence for inadequacy of fire safety is tragic failure that has raised great public concern.
We must therefore revisit evacuation, risk of ignition, fire growth, compartmentation, our understanding of fire behaviour and its production of heat, smoke and toxic gases. Linked with the structural strength of the building, effective detection and suppression systems that can all come together with human behaviour so that if firefighting becomes necessary in these complex situations we can mitigate the height and external risk.
Without a clear understanding of the construction techniques and those risks that I've mentioned high-rise can present serious problems for firefighting operations and increases the vulnerability of residents and firefighters alike, both psychologically and physically.
Firefighting can be an extremely hazardous occupation in high-rise buildings and as we await the outcomes of the London fire we do so in the full knowledge that what we need to do is revisit residential high-rise fire safety.
Posted by Bjorn Ulfsson / CTIF NEWS