High Rise Fires in the UK: Coping with an Impossible Task
By
Tony Prosser
High-rise fires, for many years have gripped the public imagination, typically, when things go wrong. From the Triangle Shirt Waist Fire in 1911 through to “the Towering Inferno” there has always been an underlying fear of being trapped above a fire in a tower block. For the most part these fears have been unfounded. But, and there’s always a “but”, in the last five years there been a number of spectacular high-rise fires including the Windsor Tower in Madrid in 2005, the 44 storey Mandarin Oriental hotel in Beijing in 2009. More recently, there has been a spate of fires involving high-rise buildings in United Arab Emirates - the Al Baker Tower on January 25 2012, Dubai, the Al Tayer Tower (Dubai again) in April 2012 in the Tamval Tower in November 2012. What all these fires have been common is a rapid spread of flames from the outside of the building, rapidly extending more than 10 floors. It is ironic that, 40 years on from the Summerland disaster on the Isle of Man, we are seeing very similar images on TV screens and in newspapers of other rapidly developing fires, spreading from the outside up and in. To date, there have been very few building fires in the UK where the fire has spectacularly leapt from floor to floor and not being effectively controlled in a reasonable time. Unfortunately, due to the age of many high-rise buildings in the UK, they are now being refurbished both inside and outside and this may have serious implications for residents, the wider community and firefighters in time.
External spread of fire outside the building has been a firefighter's consideration for many decades. Even before the Second World War, firefighters knew about the potential for fire spread atthe buildingsurface due to what is known as the coanda effect (named after Henri Coanda, a Rumanian aerodynamics engineer), with flames escaping from a compartment in a lower floor "sticking to" the external wall and impinging on windows or balconies above. Where there are flammable materials inside the Windows or balconies, the fire could extend onto the higher floor. Where windows have been left open, access by flames and is even more likely, as happened at Lakanal House where burning debris is believed to have fallen into rooms.Obviously, if external cladding is in it combustible then this will add to the fire loading and help accelerate the fire at a far faster rate than in where the more traditional concrete face constructed buildings. In the USA the term "autoexposure" has been coined to describe, the external spread of fire up a building and is commonly used to describe the jumping from one floor to the other on the external face. This process, one that occurs in any event will be accelerated by the coanda effect and the convection of heat and flames. Where the cladding is combustible, the effect is even more pronounced. It would appear that the vast majority of the recent serious fires in United Arab Emirates were as a result of combustible external cladding spreading the fire from floor to floor.
It is important to remember though, that “autoexposure”is not the only way of extending fires up through building: the age and type of construction can also have a major impact on the political spread flames internally. Many of the high-rise buildings in the UK are nearing their half-century since construction. When poor construction or materials or inferior quality have been used, there is often a decay or failure of components. If not remedied, early failure of its components could mean gapsbeing created through which flames and heat can pass readily. During the fire, is quite likely that temperatures in excess of 1000°C can be achieved in a quite a short time. Any metal components, particularly those made from alloys, if unprotected themselves can fail exposing major elements of structure and also, in the case of fire protected elements of construction, the failure of that fire protection for structural components. In many buildings, service ducts and the access channels for facilities can run throughout the length and height of the building, giving rise to potentially chimney through which fire will spread upward unchecked if precautionary measures are absent. Staircases and hallways are normally protected by construction and fire resisting doors. As has occurred in several instances, doors have been wedged open or, within individual apartments, removed to provide ventilation, particularly in hot spells, where no air conditioning system is available. Again, this creates a chimney which fires in lower floors can be spread vertically.
Apart from the issue of defective construction and the misuse of protective equipment, there has been widespread reporting of the compromisingof fire separation caused by the installation of new services within high-rise blocks of flats. There have been many instances where new services including satellite TV, air conditioning systems, and in some cases, fire alarm systems have been installed with large holes being drilled in fire separating walls and not sealed with fire resistant materials. All of the above represent what could be considered as an unforeseeable issue, with the culprit ignorant of the consequences of their act. With the concerns raised as a result of the Friars in the Middle East, a risk that is reasonably foreseeable in the UK, that of external spread of fire at high-rise building, is likely to increase due to the well-meaning attempts of owners and landlords to improve the look and feel of these buildings.
It is becoming common practice now when high rise buildings are being refurbished, to not only improve the interior aspects of the block but also to develop a feeling of modernity by installing external cladding of bright and vibrant colours. According to experts, it is becoming common practice to fix 10 cm thick polystyrene blocks (to improve insulation and reduce heat loss) to the surface, cover with mesh and rendered with a non-combustible surface. This meets the British Standard BS 476 pt. 6 in terms of surface spread of flame and low fire propagation. Deterioration of the fabric of the building over time, particularly external construction elements could compromise the integrity of the external surface and provide a combustible material on the outside of the building which, once ignited could rapidly cause delamination and combustion of the whole slab releasing large amounts of heat and flames, helping to propagate the fire up the outside of the building.
As the external material of the building should only be of "limited combustion" under UK Building Regulations,these restrictions should prevent the sort of fires seen in the UAE and elsewhere. There have already been instances in the UK where fire has developed over nine storeys through the external spread. Therefore, it would appear that it is entirely possible that fires of this sort could start to become more common in the UK. In the event of fire involving rapid external spread, there are number of serious issuesthatneed to be taken into account, particularly in the case of occupants of the building and the firefighters who will be called upon to tackle such an incident.
The "normal" approach taken in the UK when fire breaks out in a high-rise building, is for the residents of the apartment involves to evacuate and the remainder of the residents of the building to remain in their property. This is achieved through fire resisting construction and doors to each flat. This approach is predicated on a fire in one apartment being contained for a time to enable firefighters to attend, deploy and extinguish the fire. Where the fire spread is through external means, “autoexposure”, residents will be faced with a fire approaching them from the outside, forcing them to evacuate their apartments. It has been shown in studies undertaken in America and Canada that the most likely place a resident of a high-rise block will die in a fire, is in the staircase whilst evacuating. This is due to the smoke from a developed fire penetrating the staircase enclosures. It is entirely possible to imagine a scenario where mass numbers of evacuees, forced from their apartments due to fire penetration from the outside being forced into smoke logged stairways, exposing them to excessive risk.
For firefighters, there is a risk, as shown by numerous fires in high-rise blocks that attacking the fire in a substantial way will be very difficult. This will be partly due to the logistical issues of gathering sufficient resources to tackle a multilevel fire, possibly simultaneously, and also of acquiring sufficient water resources to be able to sustain an attack on the fire inside while simultaneously chasing it up the outside of the building. By way of example, the fire in the Windsor Tower, Madrid was eventually left toburn, as it was impossible to extinguish it safety. Like the fire in the First Interstate Bank in Los Angeles in 1988, it is likely that any fire that is not extinguished within four or so hours will be likely to compromise the floor fire resistance (assuming no decay or damage previously) and continue to burn upwards. There is also a not insignificant risk that fires above four stories can be actively susceptible to the effects of wind, which increases with every floor level. This has the potential to expose firefighters within the building to rapid changes in temperature that can go from just above ambient to over 1000°C in seconds if a fire resisting door to a fire compartment failsallowing the wind to “drive” the fire into corridors. In the event this does occur, studies from the New York Fire Department have shown that survival is untenable in corridors and a major rethink on tactics will be required.
So there are a number of problems facing occupants and firefighters from addressing the issues of high-rise buildings. Much of the knowledge about the risks is already available and with numerous examples of what has occurred in the past and where things have gone wrong. The Regulatory Reform (Fire Safety) Order concerns itself mainly with the safety of occupants in the common areas of blocks of flats and housing legislation considers safety within those flats. Despite Building Regulation restrictions on external combustibility, the potential for fire such as those seen in other countries is possible to get in the UK. In the event of such a fire occurring, it will be very difficult to argue that no one already identified the issues as they are already recognised in other parts of the world. The question for fire service managers is "do you feel lucky?"
ENDS