William Makant asks whether traditional fire suppression standards and techniques are keeping up with new building methods.
To be effective and to continue saving lives, it is imperative that fire protection measures move with the times, keeping pace with changes in building construction, occupancy and use. Rather than relying on tried-and-trusted techniques and standards formulated decades previously, we constantly need to question if these are still fit for purpose in today’s world.
The way we build homes has evolved to cater for rising housing demand, alongside the drive to reduce our buildings’ carbon footprint. This brings a new set of risks in terms of fire protection. In recent times we have seen three key trends:
Modern methods of construction
More homes are being built in this way to improve efficiency, quality and speed of housing delivery. While timber-frame construction might generally be considered by many as riskier than traditional methods, poor craftsmanship is what will make any building’s passive fire protection ineffective from the outset. On the other hand, risks generated over the lifetime of the building by breaching passive fire protection measures will require the use of active fire suppression. This – along with the fact that buildings are progressively being built off-site in a controlled factory environment with stringent quality checks – can in fact result in a much safer property.
Densification
The demand to build more homes, alongside a shortage of available land, results in developers maximising the number of properties they build on a given plot. This densification of housing brings its own challenges in terms of fire protection. Higher multi-storey buildings mean longer escape routes and a greater chance of fire spreading between flats due to a breach in compartmentation.
Energy efficiency
Energy efficiency measures to minimise a building’s environmental impact bring many benefits, not just to the planet but also for residents in terms of a warmer, more comfortable home, together with lower fuel bills. But this, too, is not without risk. Although there were undoubted good intentions behind Grenfell Tower’s improved insulation, the tragedy that later unfolded serves as a stark warning of the dangers of poor specification and craftsmanship.
Modern occupancy
Most importantly, there has been a shift in terms of the people inhabiting homes and what items they keep in them. It is predicted that people aged 65 and over will comprise 24% (17.4 million) of the UK population by 2043, with those aged 75-plus making up 13% of the population and 85-plus rising to 4% (from 2% in 2018).
Statistical analysis reveals that people aged 80-plus have a disproportionally higher fire-related fatality rate, mainly due to a drop in mobility and reduced awareness of their environment. According to the detailed analysis published by the Home Office of fires attended by fire and rescue services in England, for every million people there were 4.3 fire-related fatalities in 2019/20. The fatality rate was highest among older people: 8.4 people per million for those aged 65 to 79 years old, and 16.9 per million for those aged 80 and over.
We live in a hi-tech digital age, with all the ease and convenience that provides. But this means we now have many more electronic devices with lithium batteries in our homes. These batteries are constantly being recharged so, together with the plugs and extension cables to feed them, they bring with them an increased risk of fire from worn connectors and damaged cables causing over-heating or short circuiting.
Finally, and most importantly, modern households tend to have many different types of large electrical domestic equipment in their properties. White goods are the most common cause of fires in homes. These concealed fires grow slowly, burning through flame-retardant plastics, resulting in relatively low heat but a high output of toxic smoke over a longer period of time.
Fire growth
A typical fire growth curve starts with ignition, followed by a period of incubation. The fire progressively grows as it spreads, in turn releasing progressively higher levels of heat output. This grows parabolically, as a function of time squared.
During this fire growth there will be a limited amount of time for a person to be able to escape (the Available Safe Escape Time) until the conditions become untenable due to exposure to heat or smoke, or both, reaching the tenability limit.
In light of the trends in our buildings and their occupancy, the increased toxic smoke production from electrical goods will make this the limiting factor on the available escape time. In the meantime in practice – bearing in mind that older less mobile residents will need longer to escape – the required escape time has increased over time.
However, traditional fire suppression using frangible bulb (traditional fire sprinkler and watermist) systems rely solely on heat release to activate, so if the fire grows very slowly, they may take a very long time to activate. This is fine if their purpose is just to limit the fire to the room where it started, regardless of smoke output, to protect building integrity. However, it is not fulfilling the wider objective of protecting the occupants if people close to the fire, or in connected rooms, will suffer from the fire’s toxic fumes.
Internationally, the standard test to validate residential sprinklers and watermist systems is heat driven, involving a large flame developing very quickly (2MW within three minutes). Hence, to my mind, the current safety standards were not designed to address the type of increasing fire risks present in a modern home with modern occupancy. The resulting approved fire protection measures may well protect the building, but they may not sufficiently protect the people inside.
A report by the Building Research Establishment (BRE) on slow-burning fires in 2005 looked at the effectiveness of sprinklers in residential premises. It concluded that ‘sprinkler protection was not found to be a complete panacea; slow-growing and shielded fires can be a problem. ’A further BRE report exploring the causes of fire fatalities and serious fire injuries in Scotland, and potential solutions to reduce them, highlighted the need for faster activation of suppression systems to tackle fires sooner.
Electronically controlled fire supression
Electronically activated suppression offers a more sophisticated and effective solution to these modern-day challenges. These systems use smoke detection technology to initiate thermal scanning of the room by infra-red sensors, and then trigger suppression if the presence of a fire is validated. The objective is to tackle the fire much sooner, while it remains small, regardless of whether it is slow burning or fast burning. This system also uses less water because it activates when the fire is still relatively small,and it directly targets the area where the fire is.
I believe this type of system provides an effective alternative approach to fire suppression – tailored to the needs of the building and, crucially, its occupants. As a member of BSI’s watermist technical committee, I personally strive to ensure a person-centred approach is central to our development of British Standards, regardless of technology, to allow innovations to improve life safety.
The use of sensors and electronics for the purpose of fire suppression opens up a world of wider opportunities to create a smarter, safer building. By connecting to the internet, it can instantly flag up issues such as loss of power, water, tampering, near-misses and the need for maintenance. In the event of a fire, the system’s thermal imaging capabilities can help rescue services to identify whether people are in the building and where they are. This could prove invaluable in saving lives, and is particularly pertinent at a time when there is growing emphasis on personal emergency evacuation plans to protect vulnerable people and those with disabilities or mobility issues.
Data from the sensors can also link in with other building management systems, monitoring temperatures to control heating, ventilation and air conditioning systems more efficiently. In addition, this can help us rise to the climate change challenge by using such information to make a home more energy efficient, reduce heating bills and lowering emissions.
It is my belief that fire protection systems should be evolving at the same pace as changes in our buildings and their construction, along with the needs and expectations of their occupants. By failing to harness electronics in fire suppression and realising its benefits, we run the risk of seeing its wide-ranging value going up in smoke.
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William Makant is co-founder and CEO at Plumis.