Following a number of significant fires in occupied light timber-frame buildings where it appeared the fire had entered from outside, the FPA was asked to help investigate contributing factors. Whilst it seems extraordinary that a fire could get into the combustible cavity from outside of the building, the resilience of the external envelope to fire ingress is barely addressed in building codes, which focus on the combatting and control of fires emanating from within.
Common to these fires were plastic “air bricks” inserted into the masonry skin to provide ventilation to under-floor cavities.
In a remarkable demonstration at the FPA’s laboratory open day on Friday, technical director Dr Jim Glockling demonstrated how quickly one of these vents — which are commonly used in timber-framed homes — can catch fire using nothing more than a cigarette lighter. Within between three to five seconds the vent was alight, with the flames gradually being pulled inwards and causing a much larger fire to take hold within the timber-framed wall cavities.
Click on the image below to see a full gallery from the FPA demo:
This is a worrying new discovery, and the FPA is now in initial steps to work with the UK Timber Frame Association, CFOA, HSE, and British Standards Institution to try and control it. Currently this style of plastic venting brick is not subject to flammability tests or requirements, something the FPA and other stakeholders are keen to see resolved. Experiments with other plastic fittings such as domestic waste pipes, bathroom vents, and dryer outlets, demonstrated them to be equally ignitable and likely to transmit fire into the timber frame.
Dr Glockling told the audience of fire safety experts and professionals, as well as insurers and builders, that if the knowledge of how potentially flammable these items are became widely known, that would provide a risk to consider for home and building owners who could be vulnerable to arsonists. He is keen to see a change to the guidance given on product selection for all fixtures and fittings that could form a fire “weak-spot” in the external envelope of these and other combustible structures, he said.
Dr Glockling also demonstrated the result of a research programme that the FPA has undertaken on behalf of the Royal Navy to try to adapt existing technologies to the task of robotically fighting fires aboard ships.
Using basic CCTV cameras in association with a flame recognition system, Dr Glockling demonstrated how two cameras, with a known location, could be used to pinpoint the seat of a developing fire and — combined with a steerable firefighting branch — quickly and automatically provide a targeted jet of water to the seat of the fire before it was able to develop significantly.
The cameras in the test were combined with a video flame detection system, SigniFire, to identify the presence of flames. The results were impressive, with videos showing a fire being extinguished using water with no direct human interference.
The project to develop a Shipboard Intelligent Fire Suppression System (SIFSS) was shown by Dr Glockling and his team to be practically possible, and the use of CCTV cameras shows that this technology could be retrofitted to existing surveillance cameras.
Other means of accurately pinpointing fire location are being tested, including IR devices, which, unlike cameras, will be resilient to smoke logging, and fiber optic systems for use in highly cluttered spaces. These systems have the potential of keeping their sailors out of harm’s way by reducing the incidence of their having to fight fires on board the Royal Navy’s vessels.
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Quite astonishing really Rob! It’s like having plasticine fastenings on your suit of armour. Maybe they should reintroduce brick based ‘air-bricks’?
I find it incredible that flammability would not have been taken into account when the bricks were first looked at. Good point re. brick airbricks! I know these ones had a little plastic duct which went downwards on the inside of th cavity, so possibly that’s the reason it’s not a brick… brick.
Anything that can assist/promote a fire (i.e. act as a fuel source) to reach the cavity is then going to be drawn in rapidly as the “chimney” affect of the cavity assist the fire to produce a blowtorchaction on anything combustible in or adjacent to the cavity. Same for external cladding with a cavity behind the cladding. Horizontal fire breaks (e.g. fixed mineral wool firebatts) in these cavities just above the vent will usually prevent any further fire damage. There surely are self-extinguihing and/or low combustible “plastic” airbricks although looking at the most commonly available, none mentionned fire resistance!
The additional issue that was highlighted during this demonstration was the fact that the linings used in these cavities are often also non retardant, so once these air bricks had caught light the fire rapidly spread throughout the void. It was also discussed where more retardant linings were used, the fire was still able to travel horizontally and /or in a downwards direction.
It is indeed, a worrying finding!
I’ve seen a four storey block of flats cave in on itself due to a fire taking hold via the air bricks – this was approximately 6 years ago and the issue has been known about for some time. Its not only arson but more people are smoking outside the front doors of their flats or out of the window and throwing butts out that can get blown around in the wind.
it is strange that fire ingress did not claim the importance it deservers (yet many of us including myself was surprised with the findings!) but with fire temperatures reaching 700C+ in a very short period, this is a hot topic to be discussed without delay.
Hal-Luke Savas
http://www.hallukesavas.webeden.co.uk
Rob, I am sorry to say that I am not suprised about the range of products that are installed in buildings that present an excessive fire risk, the brick it would appear is just one.From my experience in the construction sector as well as fire, there is little understanding as to the level of combustibility or flammability of building products by designers and members of the design team.It is true there is a slightly better understanding of the finished structural build and we have building control amounst others who I am sure remind designers of the nsafety aspects for the… Read more »
Not all plastic is flammable, of course. It is possible to set fire to some plastic components built into construction. It is possible to set fire to some plastic damp proof products, plastic cavity closers, or the metalised plastic films on even otherwise non-flammable insulation boards. These components can support flame which may then set fire to other components such as a timber frame.
How far do you go in considering such products a potential fire risk?
A Plastic Air Brick could be set fire by an arsonist. But a determined arsonist can find many ways to set fire to a building.
I would suggest that the threat of fires in timber frame buildings is not a new threat. I was involved in a fire as a first responder to a single flat fire in 2009, which led to a quarter of a building having to be dropped, at a cost of over £2 million. The cause of fire spread being that the services installed by trades working on site had breached the fire resistant boards used to compartment each flat. The result was truly devastating, and if it had occurred at a different time of day, ie. not 7pm, could have… Read more »
There is no building legislation against an arsonist other than criminal enforcement by the police. An accidental fire within a timber framed dwelling room can escape via the “hit & miss” type wall vent and the invariably 110mm plastic underground drainage pipe used as an air conduit to the outside. That does not need an arsonist. Look up web site known as “FIREBAR.IE” or FBII.ie and look at the pictures for numerous real examples of fires both fatal and otherwise. The plastic vent as well as many other timber framed potential fire problems have been around for a long time.… Read more »
Horizontal fire breaks would make sense, definitely. Re. your last sentence, I think that’s the issue here. Fire resistance for these bricks isn’t a requirement at present. But evidently it should become one, and it’s good to see the FPA working with BSI to look into this.
So more of an overall fire safety engineering philosophy if you will? I have often wondered about the level of fire protection a building has during construction. Naturally, once occupied a fire risk assessment will be undertaken, but what level of protection is there for people on a site during construction?
Interesting, I think I must have missed that detail taking photos, thanks for that. Retardent linings are a help though I’m sure?
Interseting, I didn’t realise this has been known about for so long. And yes, it seems that accidental factors could come into play here, certainly. If known about for 6 years, why aren’t all air brick subject to flammability requirements?
Hot topic, very good, very good.
Well that’s true. One cannot simply not build buildings because an arsonist ‘might’ burn it down. There’s a balance that should be struck, but I do find the ease with which this vent will catch fire slightly worrying… hence the title, obviously.
Be careful indeed, but as you say, little can stop a determined arsonist, except perhaps a decent security system.
Are you suggesting that homeowners/building owners should have better education on how their DIY might impact on the fire proofing of their own homes? I would certainly back that. In fact, broadening it out from just fire, there’s innumerable incidents that are caused by DIY. If education could reduce these, you could save the NHS, fire service etc. a lot of money, potentially.
Does this sound familiar to anyone? – it mentions a fire in the vent and the spread seems to have been further than it should have.
http://www.cambridge-news.co.uk/news/local-news/newmarket-fire-flats-george-lambton-12874738