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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: Firewolf on July 20, 2006, 04:38:57 PM
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Heres a quick poser for you
Imagine a store cupboard under a staircase.
The cupboard is fire resisting and it has a fire door leading into it fitted with cold smoke seals and intumescent strips.
There is no AFD in the cupboard.
In theory a fire could start inside the cupboard and effectively go unoticed until it has breached the door at some point nearing the 30 minutes FR of the fire door.
What I guess Im asking is this: Wherever we look to provide Fire Resistance in isolated spaces or little used rooms such as cupboards should we also be asking for AFD to give early warning of a fire starting within them?
And by that logic could we therefore state that FR or AFD isn't req'd because a fire in a cupboard without FR or AFd would breach the door very quickly and be spotted by someone!!
Its an argument someone threw at me earlier today and it has me stumped for I feel this is quite plausible in certain applications other than residential premises and high risk etc.
What are your thoughts on this?
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Two factors to take into account. If the cupboard is fire resisting and with the seals, the most likely outcome is that the fire would self extinguish by using up the oxygen before it has a chance to breach the half hour door.
The other factor is the MOE. If the stair case is the sole MOE from the upper floors the case is different from where there are alternative MOE.
It would appear to me that it all falls back on the Risk Assessment. Take into account the materials stored in the cupboard, potential sources of ignition etc. then the severity of the result and base your actions on this. Decide what is "reasonably practicable".
I am afraid we are going to have to get used to the idea that there are no fixed answers under the new regime.
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My personal opinion is that it would depend on numerous factors, two being:
The presence of any possible ignition sources within the cupboard
My opinion on how well the fire resisting elements of the cupboard will remain maintained
And, yes, it will depend on the fire safety risk assessment.
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Good point Firewolf....for years we have been asking for stores in stairs to be enclosed in FR without detection it is pointless exercise. It matters not a jot Chris how well the the fire resisting elements will remain intact...without AFD you won't know that there's a problem until it's too late
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The question we should ask first is could a fire in the cupboard cut off the means of escape for people using the building. In many circumstances in commercial buildings the staircase may not need to be a protected route - if there is an alternative way out from the upper floors, if a fire could not affect both routes at the same time and if travel distances are reasonable there may not be a need for fire resistance or detection.
But if it needs to be a protected route it needs BOTH detection and FR. Then the detector will cause the alarm to be raised giving people time to pass the fire within the protection window offered by the structure.
The Risk assessment will determine whether the route needs to be protected or not.
But assuming we come across the situation in the real world and if we decide we need a protected route then as Chris points out our first thoughts should be to eliminate the risk- ignition sources and combustible materials. Sealing up the cupboard may be a solution that eliminates the need for anything else. Depends on how much confidence we have on it being maintained. If the stakes are high- eg sleeping risk - then its reasonable to provide AFD and FR - ie protected routes throughout and full AFD because of the potential consequences of the fire. Slow response, occupants asleep, possibly unfamiliar with the building etc.
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By coincidence I was looking at some past work I did at the Fire Research Station in the 1980s in response to another question in this forum. It was for the Home Office regarding the siting of detectors in corridors of hotels and other sleeping accomodation. We were asked to see if smoke detectors in the corridor could be relied on to give an alarm from a room accessed from the corridor, and the effect of different sorts of door on the speed with which the alarm was given.
We used ordinary domestic doors, FR doors without intumescent seals and FR doors with seals.
In summary:
Domestic doors always allowed enough smoke out to trigger a detector well before the corridor became impassable to people due to smoke or flame penetration.
FR Doors without seals - those with a poor fit gave a longer time to alarm from the start of the fire than a domestic door of any fit did. Well fitting FR doors could allow a 'plug' of smoke to build up in the corridor which rendered the corridor impassable often well before the alarm was raised by a corridor detector.
FR Doors with seals - poor fitting ones would allow smoke plugs to form, well-fitted ones often resulted in only cool, low-level smoke, undetectable and not hindering passage.
The conclusion was that if FR doors were to be fitted, a heat detector should be put in each room accessed from the corridor. It would not necessarily save the life of the room's occupant, but it would raise the alarm well before the corridor was rendered impassable. It would also be less susceptible to false alarms from any activity of the occupant.
So I would suggest that if you cannot control what is put away in the cupboard, fit it with an FR door and put a heat detector in it.
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John
Please correct me if I am wrong ( again) but I thought the reason that heat detectors were specified for rooms following your research ( and I do remember that very well at the time and some excellent mock ups to demonstrate your findings) was because then many people smoked and there was a need to control unwanted signals? We were not interested then in protecting the occupant of the room- we were simply wanting to focus on raising the alarm before the means of escape was jeopardised?
So I would have thought that a smoke detector would have given an earlier response to a fire in the cupboard- and thus enhance everybodies safety.
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I suggested a heat detector for the cupboard location as they are cheaper than smoke detectors and less likely to give any false alarm through dust and the like - if, for example, the cupboard is used for housing cleaning equipment. Also potentially more robust and therefore more likely to resist any bump from whatever is being stored. And in a small cupboard I would expect a heat detector to give an alarm quite quickly because the heat would build up faster than in a large room. Just a bit of pragmatism on my part as far as Firewolf's scenario goes.
What about Para 5.29 of AD 'B' which says that a protected stairway "needs to be free of potential sources of fire"? A cupboard with FR construction is allowed but only if it is not the only staircase to the building. Can Firewolf enlighten us as to whether this is the case or not?
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My experience (of working in the fire alarm industry) is that the price between a point heat detector and a point smoke detectors did not vary by more than £1 in terms of cost.
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This discussion is based on the assumption that smopke from a fire in the cupboard won't find its way into the stairwell.
Even a well fitted door with smoke seals will leak enough smoke to trigger a smoke alarm well before it becomes a threat to anybody.
so don't worry about it.
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Wee Brian...the smoke will find its way into the stair but it may have lost it's bouyancy...I think it was B.K.Ghosh that provided evidence of this in his research.....but I'm sure someone can elaborate.
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The work on doors and corridors mentioned in my post #6 above also involved Mr Ghosh. It is possible he wrote something about the work after the Home Office considered our results, but I have nothing in my records - I'd been moved onto work on fire-fighting foams by then.
But I confirm that a well-fitted* FR door, with or without seals, will not usually allow bouyant smoke through until the later stages of a fire. In the corridor this resulted in the formation of a 'plug' of cool smoke which blocked the corridor but did not move towards a detector in the corridor.
How this would translate into a vertical stairwell I am not certain, but if there was only a detector at the top of the stairwell I suspect we could end up with cool smoke filling the bottom of the stairwell and no detection. And could an understair cupboard contain sufficient fuel to eventually breach an FR door? Where would the air for combustion get in?
I continue to think that the best solution is to put a detector in the cupboard. This will give an early alarm before there is any loss of visibility in the stairwell.
*Well-fitted means a 1mm gap around the door between the door frame and door edge. Door stops firm against the corridor side of the door, the door opening into the room. Doors with a 3mm gap but fitted with seals behaved rather like the 1mm gapped doors without seals.
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I'm aware of the work you are talking about. obviously a detector in the cupboard is ideal but i don't think its necessary.
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Well, I did query in my last post about the ability of a cupboard's contents to sustain a fire for any length of time. If the risk assessment shows that the nature of the contents is such that it is unlikely a fire would start and be sustained, then relying on the FR door would be OK with me.
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Thanks for your replies so far its been a very big help.
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I think the 'heat detector in bedroom' argument may now out of date-as the new FSO talks about safety of relevant persons etc-so we cannot discount their safety ie sacrifice them.
Also is AFD (smoke) better than F.R.-as suggested as an alternative for dead ends(except sleeping of course).Better to have early warning than for it to burn through an f.r. door and find out too late.
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The detector in the bedroom is not there for the safety of the person in the room. It is there to provide warning for othersbefore the corridor is compromised.
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exactly my point-as a relevent person their safety cannot be ignored,therefore heat detection not enough,and should be changed to a smoke detector.
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Whoa there.
Dont forget the magic word "reasonable". you cant go sticking a smoke detector in every place that a relevant person happens to be standing.
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Oh no..I agree with Wee Brian. Pip do you have a detector in your bedroom, probably not. The person in the room should be aware of the problem.
Also consider the problems of unwanted fire signals in hotel bedrooms.
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actually, yes I do (optical and ionisation where appropriate, and in my childrens bedrooms, and every other room including loft except my kitchen and toilets, and CO detectors in my hallway, and I shut every downstairs door at night,and we have an escape plan-it may not be perfect,, but it is better than average!. Whilst acknowledging the original argument for putting H.D. in hotel bedrooms, the question I am asking is would this now be accetable under the F.S.O?I don't think that we can accept that we can say to the individuals sleeping in a H.D. protected room 'sorry mate, the detector is there for everyone elses benefit, not yours'.So how is each individual going to be protected from a fire in their own room?Is it 'reasonable' to stiill accept the sacrifice of that person?
My local Fire Authorities policy is to recommend the provision of smoke detectors in all hotel bedrooms, at the same time making the occupier aware of the higher incident of false alarms that may occur because of the installation of this type of detector. To obviate excessive false alarms it will be necessary to incorporate a device in the alarm system to achieve a 90 second delay between the automatic system operating and a general alarm being raised. Operation of a manual call point or smoke detector, other than those in bedrooms, must still cause an instantaneous general alarm. Once a detector has operated it must be acknowledged at the control panel within 10 seconds or the system will override the 90 second delay and go to general alarm. This is to ensure that the reception is continuously manned.
The 90 second delay should, in general, give sufficient time for the alarm to be investigated. If the alarm is not reset within 90 seconds then the system should initiate a full general alarm. There may be a need to extend the 90 seconds delay but this must not go beyond 3 minutes without the approval of the Divisional Fire Safety Management.
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Well Pip I'm afraid the fact is that there is not really a problem for the person in the room so why spend a lot of money that could be best used elsewhere.
Your house is very safe, but we cannot and should not impose that standard on everyone regardless of the risk or cost involved.
Reasonable in the circumstances of the case, risk appropriate....not new terms but terms some have trouble understanding.
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I don't understand why you say it is not a problem for the person in the bedroom-if they are not alerted soon enough-and H.D. I would suggest is not going to in most cases,they are lost.Fire services across the country are currently fitting S.D. in domestic house's bedrooms-to give warning to the occupants of the room and others within their house.
I am just suggesting that the use of H.D. in sleeping accommodation, with the reasoning behind it, would not satisfy the F.S.O.
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pIp.
common practice in Hotels these days is to stick smoke detectors in the bedrooms except for the ones where smoking is allowed where HDs are provided.
Not sure how the smoking ban will affect this.
The fact that some Fire Services are doing something does not necessarily mean that its a good idea.
It still comes down to what is reasonable. In many cases the occupant of the room on fire will know about the fire. It gets kind of hot and smokey. Clearly if they are in a deep (beer induced) sleep then they may not wake soon enough. I dont think it is reasonable to apply the Order in the way you suggest.
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I don't understand why you say it is not a problem for the person in the bedroom-if they are not alerted soon enough-and H.D. I would suggest is not going to in most cases,they are lost.Fire services across the country are currently fitting S.D. in domestic house's bedrooms-to give warning to the occupants of the room and others within their house.
I am just suggesting that the use of H.D. in sleeping accommodation, with the reasoning behind it, would not satisfy the F.S.O.
Pip can you tell me when was the last fire death involving a guest asleep in an hotel when the fire started in the room of origin?
I think you'll find if you research the matter that there isn't really a problem.
HMOs, different problem..........and in those cases I think we should be looking at diifferent solutions e.g. sprinklers.
The FSO requires the responsible person to take such general fire precautions as are reasonably required in the circumstances of the case.
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Well,if number (or rather lack of ) of deaths in Hotels suggest that is the case, then I can understand your reasoning.The risk is low,even if the hazard may not be, and therefore may comply under the 'reasonable and practable'.
Can I ask why this concept was not then applied to non sleeping risks?Surely if people were to be awake in these H.D. protected rooms eg offices, then the same criteria would apply, along with reducing unwanted AFA's.
If as mentioned by Wee Brian it is common in most hotels to put in S.D. ( and of course it is in my area-and unfortunately I dont get to stay in hotels very often outside my patch to know any different) then why?if H.D. is 'recommended'. I can understand the argument that, as lives lost in H.D. protected hotel rooms is neglible,and therefore accept that the balance of cost of replacing with S.D. would not be reasonable and practable, is it still not better to recommend S.D in new builds/conversions/rebuilds etc where the False alarms can be managed?
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Most - non sleeping risk do not need any fire detection at all. Lots of them have it but thats just because people don't know what they are doing.
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yes I know,usually put in as bog standard for life/property protection to cover all bases whether needed or not, but what about inner rooms, or as shown in the new guides,instead of F.R. in dead ends?
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This cannot go on...I agree with Wee Brian again!!!! People are the best detectors so most offices would not normally require AFD.
Pip I would agree that in a new build hotel afd should incorporate smoke detection in rooms with suitable management. The problem of false alarms can be overcome with modern alarm systems.
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Blimey - at this rate we'll be exchanging xmas cards!
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well I could send you a postcard, as I am on my hols next week!
Nothing like promoting discussion-helps prevent the fables that develope when your workplace is insular!
The benefit of you more experienced engineers is that you know the history of why some decisions were made, the though processes behind them.For us more junior practishioners, that reasoning has not always been passed on, no matter how many courses etc we have been on.We sometimes also have to second guess, which adds to the mix.When I first started in FS, I was told ask 5 different inspectors and they will give 5 different answers-how true-and all of them plausible!
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It will be interesting to see what the Rosepark Care Home fire Report has to say about fire in cupboards, it would seem in this case that the fire started in a cupboard on the ground floor and smoke killed 14 service users on the first floor, even with smoke detection in the building.
How carefull can you be?
Any one now if the report is expected to be made public and if so when.
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possibly one of the reasons that there may not have been any smoke seals on any of the bedroom doors-ala 'draft green guide'.