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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: boro on September 18, 2010, 04:56:21 PM
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Dear All
I have a situation with a newly renovated 3 story building that will be used as an office/administration block. The architect/project manager wants the new P2 fire alarm system during the hours of 0700 - 1800 hours to change all detectors to heat detection mode only and after 1800 hours the Fire Alarm Panel will revert all detectors back to dual mode (smoke and heat). Saturday / Sunday operation will be dual mode smoke and heat 24/7. I am not comfortable with this instruction on the basis that there are kitchens on each floor, I would guess that the corridors won’t be 100% sterile environments together with the building having a facility to allow access to persons with mobility impairments, but the lifts themselves aren’t evacuation type and access to the top level is via a lift platform only and the staircase landing will also act as refuge points. Other reasons why I am not in agreement with this, is that in my opinion, the occupants and assists are being put at unnecessary risk due to delay of a fire/smoke being detected at a very early stage. I would still recommend that the detection remains in its original state 24/7 in dual mode (smoke and heat). I would only recommend that heads are switched to heat only where there is possibility due to the activity within the rooms/building the chance of unwanted fire signals may occur. I would greatly appreciate your views in this issue.
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The benchmark standard for life safety in an occupied workplace is a manual only system with smoke detection to cover inner rooms, unprotected dead ends or high risk areas where a fire may occur and not be detected by people. I guess anything over this level is a bonus- unless of course the detection forms part of an engineered solution such as reductions in structural separation, extended travel distances etc.
But then since the system is already installed it is difficult to justify the ALARP principle if you disable functions that are otherwise already offering additional protection. I see where you are coming from and unless there are other over riding considerations over the risk to business continuity that may arise eg rooms where students sit exams, then I would tend to agree with you on this one.
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Boro
Agree
We all know that in most cases the corridor SD will pick up a problem well before the kitchen HD
I appreciate the need to reduce UWFS but nothing in your topic indicates any particular risk other than the kitchens
Incidentally, will any fire signal after 1800 go anywhere or rely on passers by?
If not, whats the point?
davo
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Hi Davo
Yes the signal from the alarm in this building goes to our security gate house which is maned 24/7 and they are all trained to investagate all signals. Unless a call backs up the signal confirming fire.
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Thanks Kurnal
your comments are appreciated. I just don’t understand the logic why the project manager as suggested the switching, its doesn’t benefit the occupants and it certainly reduces the protection of assists from fire and smoke.
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Hi boro,
I sympathise with your lack of understanding. It's no good elements of the fire strategy residing in someone's head. All details and supporting rationale should be written down, hopefully in some sort of fire safety manual. I spend a fair bit of time writing retrospective fire strategies for large buildings and I have a never ending struggle trying to find out what has been installed in the building and, just as importantly, why.
Don't let it rest, badger the project manager for his reasoning and then get it recorded for the fire strategy (even if it's not written yet).
Also, it sounds like a complicated system for a simple office building. Why are they making things so complicated? It all sounds like overprovision to me.
Incidentally, I was going to say this.... "this may sound cynical but is the project manager's fee proportional to the cost of the project? There are very many cases where this form of relationship leads to overprovision, and a symptom of this is an inability on the part of the project manager to produce a good reason for undertaking the work" ....but then I thought better of it.
Stu
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All sounds fine to me, sounds like the designer is a thinking man.
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Colin
Could i ask what do you think is stragety is by switching the heads, other than reducing the posibility of unwanted signals in an office environment?
boro
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Avoiding false alarms at a time that the smoke detection is not necessary.
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The benchmark standard for life safety in an occupied workplace is a manual only system with smoke detection to cover inner rooms, unprotected dead ends or high risk areas where a fire may occur and not be detected by people. ..............
I'm interested in this comment Prof. As a fire alarm engineer I'm mostly interested in the recommendations of BS5839-1, but try to take on board all the other advice, recommendations, rules and laws. In my belief it has always been most important to protect escape routes etc. with automatic detection than what appears to be suggested by your description 'with smoke detectors to cover inner rooms' or did you mean 'detectors that provide coverage for escape routes from inner rooms'? I don't see the point in putting a smoke detector in an inner room when the escape route from it has no detection.
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Hi Boro
The big question to ask yourself is whether or not automatic fire detection is required for life safety purposes in this scenario.
Could a fire occur and then spread undetected, rendering escape routes impassable before occupants become aware of the blaze and can evacuate?
If the answer is no then I don't see why this needs to be a big issue. I note you mention that the catergory of alarm system is P2 - a property protection system, not a life safety system.
So you need to balance it up, I appreciate the system could be used for life safety purposes, and if your risk assessment tells you that it is needed for life safety then so be it. But if not, what is the problem? Heat detection is the preferred detector in kitchens. Plus where fire resistance is of the correct standard we know Heat detection is permitted in rooms directly off means of escape (hotel bedrooms being the topical case in point)
What about MOE? does that need the protection of AFD? or will the occupants act as "fire detectors". Are you in single direction of travel? Or at there multiple ways of travel?
To answer Wiz's question. With inner room conditions you have a main corridor, off the corridor an access room and then off that the inner room. The aim is to ensure that the occupant of an inner room can be warned of a fire occuring in the access room, travel through it, and get to a means of escape safely (ie. the corridor)
To achieve this you can consider fitting a vision panel within the door to the inner room or window so the occupant can see a fire occuring in the access room,or the partion between the inner room and access room should have a 500mm a gap at the top so occupant can see or hear smoke / fire, or you can install smoke detection in the access room which raises the alarm.
Whilst in the inner room the occupant is in single direction of escape and has to travel through the access room.Once you get out onto the corridor, there may well be multiple directions of travel thus AFD may not be required in the corridors.
Again it comes back to means of escape and whether fire would occur, go undetected and affect MOE before people are aware of it and safely evacuate. If you have a busy office block where people are up and down the corridor all the time, and would thus act as human detectors if a fire occured , and you have two or more ways out, a manual fire alarm system would suffice.
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That all makes sense M.F. but Prof. K's reply gave the impression was that detection was required in the 'inner room' only, not in the access room.
With respect to your answer M.F. I wouldn't want to be sitting in the inner room in your scenario. The access room might have automatic detection but without automatic detection in the corridor ( no detection because you say it might provide multiple directions of travel) I could still become trapped through not being able to access the smoke- logged corridor (which it is likely to be by the time the smoke has made it's way from the unprotected corridor to the detector in the access room.
I maintain that it is pointless having detectors in an access room (or a vision panel in the door between the access room) without automatic detection in the corridor. In my view the basic automatic detection coverage is always in the escape routes (including the corridors) and, in fact, in your scenario, the access room becomes part of the escape route from the inner room and therefore automatically also requires automatic detection in systems L4 and upwards.
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That all makes sense M.F. but Prof. K's reply gave the impression was that detection was required in the 'inner room' only, not in the access room.
I think you are misreading the statement by K Wiz. Detection require to cover inner room not put in inner room.
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With respect to your answer M.F. I wouldn't want to be sitting in the inner room in your scenario. The
Hi Wiz
If the main corridor only had single direction of escape then yes you would look at AFD protecting the route.
But the bread and butter principles of means of escape, where you have two or more directions of travel available to you, in a building where fire will be readily detected by persons in the building, there may not be any need for AFD in your escape routes at all. I say "may not be required" quite deliberately, because there will always be odd exceptions.
Even then you will still need one of the measures I mentioned earlier to protect an inner room scenario, otherwise you may never even get as far as the main corridor to make you onward escape.
If we were talking about hotels or other sleeping risks then I'd agree with your comments totally.
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Yes sorry Dr Wiz if I was not clear, the detector needs to be in the access room if it is to offer some protection to occupants of the inner room. Thats what I meant, trouble is I have been pushed for time these days and have been guilty of hasty posts and sweeping unjustified generalisations.
I used to read things through carefully before posting but these days I always seem to be in a rush, just bang it out press the send button and its gone warts and dfdgfld w[ofgik;sz
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I think you've answered your question in the OP. If it's a P2 system (or more correctly I would guess it's a P2/M) then the AFD is not there for the occupants - the 'M' component is for life and the detection and alarm panel monitoring is for property protection only.
In a single occupancy office it's considered that the power of the human nose will outperform a smoke and the usage of the buliding such that persons will indeed be present and moving around such that they will detect a fire far before MoE is threatened, the 'M' system allowing the human detector to spread the message.
Also inner room situations etc. don't always require AFD, a suitable vision panel will suffice a lot of the time.
That's why the codes say an 'M' system does the business in this type of occupancy unless you start having specific situations within the building requiring otherwise (such as phased evac, inner rooms no VP, etc)
So if this is a 'typical' office and the AFD isn't part of an engineered solution for a structural departure etc then it doesn't bother me - we've at least one large office block were for several years AFD on the floors and kitchenettes has been heat in day mode and smoke at night - BCO, Insurers, FRS & our FRA found it acceptable and the reduction in UWFS has pleased tenant managers, the FRS and improved the response when the alarm does go off.
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With respect to your answer M.F. I wouldn't want to be sitting in the inner room in your scenario. The access room might have automatic detection but without automatic detection in the corridor ( no detection because you say it might provide multiple directions of travel) I could still become trapped through not being able to access the smoke- logged corridor (which it is likely to be by the time the smoke has made it's way from the unprotected corridor to the detector in the access room.
With respect Wiz you don't understand the basic principles regarding means of escape. AnthonyB best describes those principles
I think you've answered your question in the OP. If it's a P2 system (or more correctly I would guess it's a P2/M) then the AFD is not there for the occupants - the 'M' component is for life and the detection and alarm panel monitoring is for property protection only.
In a single occupancy office it's considered that the power of the human nose will outperform a smoke and the usage of the buliding such that persons will indeed be present and moving around such that they will detect a fire far before MoE is threatened, the 'M' system allowing the human detector to spread the message.
That's why the codes say an 'M' system does the business in this type of occupancy unless you start having specific situations within the building requiring otherwise (such as phased evac, inner rooms no VP, etc)
So if this is a 'typical' office and the AFD isn't part of an engineered solution for a structural departure etc then it doesn't bother me - we've at least one large office block were for several years AFD on the floors and kitchenettes has been heat in day mode and smoke at night - BCO, Insurers, FRS & our FRA found it acceptable and the reduction in UWFS has pleased tenant managers, the FRS and improved the response when the alarm does go off.
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That all makes sense M.F. but Prof. K's reply gave the impression was that detection was required in the 'inner room' only, not in the access room.
I think you are misreading the statement by K Wiz. Detection require to cover inner room not put in inner room.
See below
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Yes sorry Dr Wiz if I was not clear, the detector needs to be in the access room if it is to offer some protection to occupants of the inner room. Thats what I meant, trouble is I have been pushed for time these days and have been guilty of hasty posts and sweeping unjustified generalisations.
I used to read things through carefully before posting but these days I always seem to be in a rush, just bang it out press the send button and its gone warts and dfdgfld w[ofgik;sz
I thought it must be so, Prof. But I just wanted to check.
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With respect to your answer M.F. I wouldn't want to be sitting in the inner room in your scenario. The
Hi Wiz
If the main corridor only had single direction of escape then yes you would look at AFD protecting the route.
But the bread and butter principles of means of escape, where you have two or more directions of travel available to you, in a building where fire will be readily detected by persons in the building, there may not be any need for AFD in your escape routes at all. I say "may not be required" quite deliberately, because there will always be odd exceptions.
Even then you will still need one of the measures I mentioned earlier to protect an inner room scenario, otherwise you may never even get as far as the main corridor to make you onward escape.
If we were talking about hotels or other sleeping risks then I'd agree with your comments totally.
Interesting M.F.
I still can't see the point in worrying about putting detection in the access room when there is none in the corridor that the access room leads onto.
I can see myself working in my inner room and the alarm goes off; Caused by smoke seeping into the access room from the corridor and operating the smoke detector thoughtfully provided in the access room. However, the corridor is now full of smoke and although the corridor provides two escape routes, I can't even get into the corridor due to the heavy smoke! Obviously, if there had been a smoke detector in the corridor It would have hopefully operated early enough for the corridor still to be used.
If the two exit route principle for determining detector requirement, is as you say,the principle fire officers might use, it seems to me, that it could be at variance with the design principles of BS5839-1. I learn something new every day!
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There should be nothing to burn in the corridor, therefore a fire should have started in another room. If a cat M alarm is sufficient, then it is only sufficient providing that people are around to raise the alarm manually. If this is the case then someone should walk out and manually set the alarm off which should give you warning in your inner-room.
In the real world, this would almost never be the case, to guarantee that someone would be there to raise the alarm. If this is the case then I agree that further detection would be required in any rooms where a fire could start unnoticed.
The commentary from the BS seems to point towards Wiz's argument.
If the objective is to protect the occupants of a building in which no one sleeps, and fire is likely to be detected
by people before smoke seriously reduces visibility in escape routes, automatic fire detection might not be
necessary: a Category M system might suffice.
In some buildings, a fire risk assessment might determine that unacceptable risk to occupants can be
reduced by the installation of fire detectors in only selected rooms or areas in the building.
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The commentary from the BS seems to point towards Wiz's argument.
If the objective is to protect the occupants of a building in which no one sleeps, and fire is likely to be detected
by people before smoke seriously reduces visibility in escape routes, automatic fire detection might not be
necessary: a Category M system might suffice.
In some buildings, a fire risk assessment might determine that unacceptable risk to occupants can be
reduced by the installation of fire detectors in only selected rooms or areas in the building.
No I disagree.
It actually echoes what the majority of people have already said; That you can have means of escape which is not protected by AFD, (which Wiz feels is risky) but on a risk assessment basis there may be occassions where you will need AFD.
Wiz its not the principles that Fire Officers use, its the principles of means of escape fire safety professionals in general use.
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.....Wiz its not the principles that Fire Officers use, its the principles of means of escape fire safety professionals in general use.
I thought they were one and the same thing!
I have no problem understanding that some buildings do not require automatic detection and this has nothing to do with the point I am making.
I have no problem understanding that a fire risk assessment may conclude that something completely at variance with the design principles of BS5839-1 is required in some exceptional circumstances, and this has nothing to do with the point I am making.
What I don't understand is that 'the principles of escape that fire safety professionals generally use' could include installing an automatic smoke detector in an 'access' room to 'protect' the occupants of an 'inner' room, but deciding that no automatic detection was required in the corridor serving that 'access' room just because the corridor itself 'provided two different means of escape'. If that corridor itself was smoke-logged (before someone tried to escape from the 'inner' room) because it had no automatic detector installed, then the detector in the 'access' room has hardly provided a solution to the person potentially being trapped in the 'inner' room! It might as well not be installed - they are trapped anyway.
If any automatic detection is to be installed in a building then surely covering all the escape routes is the first basic design objective (Cat. L4)?
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Ok you said you are happy that you can have buildings without AFD.
Forget about this concept of smoke filled corridors - there shouldnt ever be a case in any building where you will get smoke logged corridors which are untennable or unpassable before the alarm is raised by either by humans or (if it is a building where humans are unlikely to detect the fire because they are asleep for example) then automatic detectors.
If you do have smoke filled corridors /means of escape before people evacuate something has gone horribly wrong!!!!
Automatic detector in an access room is one of several solutions to address an inner room situation. It forms if you like localised protection - infact the bit Civvy FSO coppied from BS5839 talks about that!
Now I agree that it seems daft just whacking in a solitary detector in an access room when the rest of the building doesnt have and doesnt need any other form of AFD - far better to perhaps stick a vision panel or window in the door to the inner room probably.
By fire officer I wondered if you meant fire service inspecrs, I was pointing out that all fire safety professionals, consultants, enforcers, assessors will ( or atleast should ) be aware of these basic principles.
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Ok you said you are happy that you can have buildings without AFD.
Forget about this concept of smoke filled corridors - there shouldnt ever be a case in any building where you will get smoke logged corridors which are untennable or unpassable before the alarm is raised by either by humans or (if it is a building where humans are unlikely to detect the fire because they are asleep for example) then automatic detectors.
But in these days of flexitime and people working late/starting early there is a much higher risk of people working obliviously in their isolated offices in large office complexes and not enough "human detectors", so it's quite feasible a fire starting in an office with no AFD could prevent use of a common MoE corridor.
As a designer of fire alarm systems it seems far simpler and safer to specify L4 minimum coverage than a solitary detector in an access room that you have to explain to the client is technically only there as a solution to the risk posed by constructing his inner room.
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Whilst still agreeing with the L4 point made by Dave above, I also accept Midland's point about the 'human detectors' quickly picking up fires likely to affect corridors, and bow to his superior knowledge that corridors should never become unpassable before the alarm is raised by humans. On this basis, I can see the point that a detector in the 'access room' would provide detection before possibly a 'human detector' and this would allow the person in the inner room to reach the still passable corridor in good time. Obviously this would then be an L5 system.
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Whilst still agreeing with the L4 point made by Dave above, I also accept Midland's point about the 'human detectors' quickly picking up fires likely to affect corridors, and bow to his superior knowledge that corridors should never become unpassable before the alarm is raised by humans. On this basis, I can see the point that a detector in the 'access room' would provide detection before possibly a 'human detector' and this would allow the person in the inner room to reach the still passable corridor in good time. Obviously this would then be an L5 system.
Yep thats it Wiz
Dave Rooney also makes a good point picks up on the dynamics of building occupancy, and again, although it does sound rather wooley, this is where risk assessment should address such issues.