Heat detection throughtout a 3 story office building during the day

[boro]

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.

[kurnal]

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.

[Davo]

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

[boro]

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.

[boro]

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.

[Phoenix]

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

[colin todd]

All sounds fine to me, sounds like the designer is a thinking man.

[boro]

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

[colin todd]

Avoiding false alarms at a time that the smoke detection is not necessary.

[Wiz]

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.

[Midland Retty]

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.

[Wiz]

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.

[nearlythere]

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.

[Midland Retty]

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.

[kurnal]

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