Heat detection throughtout a 3 story office building during the day

[AnthonyB]

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.

[Clevelandfire 3]

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.

[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.

I think you are misreading the statement by K Wiz. Detection require to cover inner room not put in inner room.

See below

[Wiz]

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.

[Wiz]

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!

[CivvyFSO]

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.

[Midland Retty]

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.

[Wiz]

.....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)?

[Midland Retty]

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.

[David Rooney]

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.

[Wiz]

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.

[Midland Retty]

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.