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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Technical Advice => Topic started by: David Rooney on April 01, 2010, 07:00:10 PM
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Scenario:
In the process of installing a project we come across a variation - in this case, a large high open area has three beam detectors installed - all looks good on paper.
In reality there is a large lantern light structure taking up at least 20% of the total ceiling area and is at least 2m higher than the rest of the ceiling.
For all the reasons listed in the BS section 22 this lantern light needs a detector in the apex - due to the overall height it actually needs an additional beam detector.
Someone up the chain has said no to the installation. We have said then this is a deviation from the objective of the system (being L1/P1), doesn't comply and would be listed on ensuing certification.
However, this prompted the thought, in order for this or any variation to be an "agreed variation" who exactly needs to agree it - who exactly are "all interested parties" and whos responsibility is it to get all these parties to sign up to this "agreement".
The BS commentary says "........ variations may be based on the engineering judgement of a competent person......" does this mean we can accept the word of the "consultant" and write this in as an agreed variation even if in our opinion he's an incompetent numpty?
(no offence to numpties...:))
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Any mitigating factors?
Eggshells here, obviously the Architect, the owner of the premise and your good selves who should compose the wording.
Presumably you will mark his card and steer well clear in future?
davo
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i would say yes but get him to sign for it. (if he agrees)
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David,
As innocent by-standers, we do not know why the person "up the chain" said no detection was required. Also we have no justification from you, other than that the standard says so, as to why the detection is required.
If, for example, there is no reasonably foreseeable location and type of fire that could lead to smoke entering the lantern light without, en route, activating one of the installed beam detectors, then what would be the point of detection in the lantern light? In this case I would suggest that all parties could safely agree to the variation.
On the other hand, if it is foreseeable that a fire could start in a location that would fill the lantern light with smoke without activating the installed beam detectors then we have to consider this: Does it matter? That is to say, this scenario would indicate that there is a delay in the actuation of the fire alarm system (presumably the smoke will descend, eventually, to reach the beam detectors). This delay in actuation is very likely to have negative consequences on the fire safety provisions in the building but only someone with a full knowledge of the fire strategy can know this.
So I would suggest that you ask yourself: 1) Is there a foreseeable location and type of fire that will not be detected by the installed beam detection? 2) If so, would a delay in alarm actuation have a significant effect on the fire safety provisions in the building?
If you feel that fire safety is not compromised then the variation can be agreed; if you feel that fire safety is compromised then all parties cannot agree to the variation and the certificate cannot be signed to say the the system complies with the standard. In other words, if all parties cannot agree then the system cannot comply with the BS. In other, other words, if the standard is to comply then all parties must agree.
Stu
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Scenario:
In the process of installing a project we come across a variation - in this case, a large high open area has three beam detectors installed - all looks good on paper.
In reality there is a large lantern light structure taking up at least 20% of the total ceiling area and is at least 2m higher than the rest of the ceiling.
For all the reasons listed in the BS section 22 this lantern light needs a detector in the apex - due to the overall height it actually needs an additional beam detector.
Someone up the chain has said no to the installation. We have said then this is a deviation from the objective of the system (being L1/P1), doesn't comply and would be listed on ensuing certification.
However, this prompted the thought, in order for this or any variation to be an "agreed variation" who exactly needs to agree it - who exactly are "all interested parties" and whos responsibility is it to get all these parties to sign up to this "agreement".
The BS commentary says "........ variations may be based on the engineering judgement of a competent person......" does this mean we can accept the word of the "consultant" and write this in as an agreed variation even if in our opinion he's an incompetent numpty?
(no offence to numpties...:))
The interested parties would normally be:
1) The persons responsible for how the the premises are being used
2) The persons owning the premises
3) The company insuring the premises and insuring the use of those premises.
4) The licensing authority for the use of the premises. (if required)
I would say it is the designer's task to get the variation agreed.
If the 'consultant' has taken on the role of the designer of the system then I would say it is assumed he is a 'competent' person.
However you mention someone further up the chain has said NO to the installation of the additional detection. But who is saying that their 'engineering judgment has determined that additional detection is not required?
Further to Stu's answer, the chances of smoke by-passing the beams are pretty high. With the beam detectors being mounted within 600mm of the ceiling then it wouldn't take very long until before the smoke filled up the space and was finally detected by the beams. The size of the lantern light is such that the 'space' has been significantly increased; this will delay sensing by the beams even longer. It could be determined, by calculating the volume of the extra 'space' provided by the lantern light, the extra time taken for the detection to respond - if it creates 10% extra space, it could be argued that it would take 10% longer to respond. Would 10% longer matter?
However, no-one has yet mentioned whether the lantern light is also used for ventilation. If it is, then the lantern light needs additional detection in it, no matter what!
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Hello Stu
To clear up a couple of points...
David,
As innocent by-standers, we do not know why the person "up the chain" said no detection was required. Also we have no justification from you, other than that the standard says so, as to why the detection is required.
The person "up the chain" I believe, is the money man working for the Builder and trying to keep costs down. The justification is exactly what you say - the standard says so and the specification from the consultant says we have to meet current standards etc. The building is a museum and open to the public by the way.
If, for example, there is no reasonably foreseeable location and type of fire that could lead to smoke entering the lantern light without, en route, activating one of the installed beam detectors, then what would be the point of detection in the lantern light? In this case I would suggest that all parties could safely agree to the variation.
As a fire company we are told we are not risk assessors and according to BS the client (or representative) should do the RA and surely decide whether its necessary - I don't think it is for us to advise against it. Regarding the smoke plume setting off a beam en route, technically the existing beams are probably 3m distance from the top of the lantern which brings in other issues regarding spacing of beams etc.
On the other hand, if it is foreseeable that a fire could start in a location that would fill the lantern light with smoke without activating the installed beam detectors then we have to consider this: Does it matter? That is to say, this scenario would indicate that there is a delay in the actuation of the fire alarm system (presumably the smoke will descend, eventually, to reach the beam detectors). This delay in actuation is very likely to have negative consequences on the fire safety provisions in the building but only someone with a full knowledge of the fire strategy can know this.
So I would suggest that you ask yourself: 1) Is there a foreseeable location and type of fire that will not be detected by the installed beam detection? 2) If so, would a delay in alarm actuation have a significant effect on the fire safety provisions in the building?
All of this is absolutely true but my point is that I don't think it's down to us (or a Quanity Surveyor) to make these decisions - again, the Spec says L1/P1 - earliest level of detection - if we don't install the extra beam technically we are in contravention.
If you feel that fire safety is not compromised then the variation can be agreed; if you feel that fire safety is compromised then all parties cannot agree to the variation and the certificate cannot be signed to say the the system complies with the standard. In other words, if all parties cannot agree then the system cannot comply with the BS. In other, other words, if the standard is to comply then all parties must agree.
Stu
In this very contractural job, we only have direct correspondence with the Electrical Contractor and there is at least another three levels of contractor involved until you get to the Architects/Consultants and the end user. We don't know that the end user has a clue as to what protection is being afforded - these jobs are always down to small print and the money men paid by the Builders to generally get away with installing the bare minimum to meet the contract.
I'm not trying to get technical answers to this specific site or justify this beam, I was trying to broaden the whole issue of who ultimately has the right to make decisions regarding variations = "leaving bits out" when we are contractually obliged to meet BS and are basically being told (in this case by a QS but it could be a consultant etc) not to meet the requirements for an L1/P1 system.
Dave
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The interested parties would normally be:
1) The persons responsible for how the the premises are being used
2) The persons owning the premises
3) The company insuring the premises and insuring the use of those premises.
4) The licensing authority for the use of the premises. (if required)
I would say it is the designer's task to get the variation agreed.
All agreed Wiz..... but are we saying that we (as designers) should be attempting to make contact with all these people - and the National Charity putting up the money for the job, they have a vested interest too.... and getting them all to sign up to a variation before we can officially list it as "agreed"?
Have you ever had an agreement from insurers etc ?
If the 'consultant' has taken on the role of the designer of the system then I would say it is assumed he is a 'competent' person.
However you mention someone further up the chain has said NO to the installation of the additional detection. But who is saying that their 'engineering judgment has determined that additional detection is not required?
Further to Stu's answer, the chances of smoke by-passing the beams are pretty high. With the beam detectors being mounted within 600mm of the ceiling then it wouldn't take very long until before the smoke filled up the space and was finally detected by the beams. The size of the lantern light is such that the 'space' has been significantly increased; this will delay sensing by the beams even longer. It could be determined, by calculating the volume of the extra 'space' provided by the lantern light, the extra time taken for the detection to respond - if it creates 10% extra space, it could be argued that it would take 10% longer to respond. Would 10% longer matter?
However, no-one has yet mentioned whether the lantern light is also used for ventilation. If it is, then the lantern light needs additional detection in it, no matter what!
I still haven't got an answer on that, but as stated it needs a beam for all the reasons listed in clause 22 regardless of ventillation...
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Dave, you are trying to comply with the BS. The lanterns give you a problem in complying. BS offers a way out - agreed variation! To take this option, you must comply with the recommendations for it no matter how difficult they may be. Otherwise don't try to comply with the BS at all.
If the agreed variation route is to be taken, then someone has to take responsibility for organising it otherwise it doesn't happen!
If the insurance company won't respond, or won't agree, to the variation then either try a new insurance company or just accept that the agreed variation option is not available and put a detector in the lantern.
The comment about ventilation was just a reminder that the 'engineered solution' of ignoring the recommendation for a detector in the lantern might not be as acceptable if the lantern light was actually also used for ventilation.
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Dave, you are trying to comply with the BS. The lanterns give you a problem in complying. BS offers a way out - agreed variation! To take this option, you must comply with the recommendations for it no matter how difficult they may be. Otherwise don't try to comply with the BS at all.
If the agreed variation route is to be taken, then someone has to take responsibility for organising it otherwise it doesn't happen!
If the insurance company won't respond, or won't agree, to the variation then either try a new insurance company or just accept that the agreed variation option is not available and put a detector in the lantern.
a. we don't know who the building insurer is - that's the client's choice
b. i think you're thinking I'm talking about our compan insurance which I'm not....
c. why is it down to "us" as the alarm company to gather all this information just to get a variation agreed - is it not down to the end user and the fabled RA - if he doesn't want it then justify it ??
The comment about ventilation was just a reminder that the 'engineered solution' of ignoring the recommendation for a detector in the lantern might not be as acceptable if the lantern light was actually also used for ventilation.
True but then that begs the question "when is a variation acceptable and when isn't it..??!"
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Most of the reasons i get for a variation from a consultant and/or customers are:
. Not needed.
. too expensive
. too much hassle
. Old classic-BS not law
. Your being over the top Sonny
. "what's the chances of ever getting a fire in there"?
etc etc
The last big install i did,all my correspondance with the Consultant regards all the variations in his design were done by e-mail,so i had a paper trail.
His justification for most things were-"not needed". If this is the only reason we are going to get and they are not going to install a device despite it being flagged up by the installer,then why can't this just be taken as the justification ? Not based on and engineering basis but it's all the information we are likely to get from them. Also as they are the "all knowing" Gods of the Construction world-then who am i to argue with them? :-X
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Hi David,
The picture is becoming clearer. As is your problem.
I believe the detection in the lantern light is required solely for the L1/P1 classification. So its purpose is not to protect life but to protect property (the structure and contents of the museum). Ultimately, therefore, it is the building user and the building owner who stand to sustain additional losses because of the variation (no one's going to die because of it). I would say that it is they who should make the judgement as to whether the detection is required or not. It certainly should not be the builder's "money man" who makes the decision!
The building user and building owner should make their decision by weighing the (really quite small) additional risk posed by the omission of the detection against the real cost of installing the extra detection. If they are happy to accept the small additional risk and make the real cost savings then, I would say, you could safely list the variation with brief supporting comments.
Just to clarify slightly further, in this case, the "interested parties" would not necessarily include the fire service as they have to restrict their legislative interests to life safety matters and provided that there is a fire alarm that, at least, covers the life safety requirements they can ask for no more. Also, at this stage the insurers are not relevant. They should be given sight of the certificate, with the variation listed, when they take on the risk and can take account of the variation in their decision to accept the risk and in the premium they require.
Stu
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Stu, the requirement for detection in lantern lights (within a protected area) has nothing to do with the category of a system.
In any event I can't understand your comment of a L1/P1 category only applying to property protection. It surely also covers life.
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David, I understand your frustration, but you only have three options.
1) To comply with BS, install the recommended detection in the lantern light(s)
2) To comply with BS, don't install the detection but get an 'agreed variation' based on sound principles
3) Don't comply with BS.
Graeme, also mentions the responses to someone highlighting items that don't comly with BS.
If you are only the system commissioner, then so what? Just include the variation on the certificate and let others sort the problem out. If they don't like you highlighting the variation on the certificate, again it is not your problem.
However, if you are the system designer then it is more of a problem. If BS recommends something you either have to provide it, or agree a variation, if you want to comply with BS. BS confirms who needs to 'agree'. Again, if you can't get these parties to agree then it is a problem.
I believe your customer should be the one to make contact with his insurer to negotiate the agreed variation. Although I'm sure the customer will need you to tell them what they have to ask the insurer.
I don't agree with Stu's comments about the insurance if such is already in place. The customer will have to tell his insurer about the varaition, but probably only if their policy clauses include mention of a level of fire detection system or similar. I agree with Stu that upon insurance renewal the option to find an insurer who will take the risk as presented might be necessary.
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I only have a basic knowledge of Fire Alarm Systems and no practical experience so be gentle.
The way I understand it there are four people concerned the designer,installer,commissioner and maintenance engineer. I would have thought the designer is the one to sort out variations and if he has missed something then he/she has made a mistake. Then it would be up to the others to bring it to the attention of the Responsible Person or the person responsible, that the fire alarm system is not in accordance with the BS and let him/her sort it out. Ensure its all done in writing and recorded it in their appropriate documentation. If the designer agrees to a variation with all interested parties and records it on his design certificate or corrects his/her mistake then no problems.
Cover your back. ;)
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Thanks men... it's all interesting stuff and tis true I'm completely frustrated !!
TW you're right in what you say and and it would all work "by the book" if we were working directly for the end user and we could converse in writing and tell them to talk to their insurer and explain the reasoning behind design issues etc etc etc .
But I suppose what I'm griping about really is the fact that when you're involved in any "large" job that involves Electrical contractors/M&E contractors god knows how many design teams /Arcitects /Consultants etc, then we become the tadpole at the end of the food chain swimming amongst sharks.
And it doesn't matter how much we spout the BS and tell everyone what their roles should be and what BS says we should all do, basically no one else gives a monkeys except us !
.... and apart from all that, it just seems quite difficult to apply this bit of the BS to a real world scenario....:)
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Thanks men... it's all interesting stuff and tis true I'm completely frustrated !!
TW you're right in what you say and and it would all work "by the book" if we were working directly for the end user and we could converse in writing and tell them to talk to their insurer and explain the reasoning behind design issues etc etc etc .
But I suppose what I'm griping about really is the fact that when you're involved in any "large" job that involves Electrical contractors/M&E contractors god knows how many design teams /Arcitects /Consultants etc, then we become the tadpole at the end of the food chain swimming amongst sharks.
And it doesn't matter how much we spout the BS and tell everyone what their roles should be and what BS says we should all do, basically no one else gives a monkeys except us !
.... and apart from all that, it just seems quite difficult to apply this bit of the BS to a real world scenario....:)
Hi David
I can understand why you are frustrated, and its a common problem.
As TW said all you can do is cover your back, inform them that what they are getting isn't compliant (In writing) and if they choose to ignore you then on their heads be it!
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And it doesn't matter how much we spout the BS and tell everyone what their roles should be and what BS says we should all do, basically no one else gives a monkeys except us !
bingo. thats it in a nutshell Dave.
Large installs as mentioned are the worst
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Thanks men... it's all interesting stuff and tis true I'm completely frustrated !!
But I suppose what I'm griping about really is the fact that when you're involved in any "large" job that involves Electrical contractors/M&E contractors god knows how many design teams /Arcitects /Consultants etc, then we become the tadpole at the end of the food chain swimming amongst sharks.
And it doesn't matter how much we spout the BS and tell everyone what their roles should be and what BS says we should all do, basically no one else gives a monkeys except us !
.... and apart from all that, it just seems quite difficult to apply this bit of the BS to a real world scenario....:)
Your frustrations as an alarm engineer mirror mine as a fire risk assessor. Invariably we come across half baked ill considered mix and match solutions to fire safety in which all contributors are responsible only for their element and nobody looks after the bigger picture and co-ordinates things to ensure that everybody is rowing in the same direction.
Sometimes the mistakes are so obvious and fundamental you cannot imagine why the qualified engineers do not pick it up and get it dealt with, usually the response is its someone elses problem and not in my contract. Nobody is thanked for rocking the boat.
No wonder I have no hair left and look 56 when I am really only 28.
I remember one top flight brand new football stadium with every possible bell and whistle - trouble was every body had taken their supply for their equipment from the same circuit and nobody had done the simple sums. I raised it from a fire point of view asking simple firemans questions and was roundly criticised - you are a fireman stick to fire, keep your nose out and leave the electrical side of things to us engineers. On the first match the circuit breaker melted, the floodlights cameras and PA all died.
Another industrial plant handling ethanol - the plant was beautiful but required zoning under the DSEAR Regs, nobody told the fire alarm designer of this simple fact, or the ventilation engineer who sourced his make up air for another area from the hazardous zones, and nobody took the sprinkler system flow into account when designing bunds.
Now- soap box out- What are the contributory factors?
Poor standards of design and project management, too much fragmentation and sub contracting for sure. But then
Do we still have Clerks of works?
Is the Building Control system part of the problem?
Or is it the Design and Build concept?
Do QA schemes for contractors really make any difference?
Are Approved inspectors in the pockets of the developers?
Do the different definitions and role of duty holders under the CDM Regs compared to those under the Fire Safety Order contribute?
Should the Designers, Principal Contractors and CDM Co-ordinators be defined as persons having control and held responsible under the Fire Safety Order at least for the warranty period of the building? Now that would make a difference!
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Prof., I've met some Bozos in my time in this game but never an electrical design engineer who didn't know anything about electrical distribution systems!!
It is the lifeblood of any electrical engineer and the basis of all initial calculations; First, is the electrical supply to the premises of sufficient capacity? Secondly, calculate cable sizing and fusing requirements for the electrical supply distribution.
Are you sure they hadn't used the club's centre-back clogger as their design engineer?
I agree with you that all too often all the different elements of a project stick rigidly to their own areas, knowing that raising questions and concerns about something that is not seen as being their responsibility will only 'rock the boat' and work against them in the long run. It is almost always better (financially to yourself) to ignore obvious problems in other people's responsibilities and let them take the flack when the proverbial hits the fan (or fuses the lights!)
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Thanks men... it's all interesting stuff and tis true I'm completely frustrated !!
But I suppose what I'm griping about really is the fact that when you're involved in any "large" job that involves Electrical contractors/M&E contractors god knows how many design teams /Arcitects /Consultants etc, then we become the tadpole at the end of the food chain swimming amongst sharks.
And it doesn't matter how much we spout the BS and tell everyone what their roles should be and what BS says we should all do, basically no one else gives a monkeys except us !
.... and apart from all that, it just seems quite difficult to apply this bit of the BS to a real world scenario....:)
Is the Building Control system part of the problem?
Yes. I certainly think that there is a general lack of knowledge in BC when it comes to fire seperation.
Had another issue last week with a brand new build. BC had been day before for final inspection and picked up a 50mm high threshold "step" at a final exit from stairway enclosure. Wasn't right from point of view of wheelchair users but accepted it as there was two other exit routes out of the enclosure.
I had a look above false ceiling in same stairway and found smoke stopping around plastic pipework & trunking ok but no fire stopping. And this is an enclosure containing a wheelchair refuge.
Commencement of FSO in NI posponed for number of reasons and I understand one being BC not happy that they may lose some work. (Can't think why they didn't flag it up at consultation stage.) But from my dealings with new builds & BC there is certainly a training need.
That coupled with the ongoing depletion of experience in FS Depts there are interesting times ahead.
Is it just me being too fussy or is a lot of a FRA more like a snagging list?
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Prof., I've met some Bozos in my time in this game but never an electrical design engineer who didn't know anything about electrical distribution systems!!
It is the lifeblood of any electrical engineer and the basis of all initial calculations; First, is the electrical supply to the premises of sufficient capacity? Secondly, calculate cable sizing and fusing requirements for the electrical supply distribution.
Are you sure they hadn't used the club's centre-back clogger as their design engineer?
Dr Wiz the problem in that case was too many sub contractors each only looking after their own bit and a lack of overall management and supervision of what was happening at the right level.
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Dr Wiz the problem in that case was too many sub contractors each only looking after their own bit and a lack of overall management and supervision of what was happening at the right level.
And I don't think anything has ever changed on any job ever since, it's every man for himself.
Fire detection and alarms are still generally seen as just a necessary evil and generally at the bottom of everyone elses list.
I think this "talk to all interested parties" stuff is too vague on these larger jobs and if there is going to be provision to do things differently from the "Standard" there needs to be a clear statement of who is taking responsibility for the fire detection system from the client's perspective at building stage perhaps written into the Building Regs.
I know this is probably written into the BS about defining roles but it's no good when no one else in the world has read it or cares.
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Dr Wiz the problem in that case was too many sub contractors each only looking after their own bit and a lack of overall management and supervision of what was happening at the right level.
And I don't think anything has ever changed on any job ever since, it's every man for himself.
Fire detection and alarms are still generally seen as just a necessary evil and generally at the bottom of everyone elses list.
I think this "talk to all interested parties" stuff is too vague on these larger jobs and if there is going to be provision to do things differently from the "Standard" there needs to be a clear statement of who is taking responsibility for the fire detection system from the client's perspective at building stage perhaps written into the Building Regs.
I know this is probably written into the BS about defining roles but it's no good when no one else in the world has read it or cares.
I used to be a mechanical services engineer, and the problems you described are typical of any major project. I wouldnt say its every man for themselves however.
Instead there is often so much going on that even the most seasoned project managers are unable to co-ordinate it all effectively. Trying to get Joe Bloggs on site to meet with John Smith is difficult as subbies are often all over the place on other jobs in between popping back to site to do their bit.
Time costs money and subbies cant afford to turn down other work simply to attend a site meeting.
This leads to cock ups, things get missed or left out, and all the usual trappings that go along with it can snowball.
This is why detailed plans and comprehensive job specs are crucial.
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In any event I can't understand your comment of a L1/P1 category only applying to property protection.
You're generalising my specific comments. This building is a museum. It is likely to have lowish fire loading, highish ceilings and valuableish contents. I was guessing that the lack of detection in a lantern light, high in a ceiling, might not entirely jeapordise means of escape but might lead to increased damage due to delayed detection out of hours when no one is around.
Stu, the requirement for detection in lantern lights (within a protected area) has nothing to do with the category of a system.
Who said this is in a protected area?
Stu
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In any event I can't understand your comment of a L1/P1 category only applying to property protection.
You're generalising my specific comments. This building is a museum. It is likely to have lowish fire loading, highish ceilings and valuableish contents. I was guessing that the lack of detection in a lantern light, high in a ceiling, might not entirely jeapordise means of escape but might lead to increased damage due to delayed detection out of hours when no one is around.
Stu, the requirement for detection in lantern lights (within a protected area) has nothing to do with the category of a system.
Who said this is in a protected area?
Stu
Your earlier post said 'I believe the detection in the lantern light is required solely for the L1/P1 classification. So its purpose is not to protect life but to protect property'
The L1 part of the catetgorisation relates to Life. I can't see why you said So its purpose is not to protect life but to protect property .[/b] Surely, the detection recommended is equally important for the protection of Life as it is for the protection of property where the category includes the L designation?
The term 'protected area' in this BS clause and context means the lantern light is in an area that requires automatic detection. Whilst the clause is mentioning lantern lights in general it doesn't mean that every lantern light in every situation in every building requires protection. Only those in 'protected areas'. It therefore also means that in the circumstances that no automatic detection is required in an area (unprotected area), then even if that area has a lantern light then it doesn't require anything in the lantern light even though the clause seems to mention lantern lights in general. The lantern light in this query is in a 'protected area' (the area has beam detectors fitted and an L1/P1 system has detectors virtually everywhere anyway) so the clause applies.
Your earlier post said I believe the detection in the lantern light is required solely for the L1/P1 classification. The point I was making in my reply was that the requirement equally applies if it is, say L3 or P2 and not solely L1/P1 category. If the lantern light is in a 'protected area' the lantern light may also need automatic detection.
I am not being pedantic, Stu. If there is any chance of confusion in the way posts are written, I think it is important to clarify things for all readers.
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Fair enough.
To me the name of the category of the system is of secondary importance after its purpose. The fact that this one is supposedly designated L1/P1 tells me a little about its purpose but it is possible to glean more about the purpose of different parts of the system from the nature of the building. The facts about the building tend to indicate to me that some of the detection is for property protection and not solely for life protection. I don't know but I would still suspect that the advantages to be gained from the lantern light detection would be in terms of property protection and not life. Maybe David will elucidate us on this point. I'm not a great one for putting detection where it will serve no useful purpose.
Stu
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I think the BS recommendation for possible automatic detection in a lantern light is all to do with the volume of smoke that could be contained within that lantern light (without detection in it) before it 'spilled out' and reached the automatic detection on the ceiling level. The BS recommendation's mention of only lantern light's of a certain size seems to support this.
One would assume that the amount of smoke taken to fill a large lantern light (without detection in it) is probably proportional to the size of the fire. Therefore if the lantern light is very big it will take a lot of smoke to fill it before the smoke spills out and reaches the automatic detectrion on the normal ceiling level. At this point the fire may be very big.
So BS recommends automatic detection in lantern lights over a certain size to provide detection earlier than would otherwise happen with only ceiling level detection.
Also, the actual installed detection mentioned in this post is beam detectors. These could be mounted up to 600mm below the ceiling level. I would suggest that much more smoke would be needed to fill the lantern light, overspill into the 'room' and then fill up the 600mm gap than would be needed to reach point style automatic detectors which might have sensing chambers only 50mm below the ceiling level.
I think any earlier warning of smoke could be considered equally as important in both Life and Property category systems and I think it applies to the system that is mentioned in this thread because it has been designated a category of L1/P1. In fact, I would suggest that the L part of the category is the most important if a life is considered more important that a museum exhibit. Even BS allows higher ceiling limits (lower response times) to automatic detection in just P systems. Surely everythings points to L being more important than P!
At this point, I would confirm that the BS recommendation also calls for automatic detection in any size lantern light where it is also used for ventilation (even opening windows?) because, I assume, it believes the air-flow in a fire is likely to take any smoke away from the ceiling-mounted detection and therefore a detector is always required very close to the point of potential ventilation..
I don't disagree with Stu's principle that every situation needs to be looked at individually to ascertain how important any BS recommendation might be to that application. If the benefits are far outweighed by the cost then there might be grounds for ignoring the recommendation. However, BS also recommends that a proper 'agreed variation' is sought for this BS non-compliance. BS explains exactly what is considered to be an 'agreed variation'.
I don't agree that just because this building is a museum that the fire detection system is automatically primarily designed for the protection of property. But even if it was, the automatic detection requirements would be virtually the same (other than the maximum ceiling height limits mentioned above). There are no big differences in the BS requirements for location of automatic detection in a L1 or P1 system. P systems generally only differ from L systems in that they may have longer standby battery duty and automatic off-site signalling.
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I think we are all getting too hung up on whether the lantern light needs protection or not.... that wasn't the issue.
But for what it's worth, the objective of a Category L1 or P1 system is to offer the earliest possible warning of fire, therefore to me that means a detector is required in the lantern light for all the reasons quoted by Wiz above and simply because the objective of the category calls for it along with all teh other reasons I quoted earlier.
My question/gripe is that we could have anyone of several people including the QS, consultant, client, arcitect etc stop us from installing this device and by doing so we no longer meet the objective of the category.
This to me is a bit deeper than mounting a call point at 1000mm from ffl.