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FIRE SAFETY => Fire Alarm Systems => Topic started by: David Rooney on June 01, 2013, 10:19:08 PM
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6 storey property deemed unfit for a stay put policy by the powers that be with over 40 apartments is now required to extend the fire alarm system into the privately owned flats.
75db at the bed head has been specified by the fire officer .....
In view of pt 6 allowing 85db at the bedroom door is this reasonable or correct ?
Thanks
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Hi David its good to hear from you again.
It is difficult to speculate on why a full evacuation strategy has been determined as a suitable strategy in this case and the reasons behind it. One must trust it has been properly thought through as the best solution. The extent of the detection is not specified.
However my gut feeling is that it is wrong to mix and match standards in this way. I would argue that Part 6 systems were designed for use in specific domestic situations and are really only appropriate for individual dwellings though this is then stretched to cover some smaller HMOs. I would speculate that part 6 was probably a compromise, written around the best available sounder technology and what could be driven by a small battery supply.
It would not make it appropriate to extend the standard acceptable in a small individual dwelling to a completely different scenario, with far greater potential for persons to get hurt if something goes wrong.
If the alarm is needed because people are likely to get hurt if they dont leave the building then it should conform fully to the part 1 standard in my opinion.
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Hello Kurnal
I'm never far away !
Long story short, the detection is L3 with a heat detector only inside each flat, the escape routes are covered and alarm levels in the escape routes are fine as this was designed as a stay put strategy (by others I might add).
Suffice to say the men in black have now decided the place must be a one out all out due to compartmentation issues.
We have nothing to do with the design but I'm interested to know why the 85db in the flats can't be applied? Regardless of the size and complexity of the building each flat is a flat and if it were a new build and smoke alarms were fitted then 85 would be acceptable.
So why could 85db at the bedroom door not be acceptable from the house system?
I've seen lots of similar properties with a detector/sounder in the lobby to the flat, never with sounders in every bedroom .....
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I might well agree with you Dave if I came across it too.
I suppose it depends on what the compartmentation issues are- where the problems lie. If as an extreme you have six storeys of flats over each other with no compartmentation between the floors and for example unprotected ventilation shafts then I would want to make absolutely certain that in the event of a fire in the ground floor flat the people on the top 4 floors were alerted as quickly and reliably as possible bearing in mind they are reliant on the heat detector in the flat lobby in the flat on fire. If we require to wake people from sleep as a result of a fire elsewhere in the building and if a part 1 system is appropriate then we should work to the 75db at the bedhead standard as a benchmark.
Having said that I would much rather work on improving the compartmentation to support stay put!
But I could also think of many other practical situations in which I would accept the L3 system and a variation in respect of sound levels. If I came across a system with a detector sounder in the lobby I would be unlikely to ask for it to be retrospectively upgraded, but if designing a new system as a compensatory feature I would design to part 1.
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Thanks Mr K .....
Thought provoking as ever :)
I'm not privvy the "issues" but as you allude to, if you're that worried about the alarm levels and the compartmentation is that bad then I suppose it should equally justify installing detectors within the flats on the house system as well.... which would be a nightmare !
Apart from none of the residents wanting the detectors or to pay for them, we are back to the "what happens when you burn the toast" scenario .....
Tis a bit of a nightmare ......
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So, Big Al, let me see if I am understanding your always irrefutable and sound logic right. People have a fire in their own flat, which surely is an immediate threat to them big time, but there is a fire elsewhere in the block that might just happen to threaten them, but might not, so the sound pressure level to rouse them from sleep has to be such that the alarm is more than twice as loud?????????????
Yep, makes perfect sense I am sure, I just am missing something critical.
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Yes Colin I agree.
So what is your helpful advice for the OP?
Dave you are right, one out all out strategies don't work, wont work and never will in flats. Such a strategy should always be the last resort if all else has failed.
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You agree with what? And what is an OP. (I know the police use the term as an observation point).
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An Original Poster. It is an oft used abbreviation by regular forum users.
I agree that prima facie persons are likely to be in greater immediate danger from an alarm originating in their own flat.
If I recall someone wrote a standard for domestic life safety fire alarm systems and a different standard for other fire alarm systems covering other types of premises.
We are of course used to the concept of mixed systems but that was not the original question. It subsequently became apparent that this was an existing system under discussion and not a new design.
Do you have any practical advice in response to the original question?
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Hi David,
Not wanting to stand in the way of the resident experts, who both have valid points, and have both helped me out in the past.....
We often come across this in Central London, and often we never get to see the inside of any apartments. It came from an old Westminster Council Guide and probably ecisted before that, and we still (when asked) install the same, we make ot very clear that we have not allowed for 75db at the bedheads of the bedrooms, but have allowed for a combined sounder/detector adjacent to the front door to provide a means of detection within the flat before the door is breached, and a means of alarm within the flat to indicate an external fire. We then provide an additional cost for any extra sounders where a second floor is in place or where there is an additional door between any bedroom and the front door.
This we ALWAYS state should be in addition to the homeowner/tenant/occupier etc providing their own internal part 6 system. Part 6 states there appears to be no evidence to show that lives are being lost due to inadequate audibility of the fire alarm signal from smoke alarms, except where people are incapacitated to such a degree that even much higher sound levels would not waken them. This might be because, in their own homes, people can be roused by an unusual sound of relatively low level compared with the sound level that may be required to wake them in premises with which they are unfamiliar (e.g. a hotel).
If we all agree on this then it is put onto a part 1 certificate as an agreed variation. If preferred than it really is a sounder into each sleeping space, which will be additional cost and disruption to the aesthetics.
There isnt a one size fits all solution that i am aware of....but happy to be corrected, and always willing to learn!
Bill
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Thanks Bill thats exactly the type of helpful response that made has firenet such a valuable resource in the past.
I hear tales that such a arrangement is common in London even in premises with a stay put strategy?
Yes part 6 does include the "no bodies on the streets" argument and it is a valid point. It might also be argued that perhaps 75dbA at the bedhead is more than is necessary to wake most people. After all alarm clocks are in the business of waking people up and very few on the market deliver 75dbA. It would be interesting to know the background to the range of sound pressure levels recommended in Part 1.
Having said that the bottom line for me is that if a system is to be installed then it must be fit for purpose. In a building with a stay put strategy there should be no need for an alarm in the communal areas. Where one is installed it is because a stay put strategy is inappropriate for that particular building and there is no practicable alternative. Often a heat detector sounder combination in each flat lobby will be sufficient but often in these buildings internal flat layouts and travel distances are such as to make this inappropriate. We regularly come across sounders in the common areas only.
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oooo hang on a minute.... owner/occupiers fair enough... but you expect tenants to install part 6 systems?. Sorry not sure that is particularly right... sorry Kurnal would you like to thank me for bringing this up????....apparently you take me for granted, so..... ;D ;)
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Audibility is only half the issue, detector provision in relation to the structure surely is the other. A heat in the lobby is little use if the fire has breached the floor above the room of origin or a shaft adjacent to the RoO because the compartmentation is so poor in these areas, the doors aren't the only vulnerability. In fact I recall one site where the internal doors would still be standing long after the ceiling failed and they had gone for smoke heads with loop sounder bases off the common system throughout each flat to compensate (all done well before the RRO was even a gleam in the lawmakers eye).
Unless you are party to all the relevant information it's difficult for you to comment.
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The following is taken from BS5839-6
13.1.2 Audibility
A fire detection and fire alarm system only provides satisfactory protection of life if it is capable of rousing the principal occupants of the dwelling from sleep (e.g. the adult occupants in a typical single-family dwelling). No particular sound pressure level is certain to rouse all occupants of a dwelling in all circumstances. Depth of sleep varies during the course of the sleep period and also varies from one person to another. Greater sound pressure levels are often required to rouse children from sleep than are necessary in the case of adults. BS 5839-1 recommends that, if an audible alarm is intended to rouse sleeping persons, a sound level of 75 dB(A) should be achieved at the bedhead when all doors are shut, although this will not guarantee that every person will be awakened, particularly if they are under the influence of alcohol or drugs.
Most fire detection and fire alarm systems in dwellings comprise smoke alarms, which are usually fitted in, at least, the circulation areas, such as hallways and landings. BS 5446-1:2000 requires that the sound output of a smoke alarm be at least 85 dB(A) at three metres. Most domestic doors attenuate sound by around 20 dB; greater attenuation can occur in the case of solid doors, such as fire doors. It is therefore unlikely that a smoke alarm on, for example, the upstairs landing of a two-storey house will produce a sound level of 75 dB(A) at the bedhead in each bedroom, particularly if the bedroom doors are shut; levels of 55 dB(A) to 65 dB(A) are more likely. There appears to be no evidence to show that lives are being lost due to inadequate audibility of the fire alarm signal from smoke alarms, except where people are incapacitated to such a degree that even much higher sound levels would not waken them. This might be because, in their own homes, people can be roused by an unusual sound of relatively low level compared with the sound level that may be required to wake them in premises with which they are unfamiliar (e.g. a hotel).
As far as I can see the last sentence of the commentary is not based on any research though I would be pleased to be corrected.
It is widely taken as custom and practice by many alarm engineers and most electricians that in a mixed system, if 85db at the bedroom door measured with the door ajar is good enough to wake you in your own home then the same alarm level is all that is required from the pt 1 communal system.
The crux is whether this should be viewed differently when there is a duty of care toward the occupants of the dwelling.
Oh and I am grateful to my honorable colleague monsignor martian for his valued contribution. ;)
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I have been asked to install a part 1 system within the common areas to L2 but no afd or sounders in the flats.
Looking at the area i doubt the system will outlast the panels stand by duration. :)
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Big Al, I do not have advice to offer the observation point, because I regard myself as an angel who fears to tread. I do consultancy all day, usually on a good day with proper information on which to give advice. I have no real desire to solve problems for buildings which, as Tony says, you have inadequate information about.
However, for your eddification, the 75dB(A) comes from research with American students in the 1960s, while most sleep researchers (no not the old ccodgers on the park benches in Matlock) could tell you about the sound pressure levels to rouse you from sleep in your own home. I was not aware you were familiar with sleep research , such that you would be aware of it. Was this gained in the beds in Matlock fire station or the effect on Mrs Kurnatowski of your response to her question as to whether you had a nice day in your tower block office that overlooks the Derbyshire dales.
With regard to the level of detection when the ceilings are naff, if fire is beginning to cause lath and plaster to fail, it must be fairly severe, but hopefully residents threatened would still be able to use the common escape routes if warned by a H/d before the FED failed.
Hope this helps.
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There are no beds at Matlock Station Colin and there never have been. It has been a day staffed station since 1956 and the fire fighters have been wakened instantly in their homes by their pocket alerters the sound pressure level of which is covered by a JCDD spec. But in my day they always slept with one eye open whilst on their 96 hour tour of duty. Can you imagine that Colin- 96 hours at a stretch? After a busy tour it would take big ben to wake them. Mind you it has been said your one day courses felt like 96 hours....
I note a new edition of BS5839-6 has just been published, I will buy a copy and eagerly look for the undoubted new references to sound pressure levels with mixed systems.
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It is widely taken as custom and practice by many alarm engineers and most electricians that in a mixed system, if 85db at the bedroom door measured with the door ajar is good enough to wake you in your own home then the same alarm level is all that is required from the pt 1 communal system.
The crux is whether this should be viewed differently when there is a duty of care toward the occupants of the dwelling.
I agree with that Kurnal, and that is my view ....
However, your last sentence is the important part, in that we have a fire officer that has demanded 75db at bed head on an Enforcement Notice.
Now a few of our "millionaire home owners" didn't want a detector in the hall way, let alone sounders in the bedrooms..... and the first time this system goes off they won't be ringing the Fire Officer ....!
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Since the BS does not offer clear guidance in respect of this very cmmon scenario, an appeal against the enforcement notice might be useful as a first step to achieving a precedent and / or a consensus.
From the opposite point of view we see very many new blocks of flats, some with self contained part6 and some with part 1 systems installed in the communal areas (nothing in flats) where no communal areas fire alarm is required.
I am often told by builders that they are put in because approved inspectors employed by NHBC require them in all blocks irrespective of the evacuation strategy. I dont know if this is correct. (I am not referring to detectors that control the ventilation system.)
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I found one shiny new block recently with a manual alarm system but no sounders anywhere - the only alarm it sounded was a pop up on the concierge's computer screen; the concierge worked 8-6 weekdays! I assume if he happened to be at work he was then going to run around all hundred flats on ten floors knocking on all the doors.
Its definitely worth asking the question of the fire authority as they may just have cold feet with respect to an issue with compartmentation that may even be easier to resolve. There is nationally approved guidance with respect to this issue and a number of people are starting to get wobbly because of an isolated incident where, by and large, a badly designed and poorly built/maintained building did its job for a considerable length of time.
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Well said, Silver. far from causing people to panic about PBBF, Lakanal Houese would suggest quite the opposite.
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Did anybody see BBC Breakfast this morning which featured Dave Coss from Derbyshire Fire and Rescue Service explaining his work with Newcastle Uni researching why children, especially boys, are not woken by smoke alarms? I saw the first segment but had to leave before the second segment.
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I saw a very short bit of that too, he was saying that smoke alarm sounders using the same frequencies as the Mosquito 'anti-youth' sound systems may be worth trying.
For those unaware of Mosquito: http://en.wikipedia.org/wiki/The_Mosquito