Sound level on new system

[lyledunn]

I have inspected and tested a Part 1 addressable fire alarm system in a relatively new block of 8 apartments over 4 floors. It is part of a "mixed" system. The domestic systems were not within the scope of my inspection. However, the sound pressure levels were as low as 45dbA at the bed head in many units on alert from the central system. Now there is only one means of escape although it appears to be fairly sterile and each unit will have, no doubt, appropriate compartmentation. I was wondering what take you fire safety professionals would have on this. I know that we discussed sound levels in general terms before but this is a very straightforward situation where whilst there is only one means of escape perhaps folk could sit it out and thus it might be argued that there is no need for coverage in the common stairway at all??

[kurnal]

If the block is purpose built in accordance with Approved document B etc and has been designed to support a "Stay Put" policy then there is no need for a fire alarm in the communal areas and indeed to provide one can create more problems that it will ever resolve. Problems with unwanted alarms, lack of maintenance and testing, nobody to take charge and investigate and reset alarms leading to frustration and vandalism etc.

If it is not necessary the best solution may be to take it out. Before doing so ensure it is not providing the detection necessary to operate the staircase or lobby ventilation system. If it is then consider whether it needs sounders and whether there is a facility to close the vents - this is often missed where fire alarm panels are incorrectly used to control the vents.

If on the other hand the building will not support a stay put strategy and evacuation is necessary (unlikely in a new building) then the alarm should achieve 75db at the bedhead.

[nearlythere]

That is an old chestnut Lyle.
If something does not have to be installed, because standards says it doesn't, but is, how can one apply the recommendations of another standard?

[Mike Buckley]

Lyle,

Have a look at the document from the Local Government Group. "Fire Safety in purpose built blocks of flats" you can download it free from their website www.local.gov.uk . Also have a look at the LACORS Housing -Fire Safety document. If nothing else it will give you some backup on what you want to do.

[David Rooney]

In a similar vein .... purpose built 2 storey sheltered accommodation ...  stay put policy ........ LD3 within the dwellings and an L2 system in the common parts .... obviously no need to have alarm sounders within the dwellings from the "common" system.

There is generally a single member of staff sleeping on site over night.

In the event a fire broke into the common escape route and an area is required to be evacuated who is responsible for warning the occupants and what is an acceptable method of providing the warning.... ie. will the brigade go knocking on doors or is this down to the member of staff?

Thanks

(Sorry Kurnal this kind of followed on from the OP .... feel free to create a new thread if you wish... ta)

[AnthonyB]

Manual fire brigade evacuation seems the acceptable norm, but there are other ways around it.

In one multi use complex I assessed the 'firemen knocking on the door' issue was resolved by the complexes main fire alarm system covering the flats with some very complex cause and effect.

Basically the devices to an individual flat would only sound their own alarms upon a fire. The central control panel in the fire control room would also flag this up allowing security or the concierge to check and the fire brigade be called. However other flats and other parts of the complex would be silent.

If the other parts of the complex began their alarm and phased evacuation, the flats would remain silent as 'stay-put' is in use.

Should the fire brigade wish to evacuate some or all of the flats instead of relying on door knocking alone the complexes fire control room has a bank of key operated switches, one for each flat. Turning the key activates the sounders in the flat in question, which provide 75dB bed head.

[David Rooney]

Blimey .... I can see that being effective if not a little OTT .....

We did suggest sounders in the flats controlled by a key switch to sound the evacuate in certain areas if need be but the risk assessor is still not keen on the idea simply saying the sounders are not necessary and the locals FB don't want them.

If there were a fire in a corridor would the brigade go knocking on doors or would they expect the staff to manage it ??

What's the most likely real life scenario .....?

[Mike Buckley]

If there was a fire in a corridor the last thing you would want to do is turf people out of thier flats into the corridor.

Factors to consider, if the flats are constructed to enable a "stay put" policy the people inside the flats should be safe enough for at least 30 mins and at least one hour if they retire into one of the rooms and shut the door. If there is a fire in a corridor how did it start? the corridors should be kept clear of combustible items and there are normally very few sources of ignition. If the fire is severe enough to warrent full evacuation the fire brigade would probably want to be in charge of evacuating the affected floors so they can control the movement of people in the danger area.

If the place is not suitable for a "stay put" then it is a case of detection and alarms in the common areas, heats in the flats connected to the communal system and achieve the minimum sound levels in the flats.

My advice would be stick to these two scenarios which will cover most buildings until you get to the really large blocks of flats without a "stay put" policy where you need to look at staged evacuation procedures, if it that big then you probably need to liaise with the fire brigade on an operational level.

[AnthonyB]

Blimey .... I can see that being effective if not a little OTT .....

To be fair it's a pretty unique building & the set up is part of a series of engineered solutions to the way the site is built, more often or not it's all or nothing with resort to alarms in flats

[lyledunn]

Nearlythere, you are bang on! However, I have established that the system was installed to meet HMO Licence requirements and was not specifically asked for by BC ( new-build flats only 3years old). Knowing what I know about this particular licence authority there may not be a whole hell of a lot of sense in any of their diktats.
The system is clearly unsatisfactory in terms of sound pressure levels but I compromised and determined it to be satisfactory with the caveat that consultation with the licencing authority should be made. Since they are the ones who require the certificate then I guess they can wrestle with the intricacies!

[David Rooney]

Thanks Mike ..... when you say "achieve minimum sound levels" in the flats, would you expect 75db at bed head or would you say that pt 6 alarm levels would be suitable ie. 85db at the bedroom door for the reason given in pt 6 that people are more likely to be woken by lower noise levels in their own homes etc ....?

[colin todd]

Lyle there will be a one day course on the LGA guide in NI quite soon. It may help you with the fire safety concepts of purpose built blocks of flats.