Use of Carbon Monoxide detectors

[kurnal]

I have come across a student accommodation block comprising purpose built cluster flats (6 bedrooms)in which the fire alarm designer has installed an L1 fire detection and alarm system and a full block evacuation strategy.

The system is stable and not giving any false alarms, having been in place for 7 years. It is an ADT MX panel with 800 series detectors.

The installer has put optical smokes in the communal staircase, heat detectors in all rooms of each flat and CO/Heat detectors in the flat lobbies.

Therefore the residents of each cluster flat rely soley on a CO detector to alert them to smoke in the communal corridor though there is the benefit of a heat detector in every room (which would perhaps be ok if we could rely on them not to wedge doors open.)

BS5839-1 +A2 2008 recommends that carbon monoxide detectors may be installed in escape routes in conjunction with smoke detectors but goes on to add that manufacturers guidance be sought on specific applications. I seem to recollect ADT promoting the wider use of CO in lieu of conventional smoke detection and making claims that due to diffusion a CO detector in the corridor may detect a fire in an adjoining room before the smoke detector but havent found anything definitive. It seems from BSI online that BS EN 54-26 is still in draft after 4 years in consultation. Can anyone add any updates to this please?

I would be grateful if anyone can advise me of further reference material before I recommend exchange of monoxide for optical at considerable expense and at risk of unwanted alarms where previously there have been none.

Many thanks.

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[colin todd]

You have answered your own question, Big Al. It is as the BS says if yu want a BS cert.

[Stinky]

I did some digging on googley to try and find information about CO detectors.  Have a search on a search engine.  I was looking as the Gent S-Quad system has gold rings on the detectors to highlight CO detectors. 

Documentation I found indicates that a CO detector located outside a store cupboard, with the door closed, would detect a CO before smoke was visible. CO detectors are apparently also immune from false alarms from insects, dust and steam.

And if you are doing a risk assessment, maybe you consider that the risk is acceptable? It offers detection and warning. Is the expense of changing the detectors going to increase life safety enough to justify the cost of changing the heads?

[kurnal]

Thanks Stinky, My understanding of Gents position on this (albeit haven't checked in a while)is that they dont advocate the use of the CO sensor on the sQuad in isolation, and intended it to be used in conjunction with the dual chamber optical and heat to eliminate the risk of unwanted alarms. But I am happy to be corrected on this.

Thanks Colin just wanted to check if there is any further work going on in the background after all the latest revision of 5839 is now 4 years old and coming up for review. And EN54- 26 appears to have been in draft for 4 years? Is nothing happening?

[colin todd]

Big Al, work on some amendments to BS 5839-1 is about to progress, but there is nothing planned re CO detectors. Stinky, it is bound to be the case that there is no CO in insects, steam or dust, so the claim to which you refer is simply an obvious truism.

[kurnal]

Thanks Colin.
Yes Stinky I believe these CO detectors can be very good and especially where a fire is smouldering or enclosed. But bearing in mind the chances are the doors to all rooms will be wedged open so there is likely to be a plentiful supply of oxygen in any fire scenario, despite the best efforts to educate them and remebering that all rooms have heat detectors I just feel a little uneasy about putting all my life safety eggs in the one basket for which there are no standardised performance criteria or thresholds.  Unless someone knows better?

[colin todd]

Why do you think that there are no performance criteria?

[kurnal]

I understand there to be no standardised performance criteria on the basis that  EN 54-26 is still in draft after 4 years in consultation.

Whilst there is a wealth of tenability criteria for CO,  I have found no research documents that detail the necessary performance criteria for CO detectors to be used in isolation for a life safety fire alarm and detection system.

[jayjay]

I have recently had three false fire alarms in a small relatively new residential care home that I look after. The detector causing the alarm was in a plant room. On each occasion the fire brigade attended and confirmed that there was no fire. After the third false alarm within a few days the installer was called to test the system.
It turned out that the detector installed within the plant room was a carbon monoxide detector and it was quite correctly detecting high levels of CO.
Unfortunately the installer had failed to indicate the type of detector installed and on each alarm the plant room was checked by a fire crew, not wearing BA as there was no sign of fire.
Luckily the plant room is not large and accessed direct from open air and the fire crews suffered no ill effects. 
As there was no notification that the alarm was triggered by CO we have decided to replace the CO detector with a heat detector and install a standalone CO detector.

For the technicians out there can you advise if there is any requirement to indicate CO detectors on a system as this could have had serious consequences if staff had went to the plant room and stayed for any length of time?

[SamFIRT]

It does beg the question .... what is the operating threshold for a CO detector being used as part of a fire alarm system as opposed to CO detectors being used to detect an irrespirable atmosphere.
From memory I believe the TWA for CO is 50 PPM. Personal alarms I have used activate at that threshold therefore. But what is in use out there and what are they set at?

[kurnal]

We have discussed this before and here is the thread.

http://fire.org.uk/forum/index.php?topic=5396.0

[SamFIRT]

So we did.

I must be getting old.