Detectors in Riser Shafts

[Northern Uproar]

Morning,

Just wanted an opinion on the siting of detectors in protected riser shafts -if a system is installed to an L1 category, how would the detectors be located within a riser shaft? Is there one at the top, or one at each level? Is there a spacing limitation? Can't seem to find the requirement in the BS.

Thanks

[Phoenix]

If the shaft is open between floors you would probably just want one at the top.  This can depend on the size, shape and contents of the shaft.  If the shaft is sealed between floors treat it like cupboards.

Stu

[Davo]

Spacing requirements for L1 might mean at the top and every other floor,but I would use my judgement, ie size of riser, height, contents, access doors etc

davo

[kurnal]

A chap called Todd has written a book on the subject of fire alarms-"the Design, Installation, Commissioning, and Maintenance of Fire Detection and Alarm Systems" and his advice is as follows:
"The areas in which detectors should be sited will be defined by the category of system, which in turn, should be such as to meet the specified fire safety objective. Having decided the areas that are to be protected, other than in category L4, L5 and the two systems, a fire detector should be sited at the top of any shaft or enclosure that penetrates through ceilings. In addition, on each floor, a detector should be sited within approximately 1.5 m of the penetration. Even in the case of category L5 or P2 systems, the code suggests that the need for detectors in these positions should be considered at the design stage."

[Tom Sutton]

Check out BS 5839-1:2002+A2:2008 page 50 clause 22.2. (c)

[kurnal]

Yes thanks Tom.

Personally I make a judgement based on other factors too- the size of the shaft, the height of the shaft, openings into the shaft,  compartmentation, whether it passes through different purpose groups, whether detectors in the shaft would be accessible for maintenance purposes (this determines type more than anything) whether there are fire risks or loading within the shaft, whether there are any platforms etc at intermediate levels  to which detectors could be fitted to name a few.    Sometimes intermediate detectors within the shaft  are more appropriate than those on the floors adjacent to the shaft opening. Consider also how the building is zoned.

[Davo]

Agreed, K

Never did see the need for the 1.5m assuming of course full FD30S!
I stand to learn, of course

davo

[Northern Uproar]

Thanks for the replies.

I had read clause 22.2 as an opening that is not enclosed - like the stair example: a hole in the ceiling open to the floor. These risers are the service ones you see between rooms in a hotel, so enclosed in FR, so didn't think that rule applied. Does it apply to enclosed risers?

At the ned of the day, I'm looking at it for someone, but I'm not the installer. I don't want to say anything that would affect the classification on the cert as it may be a contractual issue to install an L1, not an 'L2 with enhancements', regardless of any risk based approach to location of detectors.

[kurnal]

I dont think anything in BS5839 covers exactly this scenario and I dont know about you but I see so many variables in respect of these risers. Some nightmare scenarios and some of such negligible risk I would not even ask for a detector in the head of the riser.

Worst case scenario- very very common in some current lodge type hotels- hole left in the floor throughout the height of the building. Bathroom pods dropped either side of the hole and the wall of the bathroom pod creates the "protected shaft". If you encounter this just do as I did- ask to see the certificate for the fire rating of the pod walls. You may have an unpleasant surprise. Detection anywhere will not fix this problem.

Mid case scenario- horses for courses- large size shaft, or penetrates full height of building, or used for ventilation as well as pipes- very common - is it shunt ventilation? May contain ignition sources such as IT hubs or TV distribution. May have pipes without collars or poor fire stopping round pipes and services.  Consider if detection in shaft practicable and appropriate.

Best case scenario- small diameter pipes penetrate from each room either of a size below that which are recommended for intumescent collars or are fitted with an intumescent collar. Shaft size small and in multi storey fire stopped every few floors at floor level. Construction - a proper protected shaft nothing to burn no ignition sources. FD30S door at each level. No need for detection in the riser.

Finally also consider the situation - dead end bedroom corridors may need a more stringent approach.

Hope these ramblings are of interest as discussion points.