Author Topic: point detection near acoustic baffles/downstands (Read 5406 times)

BCO · « **on:** October 22, 2008, 05:58:19 PM »

Any alarm experts out there, can you please help me answer this problem. Would it be permissible to have point type smoke detection, attached to the sofit (ceiling) and then to have acoustic baffles/downstand hanging from the ceiling. If so what are the restrictions. The baffles are 50mm from the ceiling so they don’t provide a solid barrier as with a normal downstand. They are about 400mm in depth and spaced at about 2-3m centers and extend almost the full width of the room. The building is used for educational purposes.
Many thanks

kurnal · « **Reply #1 on:** October 23, 2008, 01:58:07 PM »

I have not consulted the BS for this response but I would disregard the 50mm personally and treat them as beams. (If they are less than 10% of the floor to ceiling height they may be disregarded- but dont site closer than 400mm. If they are greater than 10% then detectors will be needed either side.)

I think its impossible to be prescriptive in these cases because it depends on the heat energy of the fire plume as to whether the smoke will penetrate the gap aat ceiling level or start to curl downwards.

If they are not full width of the ceiling I may reduce the area of coverage for each detector to ensure that no part of the ceiling was more than 7.5m from a detector following the actual path of the smoke.

Wiz · « **Reply #2 on:** October 23, 2008, 07:50:35 PM »

Good reply Prof., although I think the 400mm figure you quote should be 500mm.

kurnal · « **Reply #3 on:** October 23, 2008, 09:34:55 PM »

You beat me to it Wiz was just about to try a crafty amendment without anybody noticing.
Thought I might get away with it before that Mr Todd logged in and beat me over the head with my own incompetence. Now I shall have to pretend it was a deliberate mistake but dont tell anyone.

BCO · « **Reply #4 on:** October 23, 2008, 11:05:29 PM »

Thanks for these answers. The depth of the baffles is about 400mm (450mm if you count the gap between the baffle and the ceiling) and the floor to ceiling is 3.0m so they exceed the 10% rule. Therefore it appears a detector would be required between every baffle. This is probably unworkable. Any other suggestions?

kurnal · « **Reply #5 on:** October 23, 2008, 11:39:45 PM »

I would take a good look at 5839 - in respect of the ceiling and beam configurations and take a dose of propoertionality. I would ascertain the reason for the detection in the first instance. And I would remember that it is possible for smoke detectors to be mounted as fas as 600mm below the ceiling. And then decide.

Wiz · « **Reply #6 on:** October 24, 2008, 08:53:00 AM »

Quote from: kurnal

You beat me to it Wiz was just about to try a crafty amendment without anybody noticing.
Thought I might get away with it before that Mr Todd logged in and beat me over the head with my own incompetence. Now I shall have to pretend it was a deliberate mistake but dont tell anyone.

I know that you were really only testing if i was awake or not.

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Author Topic: point detection near acoustic baffles/downstands (Read 5406 times)