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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: Sherpa on June 03, 2008, 06:29:04 PM

Title: Forced air ventilation
Post by: Sherpa on June 03, 2008, 06:29:04 PM
If a detector is mounted near an air conditioning unit output, surely they should be at least one metre away, howevever BS5839 only refers to siting them 1 metre from air inlets?

''Detectors should not be mounted within one metre of any air inlet of a forced ventilation system''
Title: Forced air ventilation
Post by: messy on June 03, 2008, 08:08:12 PM
Doesn't that mean the vent where the cooled air comes IN (inlet) to the compartment???
Title: Forced air ventilation
Post by: Paul2886 on June 04, 2008, 12:12:36 AM
Also, how many times do you see a detector head that has a ceiling fan close by pushing the smoke away
Title: Forced air ventilation
Post by: Wiz on June 04, 2008, 09:21:35 AM
Quote from: Sherpa
If a detector is mounted near an air conditioning unit output, surely they should be at least one metre away, howevever BS5839 only refers to siting them 1 metre from air inlets?

''Detectors should not be mounted within one metre of any air inlet of a forced ventilation system''
I've often wondered about this one as well.

I have presumed that a detector being too close to an inlet means it could end up in a 'dead spot' of the air currents being sucked in and thereby miss any smoke. If so, why would this also not be true of outlets and therefore require a BS recommendation to mount detectors a certain distance away from outlets?

I await all you H & V experts to provide an explanation!
Title: Forced air ventilation
Post by: kurnal on June 04, 2008, 04:53:37 PM
I dont think we should be too pedantic. The important thing is that we all have an understanding of factors that could lead to a delay in our goal of suitably early warning of fire and design accordingly.

BS5839 has evolved over the years and detectors can be used for  protecting a space, protecting escape routes, protecting business continuity or to operate plant, equipment and systems. I dont think the meaning of every word was reconsidered as the document was extended and reviewed. I think messy makes a good point and the clause was probably written with his scenario in mind.