Forced air ventilation

[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''

[messy]

Doesn't that mean the vent where the cooled air comes IN (inlet) to the compartment???

[Paul2886]

Also, how many times do you see a detector head that has a ceiling fan close by pushing the smoke away

[Wiz]

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!

[kurnal]

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.