Ceiling void detection

[Rosjes]

I am looking at a job which has substantial ceiling voids over 800mm depth and have duly allowed detection within. I am now informed that the void is to be used as a return air plenum. What do you think the requirements are now for void detection?

[Allen Higginson]

Supplementary detection (aspirating system) across the outlet grill which shuts down the airflow in the event of detection of smoke then the primary detection picks up anything thats in the void?

[kurnal]

This is just my guess but I reckon it depends on the flow rates and volume of plenum. These ceiling voids are commonly used in this way.

The plenum will act as a reservoir and as such will probably have a large volume compared to the flow in and out. The HAV engineer will probably be able to advise on this. point detection carefully sited will probably be most appropriate in my opinion.

If I am talking out of my backside please someone correct me!

[Allen Higginson]

This is just my guess but I reckon it depends on the flow rates and volume of plenum. These ceiling voids are commonly used in this way.

The plenum will act as a reservoir and as such will probably have a large volume compared to the flow in and out. The HAV engineer will probably be able to advise on this. point detection carefully sited will probably be most appropriate in my opinion.

If I am talking out of my backside please someone correct me!

Actually,you're not far off there - on extinguishing systems in computer rooms for example it is important to know the flow rate in voids that use this method and so increased point detection is needed to cover this.

[Rosjes]

Thanks for the advice all. I will speak with HAV to determine air flow and might post again on this topic.