do smoke detectors a must on AHU's

[Rehacayli]

Hello,
I've searched several threads and NFPA 90A but couldn't find an exact answer for my problem. I've 14 stories building with detectors and sprinklers inside the floors. I've fresh air supply units bigger than 20000 CFM each which serves around 2000 people. there has been a concern that if there is a fire outside the building the AHU's will blow the smoke inside the building and create a panic so we are searching if this is a must according to NFPA or BS or it is nice to have.
does anyone know if there is a clear statement on a respected literature that says "if the building is x occupancy; y air flow need, there must be smoke detectors on the discharge of AHU's"

Thanks beforehand for the replies.

 

[cdafd]

From NFPA 90A,

Depending on the size of the system:

6.4.2.1 Smoke detectors listed for use in air distribution systems shall be located as follows:


(1)
Downstream of the air filters and ahead of any branch connections in air supply systems having a capacity greater than 944 L/sec (2000 ft3/min)


(2)
At each story prior to the connection to a common return and prior to any recirculation or fresh air inlet connection in air return systems having a capacity greater than 7080 L/sec (15,000 ft3/min) and serving more than one story

 

[chicopee]

I would also advise that you look into fire/smoke dampers actuated by the fire/smoke alarm system at the inlets of duct openings and also to shut down the air handling units.

 

[Rehacayli]

Thank you for your replies. let me widen the question a bit. we have a fire alarm and detection system in the building. if it detects fire in any floor either from detectors or manual call points the AHU's stop and fire dampers on the related floors close to seal the floor.

cdafd;
I've read that part in 90A but I thought that it says "if you put a detector, these are the locations that you can put" ; I didn't understood it as "you must put this detector if it is above x value air quantity".

What is your opinion on this? Is there a clarification that you have seen anywhere?

 

[cdafd]

If your building is governed by NFPA 90a or you want it designed to it, than the key words are::::


6.4.2.1

""shall be""

Shall means what it says.

 

[Rehacayli]

Thank you for the help. much appreciated.