Exhaust stack fans deenergize whan Fire alarm activates at panel

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hingusus
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Exhaust stack fans deenergize whan Fire alarm activates at panel

Post by hingusus » Thu Feb 15, 2018 9:07 am

Why do the fans shutdown verses go to full exhaust when fire alarm system within building sounds?
tim

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Re: Exhaust stack fans deenergize whan Fire alarm activates at panel

Post by Old fire alarm guy » Fri Feb 16, 2018 11:19 am

So you don't feed the fire with more air.
I've forgotten more than I remember.

theboginator
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Re: Exhaust stack fans deenergize whan Fire alarm activates at panel

Post by theboginator » Mon Feb 19, 2018 10:56 pm

Even though it's exhaust, it's creating negative air pressure in the area, which draws in more fresh air from the surroundings. Great for clearing smoke after the fact but definitely hazardous in a real fire. Also, the system is shut down to prevent other AHUs from sucking in smoke and blowing it to other areas of a building, since smoke is toxic.
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