Douglas Krantz - Technical Writer - Describing How It Works
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Why Doesn't the SPF Turn-On with Smoke in the Stairway?

When there's smoke in the stairwell, if the Stair Pressurization Fan turned on, it would push the smoke laden air out of the stairwell and into the rest of the building. If there's smoke inside the stairwell, it is better not to turn on the SPF.

Why Doesn't the SPF Turn-On with Smoke in the Stairway?


Why Doesn't the SPF Turn-On with Smoke in the Stairway?


Greetings Douglas,

I'm working in the fire and safety department here and am wondering about the smoke detector and the Stair Pressurization Fan (SPF).

When the staircase smoke detector is activated, there is no action on the SPF. Is that correct? The rest the smoke detectors activate the SPF, but is it a different scenario inside the staircase? Please clarify.

Thank you, AS

More people die in a fire because they breathed smoke than people die because they were burned. Because of that, so that people can escape both fire and smoke, they use the narrow stairwell as an escape route. The stairwell has to be free of smoke.

A Stair Pressurization Fan (SPF) uses fresh outside air to increase the air pressure inside the stairway. The increased pressure from the fresh air pushes the building's smoke laden air away from the escape route inside the stairwell. See What is a Stair Pressurization Fan (SPF)?

But there's a problem.

If there's smoke inside the stairwell, turning on the SPF to increase the pressure inside the stairwell pushes the smoke from inside the stairwell into the rest of the building. Pushing smoke into the rest of the building is often worse than not turning on the SPF.

To keep the SPF from pushing smoke into the rest of the building, the smoke detector inside the stairwell doesn't turn on the SPF.

Douglas Krantz

facpdoug@douglaskrantz.com
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