Why Do Stairwells Have Fans During Alarms? (Video)

“Hi, my name is Greg Batista here to answer another question from the internet.

FireSafeFran asks: Why do stairwells have fans blowing during fire alarms?

That’s called stairwell pressurization. Fans push air into stairwells to create positive pressure, which keeps smoke from entering. Smoke is far deadlier than flames — the NFPA reports that smoke inhalation causes more than 50% of fire-related deaths. In tall buildings, stairwells can act like chimneys, pulling smoke upward, which makes evacuation dangerous. Pressurization systems give residents a clear escape path and firefighters a safe way in. In Florida, building codes require these systems in high-rises because time is everything during an emergency. While you may not notice them during normal operation, those fans could be the difference between life and death when alarms go off.

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Authoritative references: NFPA 92 – Smoke Control Systems; Florida Building Code life safety rules.

The author, Greg Batista, PE, CGC, SI is owner of G. Batista Engineering & Construction and is a nationally-recognized engineer and contractor with more than 35 years of experience and offices in Fort Lauderdale, Florida.