Stairwell Pressurization Test

On-site testing of stair pressurization systems to NFPA 92. We measure the pressure difference and door opening force at every stair door, check the fans start on fire alarm, and document the results floor by floor.

Keeping smoke out of the escape stairs

A stair pressurization system uses fans to blow fresh outdoor air into the escape stairwell when the fire alarm operates. The higher pressure inside the stair stops smoke on the fire floor from leaking in, so people can escape and firefighters can use the stair safely.

The pressure must be high enough to hold smoke back, but not so high that people cannot open the stair doors. Testing proves both, floor by floor — before Civil Defence inspection and at regular intervals after handover.

With the fans running and all stair doors closed, our engineers check every floor:

• Pressure difference between the stair and each floor
• At least 12.5 Pa in sprinklered buildings under NFPA 92, with higher values for unsprinklered buildings
• Door opening force at each stair door — no more than 133 N (30 lbf) under NFPA 101
• Fan speed, airflow and relief damper operation
• Any floor or door outside the limits flagged for adjustment

We test the full sequence from the fire alarm: the fans must start automatically, build up pressure and hold it as doors open and close. We check fan run and fault signals, standby fans, motorized and relief dampers, and the manual controls.

As per NFPA 92, we also repeat the pressure readings with the design number of stair doors open, to prove the system still holds smoke back during evacuation. Results are written up floor by floor, with the adjustments needed for the system to pass Civil Defence inspection.