Design Considerations for Staircase Pressurization System
In a high-rise building, the stairs typically represent the sole means of egress during a fire. It is imperative for the exit stairs to be free of smoke & to incorporate design features that improve the speed of occupant egress.
Most building codes require the fire stairwells in a high-rise building to be pressurized to keep smoke out.
The idea behind the stair pressurization is that during a fire the stairway should have more pressure than the rest of the building. That way, when the doors open, the higher pressure in the stairwell pushes the smoke back onto the floor, keeping the escape route clear of smoke.
As per NBC 2016, the pressure difference for staircases shall be 50 Pa.
Further, the pressure differential for enclosed staircase adjacent to such lobby [or corridors] shall be 50 Pa.
The natural ventilation requirement of the staircase shall be achieved through opening at each landing, of an area 0.5 sq.mt in the external wall.
A cross ventilated staircase shall have two such openings in opposite/adjacent walls or the same shall be cross-ventilated through the corridor.
Enclosed stairs leading to more than one basement shall be pressurized.
For pressurized stair enclosure systems, the activation of the systems shall be initiated by signalling from the fire alarm panel.
Pressurization system shall be integrated & supervised with the automatic/manual fire alarm system for actuation.
Wherever a pressurized staircase is to be connected to an unpressurized area, the two areas shall be segregated by 120 min fire resistant wall.
Fresh air intake for pressurization shall be away [at least 4 m] from any of the exhaust outlets/grille.
Importance of stairwell pressurization:
Facilitate the fire & rescue operation by improving visibility in the building for the firefighting crew.
Protect life & reduce damage to property.
Creates a safer escape route.
Reduces the amount of smoke that will enter the fire exit stairwell.