pressurized stairwells

A pressurized stairwell is an interior shaft in a structure holding one or more stairways, in which the air pressure is controlled and set to a level higher than the surrounding spaces in the structure. This is done to limit smoke entering stairwells, and to facilitate the safe evacuation of occupants in an emergency.

The controlled pressure in the stair shaft is higher than in adjacent spaces. The comparison is relative to those surroundings rather than a fixed pressure value in this definition.

The feature helps keep smoke out of the escape route. A shaft can contain one or several stairways without changing the pressure-control principle.