According to the National Fire Protection Association, the process of evacuating some of today’s largest high-rise buildings may take upwards of two hours. This is by far the most compelling argument for effective smoke control in building stairwells. Pressurized staircases keep exit routes smoke free in the event of a fire, lending precious minutes to building occupants during an evacuation. The pressures specified to keep a stairwell pressure positive vary by code.
However, the universal goal is to restrain smoke but still allow the opening of doors in the stairwell shaft. This is where stairwell pressurization control gets tricky. In the event of a fire and a subsequent evacuation there will be intermittent losses of pressure inside the stairwell as stairwell doors open. An effective pressurization system will have supply air fans with sufficient capacity to provide pressuriza tion to prevent smoke entry when doors are open
