SFS (staircase smoke exhaust) systems are appropriately engineered to allow the exhaust of smoke that could enter the stairwell during evacuation.
The minimum requirements for a protected staircase are:
Top opening: a ventilation opening must be located at the top of the staircase (top of the stairwell).
Minimum surface area: this opening must have a net surface area of no less than 1 m².
Operation: the door must be openable. The opening command must be activated either manually (via a device located near the entrance or on the ground floor) or automatically if interfaced with a fire detection system.