Fire Safety Science Digital Archive

Stairwell pressurization systems should ensure a sufficiently high velocity at open doors between the stairwell and the fire floor without exerting large forces on closed doors in the stairwell. It appears, however, that strong winds may make it difficult, and many times impossible, to fulfill simultaneously these two requirements in tall buildings. A simple model is used for evaluating the possible use of different design parameters, such as the shape and size of the stairwell, the flow resistance of the exit path, the orientation of the exit door, relative to the direction of prevailing strong winds, additional lobbies, pressurization of the elevator shaft, and the type and location of the injection system, for mitigating the effect of winds on the performance of pressurization systems. Several examples are presented and compared. One novel finding is that the use of a helical stairwell configuration, which has a relatively low flow resistance, may drastically reduce adverse wind effects. Results of a 1:10 scale model study of flow in a helical stairwell are presented, which show that its resistance to flow resistance is approximately one quarter of that of convectional type stairwells.