Describes investigations in a 10-storey experimental fire tower, of stairshaft pressurisation systems under various schedules of stair door operation, nonfire/fire conditions and the fire floor vented with an exhaust fan. The four systems tested had overpressure relief features of exit door relief, barometric damper relief, feedback control with fan bypass and feedback control with variable-speed fan. States the tests indicate that with any one of the stair pressurisation systems on and with any mechanical venting of the fire floor, the stairshaft was kept smoke-free with four stair doors open.

KEYWORDS: Testing, smoke, USA, fire protection, stairwells, pressurised stairs, performance, ventilation, mechanical ventilation.