Describes investigations of stairshaft pressurisation systems in a 10-storey experimental fire tower with operation of the stair doors under nonfire, fire and summer/winter conditions with and without exterior wall venting of the fire floor. The four stairshaft pressurisation 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 under the conditions tested with any one of the stair pressurisation systems on, smoke contamination of the stairshaft can be expected when the stair door on the fire floor is open and the fire floor is not vented to the outdoors. Smoke contamination of stairshaft was prevented when the fire floor was vented by means of outside wall openings. However, the stairshaft was contaminated when one or more additional stair doors were opened.

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