Tests were conducted in December of 1976 on the vestibule pressurization system of a 17-story apartment hotel tower situated in Ottawa and built in 1974. It was designed to protect from smoke contamination both the one stair shaft and 2-car elevator shaft, located at one end of the corridor. Although the stair shaft was provided with a pressurization system, the test results reported in this paper were obtained with this system shut down. To evaluate the performance of the vestibule protection system alone, tests were also conducted with the building ventilation systems in operation and shut down and, also, with various combinations of vestibule, room and balcony doors open to assess the probable movement of smoke in the event of a fire in a room.