Pressure differences for nine-storey building as a result of chimney effect and ventilation system operation.

Discusses theoretical pattern of pressure differences inside a tall building and describes measurement of pressure made on anine-storey building in Ottawa. Pressure differences were measured across external walls, vertical shafts, stairwell doors and elevator doors with the mechanical ventilation system both on and off. Concludes that pressure differences across external walls depend on the distribution of openings in the exterior wall and of the ratio of resistance to air flow inside the building to that across the exterior wall. These can be measured by the position of the neutral zone and the ratio of actual to theoretical draft.