The stack effect provides the driving force for vertical air movement within buildings. Its effects are especially pronounced in high rise developments, where the air leakage associated with elevators, stairs and service shafts can be a major concern. Stairwells and lift shafts themselves provide occupant access to those floors above or below ground level as well as providing routes for the movement of air. A knowledge therefore of the air movement characteristics if such shafts is vital in understanding the ventilation and leakage patterns in medium and high rise buildings.
The quantity of air in several rooms lying in a stack connected by means of fresh air and exhaust air ducts is considered as a simple model of amultistorey building. Negative pressures set up within the rooms can be equalised by adjusting the