A PASSIVE VENTILATION STACK

摘要

A passive ventilation stack for a room, building or the like comprises an interior space and first and second openings providing fluid communication between the interior space and a room to be ventilated, and the outside atmosphere. A control system is provided for varying the size of the opening s, so as to cause natural heat exchange between relatively cool ventilation air entering the stack from outside and relatively warm air entering the stack from a room or building to be ventilated.