A fire-engineering measure that introduces positive pressure into the hoistway to prevent smoke ingress during a fire.
Full Definition
Elevator shaft pressurization is an active fire protection strategy in which a dedicated mechanical supply-air fan pressurises the hoistway to a positive differential pressure (typically 25–50 Pa above the floor pressure at landing door level) so that when a landing door opens during a fire, air flows outward from the shaft to the fire floor rather than allowing smoke to enter the shaft and migrate to other floors. This approach is used in fire-fighting lifts (EN 81-72), evacuation lifts (EN 81-76), and tall buildings where shaft smoke propagation is identified as a major life-safety risk. The pressurization system is activated by the building fire alarm and controlled by the fire-fighting elevator controller. Pressure sensing ports at the lowest and highest landings continuously monitor differential pressure; a feedback control loop modulates fan speed to maintain the design pressure band under variable stack effect and door-open conditions. EN 81-72 requires that the system maintain the specified differential pressure during a 90-minute design fire event with all landing doors closed and with the fire landing door open. Pressure relief dampers at the top and bottom of the shaft protect the structural envelope from over-pressurisation during the all-doors-closed condition. Annual commissioning testing per BS EN 12101-6 or equivalent verifies design performance.
