Pressurization Fans (Staircase / Lift Shafts)

Pressurization Fans (Staircase / Lift Shafts): A Small Article What they do Pressurization fans are used to create and maintain a controlled positive air pressure in vertical spaces such as staircases and lift shafts. By delivering clean air into these escape routes and/or exhausting air from them, they help keep smoke from seeping into the stairwell or shaft during a fire. This improves visibility, reduces inhalation risk for occupants, and can protect or delay the spread of smoke through the building. Where they are used - Staircases: The most common application. Positive pressure helps keep stair doors and passages tenable for occupants during evacuation. - Lift shafts/hoistways: In some designs, shaft pressurization reduces smoke migration up the shaft and into the lift lobby or upper floors, preserving the integrity of escape routes and equipment for as long as possible. How the system works - A dedicated supply fan (or fans) pushes air into the protected space, creating a slight positive pressure relative to surrounding spaces. - Leakage and door openings cause some air to escape, which is balanced by exhaust or relief through dedicated ducts or through a controlled vent to the exterior. - The system is typically automated: a fire alarm or smoke detector triggers the fans, and dampers and controls ensure the target pressure is maintained across floors. - In many designs, the stair enclosure or shaft is separated from adjacent spaces by fire-rated walls and doors, with automatic doors or intumescent closures coordinated with the pressurization system. Key design features - Dedicated equipment: Separate fans and ductwork for the pressurized space to avoid interference with the building’s general HVAC. - Pressure targets: Designers specify a small positive differential (often on the order of a few dozen pascals) to keep doors from being pushed open by smoke-laden air while not wasting energy. - Controls and interlocks: Smoke detectors, fire alarms, and manual controls integrate the system. The fans may auto-start on alarm, with dampers closing to isolate floors as needed. - Redundancy and reliability: Often includes backup power (UPS or generator), spare fans, and fault monitoring to keep the system operational during a fire event. - Duct design: Low-leak, fire-rated ductwork with smooth internal surfaces to minimize pressure losses; fire dampers at penetrations. Common configurations - Staircase pressurization: Supply air into the stairwell with an exhaust path to the exterior or to a dedicated relief point. The aim is to keep stair doors more resistant to smoke infiltration. - Shaft pressurization (lift hoistways): Aimed at limiting smoke movement into or along the shaft. May involve supply into the shaft and control of leakage paths at shaft openings and doors. Code and standards (general guidance) - Many regions reference standards such as NFPA 92 (Smoke Control Systems) and EN 12101 (Smoke and heat control in buildings) for performance criteria, testing, and commissioning. - Local codes will specify required pressure differentials, response times, and testing frequencies. It is essential to design, install, and commission systems with qualified fire-protection engineers and to follow the applicable code provisions. Operational considerations - Testing and commissioning: Regular testing ensures the system reaches and maintains the intended pressure differential and that interlocks operate correctly. - Maintenance: Fans, dampers, and control systems require periodic inspection to prevent degraded performance. - Energy use: Pressurization is usually small-scale energy-wise, but it is important to balance performance with energy efficiency and insulation against heat loss or gain. - Occupant experience: Noise, drafts, and door feel can affect occupant comfort and should be considered in design. Benefits - Slows or prevents smoke from entering escape routes, aiding safe evacuation. - Improves visibility and reduces toxic exposure in stairs and lobbies. - Helps protect elevator lobbies and shaft areas, preserving access to egress routes and critical components during a fire. Notes for project teams - Work with qualified fire protection engineers to determine the appropriate pressure targets, fan sizing, and duct routing for your specific building. - Ensure coordination with other life-safety systems (fire alarm, detection, emergency lighting) and with the building’s HVAC to avoid conflicts. - Plan for testing, maintenance regimes, and documentation so the system remains reliable over the building’s life. If you’d like, I can tailor this to a specific region or building type (high-rise, campus, retrofit) and provide a shorter version or a longer, more technical draft.