Lift Shaft Pressurisation Systems

A tall, vertical shaft with openings on every floor behaves like a chimney. Warm smoke rises up the shaft and spreads out through landing doors on upper floors. This lift shaft stack effect grows with building height.

Upper floors can fill with smoke even when the fire is many floors below, endangering people who were never near the fire. Positive pressure in the shaft blocks this route.

Fire lifts let crews and equipment reach upper floors in minutes. A smoke-logged shaft or landing makes the lift unusable just when it is needed most. Fire lift shaft pressurization keeps it in service.

Air leaving a pressurised shaft through landing doors helps keep the lift lobby clear, working together with lobby pressurisation to protect the whole lift core.

Indian building bye-laws call for about 50 Pa in core lift shafts of buildings 15 m and above, together with pressurised lift lobbies. A correctly designed, tested lift shaft pressurisation system supports Fire NOC approval.

Axial or centrifugal lift shaft pressurization fans are sized for the large airflow that landing door leakage demands, usually as a duty-standby pair on emergency power.

The lift shaft fresh air intake is placed away from smoke exhaust outlets, basement vents and kitchen exhausts, with a duct smoke detector that stops the fan or switches to a clean intake if smoke is detected.

A lift shaft pressurization duct carries air to one or more openings into the shaft. Injection points are positioned to avoid blowing directly onto cars, ropes or landing doors.

A motorised damper fitted in the shaft's top vent stays open in normal use and closes on fire alarm so the shaft can hold pressure. Its fail-safe position is agreed with the fire authority.

A lift shaft pressure relief damper vents excess air when landing doors close, protecting lift door operation in fixed-speed systems.

Lift shaft differential pressure sensors at several heights – low, middle and high – capture the variation that stack and piston effects create along a tall shaft.

The lift shaft pressurization VFD adjusts fan speed to hold pressure within its band as doors open, close and cars move.

Monitored modules link the system to the fire alarm and the lift controller, so pressurisation, recall and firefighter operation follow one agreed sequence.

Fire-survival cabling from an emergency-power-backed supply keeps fans and controls running during a fire.

A panel in the fire control room shows shaft pressurisation status and lets fire officers start or stop it manually.

A fire lift shaft pressurization system protects the shaft of the lift reserved for firefighters. It is the most common and most critical application, usually paired with a pressurised fire lift lobby.

In tall buildings, passenger and service lift shafts in the core can also carry smoke between floors. Pressurising them limits vertical smoke spread and supports evacuation elevator pressurization strategies where lifts assist evacuation.

Lift shaft and lobby pressurization are designed together, so the shaft, lobby and floor form a controlled pressure cascade. This is the preferred arrangement for fire lifts.

Single-point injection supplies air at one level, typically the top or bottom of the shaft, and suits lower shafts. Multi-point injection supplies air at several levels, keeping pressure more even in tall shafts and reducing the influence of piston effect.

The fan runs at constant speed and a relief damper vents excess air. This is simple and robust, but pressure varies more as doors open and cars move.

A closed loop lift shaft pressurization system uses sensors at several levels and a VFD to hold pressure within a narrow band. Lift shaft pressurization with a VFD controlled fan gives the best protection for lift door operation.

In lifts with a machine room above the shaft, openings between shaft and machine room must be considered in leakage and relief design. Machine-room-less (MRL) lifts have their machinery inside the shaft, so injection points and vent dampers are positioned to suit the equipment and the lift maker's requirements.

Lift landing doors have running clearances on every side, so they leak far more than stair doors. Elevator door leakage is often taken at around 0.06 m² per landing door, and a tall shaft has dozens of them, which drives very large fan airflows.

A moving car pushes air ahead of it and draws air in behind it. Research by NIST found this elevator piston effect becomes much more significant at higher car speeds, particularly in single-car shafts where little space surrounds the car, and that injecting air at both top and bottom reduced the airflow needed to keep smoke out.

Lift doors are moved by small motors with limited force. Excessive shaft pressure can stop doors closing, which takes the lift out of service. US building code practice for elevator hoistway pressurisation, for example, caps shaft pressure at 67 Pa for this reason.

Stack effect, wind and open doors at the recall floor make pressure vary along a tall shaft. Approaches developed for tall buildings include the basic elevator pressurization system, the elevator pressurization exterior vent system (venting the fire floor to outside), the elevator pressurization floor exhaust system (exhausting the fire floor), the ground floor elevator lobby system (an enclosed lobby at the recall floor) and VFD feedback control.

Indian bye-laws say lifts should not normally serve basements; where they do, the basement lift lobby must be pressurised. Basement-connected shafts need careful intake and pressure design to keep car park smoke out.

Door operator limits, landing door construction, machine-room openings and fire-mode logic all come from the lift manufacturer. Early coordination avoids surprises at commissioning.

NBC 2016 Part 4 sets the fire and life safety framework, and Indian model building bye-laws aligned with it set out specific lift rules. Lift enclosure walls must have a two-hour fire rating, and shafts need a vent of at least 0.2 m² at the top. Where lift shafts and lobbies are in the core of buildings 15 m and above, about 50 Pa is maintained in the shaft and 25–30 Pa in the lobby. Fire lifts must reach the top floor from ground level within one minute, run on a separate electrical supply, and have a grounding switch at ground level for the fire service.

The Maharashtra Fire Prevention and Life Safety Measures Act, 2006 requires owners and occupiers to keep fire and life safety installations in efficient working order at all times, and to submit a Licensed Agency's maintenance certificate to the fire authority each January and July.

The approving fire authority reviews lift shaft and lobby pressurisation at the provisional Fire NOC stage and witnesses performance before the final Fire NOC is issued. We align the design and test plan with your specific authority.

EN 81-72:2020 sets the European rules for firefighters lifts, which must operate under the direct control of the fire service, with additional protection, controls and signals. It includes protection of electrical equipment against water from firefighting. It is often specified by international lift manufacturers and premium projects.

EN 12101-13:2022 covers the design, calculation, installation and testing of pressure differential systems, including those protecting firefighting lifts, while EN 12101-6 covers the components.

NFPA 92 recognises elevator pressurisation as a smoke control method, and ASME A17.1, whose 2025 edition was published in 2026, governs elevator safety, including firefighters' emergency operation. US building codes add an elevator hoistway pressurisation option with a minimum of 25 Pa and a maximum of 67 Pa, a separate fan for each hoistway, and supply capacity of at least 1,000 cfm per landing door.

The lift shaft differential pressure must stay positive on every landing, including the fire floor, with lifts at the recall floor. Indian bye-laws commonly specify about 50 Pa for core lift shafts.

The upper limit comes from lift door operation rather than from people pushing doors. US code practice caps hoistway pressurisation at 67 Pa; we confirm the actual limit with your lift manufacturer for the specific door operators.

Lift shaft leakage calculation totals landing door gaps, machine-room openings, shaft wall cracks and the closed top vent damper. Leakage flow is estimated as Q = 0.83 × A × √ΔP (Q in m³/s, A in m², ΔP in Pa).

When lifts are recalled, landing doors at the recall floor may stand open, and during firefighting the fire lift's doors open on the fire floor. The design states which doors are assumed open and keeps the elevator shaft pressure difference positive on the remaining floors.

Temperature-driven pressure varies along the shaft, and moving cars cause short pressure swings. Margins are added for both, and very tall or high-speed shafts are checked with lift shaft pressure network modeling, for example using CONTAM.

Lift shaft pressurization fan sizing starts from landing door leakage. For example, a 30-landing shaft with 0.06 m² per door, held at 50 Pa, leaks about 10.6 m³/s (roughly 38,000 m³/h or 22,400 CFM) before any open-door allowance. This is why lift shaft pressurization CFM is usually far higher than for a staircase, and why the lift shaft pressurization calculation must use realistic door data.

Injection points are positioned to spread air evenly and counter piston effect, often near the top and bottom of the shaft for taller lifts, and placed clear of cars, counterweights, ropes and landing doors.

A sheet-metal duct leaks far less than a builder's shaft and gives more predictable lift shaft pressurization static pressure. Where a builder's shaft is used, it must be rendered and sealed.

In fixed-speed systems, the relief damper is sized to release the difference between fan output and leakage with doors closed, keeping pressure below the lift door limit.

Sensors are placed at several levels so the controller responds to the true pressure profile, and are kept away from injection points and door gaps that would give misleading readings.

Intakes are located away from smoke exhausts, basement vents and openings on likely fire floors, with smoke detection and, where needed, a second intake with automatic changeover.

Duty standby lift shaft pressurization fans with automatic changeover keep the fire lift protected if one fan or motor fails.

Fans, VFDs and vent damper actuators are fed from emergency power through fire-survival cables on protected routes. Lift shaft pressurization emergency power is planned alongside the fire lift's own separate supply.

The lift shaft pressurization fire alarm interlock starts the fans on a confirmed building alarm or a lift lobby smoke detector signal, through monitored interface modules.

The same alarm sends lifts to the recall floor and enables firefighter operation of the fire lift. Pressurisation is timed and set so recall and door operation are not disrupted.

The motorised top vent damper closes when pressurisation starts and reopens on reset. Position switches confirm its status at the control panel and fire control room.

Lift shaft pressurization with differential pressure sensors and VFD control holds shaft pressure within a band: high enough to stop smoke, low enough for lift doors to operate, even as cars move and doors open.

If smoke reaches the intake, the system switches to a clean intake or stops the fan, as agreed with the fire authority.

Airflow or current sensing proves each fan is running; failures trigger standby changeover and alarms at the fire panel and fire control room.

Lift shaft, lobby and staircase pressurisation and fire floor exhaust start in the agreed order, while AHUs serving the fire zone shut down. Lift shaft pressurization BMS integration logs every event for audits.

Positive pressure closes off one of the main vertical smoke routes in any tall building.

Clear shafts and landings let firefighters use the fire lift to move crews and equipment quickly to upper floors.

Occupants many floors above the fire are shielded from smoke that would otherwise rise through the shaft.

With the shaft, lobby and stair protected, fire crews can stage close to the fire floor and attack it with less exposure to smoke.

A calculated, tested and documented system supports Fire NOC approval, occupancy certification and Maharashtra's twice-yearly maintenance certification.

Landing doors make lift shafts very leaky, so fans, ducts and power supplies are large. Accurate door leakage data and sealed shafts keep sizes reasonable.

If shaft pressure exceeds what the door operators can overcome, doors may fail to close and the lift stops. Pressure caps and VFD control, confirmed with the lift maker, prevent this.

Moving cars create piston effect pressure swings. Multi-point injection, fast-responding VFD control and multi-level sensing keep pressure within its band.

Air escaping through narrow door gaps at high pressure can whistle. Holding pressure at the lowest effective value reduces noise.

Testing requires lifts in fire mode, cars moving and doors cycling, coordinated with the lift contractor. We plan these tests in advance so they fit the lift installer's schedule.

High rise lift shaft pressurization protects fire lifts and core lifts in apartment towers, where residents on upper floors depend on the core staying smoke-free.

Large lift banks in office towers create many shafts and landing doors; pressurisation limits smoke spread across a building with high occupancy.

Guest floors stacked above podiums with restaurants and kitchens benefit from shafts that cannot carry smoke upwards.

Bed lifts and fire lifts support patient movement and firefighting; protecting their shafts helps keep these critical lifts available.

Passenger and service lifts linking basements, retail floors and food courts need protection coordinated with mall smoke exhaust.

Residential, office and hotel uses stacked in one tower call for careful zoning of lift shafts, lobbies and control sequences.

Where lifts serve basements, shaft and basement lift lobby pressurisation keep car park smoke from rising into the building.

Offers centrifugal and axial fans commonly specified in Indian projects for pressurisation duties, including high-airflow lift shaft applications.

Provides ventilation and smoke-control fan ranges, along with dampers and air distribution products, for commercial and residential towers.

Known for centrifugal fans and fan modules suited to ducted pressurisation systems where higher static pressure is needed.

Supplies axial, centrifugal and inline fans and dampers, often specified on international-standard developments.

An Indian manufacturer of axial and smoke-control fans, widely used in Indian high-rise ventilation projects.

We also integrate other reputed fan, motorised damper, VFD and controls brands. Where a fan doubles as a smoke exhaust fan, we confirm its temperature and time rating suits that duty.

With lifts recalled and doors in their fire-mode positions, shaft-to-floor pressure is measured at every landing with a calibrated digital micromanometer and recorded against design values.

With the system running, landing and car doors are cycled on representative floors to confirm they open and close fully and on time.

The fire lift is run up and down the shaft while pressures are logged, confirming that piston effect does not drop the shaft below its minimum or push it above the door limit.

We confirm the top vent damper closes on alarm, reports its position, and reopens on reset or to its agreed fail-safe position.

Every cause-and-effect step – fan start, damper closure, lift recall, firefighter operation and override functions – is triggered and observed.

Duty fan failure is simulated to confirm the standby fan takes over automatically and the alarm reports correctly.

We prepare the system, lifts and documentation for the fire officers' inspection, and our engineers attend to demonstrate performance.

You receive calculations, landing-by-landing readings, door operation results, moving-car pressure logs, interlock checklists, instrument calibration details and as-built drawings.

Short scheduled runs confirm the fans start, rotate correctly and prove airflow, catching starter, bearing and wiring faults early.

Top vent dampers are cycled and their position switches checked; relief dampers are checked for free movement, correct setting and corrosion from Mumbai's salty, humid air.

Multi-level pressure sensors and tubing are verified against a reference instrument and recalibrated so control stays within the safe pressure band.

Intake louvres and screens are cleared of debris, nests and monsoon blockages that would starve the fan.

Control panels, VFDs, interface modules and the fireman's override panel are inspected, and the fire alarm and lift fire-mode interlocks are exercised with the lift contractor.

At least once a year we repeat landing pressure, door operation and moving-car tests, and provide the records your licensed fire agency needs for the January and July certificates.

Shaft pressure exceeds what the door operators can overcome, usually due to an oversized fan, no relief path or untuned VFD. We measure pressures with the lift maker, lower set points and add relief or VFD control.

Landing door leakage higher than assumed, an open top vent damper, unsealed builder's shafts or undersized fans. A leakage survey identifies the losses before any equipment is changed.

Pressure too low on some floors, piston effect during car movement, or a contaminated intake. Multi-point injection, faster control and intake changes restore protection.

Piston effect causes rapid swings. Multi-level sensing, retuned VFD control and additional injection points stabilise pressure.

Failed actuators, wiring faults or missing interlock logic leave the vent open, so pressure never builds. We repair the damper, add position feedback and retest the sequence.

High pressure across narrow landing door gaps. Lowering the set point to the minimum effective value reduces noise without losing protection.

Interface faults, programming errors, tripped starters or isolated power. We trace the full signal path and retest with the fire alarm and lift contractors.

We survey the shaft, machine room, terrace and core to find a practical route for the fan, intake and supply duct, then design a system that fits the existing lifts.

Adding a VFD panel and pressure sensors to an existing fixed-speed fan brings shaft pressure into a safe band and solves door-closing problems.

Fitting a motorised damper in the existing top vent lets the shaft hold pressure during a fire while keeping the vent open in normal use.

Sensors at several heights give the controller a true picture of pressure along the shaft, improving stability in tall buildings.

Old relay logic is replaced with monitored interfaces, damper feedback, a fireman's override panel and lift fire-mode integration.

Each additional landing adds leakage, so taller shafts need more airflow and larger fans. Where separate shafts serve fire, passenger and service lifts, each typically needs its own fan system and controls.

Fans in duty-standby pairs are the largest item, followed by supply ductwork to injection points and the motorised top vent damper. Sealed sheet-metal ducts cost more but reduce fan size.

Multi-level pressure sensors, VFD panels, fire alarm and lift controller interfaces, override panels and long fire-survival cable runs add cost but are key to safe lift door operation.

• Shaft height and number of landing doors
• Number of lift shafts to be pressurised
• Single-point or multi-point injection
• Fixed-speed with relief or VFD closed-loop control
• Machine-room or MRL lift arrangement
• Combined lift shaft, lobby and staircase pressurisation scope
• Fire-survival cable lengths and emergency power arrangements
• Testing with lift contractor, Fire NOC witness support and AMC
• New construction or retrofit in an occupied building

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