Combined Stair & Lobby Pressurisation System

Combined escape route pressurization keeps both the lobby and the stair clear, so people pass through protected space all the way from the floor door to the final exit.

Smoke must defeat two pressurised barriers – the lobby door and then the stair door – before it reaches the staircase. If one door is held open, the other still protects the stair.

When staircase and lobby are designed separately, the lobby can end up at a higher pressure than the stair and push air the wrong way. A combined design controls both pressures together to keep the cascade in order.

Shared-fan and cascade configurations can reduce the number of fans, intakes and shafts compared with fully separate systems, saving plant space and cost where the building suits them.

Indian bye-laws call for about 50 Pa in pressurised staircases and 25–30 Pa in core lift lobbies. A combined system designed and tested around both values gives fire authorities a clear, consistent strategy to approve.

Air moves from the stair into the lobby through door gaps, and in cascade designs through transfer grilles. The staircase lobby differential pressure must stay positive on every floor so this flow never reverses.

Air leaves the lobby through the lobby door into the fire floor, carrying smoke away from the escape route. This is the barrier that faces the fire directly.

The air entering the fire floor has to escape, through windows, leakage, or a stair lobby pressurization with fire floor exhaust arrangement. Without a release path, floor pressure rises and the cascade weakens.

Opening a door collapses the pressure difference across it and diverts airflow. Closing it again can spike pressures. The design checks every realistic combination, including multiple doors open on the stair and lobby, so the cascade holds and doors stay operable.

A dedicated staircase pressurisation fan, axial or centrifugal, delivers the stair's airflow at the calculated pressure, usually as a duty-standby pair.

Where lobbies have their own supply, a separate lobby pressurization fan feeds a vertical shaft serving every lobby, sized for lobby and lift door leakage.

In some designs, one fan feeds both stair and lobby through a combined stair lobby pressurization duct with branches and balancing dampers, reducing equipment and plant space.

Each stair lobby fresh air intake is placed away from smoke outlets and basement vents, with duct smoke detectors that stop the fan or switch to a clean intake.

Sealed shafts or sheet-metal ducts carry air to stair injection points and lobby grilles. Their airtightness strongly affects fan size.

Lobby grilles with motorised dampers can open on the fire floor and adjacent floors only, concentrating air where it is needed.

Transfer grilles let stair air spill into the lobby in cascade designs, while a stair lobby pressure relief damper vents excess air to protect door opening forces.

A stair lobby differential pressure sensor in each zone feeds a combined stair lobby pressurization VFD panel, holding stair and lobby pressures independently.

Monitored interfaces start the system and identify the fire floor, while an override panel in the fire control room gives fire officers manual control.

Fire-survival cabling from an emergency-power-backed supply keeps both zones running throughout the fire.

Each zone has its own fan, shaft and controls. This gives the most independent control and the clearest pressure hierarchy, at the cost of more equipment and space.

One fan serves both stair and lobby through separate duct branches with balancing or motorised dampers. It saves plant space but needs careful balancing so one zone does not starve the other.

Only the staircase is supplied directly; air flows from the stair into each lobby through transfer grilles or controlled openings, then on to the floor. It is simple and naturally keeps the stair highest, but lobby pressure depends entirely on stair supply and leakage.

Separate or shared fans run on VFDs with pressure sensors in both stair and lobby. This compensated stair lobby pressurization holds each zone at its set point as doors open and close.

Where the lobby serves a fire lift, the lift shaft is pressurised too, so stair, lift shaft and lobby all sit above the fire floor in a coordinated zoned smoke control system.

Smoke exhaust on the fire floor removes smoke and gives pressurisation air a place to go, strengthening the cascade and reducing the need for relief dampers.

NBC 2016 Part 4 defines pressurisation as a pressure difference across a barrier that protects an exit, stair, lobby or room from smoke. Indian model building bye-laws aligned with it require core staircases that cannot be naturally ventilated to be held at a positive pressure of 5 mm water gauge (about 50 Pa), and core lift lobbies in buildings 15 m and above at 25–30 Pa, with systems starting automatically on the fire alarm or sprinkler system and manual operation also provided.

The Maharashtra Fire Prevention and Life Safety Measures Act, 2006 obliges owners and occupiers to keep fire and life safety installations in good repair at all times and to furnish a Licensed Agency's maintenance certificate in January and July each year.

The approving fire authority reviews the stair and lobby strategy at the provisional Fire NOC stage and witnesses performance before the final Fire NOC and occupancy certificate. We align calculations and test plans with your specific authority.

EN 12101-13:2022 sets out design, calculation, installation, acceptance testing and maintenance of pressure differential systems serving stairs, lobbies and firefighting routes, with EN 12101-6 covering their components and a door opening force limit below 100 N.

BS 9999 and BS 9991 (revised in 2024) describe protected stairs, lobbies and firefighting shafts and, for taller residential buildings, expect mechanical smoke ventilation or pressure differential systems rather than natural venting. They are useful references for international-standard projects.

NFPA 92 sets minimum smoke-barrier pressure differences, such as 12.4 Pa in sprinklered buildings, and NFPA 101 limits door opening force to 133 N (30 lbf). ASHRAE smoke control guidance is widely used alongside it for stairwell and lobby pressurization calculations.

The fire lobby stair pressure difference must stay positive so air always flows from stair to lobby. With the stair at about 50 Pa and the lobby at 25–30 Pa, this step is typically around 20–25 Pa.

The lobby must stay above the fire floor, typically at 25–30 Pa under Indian bye-laws, on the fire floor and any other floors the design protects.

Stair lobby door opening force is checked on both doors, typically limited to about 100–133 N depending on the standard. Because each door sees only part of the total pressure, a well-designed cascade can make doors easier to open than a stair-only system at the same overall protection.

With doors open, protection depends on airflow. Designers commonly target around 1 m/s for escape and up to about 2 m/s where firefighters operate, depending on the standard.

The combined stair lobby open door condition is checked for realistic cases: the fire floor lobby and stair doors open together, the final exit door open, and multiple doors open in the stair and lobby during evacuation.

Stair lobby leakage calculation includes stair doors, lobby doors, lift landing doors (often around 0.06 m² each), walls and service penetrations, with flow estimated as Q = 0.83 × A × √ΔP (Q in m³/s, A in m², ΔP in Pa).

Combined stair lobby stack effect and wind on exposed facades change pressures along tall stairs and at intakes. Tall or exposed towers are checked with network airflow models such as CONTAM, or CFD where needed.

Combined stair lobby fan sizing works floor by floor. As an illustration, with one stair door (0.02 m²), one lobby door (0.02 m²) and one lift door (0.06 m²) per floor, a stair at 50 Pa and a lobby at 27.5 Pa, each lobby needs about 0.27 m³/s and the stair about 0.08 m³/s per floor with doors closed. Across 20 floors with all lobbies supplied, that is roughly 5.4 m³/s for the lobbies and 1.6 m³/s for the stair, before open-door cases are added. Lift door leakage often makes the lobbies the larger duty, which surprises many projects. This combined stair lobby pressurization calculation then sets the combined stair lobby pressurization CFM for each fan.

The design decides how much air goes directly to each zone and how much cascades from stair to lobby, then sizes dampers and transfer openings to deliver that split on every floor.

Shafts and ducts are sized for moderate velocities so smoke control static pressure stays within the fan's range and air reaches the top and bottom floors evenly.

Relief dampers are sized to release excess air when doors close; transfer grilles in cascade designs are sized to deliver the lobby's share without raising it above the stair.

Sensors are placed in both zones at representative floors, measuring stair-to-lobby and lobby-to-floor differences, away from grilles and draughts.

Intakes for stair and lobby fans are separated from each other where possible and from smoke exhaust outlets and basement vents, each with smoke detection.

Duty standby pressurization fans with automatic changeover protect each zone against a single fan or motor failure.

Fans, VFDs and damper actuators for both zones run from emergency power through fire-survival cables on protected routes. Combined stair lobby emergency power is designed for the full duration the authority requires.

The combined stair lobby fire alarm interlock starts both zones on a confirmed alarm or sprinkler flow, through monitored interfaces that report faults.

Closed loop stair lobby pressurization uses separate pressure loops for stair and lobby, each driving its own VFD or damper, so the cascade holds as doors open and close.

The fire alarm's floor address opens the lobby damper on the fire floor, with adjacent floors as designed, while other lobby dampers stay closed. End switches confirm each damper's position.

If smoke reaches an intake, that fan switches to a clean intake or stops, as agreed with the fire authority, while the other zone continues to operate.

Airflow or current sensing proves every fan is running, with automatic standby changeover and alarms at the fire panel and fire control room.

Lifts recall, fire floor smoke exhaust starts, AHUs serving the fire zone shut down and fire dampers close in the agreed sequence. Combined stair lobby BMS integration records every event.

An override panel in the fire control room shows stair and lobby status and lets fire officers start or stop each zone manually.

Occupants move through pressurised, smoke-free space from the floor door all the way down the stair.

Stair and lobby pressures are designed and controlled together, so air always flows away from the stair and doors stay operable.

The lobby takes the first impact of smoke, so even with a door held open, the stair stays protected behind a second barrier.

Shared-fan and cascade configurations can reduce equipment, intakes and plant space where the building and authority allow.

One coordinated strategy, calculation set and test report is easier for fire officers to review and witness than two systems that were designed apart.

Two or three zones, many doors and lift leakage interact. Floor-by-floor calculations and dual-zone control keep the cascade stable.

If the lobby receives too much air, it can rise above the stair and push air towards the staircase. Independent lobby control or correctly sized transfer openings prevent this.

Excess pressure on any door in the cascade makes it heavy. Relief paths and VFD control, checked by door-force testing on every door type, keep forces within limits.

Unsealed shafts, poorly fitted doors and open service penetrations waste air in both zones. Site inspections before closure are part of our scope.

Every floor, both zones and multiple door-open scenarios must be tested. We plan this commissioning in detail so it fits the project programme.

Residential stair lobby pressurization protects the lobby every resident passes through and the stair they descend, in towers where evacuation takes time.

Commercial building stair lobby pressurization supports the large numbers of people using core lobbies and stairs in office towers.

Guests unfamiliar with the building get a continuous protected route from their corridor to the street.

Hospital stair lobby pressurization protects lobbies used to move patients and staff, alongside refuge areas and bed lifts.

Stair cores serving retail floors and food courts need protection coordinated with atrium and mall smoke exhaust.

Multiple tenants and uses on different floors call for clear zoning and well-documented controls across shared cores.

Basement stair lobby pressurization stops car park smoke reaching the staircases that lead up into the building.

Widely seen on Indian specifications for centrifugal and axial staircase pressurization fans and lobby pressurisation duties.

Offers ventilation and smoke-control fans, plus dampers and air distribution products suited to multi-zone pressurisation systems.

Known for centrifugal fans and fan modules, useful where shared fans with split ductwork need higher static pressure.

Supplies axial, centrifugal and inline fans with matching dampers, often chosen for international-standard projects.

An Indian fan manufacturer whose axial and smoke-control ranges are common in Indian high-rise pressurisation and basement ventilation.

We also integrate other reputed fan, motorised damper, VFD and controls brands. Where a fan also serves smoke exhaust duty, we confirm its temperature and time rating matches the design.

With doors closed, stair-to-floor and lobby-to-floor pressures are measured on every floor with a calibrated digital micromanometer and recorded against design values.

We confirm the stair stays above the lobby and the lobby above the floor on every level, so the cascade never reverses.

A calibrated force gauge checks stair and lobby doors on representative floors with all systems running.

With the design doors open, velocity across each doorway is measured with an anemometer to confirm outflow towards the fire floor.

The agreed scenarios – fire floor lobby and stair doors open, final exit open, several stair doors open – are set up and measured to confirm the cascade holds.

Every cause-and-effect step is triggered and observed: fan start, lobby damper opening, standby changeover, lift recall, AHU shutdown and override functions.

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

You receive calculations, floor-by-floor readings for both zones, door forces, velocities, scenario results, interlock checklists, instrument calibration details and as-built drawings.

Short scheduled runs of every stair and lobby fan confirm start-up, rotation and airflow, catching faults long before an emergency.

Lobby dampers are cycled and their end switches checked; relief dampers and transfer grilles are inspected for free movement, correct setting and corrosion.

Sensors in both zones are checked against a reference instrument and recalibrated so the cascade is controlled from true readings.

All intake louvres and screens are cleared of debris, nests and monsoon blockages.

Control panels, VFDs, interface modules and override switches are inspected, and the fire alarm, lift and AHU interlocks are exercised.

At least once a year we repeat pressure hierarchy, door force, velocity and door-open scenario tests, and provide the records your licensed fire agency needs for the January and July certificates.

The lobby receives too much air, or the stair too little, reversing the cascade. We rebalance the split, reset set points, and resize transfer openings or add independent lobby control.

Low outflow through open doors, dampers opening on the wrong floor, or doors propped open. Velocity checks, damper remapping and door management reviews restore protection.

Excess pressure on one step of the cascade. Door-force measurement guides adjustment of set points, relief dampers or VFD tuning.

Fans too small for the open-door condition, or control too slow to respond. Retuned VFD loops, larger relief closure and, if needed, additional capacity fix the problem.

Failed actuators, wiring faults or incorrect fire alarm mapping. Every damper is tested against every alarm zone and repaired or remapped.

Corrosion, dirt or paint stops dampers moving. Cleaning, adjustment or replacement with corrosion-resistant units restores operation.

Interface faults, programming errors, tripped starters or isolated power. We trace the full signal path and retest both zones.

We assess the existing stair system, then add lobby supply through a new shaft, a branch from the existing fan or a cascade arrangement, whichever the building and authority allow.

Adding VFDs and pressure sensors to existing fans brings the stair and lobby under independent control, stabilising the cascade and solving door-force complaints.

Floor-wise motorised dampers concentrate air on the fire floor, and sensors in each zone let the controls respond to real conditions.

Rendering shafts, sealing penetrations and repairing doors recovers lost airflow – often the most cost-effective way to restore performance.

Relay-based panels are replaced with monitored interfaces, damper feedback, a firefighter override panel and BMS monitoring.

Each floor adds lobby grilles or dampers, wiring and testing, and each stair core adds its own fans and controls. Taller towers also need larger fans and longer shafts.

Separate fans for stair and lobby cost more in equipment and plant space but give simpler, more independent control. Shared fans with split ducts or cascade arrangements reduce equipment but need more careful balancing and commissioning.

Dual-zone VFD panels, sensors in both zones, floor-wise dampers, fire alarm and lift interfaces, override panels and fire-survival cabling form a significant share of the budget in combined systems.

• Building height and number of floors
• Number of stair cores, lobbies and fire lifts
• Separate fans, shared fan with split ducts, or cascade configuration
• Fixed-speed with relief dampers or dual-zone VFD control
• Fire-floor-only lobby dampers or all-floor supply
• Builder's shaft sealing or sheet-metal ductwork
• Lift shaft pressurisation and fire floor smoke exhaust in scope
• Fire-survival cable lengths and emergency power arrangements
• Testing, Fire NOC witness support and AMC scope

Share your core layout and floor plans for an itemised quotation.