Smoke Control and Stairwell Pressurisation
An engineer-written explanation of smoke control — why smoke, not flame, is the main killer in fires, and how pressurisation and extraction systems keep escape routes and firefighting access usable.
Most fire fatalities are caused by smoke, not by burning. Smoke spreads faster than flame, reduces visibility to near zero, and contains toxic and asphyxiating gases. Keeping smoke out of the routes people use to escape — and that firefighters use to attack the fire — is therefore one of the most important goals of fire engineering.
Smoke control systems manage where smoke goes. Some hold smoke out of protected spaces by keeping them at a slightly higher pressure; others actively remove smoke from the fire area; and many large buildings combine both. The design depends on the building height, layout, and how people are expected to evacuate.
How it works
Why smoke moves. Hot smoke is buoyant, so it rises and collects at high level, then spreads sideways under the ceiling and through any opening — doors, ducts, shafts, and gaps. In tall buildings the stack effect (warm air rising in vertical shafts) can pull smoke far from the fire. Smoke control works with or against these forces to protect specific spaces.
Stairwell pressurisation. Escape stairs are the spine of evacuation, so they are often kept smoke-free by pressurisation. A dedicated fan supplies clean air into the stair shaft to hold it at a slightly higher pressure than the floors around it (a typical target is on the order of 50 Pa with the doors closed). Because the stair is at higher pressure, air leaks outward through door gaps, so smoke cannot leak in. The system must also limit the pressure so that doors are not too hard to open.
Smoke extraction and clearance. In car parks, atria, malls, and large floor plates, the strategy is usually to remove smoke rather than pressurise. Extract fans draw smoke out at high level while replacement (make-up) air enters low down, keeping a clear layer near the floor for escape and for firefighters. In an atrium the aim is to keep the smoke layer high above the occupied levels.
Zoning and the fire floor. Smoke control is organised by zone. On detection, the system typically extracts from the fire zone and keeps adjacent zones and escape routes protected. Smoke-control dampers open or close to direct airflow, and lifts, doors, and ventilation are coordinated so the building behaves as one designed system rather than a set of independent fans.
Control, power, and testing. Smoke control is driven by the fire alarm and supervised from the fire command centre, where firefighters can monitor and override it. Because it must run during a fire, the fans, dampers, and controls are fed from a protected or standby power supply and use fire-rated wiring. The whole system is proven by commissioning tests — measuring pressures, airflows, and door-opening forces — and re-tested periodically.
Main types
In the UAE
- Smoke control design in the UAE follows the UAE Fire & Life Safety Code of Practice and is reviewed and inspected by Civil Defence (in Abu Dhabi, ADCD), especially for high-rise, malls, atria, and car parks.
- Pressurisation and extraction equipment serving life safety must run on a protected or standby supply with fire-rated cabling and be controllable from the fire command centre.
- Systems are commissioned with measured pressures, airflows, and door-opening forces, and integrated with the fire alarm so the correct zone responds automatically on detection.
How GPR applies this
As an Abu Dhabi MEP and fire contractor, GPR installs and integrates stairwell and lobby pressurisation, mechanical and car-park smoke extraction, and zoned smoke-control dampers — all wired to the fire alarm with fire-rated cabling and standby power. GPR commissions each system to measured pressures, airflows, and door-force targets and presents the results for ADCD inspection and handover.
Frequently asked questions
Why is smoke control so important in a fire?
Smoke causes most fire deaths and quickly makes escape routes unusable. Controlling where smoke goes keeps stairs, lobbies, and firefighting routes clear of smoke for evacuation and rescue.
How does stairwell pressurisation work?
A fan supplies clean air to hold the stair at a slightly higher pressure than the surrounding floors, so air leaks outward through door gaps and smoke cannot leak in, while the pressure stays low enough that doors still open.
What is the difference between pressurisation and smoke extraction?
Pressurisation keeps smoke out of a protected space by raising its pressure, while smoke extraction actively removes smoke from the fire area. Large buildings often use both together.
Does smoke control need a special power supply?
Yes. Because it must operate during a fire, the fans, dampers, and controls are fed from a protected or standby supply with fire-rated wiring so they keep running when normal power fails.
Who controls the smoke-control system in an emergency?
It runs automatically on fire detection but is monitored and can be overridden by firefighters from the fire command centre, which displays system status and manual controls.