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How does a smoke shaft system work?

A picture of two SCS Group staff inspecting a smoke control system

SCS Group has been providing smoke control solutions for 25 years

FOR 25 years SCS Group has been providing smoke control solutions and has grown to become one of the UK’s leading providers of not just smoke control, but also ventilation and building management systems (BMS).

But what exactly is smoke control? How does it work? We have a look at how a ‘smoke shaft system’ is put together and how it operates…

‘Smoke shaft’ is the common term for ventilation systems in the lobbies of tall buildings, used to maintain tenable conditions in the common escape routes in the event of a fire in the building.

They are essentially a simple ventilation system designed to extract any smoke leaking into a common lobby to protect the escape stairs. Typically, a vertical builder’s work duct rising through the building would be used to extract smoke from the lobbies. Each lobby would have a damper connected to the builder’s work duct.

For natural shafts, the head of the shaft is terminated with an automatic opening ventilator (AOV). Mechanical shafts use extract fans, mounted on the roof and connected to the builder’s work duct with sheet metal ducting.

An AOV would be mounted at the top of the stairwell and the complete system would be controlled by an addressable control system that provides automatic operation of the ventilation by interface with the fire alarm system or smoke detectors.

So, how does this eliminate smoke from a lobby?

    1. Smoke detector detects smoke which initiates the smoke shaft
    2. Lobby vent to the smoke extract shaft opens
    3. Folding arm actuator opens the door to the stairwell
    4. Stairwell vent opens to allow fresh air to enter
    5. On the roof, the fans in the smoke extract unit begin to remove smoke via the smoke extract shaft
    6. Fresh air is drawn into the stairwell
    7. Smoke in the lobby is removed via the smoke extract shaft
    8. The system becomes ready for firefighters


You can find out more about practical smoke shaft principals and specifications via our guide at http://groupscs.co.uk/wp-content/uploads/SCS-Guide-to-Smoke-Shafts-v2-JAN2017.pdf and we’ve also included a graphic below showing how a system works in more detail.

A graphic showing how a smoke shaft system works

A graphic showing how a smoke shaft system works