Quickly clear smoke…
A powered or mechanical smoke ventilation system is an industry approved alternative to natural smoke ventilation and is designed to achieve the same aim of quickly clearing smoke from protected lobbies and staircases.
A typical installation will comprise of a shaft rising through the building with a damper on each connected level venting into this vertical duct.
For powered smoke ventilation systems all products and design criteria must meet the compliance requirements of:
- Approved Document B
- BS 9991 & BS 7346-8
- EN12101-3 Powered Smoke and Heat Control Fans
- BS EN 12101-6
Smoke Control Association’s ‘Guidance on Smoke Control to Common Escape Routes in Apartment Buildings’
A set of duty/ standby smoke extract fans located at roof level will actively draw the smoke and harmful gases from a lobby, through the shaft exhausting typically at the highest point of the building.
Inlet or make up air is provided via an AOV installed at the top of the stairwell.
The smoke detection, lobby damper, stairwell AOV and fan all trigger simultaneously and are interlinked by a tailored control system specific to each building’s requirements.
The two key benefits of a mechanical system are the reduced shaft area requirement on each floor and an increased flexibility with building design and escape distances.
Due to mechanical smoke ventilation systems being an alternative method to that set out in Approved Document B, any proposed design is required to be substantiated and verified using Computational Fluid Dynamics (CFD) analysis.