Smoke vent systems are installed to ensure stairways and communal corridors remain relatively free from smoke and heat in the event of a fire to enable occupants of the building to escape safely. In tall buildings (with a floor over 18m high) these systems assist firefighters in gaining access to fight the fire from inside the building.
The top 5 smoke vent systems used by M&E Contractors
Stairwell Smoke Vents
A stairwell ventilator is an automatic opening ventilator which should provide a minimum of 1.0m² of free area located at the highest point in a stairwell. Stairwell smoke vents evacuate smoke in stairwells of small buildings and provide replacement air for a lobby smoke extract system in larger buildings.
They can take a number of forms including louvred, hatch type, windows, and roof vents.
Automatic Opening Vents (AOVs)
Smoke ventilators can be used to ventilate lobbies directly to the atmosphere. These may be a proprietary ventilator or a combination of an actuator and an existing window or roof light. They should provide a minimum free area of 1.5m².
In single staircase buildings, the ventilator should open automatically on detection of smoke in the lobby. In multiple staircase buildings the ventilator can be operated manually. In both cases, opening the AOV should also cause the stairwell ventilator to open.
Group SCS offers pre-designed AOV kits to help you specify the right equipment for the job – explore our range in our online shop.
Natural Smoke Vent Systems (BRE Shafts)
Natural smoke shafts, commonly known as BRE shafts should comprise a vertical shaft with a minimum free area of 1.5m², with a ventilator into the shaft at each lobby and at the head of the shaft of 1.0m² free area. The ventilator into the shaft should have a fire resistance performance equivalent to an E30S fire door and be opened automatically upon detection of smoke in the lobby.
For example, our UniVent Natural Ventilation System is a BRE Shaft System made up of AOV Kits. It is designed to exhaust smoke from the common lobbies through a builder’s work shaft and operates automatically via smoke detection. Visit our online shop to find out more about UniVent.
Mechanical Smoke Vent Systems
Mechanical shafts are similar to BRE shafts, but have additional extract fans in order to mechanically extract smoke from the lobbies which allow smaller shaft and ventilators to be employed. Shaft area typically reduces from 1.5m² to 0.6m² meaning that more space is freed for other use within the building. Extract fans are usually mounted on the roof. The automatic opening ventilator above the stairwell is used to provide replacement air for the smoke shaft.
To ensure effective smoke clearance, the extract shaft should be located as far away as practically possible from the stairwell, which is the source of replacement air. This is particularly important in buildings with extended travel distance.
Pressurisation Systems
Pressurisation systems protect the lobbies and staircases against the ingress of smoke by raising the pressure in these areas relative to the fire zone. In residential buildings they would commonly comprise run and standby fans to pressurise the stair and an air release path from the lobby usually via a rising duct, similar to a BRE shaft. The design procedure and equipment specifications are detailed within BS EN12101-6.
Pressurisation systems offer the highest standard of protection, however their use has declined with the rise in use of CFD modelling to design mechanical smoke shafts as these are generally simpler to install and commission.
