Stairwell AOV Systems: BS EN 12101-2 Compliant

A stairwell AOV (Automatic Opening Vent) is a motorised vent installed at the head of a stairwell that opens automatically when the fire alarm activates. Its purpose is to extract smoke from the stairwell, keeping the escape route clear for building occupants and accessible for firefighters.

Stairwell AOVs are connected to a smoke control panel that receives signals from the building’s fire alarm system. When a fire is detected, the panel powers the actuator to open the vent to its full certified free area. The vent can also be manually opened via a firefighter override switch at the building entrance.

In the UK, stairwell AOVs must be tested and certified to BS EN 12101-2 as complete natural smoke and heat exhaust ventilators. Vent Trade manufactures stairwell AOV products under the Ventec brand.

Approved Document B of the Building Regulations requires smoke ventilation for protected escape stairwells in residential buildings with a floor more than 11 metres above ground level. Stairwell AOVs are the standard solution for natural smoke ventilation in these buildings.

They are also commonly specified in commercial buildings, sheltered housing, student accommodation, and mixed-use developments where the fire strategy requires automatic smoke extract from escape stairs. The requirement is determined by the building’s fire engineering design or the prescriptive guidance in Approved Document B.

A complete stairwell AOV system typically includes:

• “AOV vent: a roof vent (such as the Ventec Ostro) or pivot window (such as the Ventec Centro or KAS S6A) installed at the head of the stairwell”
• “Smoke control panel: a BS EN 12101-10 compliant panel (such as the O Range 7) that controls the vent and interfaces with the fire alarm”
• “Battery backup: a 24V battery backup unit (such as the Ventec S420) to ensure operation during mains failure”
• “Firefighter override switch: a key switch at the building entrance for manual control by the fire service”
• “Smoke detector: an optical smoke detector in the stairwell head (if not provided by the fire alarm system)”

Vent Trade supplies complete stairwell AOV packages with all components matched and tested for compatibility.

An AOV roof vent (such as the Ventec Ostro) is designed for flat or low-pitched roof installations. It opens upward from a horizontal or near-horizontal position, providing smoke extract directly through the roof. Roof vents are the most common choice for stairwell AOVs where the stair terminates at roof level.

An AOV window (such as the Ventec Centro or KAS S6A) is a pivot or top-hung window designed for vertical or pitched installations. AOV windows are specified where a roof vent is not practical: for example, where the stairwell has a side wall rather than a roof opening, or where the roof pitch is too steep for a rooflight.

Both types must be certified to BS EN 12101-2 and provide the specified certified geometric free area for the smoke ventilation strategy.