How AOV Systems Work
When smoke is detected, the system automatically activates. A signal is sent to the AOV control panel, which then triggers actuators — motorised devices mounted on windows or purpose-built vent units — to open the ventilation apertures. In tall buildings, this typically opens roof-level vents creating an upward smoke flow. Manual red push-button stations on each floor allow occupants or firefighters to override the automatic system.
Types of AOV Systems: Natural vs Mechanical
Natural Smoke Ventilation (NSV) systems exploit hot smoke buoyancy and stack effects without fans. They work best in buildings with clear vertical paths like staircases and single-storey spaces. Mechanical Smoke Ventilation (MSV) systems use powered fans for smoke extraction in basements, deep-plan buildings, or complex layouts. Both types must comply with BS EN 12101 standards and function during power outages.
When Do Buildings Need AOV Systems?
Approved Document B (ADB) requires smoke ventilation in protected stairwells in buildings exceeding 18 metres and in residential blocks with common corridors. BS 9991 offers detailed guidance on positioning, operation, and fire alarm integration for purpose-built flats. BS EN 12101 is the overarching technical standard governing all smoke and heat control systems. The Fire Safety (England) Regulations 2022 impose additional responsibilities in buildings above 11 metres, including regular inspection and testing requirements.
Key Components of an AOV System
Smoke detectors trigger the system upon detection. The AOV control panel receives signals from detectors, manages vent opening sequences, and interfaces with the building's fire alarm — it must comply with BS EN 12101-9. Actuators are motorised mechanisms that physically open roof vents, corridor windows, or louvres when triggered. The battery backup unit ensures the AOV control panel and all actuators continue to function during mains power failure for the required duration under BS EN 12101-10. Manual override controls on every floor enable manual activation and reset.
BS EN 12101 Compliance
BS EN 12101 is a multi-part European standard governing the design, installation, and testing of smoke and heat control systems. The most relevant sections for UK installations are Parts 2, 3, 9, and 10, addressing natural ventilators, powered ventilators, control panels, and power supplies respectively. All components should carry UKCA marking indicating compliance.
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