Step 1: The Trigger — Smoke Detection
The sequence begins with a smoke detector. AOV systems are typically connected to optical smoke detectors positioned in common corridors, lobbies, and stairwell landings. When smoke enters the detector's sensing chamber and scatters its infrared beam, the detector triggers an alarm signal.
In installations compliant with BS 9991, the smoke detectors may be part of, or interfaced with, the building's main fire alarm system (L2 or L3 category).
Step 2: The Signal — AOV Control Panel
The alert is received by the AOV control panel — the brain of the system. On receiving the alarm signal, the panel identifies which detection zone has activated, determines which vents should open, sends a power signal to the relevant actuators, and logs the event with a timestamp for the fire safety record.
The panel also activates any audible or visual indicators on manual override stations at each floor level, alerting building occupants that the system has activated.
Step 3: The Action — Actuator Opens the Vent
The AOV actuator physically opens the vent. Two types are common: chain actuators (motorised chain drive pushing the vent open, common on roof lights and high-level windows) and rack-and-pinion actuators (gear mechanism for larger, heavier vent units). Both operate on 24 V DC from the control panel.
The vent opens to its designed free area — typically achieving full opening within 60 seconds of activation. Hot smoke and gases rise naturally through the open vent, drawing cooler replacement air in through lower openings.
Step 4: Battery Backup — Keeping the System Running
A fire that triggers an AOV system may also compromise mains electrical supply. Battery backup is a mandatory requirement under BS EN 12101-10, which specifies that AOV power supplies must maintain system operation for a minimum of 60 minutes under full load and 72 hours in standby following mains failure.
The battery backup unit switches to battery power automatically and instantaneously the moment mains is lost, with no interruption to system operation. It continuously monitors battery health and reports fault conditions to the control panel.
Step 5: The Reset — Closing Vents After the Event
Once the emergency is over, the AOV system must be deliberately reset before vents close — a safety feature preventing inadvertent closure while smoke may still be present. The reset procedure involves confirming with the fire service that it is safe to close vents, silencing the alarm at the control panel, and pressing the reset function to allow actuators to close.
Step 6: Testing and Maintenance
Current fire safety law — including the Regulatory Reform (Fire Safety) Order 2005 and the Fire Safety (England) Regulations 2022 — requires the responsible person to ensure AOV systems are maintained in efficient working order. This means weekly visual checks, monthly functional tests, and annual full-system inspections by a competent engineer.
AOV Direct supplies all system components including control panels, battery backup units, actuators, and detectors. All in stock for next day delivery. Call 01202 725 677.
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