An automatic opening vent needs something to open it, and that something is an actuator: a motorised device that drives the vent open on a signal from the smoke control panel. The actuator is the moving part of a life safety system, which is what sets the expectations for its power supply, its testing and its maintenance.
Chain and linear actuators
Chain actuators push a rigid articulated chain out of a housing to open a window or a louvre, and are compact enough to sit on a window frame. Linear or spindle actuators use a driven rod and deliver more force over a longer stroke, suiting heavier vents and roof lights. The choice follows the weight of the vent, the opening angle required and the space available, and the number of actuators per vent follows the width.
How a smoke vent actuator is driven
A smoke control panel receives a signal, from the fire alarm system, from a detector on the smoke control system's own loop, or from a manual control point, and drives the actuators. The panel monitors the actuator lines for faults and reports them. In a residential block the sequence typically vents the corridor or lobby of the fire floor and opens the vent at the head of the stair, and that logic lives in the panel's cause and effect.
Power supply
Smoke control systems require a standby power supply so that they still operate when the mains has failed, because a fire that takes out the supply is exactly when the vent is needed. Battery capacity is part of the design and batteries are a consumable with a finite life, which is the most commonly neglected item in a smoke control maintenance regime.
Testing and maintenance
The system is tested periodically by operating it and watching the vents open fully and close again, checking the panel reports no faults, and confirming the standby supply. Records are kept per vent. A smoke control system that has never been seen to operate is not a system anybody should rely on, and actuators seize in place more readily than most fire equipment because they move so rarely.
Questions people ask about aov actuators
Who maintains an AOV system?
A specialist smoke control contractor. It is a life safety system with its own standards, and it is not part of a general electrical maintenance contract by default.
How often should AOVs be tested?
The system should be exercised regularly and serviced periodically, with the frequency set by the system standard and the risk assessment. Monthly operation and an annual service is a common regime.
What happens if an actuator fails?
The panel should report a fault. The vent is then out of service and the building is operating outside its fire strategy until it is fixed, which is an assessment matter rather than a maintenance backlog item.
What does an AOV panel do?
It is the control end of the system: it holds the standby batteries, takes the signal from the detection or the break glass, drives the actuators and reports faults. A vent that will not open on test is as often a panel or a supply problem as a mechanical one.
Where are AOV vents usually fitted?
At the head of a protected stair and, in a block of flats, in the corridor on each floor. The point is to clear smoke from the route people escape by and the route the fire service comes up, so position follows the escape strategy rather than the roof layout.
Are AOV windows the same thing as an escape window?
No, and conflating them is a real design error. An automatic opening vent is part of the smoke control system: it opens on a signal from the detection or the panel to clear smoke from a stair or a lobby so people can escape and the brigade can work, and it is designed on a free area calculation and commissioned as a system. An escape window is a means of escape from a room, sized so a person can get out and reachable from floor level. A window that does both is possible and has to satisfy both sets of rules, so a vent that is also counted as escape needs the calculation AND the openable dimensions, and a vent fitted where an escape window was assumed leaves the room without one.