What is an automatic opening vent (AOV)?
An automatic opening vent is a window, louvre or roof vent that opens automatically on a fire signal to let smoke out of a stair, lobby or corridor.
It is the commonest form of smoke control in residential blocks, and it is usually the only fire safety plant in a building that has no engineer attached to it.
Its components are an actuator, a control panel and a power supply, and any of the three can fail silently. The vent looks identical whether it is working or not.
Manual override controls are often provided for the fire and rescue service. Those need to be accessible and labelled, which is a housekeeping matter that ends up mattering under pressure.
In practice
An automatic opening vent painted shut.
The stairwell was redecorated and the vent frame was painted along with everything else.
An AOV is a mechanical device in a location nobody visits, and the usual cause of failure is another trade's work rather than the device itself.
It is tested by operating it, which is the thing a visual inspection cannot do.
What goes wrong in practice
- Tested by pressing the panel button only, which proves the panel rather than the vent.
- Actuators failed with no indication, so the vent has not opened for years.
- Override controls obstructed, unlabelled or behind a locked door nobody has a key to.