Definitions: Intermittent operation, Manual control, Mechanical extract ventilation

Intermittent operation – a mechanical ventilator that does not run all the time, usually running only when there is a particular need to remove pollutants or water vapour (e.g. during cooking or bathing). Intermittent operation may be under either manual control or automatic control. Manual control – where a ventilation device is opened and closed or switched on and off, or its performance is adjusted by the occupants of a room or building. Mechanical extract ventilation – a system of ventilation operated by a power driven mechanism which extracts air from a room and discharges it only to the external air.