The Air Sampling Unit enables smoke detectors to be sited within ventilation extract ducts in order to assist in the prevention of the spread of smoke by the ventilation system (as required by building regulations) and in addition to form part of the Fire Alarm System.
The Air Sampling Unit works by taking a sample of air from the duct through a black perforated inlet probe into its sampling chamber, which should contain an ionisation smoke detector or optical monitor. This air is removed through a white exhaust probe. The design of the probes and sampling chamber is arranged so that air passes through the sampling chamber at approximately 25% of air speed in the duct.
The Air Sampling Unit enables smoke detectors to monitor ventilation ducts without subjecting the detectors to high air velocities which could alter their sensitivity.