The AFS is a general purpose airflow proving switch designed for HVAC, detection of blocked filters and fan suction, air flow monitoring in ducts, pipes, tunnels, and other energy management applications. It may be used to sense positive, negative or differential air pressure. The plated housing contain a diaphragm, a calibration spring and a snap-acting switch. The sample connections located on each side of the diaphragm accept a 0.25" OD tubing via the integral compression and nut. An enclosure cover guards against accidental contact with the live switch terminal screws and the set point adjusting screw. The enclosure cover will accept a 0.5" conduit connection.