Abstract: A sensing system and method for use with a gas filter in a gas conduit attached to a gas blower, having a motor for producing a first gas flow blower speed, discards readings taken when the blower is off or during blower startup and shutdown, and recalculates a clog threshold in response to changes in the fan speed of a multi-speed blower.

Abstract: A gas filter clogging detection system for monitoring filter performance and condition based on indicators of the accumulation of dirt and other particles on a filter positioned in a gas conduit, in which a notification system provides alerts and reports when the amount of clogging reaches a pre-determined threshold.

Abstract: The detector for monitoring decrease in air flow rate due to air filter clogging. It is based on combination of three essential components: the air flow sensor, a threshold detector and an indicator. The air flow sensor is built in form of a novel thermo-anemometer which contains a thermistor, a heating element, and a thermal insulator. Temperature of the sensor is maintained above the air temperature by a constant value by means of an electronic servo circuit. The threshold detector is implemented either in a hardware or software. A novel design of a thermo-anemometer (closely related to a hot wire anemometer) automatically compensates for variations in the air temperatures. The thermo-anemometer triggers the threshold circuit when air flow rate drops below a preset level. For reduction of power consumption, the detector may employ two additional sensors: one is for detection of the blower operation and the other is a presence detector to enable the alarm in presence of people to perceive the alarm.