The GeneralAire G-99 Air Filter Gage monitors filter media loading and provides visual indication when the filter needs replacing. It works this way: Air flowing into the gauge and around the calibration screw lifts a vane in proportion to the negative pressure in the blower compartment. As the filter loads, the vacuum increases, raising the vane to show that a filter change is necessary. The unit can be mounted remotely up to 10 ft away from the monitoring location. According to the company, it is compact, versatile, and is easily installed between the blower and the filter, where a slight vacuum exists due to the airflow resistance of the air filter.
General Filters, Inc., P.O. Box 8025, 43800 Grand River Ave., Novi, MI 48376-8025; 248-476-5100; 248-349-2366 (fax); www.generalfilters.com (website).