GeneralAire Air Filter Gage. The GeneralAire Air Filter Gage is an easy-to-install monitoring device to tell you when your filter needs to be changed! The GeneralAire Air Filter Gage is easy to read and interpret when the filter media is ready to be replaced. Easy to install and calibrate for new, clean filter media. Built-in filter screen removes dust from sampled ambient air to keep gage clean. May be mounted remotely up to 10 feet from monitoring location. Easy to disassemble/assemble for service. Variety of uses wherever a blower/filter combination needs to be monitored. Click Here for the GeneralAire Air Filter Gage Installation Guide & Manual