1.0-4.0" W.C. Adjustable air sensing switches are designed to replace a wide variety of air-sensing switches found in residential and light commercial applications including - furnaces, electronic air cleaners and humidifiers. Both models are found with a SPDT switch that can be actuated by positive or negative pressure or by pressure differential. Insensitive to temperature ranges of -40OF to 190OF. They are UL and CSA approved. Each switch comes with mounting hardware and an adjustable tool for easy installation and calibration