The Ductstat Plug-In Thermostat Temperature Sensitive Switch is designed to turn on and off when it detects a change in temperature from the ambient. The temperature range is between 40 - 110 Degree F. This thermostat features 3 adjustable settings. It is designed to mount the duct downstream from an Inductor fan. This thermostat also helps control various devices including alarms, heat lamps, dampers, fans and 110-Volt lights.