The Lochinvar & A.O. Smith 100113144 Blower Prover Switch is a vital safety component designed to verify proper blower operation in compatible gas-fired water heaters, boilers, and other HVAC heating equipment. It works by sensing airflow or blower pressure before allowing the ignition sequence to continue, helping ensure safe and efficient system operation. https://www.partshnc.com/blower-prover-switch-10