The Cleveland 105788 Air Prover Pressure Switch monitors air pressure within the combustion or ventilation circuit of compatible commercial steam equipment. As pressure reaches the specified 0.50" water column setting, the switch changes its electrical contact state to indicate that the required airflow condition has been established. The component connects to the air-sensing line thr... https://partsfe.com/air-prover-press-switch-for-cleveland-part-105788