The Rheem Manufacturing Company / Ruud 42-24196-81 Vent Pressure Switch 1.30" WC is a safety control device engineered for gas furnaces and induced-draft heating systems. It monitors vent and combustion air pressure, closing the electrical circuit when the 1.30-inch water column set point is achieved to verify proper airflow. https://www.partshnc.com/130wc-press-sw-vent