The Cleveland Controls NS2-0544-00 Air Pressure Sensing Switch is a precision HVAC control device designed to monitor air pressure changes within heating and ventilation systems. It operates by sensing pressure variations and activating or deactivating an electrical circuit when a preset pressure level is reached. Commonly used with furnaces, air handlers, boilers, exhaust systems, an... https://www.partshnc.com/ns2-0544-00-cleveland-controls-air-pressure-sensing-switch