Honeywell's C6097A3004 gas pressure switch serves as a safety watchdog in a variety of HVAC equipment. This diaphragm-activated switch senses variations in pressure, usually between 0.4 and 5 inches of water column, and activates the device in response to predetermined values. Pressure breaks the circuit when it drops below the setpoint, which could trigger the machine to shut down or... https://www.partshnc.com/gasair-pressure-switch-4-5-2