The A.J. Antunes 8104116203 Low Gas Pressure Switch (1–20" WC, 1/4" NPT, Auto Reset) is a precision safety device designed for gas-fired HVAC systems. It monitors gas line pressure and automatically interrupts operation if pressure falls below safe levels, protecting equipment from damage and ensuring safe performance. https://www.partshnc.com/8104116203-aj-antunes-wc-open-lo-auto-reset