HVAC gas valves control the flow of gas to the burners in a furnace or boiler. It regulates the amount of gas that is supplied to the combustion chamber, which in turn controls the heating output of the system. The gas valve is typically controlled by a thermostat or other control device, which signals the valve to open or close based on the temperature set point and the current room ... https://www.partshnc.com/ventilation-parts/furnace-gas-valve