In gas furnaces, fuel is either natural or liquefied petroleum gas. The combustion process consumes oxygen obtained from surrounding air or air supplied to the combustion chamber by a small blower. Natural gas is odorless, colorless and accumulates in upper portions of oil and gas wells. Raw natural gas is a mixture of methane, high hydrocarbons and noncombustible gases. The composition of natural gas varies with location. Heat values of natural gas can vary from 900 to 1,200 Btus per cubic foot. But the usual range is 1,000 to 1,050 Btus per cu. ft. Odorants are added to natural gas for safety purposes.

Gas governors are necessary for the safety and reliability of the gas supply system. They regulate the pressure of gas from the high or medium pressure transport network to the low-pressure system that carries gas into individual buildings. Gas governor valves for gas engines are used in other environments such as the auxiliary gas valve system for a diesel engine.