Gas stove and gas duct heater and subdivided into: direct-fired and in between, the difference is that the direct-fired and heat source of the wind blow out into the type between dry clean degree, between the heat source are relatively clean, because the internal direct-fired over a heat exchange device, more will be after the secondary processing of heat wind by the fan blow out, two kinds of cost, direct-fired price advantage to have it, some low requirements for the environment can recommend using direct-fired, equipment appearance is smaller, the other common fuels are: Natural gas, liquefied petroleum gas, coke oven gas, producer gas, blast furnace gas, and mixed gas can be used as fuels.