Steam engines belong to the broad class of external combustion heat engine. In engine of this type, the fuel is burned outside of the pressurized part of the engine, at a relatively low temperature, at atmospheric pressure, and in the presence of an abundance of air Low emission of carbon monoxide and nitrogen oxides Emission of sulfur oxides and particulates depends on the fuel being burnedSteam engines belong to the broad class of external combustion heat engine. In engine of this type, the fuel is burned outside of the pressurized part of the engine, at a relatively low temperature, at atmospheric pressure, and in the presence of an abundance of air. • Low emission of carbon monoxide and nitrogen oxides • Emission of sulfur oxides and particulates depends on the fuel being burned