Fuel Gases
. Fuel Gases, any combustible gaseous mixture used as fuel to provide energy for domestic or industrial use (see Combustion ; Fuel ). Fuel gases consist principally of hydrocarbons, that is, of molecular compounds of carbon and hydrogen. The properties of the various gases depend on the number and arrangement of the carbon and hydrogen atoms within their molecules. All these gases are odorless in the pure state, and carbon monoxide is toxic. It is therefore common practice to add sulfur compounds to manufactured gas; such sulfur compounds, which are sometimes normally present in the gas, have an unpleasant smell and serve to give warning of a leak in the supply lines or gas appliance. In addition to their combustible components most gases have varying amounts of noncombustible nitrogen and water as their end products. The devices used to burn gas for either heat or illumination consist of a burner nozzle and some means of mixing air with the gas before it reaches the nozzle, as, for e