The term “gaseous fuel” refers to any combustible fuel that exists in the gaseous state under normal temperatures and pressures. Gaseous fuels are typically composed of a wide range of chemical compounds. Low boiling point hydrocarbons (both parafns and olens), hydrogen, carbon monoxide, and inert gases (nitrogen and carbon dioxide) are among the many chemical constituents of common gaseous fuels. The purpose of this section is to introduce many of the common fuel gas mixtures used as fuel in the hydrocarbon and petrochemical industries. Commonly occurring waste gas mixtures in are systems are also described.