- CNG (Compressed Natural Gas) is primarily composed of methane (CH4), usually 80-90%, with smaller amounts of ethane, propane, and other gases. - Coal gas is produced by the destructive distillation of coal and contains a mixture of gases, including hydrogen (H2), methane (CH4), carbon monoxide (CO), nitrogen (N2), carbon dioxide (CO2), and various hydrocarbons. Hydrogen, methane, and carbon monoxide are major combustible components. - LPG (Liquefied Petroleum Gas) is a mixture of hydrocarbon gases used as fuel in heating appliances, vehicles, and increasingly petrochemical feedstock. The most common components are propane (C3H8) and butane (C4H10). - Water gas is a synthesis gas containing carbon monoxide (CO) and hydrogen (H2), produced by passing steam over heated hydrocarbons, typically coke or coal.