The combustion of all fossil fuels follows a very similar reaction: Fuel (any hydrocarbon source) plus oxygen yields carbon dioxide and water and energy.

A simple combustion reaction is given for methane. The combustion of methane means that it is possible to burn it. Chemically, this combustion process consists of a reaction between methane and oxygen in the air. When this reaction takes place, the result is carbon dioxide (CO₂), water (H₂O), and a great deal of energy. The following reaction represents the combustion of methane:

 
One molecule of methane, (the [g] referred to above means it is gaseous form), combined with two oxygen molecules, react to form a carbon dioxide molecule, and two water molecules usually given off as steam or water vapor during the reaction and energy.

Natural gas is the cleanest burning fossil fuel. Coal and oil, the other fossil fuels, are more chemically complicated than natural gas, and when combusted, release a variety of potentially harmful air pollutants. Burning methane releases only carbon dioxide and water. Since natural gas is mostly methane, the combustion of natural gas releases fewer byproducts than other fossil fuels.