What is the chemical composition of natural gas?

Methane CH₄ 90.0%

Ethane C₂H₆ 5%

Propane C₃H₈ 1%

Butane C₄H₁₀ 0.2%

Oxygen O₂ 0.0%

Helium He 0.0%

Nitrogen N₂ 2.2%

Carbon dioxide CO₂ 1.4%

Carbon monoxide CO 0.0%