Natural gas consists mainly of methane , which is the simplest hydrocarbon.
Methane molecules contain one carbon and four hydrogen atoms. In 1999-2000, for example, the composition of natural gas used in Melbourne was 90.1 percent methane, 5.8 percent ethane, 1.1 percent propane, 0.3 percent butane, 0.8 percent nitrogen and oxygen, and 1.9 percent carbon dioxide. The large proportion of methane is one of the reasons natural gas has such a good safety record. Methane is lighter than air and will easily disperse if there is a gas leak. Another reason natural gas has such a good safety record is that its use in Australia is governed by rigorous industry technical standards.