A mixture of several combustible gases which is found with most petroleum (oil) and tar deposits and some coal seams. Natural gas consists primarily of methane, but it can also include varying proportions of propane, butane, ethane and other combustible gases.

Natural gas is a highly efficient form of combustible fuel. Until recently, it was most commonly used in North America for household appliances (stoves, clothes dryers and furnaces) and commercial heating systems. Compressed natural gas (CNG) has recently found increasing favor as an alternative fuel for motor vehicles, primarily fleet vehicles such as buses, taxis and trucks that travel municipal routes.

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