Natural gas s advantages over other fuels include the following: it has fewer impurities, it is less chemically complex, and its combustion generally results in less pollution. In most applications, using natural gas produces less of the following substances than oil or coal: carbon dioxide (CO2), which is the primary greenhouse gas; sulfur dioxide, which is the primary precursor of acid rain; nitrogen oxides, which is the primary precursor of smog; and particulate matter, which can affect health and visibility; than oil or coal. Technological progress allows cleaner energy production than ever for all fuels, although the inherent cleanliness of gas means that environmental controls on gas equipment, if required, tend to be far less expensive than those for other fuels.