The gases comprising the atmosphere are in dynamic balance both with the oceans and the dry land of the continents. The mechanisms which operate to keep the atmospheric content of oxygen, nitrogen, carbon and sulphur constant are now well defined. The capacity of the system to absorb excess gaseous impurities is adequate on a global basis with the exception of carbon dioxide.Air pollution is thus a local problem resulting from the overloading of a particular air space with contaminants. The greater part of air pollution is due to the combustion of fossil fuels. Ease of control and virtual freedom from sulphur give natural gas an advantage over liquid and solid fuels as far as air pollution control is concerned. Oxides of nitrogen are produced when natural gas is burned but in smaller quantities than in the combustion of other fuels. In high capacity industrial gas burners where oxides of nitrogen may be generated in large quantities control is easier and can achieve a lower level of oxides of nitrogen than is the case with other fuels.The large scale use of natural gas to solve the air pollution problems of Pittsburgh, Los Angeles and many other cities is proof of the usefulness of gas in this respect. Specialised applications include use in incinerators and industrial after burners. Advances in removal of impurities from fuels and of air pollutants from products of combustion combined with rising gas prices will in time displace gas from its preeminent position in air pollution control. It is, however, likely to retain its advantage in small installations and in dense urban areas. In public and private transport its use will probably remain limited.While technological developments in the distant future may eventually displace fossil fuels, gas will have a large share of the fuel market until that day comes and will contribute effectively to the control of air pollution.