ABSTRACT
Rapid development of chemical, pharmaceutical, and other process industries, and the ever-increasing number of automobiles on the roads, together with emissions from the combustion of fossil fuels in power plants and similar industrial processes, is releasing large amounts of hazardous gases and vapors into the air. This puts considerable pressure on the availability of clean air. These effluents contain small amounts of a large number of volatile organic compounds (VOC). These flue gases also contain small amounts of oxides of sulfur and oxides of nitrogen, the most important being SO
and NO. These gases combine with VOC to produce smog and sometimes also produce acid or smog clouds. One such smog cloud was seen over London in 1950, and it caused several thousand human deaths due to respiratory problems.
