Earth is truly a marvelous third planet and 93,000,000 miles (150,000,000 km.) from the sun. Earths atmosphere is a gaseous envelope that surrounds the earth planet. It consists of a mixture of gases such as nitrogen, oxygen, carbon dioxide, traces of noble gases (argon, krypton, xenon, neon and helium), water vapour and small amount of ammonia, ozone, organic matter, various salts and suspended solid particles.
Air is one of the most important constituents of mans environment. It is calculated that a man breath about 22,000 times a day inhaling about 16 kg of air by weight. Therefore, clean and pure air is very essential for his health and survival. Any change in the normal composition of the air either qualitative or quantitative that may affect adversely the living system, particularly the human life inevitably cause air pollution. According to Bureau of Indian Standards, IS-4167 (1980) air pollution is the presence in ambient atmosphere of substances, generally resulting from the activity of man, in sufficient concentration, present for a sufficient time and under circumstances such as to interfere with comfort, health or welfare of persons or with reasonable use or enjoyment of property. The major air pollutants are Carbon Monoxide (CO), Carbon Dioxide (C02), Chlorofluorocarbons (CFCs), Hazardous Air Pollutants (HAPs), Lead, Ozone (03), Nitrogen Oxide (NOJ, Particulate Matter, Sulfur Dioxide (S02) Volatile Organic Compounds (VOCs), etc. The changes in climate of the Earth and the subsequent effects are called greenhouse effect.