The emissions of air pollutants depend upon the method of combustion and the type of fuel used. The combustion of all fuels results in exothermic oxidation of carbon, hydrogen, sulphur and nitrogen. In case of complete combustion, carbon dioxide, water vapour, nitrogen oxides, volatile and non-volatile trace metals such as Arsenic, Cadmium, Lead and Mercury would be the principal emission.
However, in practice complete combustion does not occur and as a result of additional particulate and gaseous pollutants result in the production of secondary pollutants. Certain pollutants undergo atmospheric oxidation to form acidic precipitation.
In addition, indoor air pollution is also considered to be of great importance in terms of personal exposure. The principal air pollutants are divided from combustion of stoves, heaters, cigarettes, building materials and furnishing air products. House hold dust is also believed to be of importance in the indoor air pollution. The impact of indoor emissions depends upon the strength of the source and the ventilation rate.