Due to heavy industrialization and transportation (modernization), CO2 concentration is increasing day by day in the atmosphere. CO2 has capacity of absorbing heat radiations and thus increases temperature. This increase in global temperature (global warming) is mainly due to CO2 concentration and is called 'green house effect'. Besides CO2 other important gases associated with green house effect are CH4 (methane), oxides of nitrogen (NOv), CFCs (chlorofluorocarbons) and O3 (ozone) and these are called 'green house gases'. Relative contribution of these gases to global warming are: CO2 (50%), CFCs (20%), CH4 (16%), O3 (8%), nitrous oxide (6%).