Vehicle population is projected to grow close to 1300 million by the year 2030. Due to incomplete combustion in the engine, there are a number of incomplete combustion products CO, HC, NOx, particulate matters etc. The pollutants have undesirable effect on air quality, environment and human health that tips in stringent norms of pollutant emission. As the technology keep on evolving and emerging, it carries along undesirable effects apart from its broad application and use. One of the main contributors is said to be the emission of harmful gases produced by vehicle exhaust lines. The number of vehicles miles travels per year continues to increase as a result of higher demand and needs. Consequently, an increase in the number led to the increase of the content of pollutants in air. Most vehicular transportation relies on combustion of gasoline, diesel and jet fuels with large amount of emission of carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx) and particulates matter (PM) are especially concern. HC and CO occur because the combustion efficiency is less than 100%. The NOx is formed during the very high temperatures (>1500 0C) of the combustion process resulting in thermal fixation of the nitrogen in the air which forms NOx. Typical exhaust gas composition at the normal engine operating conditions are: carbon monoxide (CO, 0.5 vol.%), unburned hydrocarbons (HC, 350 vppm),nitrogen oxides (NOx, 900 vppm) hydrogen (H2, 0.17 vol.%), water (H2O, 10 vol.%), carbon dioxide (CO2, 10 vol.%), oxygen (O2, 0.5 vol.%). Carbon monoxide is a noted poison that has an affinity for hemoglobin in the blood 210 times greater than the oxygen affinity prolonged exposure to levels above 9 ppm can lead to reduce mental acuity for some individuals. HC and NOx lead to photochemical smog in presences of sunlight give secondary pollutant ozone, nitro dioxide & peroxyacyl nitrate which cause also global environmental problems.

A catalytic converter is placed inside the tailpipe through which deadly exhaust gases containing HC, CO, NOx are emitted. The function of the catalytic convertor is to convert these gases into CO2, H2O, N2 and O2 and currently, it is necessary for all automobiles pursuing on roads. As primary measures many different possibilities and technical methods of reducing exhaust gas emission are used e.g. combustion of lean air fuel mixture, multistage injection fuel, exhaust gas recirculation, fuel gas after burning, loading of additional water into cylinder volume.

2. HISTORY