In present research, the combustion of CNG is simulated using the kinetic reaction mechanisms in Internal Combustion (IC) engines. These mechanisms are primarily investigated to predict the formation of gaseous pollutant such as Carbon monoxide (CO), Oxides nitrogen (NO & NO2) and ammonia (NH3) due to combustion of CNG in IC engine. In spite of the existence of some discrepancies among the simulation profiles, Mechanism-IV (consisting of 208 elementary reactions & 72 species) exhibits the closer agreement with the experimental data under the given engine operating conditions. This mechanism...