Abstract
The components of the exhaust gases emission and the legal requirements are investigated in this paper. The strict limitation of exhaust gases emission has been mentioned. The authors have made a comparison between the different methods to reduce the nitrogen oxides (NOx) into the exhaust gases. One of the solutions is the compressed air supplied into the combustion chambers of diesel engines. The authors showed the mechanism to decrease the nitrogen oxides into the exhaust gases by the compressed air supplied into the combustion chamber of diesel engine.