The production and use of I.C engines around the world are increasing day by day. Hence the pollution caused by the vehicles is great problem to whole world. The consequences of pollutants are grievous. The air we breathe and water we drink have become contaminated with chemical and that adversely affect our health. The recent developments in auto mobile technology reduce the pollutions into reasonable extent. In this report various types of emission control devices used in modern vehicles are described. The major causes of air pollution are automobile pollution. This badly affects the health of human beings. It has been linked to asthma, emphysema, cardio vascular diseases and lung cancer. It also has harmful effects on the environments. When men come to know about the harmful effects of air pollution he started thinking about air pollution control devices and he became successful in inventing some devices which reduced the pollution up to certain limit. There are certain rules and specifications that have to be followed by automobile and they have to use devices to limit as per the specifications.