A catalytic converter is an emission control device that converts toxic and polluting gases into exhaust gases to less toxic contaminants by catalyzing a redox reaction (an oxidation and a reduction reaction). Catalytic converters are used with internal combustion engines fueled by gasoline (petrol) or diesel, including lean combustion engines, as well as kerosene heaters and stoves.
The first widespread introduction of catalytic converters was in the US auto market. To comply with the US EPA's more stringent exhaust emission regulations, most gasoline vehicles beginning with the 1975 model year must be equipped with catalytic converters. These "bi-directional" converters combined oxygen with carbon monoxide (CO) and unburned hydrocarbons (HC) to produce carbon dioxide (CO2) and water (H2O). In 1981, bi-directional catalytic converters became obsolete by "three-way" converters that also reduce nitrogen oxides (NOx); However, two-way converters are still used for lean-burn motors. This is because three-way converters require rich or stoichiometric combustion to successfully reduce NOx.
Although catalytic converters are most commonly applied to exhaust systems in automobiles, they are also used in electric generators, forklifts, mining equipment, trucks, buses, locomotives and motorcycles. They are also used in some wood stoves to control emissions. This is generally in response to government regulation, either through direct environmental regulation or through health and safety standards. A catalytic converter has to be changed every 100 000/120 000 km to be efficient. It is important to recycle this part of the car.