Catalytic converters are required to comply with the legal regulations of emissions legislation. During the combustion of fuel, the oxygen in the air leads to the creation of water and carbon dioxide. As the combustion is not quite complete, other combustion products arise. These constituent elements of the emissions have a proportion of 1 %. In petrol engines, it is mainly carbon monoxide, hydrogen chlorides and nitrogen oxides that are created. The catalytic converter helps to convert these pollutants into water and carbon dioxide.