In a typical car, the catalytic converter is part of the exhaust system and under the car, between the engine and the muffler. Often manufacturers locate the catalytic converter under the passenger seat. On long trips, passengers sometimes feel the heat it produces at their feet.
Manufacturers began installing catalytic converters on vehicles in the 1970s to reduce emissions. Since lead in gasoline reacts with the catalyst to plug the converter, the introduction of catalytic converters pushed oil refiners to produce unleaded gasoline. Catalytic converters convert unburned hydrocarbons and carbon monoxide to carbon dioxide and water. They reduce nitrous oxide, one of the primary components of smog, into nitrogen and oxygen.