Catalytic-converter meaning

A reaction chamber typically containing a finely divided catalyst (usually platinum and other metals such as rhodium, palladium, and gold) into which exhaust gases from an automotive engine are passed together with excess air so that carbon monoxide and hydrocarbon pollutants are oxidized to carbon dioxide and water, and nitrogen oxides are reduced to nitrogen and oxygen gases.

A device in an automotive vehicle, designed to convert certain pollutants in the exhaust into harmless compounds by the action of a metal catalyst, as platinum or palladium.