Types of catalytic converter:

Two-way: The two-way catalytic converter was present on vehicles in the United States until 1981. They only have oxidation catalysts, which help change carbon monoxide to carbon dioxide. Hydrocarbons (which is unburned and partially burned fuel) are changed to carbon dioxide and water.

Three-way: Since 1981, the three-way catalytic converter has been used. This performs the same as the two-way converter with the addition of a reduction catalyst. As stated earlier, this is used to change nitrogen oxides to nitrogen and oxygen gases.