A catalytic converter (colloquially, "cat" or "catcon") is an exhaust emission control device which converts toxic chemicals in the exhaust of an internal combustion engine into less noxious substances. Inside a catalytic converter, a catalyst stimulates a chemical reaction in which noxious byproducts of combustion are converted to less toxic substances by way of catalysed chemical reactions. The specific reactions vary with the type of catalyst installed. Most present-day vehicles that run on gasoline are fitted with a "three way" converter, so named because it converts the three main pollutants in automobile exhaust: an oxidising reaction converts carbon monoxide (CO) and unburned hydrocarbons (HC), and a reduction reaction converts oxides of nitrogen (NOx) to produce carbon dioxide (CO2), nitrogen (N2), and water (H2O).[1]