What is the device used in cars and trucks to reduce carbon monoxide emissions?

What is the device used in cars and trucks to reduce carbon monoxide emissions?
You're probably thinking of the Catalytic converter, which is in the exhaust system and looks like a canister usually under the car around the front seats, but there are many systems imposed on vehicles to reduce emissions, such as an exhaust gas recirculation valve which takes some of the hot air from the exhaust and runs it through the engine again.