A cat converter is a device that helps to regulate the emissions produced by your car. It helps change your gas's harmful gas into a less poisonous substance. It's a device between the engine and the muffler underneath all gas-powered vehicles. It contains platinum, palladium, and rhodium, enabling harmful substances in the car's exhaust system to mix and convert to safer substances. When a poisonous gas such as carbon monoxide enters the cat converter, it combines with oxygen and comes out of it as carbon dioxide, a safer gas.