The catalytic converter is a muffler like device inserted in the exhaust system. Exhaust gases flow through the converter where a chemical change takes place, reducing carbon monoxide and hydrocarbons to carbon dioxide and water. The catalysts promoting this reaction are platinum and palladium coated beads of alumina. Because of the chemical reaction which takes place inside the converter, the temperature during operation is much higher than the exhaust gases when they leave the engine. An improperly adjusted carburetor or ignition problem (which would permit unburned fuel to enter the converter) could produce excessive heat, resulting in bulging or other distortion of the converter's shape. If the converter is heat damaged and must be replaced, the ignition or fuel system problem should be corrected first.