Catalytic Convertor

How the Catalytic Converter works
There are millions of cars on the road that are potential sources of air pollution. In a major effort to reduce vehicle emissions, carmakers have developed an interesting device called a catalytic converter, which treats the exhaust before it leaves the car and removes a lot of the pollution.

Pollutants Produced the Engine
In order to reduce emissions, modern cars have been designed to carefully control the amount of fuel they burn. The goal is to keep the air-to-fuel ratio very close to the "stoichiometric" point, which is the calculated ideal ratio of air to fuel. Theoretically, at this ratio, all of the fuel will be burned using all of the oxygen in the air. [For petrol, the stoichiometric ratio is about 14.7 to 1, meaning that for each pound of fuel, 14.7 pounds of air will be burned. The fuel mixture actually varies from the ideal ratio quite a bit during driving. Sometimes the mixture can be "lean" (an air-to-fuel ratio higher than 14.7); and other times the mixture can be "rich" (an air-to-fuel ratio lower than 14.7).]