To help reduce the emissions in vehicles even more; the catalytic converter has been developed. Before the exhaust leaves the car it is most go through the catalytic converter which treats and removes a lot of the harmful emissions.

The main emissions coming from cars are nitrogen gas, carbon dioxide, and water vapor.

Nitrogen gas passes directly through the engine unused. 78% of air is nitrogen.

Carbon dioxide is a product of combustion. The carbon in gas bonds with the oxygen in air.

Water vapor is also a product of combustion. The hydrogen in gas bonds with the oxygen from the air.

These emissions are fairly harmless to humans, but the carbon dioxide may be playing a role in global warming.

If combustion was perfect, those would be the only emissions coming from cars. Combustion is not perfect, which causes the engine to produce some dangerous emissions. These emissions include carbon monoxide, hydrocarbons, and nitrogen oxides.

Carbon monoxide is a deadly gas that is colorless and odorless.

Hydrocarbons are produced from unburned fuel that evaporates. This unburned fuel is broken down by the sun to form oxidants. These oxidants react with oxides of nitrogen to create smog.

Nitrogen oxides play a role in the creation of smog and acid rain.

The catalytic converter is designed to filter out these three dangerous emissions.

To filter out these emissions, the catalytic converter is composed of two types of catalysts. These catalysts are called reduction catalysts and oxidation catalysts.

The reduction catalysts come first and use platinum to reduce nitrogen oxide emissions. The catalyst does this by removing the nitrogen atom from the oxygen. The oxygen is released and the nitrogen is held onto until it forms a bond with another nitrogen atom which makes it benign.

The oxidation catalyst comes second and burns  the unburned hydrocarbons and carbon monoxide over a platinum and palladium catalyst. The catalysts makes the carbon monoxide and hydrocarbons react with oxygen to make it harmless.

The control system is the third and final stage in the catalytic converter. It monitors the exhaust and sends a message a  to the ECU. The ECU uses this information to send more oxygen to aid in the breakdown of hydrocarbons and carbon monoxides in stage two of the catalytic converter.