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A Short History Of US Emission Controls 1

The introduction of automotive Emission Controls was a reaction to the rapidly decreasing quality of the air we breathe.
» Part 1: Vehicle Emissions
» Part 2: Emission Controls

The introduction of automotive Emission Controls was a reaction to the rapidly decreasing quality of the air we breathe. While the average car emits only a small amount of pollution, this amount multiplied by the more than 150 million vehicles in use in the United States adds up rapidly.

California was the first state to require emission control devices on motor vehicles. As Smog worsened across the country, the Federal Government became involved in emission control regulations and standards as well.

Vehicle manufacturers are continually producing more sophisticated emission control components and systems to meet more stringent tailpipe emission standards. Fuel, Ignition and Exhaust systems have all been modified to aid in this effort. Utilizing electronic fuel injection and computerized engine control systems, today's vehicles produce less emissions, get better fuel economy, and deliver better performance and power, than those produced only a few years ago.

Vehicle Emissions

Smog or "Photochemical-Smog", the main by-product of tailpipe emissions, is produced when Hydrocarbons (HC) and Oxides of Nitrogen (NOx) mix while being exposed to sunlight.

Hydrocarbons Or HC
Hydrocarbons, formed by combining Hydrogen and Carbon molecules, make up a major portion of the pollution emitted by automobiles. Hydrocarbons are basically unburned fuel, (gasoline is a Hydrocarbon compound). Hydrocarbons are the only major automotive air pollutant that comes from sources other than engine exhaust. Hydrocarbon pollution comes from fuel system evaporation (20%), engine exhaust (60%), and vapors or blow-by gases from the crankcase (20%).

Carbon Monoxide Or CO
Carbon Monoxide (CO), a chemical compound of gasoline and oxygen, is a colorless, odorless, poisonous gas. CO is formed when the combustion process is less than complete, usually due to a rich air/fuel mixture. CO is measured primarily at the tailpipe, but may also escape into the crankcase in blow-by gases.

Oxides Of Nitrogen Or NOx
Oxides of Nitrogen or NOx are chemical compounds of Nitrogen and Oxygen, (both common in atmospheric air). NOx forms during the combustion process when engine combustion temperatures exceed 2,500°F. NOx mixes with the hydrocarbons in sunlight to produce Photochemical Smog.

» Part 1       » Part 2
Additional Information provided courtesy of and Warranty Direct
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