Diesel Engine Impact on Air Quality
Diesel engines are durable and efficient. Because they consume diesel fuel, a complicated mix of petroleum components, they do produce some pollutants. A small amount of the fuel exits the engine unburned. These airborne hydrocarbons can form larger particles in the atmosphere when they contact airborne dust and other particles.
Unlike gasoline engines, which may not get enough air into the cylinder for combustion, diesel engines operate with excess air so emissions of carbon monoxide are very low, though still measurable. Carbon monoxide is a colorless, odorless gas that combines with blood and limits its ability to transport oxygen. Since the engines are consuming fuel and air and create heat in the combustion process, nitrogen from the air can be transformed into nitrogen oxides which are reddish brown gases that irritate the lungs and eyes.
The most noxious part of diesel engine exhaust is smoke; actually, carbon particles formed from the release of energy from the fuel. When a diesel engine is operating properly, smoke emissions from new engines should not be visible. If the engine is poorly or improperly maintained, exhaust smoke can be thick, black and continuous.
New, well-designed diesel engines with computer controls limit the smoke and pollutants to very low levels, without the catalytic converters and complicated emissions reduction equipment necessary on gasoline engines. New federal standards require significant reductions of all pollutants from diesel engines, and will continue to reduce these pollutants in the future.