Regulated emissions

Air pollutants are classified as either primary or secondary contaminants.

• A primary air contaminant, such as carbon monoxide gas, or particles of unburned fuel, is added to the atmosphere as a by-product of burning gasoline in an internal combustion engine.
• Secondary emissions are emitted as gases and can combine with other airborn substances to form particles once in the atmosphere.

Air contaminants can be divided into gases and particulates.

• The primary pollutant gases from vehicles include: carbon monoxide, nitrogen oxides, hydrocarbons, and sulfur dioxide. These pollutants can have a damaging effect on the atmosphere and the natural environment.
• Particulates, often referred to as Particulate Matter, or PM, are tiny particles of solid or liquid suspended in the air. They are graded in a size range from 10 nanometers to 100 micrometers in diameter. Particulates of less than 10 micrometers are dangerous to humans because they can be breathed and reach the lungs. Smaller particles also tend to stay airborne longer than larger particles, which settle more quickly.

Different countries have recognized the global effects that the continual dispersion of contaminates in the earths atmosphere can have. As a result they have either introduced emission control standards and/or are signatories to international protocols to limit and control global pollution through emissions.

Vehicle manufacturers are required to comply with these standards and are required to ensure that the emissions from the vehicles they produce are strictly limited and have systems incorporated into them that monitor and control such emissions.

Many manufacturers are producing “hybrid” vehicles that use alternative power sources to limit emissions, however, even with alternative lower-pollutant fuels, the use of the internal combustion engine is set to remain a key power source for many years.

As a result, ever stricter emissions control is at the forefront of vehicle design and construction.

Typically the regulated emissions are:

• carbon monoxide,
• hydrocarbon,
• nitrogen oxides, and
• particulate matter.

Limit values are normally given in grams per brake horse power-hour in USA and grams per kilowatt-hour in Europe. These regulations are likely to become progressively more stringent.