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Revision as of 16:23, 4 November 2004 by 216.47.187.254 (talk) (→EPA standards in the United States)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)Emission standards limit the amount of pollution that can be released into the atmosphere. Emissions come from many places including industry, power plants, vehicles (from trains to automobiles to mopeds), and small equipment such as lawn mowers. Many emissions standards focus on regulating the amount of material that can be released by automobiles, which use the largest portion of energy in most places around the world. Regulations limit mandate the types of fuels that can be used and the amount of smog-forming material that can be released, but they generally do not directly limit fuel economy—the amount of fuel that can be consumed.
Standards generally regulate the amount of carbon monoxide (CO), oxides of nitrogen (NOx), sulfur, hydrocarbons, and particulate matter (PM) or soot that can be released. The main components of automobile exhaust, carbon dioxide (CO2) and water vapor (H2O), are not considered to be emissions in most cases. Carbon monoxide and other chemicals can generally be reduced by modifying engines to more completely burn fuel, and by using catalytic converters to convert the chemicals into less noxious compounds. Hydrocarbons sometimes leak out of the fuel system, so redesigning that to prevent fuel vapors from escaping can reduce emissions. Reducing carbon dioxide emissions can be accomplished by reformulating fuels and by reducing overall fuel consumption.
European Standards
Europe has its own set of standards that vehicles must meet. The tiers are