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Emission standards are requirements that set specific limits to the amount of pollutants that can be released into the environment. Many emission standards focus on regulating pollutants released by automobiles and other transport vehicles, but they can also regulate emissions from industry, power plants, small equipment such as lawn mowers and diesel generators. Frequent policy alternatives to emission standards are technology standards (which mandate the use of a specific technology) and emission trading.

Standards generally regulate the emissions of NO_x, particulate matter (PM) or soot, carbon monoxide (CO), or volatile hydrocarbons. The main components of automobile exhaust, carbon dioxide (CO₂) and water vapor (H₂O), have so far not been regulated by emission standards, but the European Union is moving towards mandatory CO₂ standards.

EPA standards in the United States (transport vehicles)

In the United States, emissions standards are managed by the Environmental Protection Agency (EPA) as well as some state governments. Some of the strictest standards in the world are enforced in California by the California Air Resources Board (CARB). Currently, vehicles sold in the United States must meet "Tier 1" standards that went into effect in 1994. Additional "Tier 2" standards have been optional from 2001 to 2003, and are currently being phased in—a process that should be complete by 2009. Within the Tier 2 ranking, there is a subranking ranging from BIN 1-10, with 1 being the cleanest (Zero Emission vehicle) and 10 being the dirtiest (Hummer). The current Tier 1 standards are different between automobiles and light trucks (SUVs, pickup trucks, and minivans), but Tier 2 standards will be the same for both types. A common measurement system for American standards is the somewhat confusing mixed-standard unit of gram per mile.

There are several ratings that can be given to vehicles. A certain percentage of the cars produced by major manufacturers must meet these different levels in order for the company to sell their products in affected regions. Tier 1 has been the baseline used. Beyond Tier 1, in increasing stringency, there are

• TLEV – Transitional Low Emission Vehicle
• LEV – Low Emission Vehicle
• ULEV – Ultra-Low Emission Vehicle
• SULEV – Super-Ultra Low Emission Vehicle
• ZEV – Zero Emission Vehicle

The last category is largely restricted to electric vehicles and hydrogen cars, although such vehicles are usually not entirely non-polluting. In those cases, the other emissions are transferred to another site, such as a power plant or hydrogen reforming center, unless such sites run on renewable energy. However, a battery-powered electric vehicle charged from the California power grid will still be up to ten times cleaner than even the cleanest gasoline vehicles over their respective lifetimes.

The above standards are being made even more stringent. Tier 2 variations are appended with "II", such as LEV II or SULEV II. There are other categories that have also been created.

• ILEV – Inherently Low-Emission Vehicle
• PZEV – Partial Zero Emission Vehicle
• AT-PZEV – Advanced Technology Partial Zero Emission Vehicle
• NLEV – National Low Emission Vehicle

PZEVs meet SULEV emission standards, but in addition have zero evaporative emissions and an extended (15-year/150,000 mile) warranty on their emission-control equipment. Several ordinary gasoline vehicles from the 2001 and later model years qualify as PZEVs; in addition, if a PZEV has technology that can also be used in ZEVs like an electric motor or high-pressure gaseous fuel tanks for compressed natural gas (CNG) or liquified petroleum gas (LPG), it qualifies as an AT-PZEV. Hybrid electric vehicles like the Toyota Prius can qualify, as can internal combustion engine vehicles that run on natural gas like the Honda Civic GX. These vehicles are called "partial" ZEVs because they receive partial credit in place of ZEVs that automakers would otherwise be required to sell in California.

European standards

Main article: European emission standards.

The European Union has its own set of emission standards that all new vehicles must meet. Currently, standards are set for all road vehicles, trains, barges and 'nonroad mobile machinery' (such as tractors). No standards appply to seagoing ships or airplanes. Find below the standards applicable to heavy duty engines to be fitted in vehicles with a gross weight over 3.5 metric tonnes. The tiers are:

• Euro 0 (1988-1992) limits emissions to 12.3 g/kWh CO, 2.6 g/kWh HC, 15.8 g/kWh NOx
• Euro I (1992-1995) limits emissions to 4.9 g/kWh CO, 1.23 g/kWh HC, 9.0 g/kWh NOx, 0.4 g/kWh particles
• Euro II (1995-1999) limits emissions to 4.0 g/kWh CO, 1.1 g/kWh HC, 7.0 g/kWh NOx, 0.15 g/kWh particles
• Euro III (1999-2005) limits emissions to 2.1 g/kWh CO, 0.66 g/kWh HC, 5.0 g/kWh NOx, 0.1 g/kWh particles
• Euro IV (2005-2008) limits emissions to 1.5 g/kWh CO, 0.46 g/kWh HC, 3.5 g/kWh NOx, 0.02 g/kWh particles
• Euro V (2008-2012) limits emissions to 1.5 g/kWh CO, 0.46 g/kWh HC, 2.0 g/kWh NOx, 0.02 g/kWh particles

Currently there are no standards for CO₂ emissions. The European Parliament has been suggested to introduce mandatory CO₂ emission standards to replace current voluntary commitments by the automanufacturers and labelling.

See also

• Automobile emissions control
• AP 42 Compilation of Air Pollutant Emission Factors
• Corporate Average Fuel Economy
• European emission standards

References

1. European Parliament resolution on "Winning the Battle Against Global Climate Change", 16 November 2005]

External links

• Dieselnet pages on vehicle emission standards

• Emission standards
• Air dispersion modeling