Motor vehicle exhaust emissions are a significant source of pollution, including carbon monoxide, nitrogen oxides and hydrocarbons. These pollutants can be harmful to human health and the environment and lead to the formation of ground level ozone (smog). Exhaust emissions from cars and trucks are one of the single greatest sources of air pollution in the Chicago and Metro-East St. Louis areas.
The Illinois EPA's vehicle emissions inspection program plays an important role in improving air quality and public health in Illinois. The federal Clean Air Act (42 U.S.C. § 7511a) requires vehicle emissions inspection programs in large, urbanized areas that do not meet the National Ambient Air Quality Standards (NAAQS) for ozone. Although Illinois has made significant strides to clean its air, levels of air pollution in the Chicago and Metro-East St. Louis areas still exceed the ozone NAAQS. Additionally, the Illinois Vehicle Emissions Inspection Law of 2005 (625 ILCS 5/13C) requires a vehicle emissions inspection program to reduce air pollution from motor vehicles in these areas of Illinois. For these reasons, the vehicle emissions inspection program is part of Illinois EPA’s strategy to reduce air pollution in Illinois and bring the Chicago and Metro-East areas into attainment of the ozone NAAQS.
Through the On-Board Diagnostic (OBD) test, vehicle emissions inspections in Illinois identify malfunctioning emission control systems that often result in vehicles exceeding federal emission standards. Requiring repairs on such vehicles helps clean the air while improving the vehicle's performance and fuel economy.
Most 1996 and newer gasoline-powered passenger vehicles are subject to emissions inspections after they are four years old (e.g. 2012 vehicles are being inspected in 2016 for the first time). The inspection month coincides with the expiration date of the vehicle license plate. Typically, even model-year vehicles are inspected during even years, and odd model-year vehicles are inspected in odd years.
The Illinois EPA oversees its vehicle emissions inspection program that is operated by its contractor. The Illinois EPA enforces the vehicle emissions inspection requirement by partnering with the Illinois Secretary of State’s Office to deny vehicle license plate registrations to non-complying vehicles.
Additional information about the Illinois EPA’s vehicle emissions inspection program can be found at
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