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Vehicle Emissions Inspections and Maintenance

Vermont’s Vehicle Emissions Inspection and Maintenance Program helps to ensure that Vermont vehicles remain clean throughout their useful lives by requiring annual testing of vehicle emissions control systems and repairs if needed. The program is managed jointly by the Department of Motor Vehicles and the Air Quality and Climate Division.

The State of Vermont requires, on a statewide basis, that all motor vehicles be inspected annually. There are approximately 1,100 official inspection stations that are licensed to perform vehicle inspections. The annual vehicle inspection includes both a safety check and an emissions check. The safety check consists of an evaluation of wheels and tires, steering and suspension, brakes, lights, glass, body and sheet metal, exhaust system and fuel system. The emissions checks consist of a visual inspection of the catalytic converter and gas cap for all vehicles, and an electronic inspection of the On-Board Diagnostic (OBD) system for vehicles that are 16 model years old or newer.

Why Are Vehicle Emissions Inspections Important?

Motor vehicles are a significant source of air pollutants in Vermont including air toxics, the ozone precursors (volatile organic compounds and nitrogen oxides), and carbon monoxide. Motor vehicles also represent the largest source of greenhouse gas emissions in Vermont. Both gasoline and diesel vehicles are equipped with emissions control systems designed to reduce harmful air pollutants including the following:

Vehicle Emissions and Related Effects
  • Nitrogen Oxides react with volatile organic compounds in sunlight to form ground-level ozone ("smog").
  • Smog damages lung tissue and aggravates respiratory disease.
  • Carbon Monoxide displaces oxygen in the bloodstream.
  • CO is of particular concern to people with heart disease.
  • Carbon Dioxide is a greenhouse gas (GHG), which contributes to global warming.
  • Sulfur Dioxide contributes to the formation of acid rain.
  • SO2 exposure is linked to a variety of adverse respiratory effects.
  • Volatile Organic Compounds react with NOx in sunlight to form ground-level ozone ("smog").
  • VOCs include toxic and carcinogenic pollutants.
  • Particulate Matter is emitted in diesel exhaust.
  • Fine PM, or PM2.5, is of particular concern as it can easily travel deep into lungs and may even reach the bloodstream adversely affecting the lungs and heart.

What is OBD?

On-board diagnostics (OBD) is a computer-based system intended to monitor the performance of engine components, including emissions control systems. Beginning with model year 1996, all light-duty vehicles have OBD systems that are designed to alert drivers when something in the engine management or emission control systems begins to deteriorate or fails.

In addition to the safety equipment inspection, gasoline and diesel powered vehicles that are 16 model years old or newer, having a gross vehicle weight rating of 8,500 pounds or less, must have an inspection of the OBD system to ensure that it’s working properly.

For more information regarding the Vehicle Emissions Inspection and Maintenance Program, detailed inspection information, and locations of inspection stations, please visit the Department of Motor Vehicles web site.

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