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Vehicle and Engine Certification

Overview of Certification and Compliance for Vehicles and Engines

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About Certification and Compliance

EPA regulations apply to virtually every vehicle, engine and gallon of transportation fuel sold in the United States. It is EPA’s job to ensure that sources comply with emissions and fuel economy requirements. Compliance activities are critically important to achieving the air quality benefits promised by emissions regulations.

EPA uses a variety of testing and reporting programs to monitor compliance with emissions regulations. The programs may apply to vehicles and engines before they are produced (pre-production), while they are in production and after they are in customer service (post-production). 

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Certificates of Conformity

The Clean Air Act requires that all engines and vehicles be covered by a certificate of conformity before they can enter into commerce. A certificate of conformity demonstrates that the respective engine or vehicle conforms to all of the applicable emission requirements. The certificate represents engines and vehicles covered by a specific engine family or, in the case of light-duty vehicles, a specific test group for each manufacturer. 

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How to get a copy of the Certificate of Conformity:

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All of EPA’s emission regulations specify test procedures to measure engine or vehicle emission levels. EPA uses the test results to determine compliance with the applicable emission standards. 

  1. Certification testing is a form of compliance testing that is required as a condition of certification and is generally performed prior to issuing a certificate.
  2. Confirmatory testing is conducted by EPA to confirm emissions data submitted by manufacturers.
  3. In-use testing occurs after the vehicles or engines have been certified and after they have been in customer service for some period of time. Testing is generally conducted on privately-owned vehicles or engines.
  4. Production line (or assembly line) testing audits emission levels of vehicles or engines that are in production, but not yet in service.
  5. Fuel economy testing is used on light-duty passenger cars and trucks to determine values for the Fuel Economy and Environment Label.

The number and types of tests vary according to the regulated sector.

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Progress Reports

EPA releases multiple reports annually about the progress of their vehicle and engine programs:

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