Mobile Sources Compliance Monitoring Program

Compliance with the vehicle and engine emissions standards is the responsibility of the vehicle or engine manufacturer. Vehicles and engines used in the United States must be manufactured under the terms of an emissions certificate of conformity issued by EPA.  Imported vehicles and engines must be EPA-certified, with certain very limited exceptions. The removal or disabling of vehicle or engine emission controls by any person is prohibited.

Refiners and fuel importers have the primary responsibility of compliance with the motor vehicle fuels standards. Parties in the fuel distribution system are responsible for ensuring that motor vehicle fuel is not contaminated and is used in the proper locations and times.  For example, more stringent gasoline standards apply during the summer high ozone season and to reformulated gasoline used in certain ozone nonattainment areas. Vehicles and equipment may only use fuels designated and registered for that type of vehicle or equipment.

Compliance Monitoring

EPA reviews applications for emissions certificates from vehicle and engine manufacturers, and conducts emissions testing of vehicles and engines on the production line and in-use following introduction into commerce. EPA works in conjunction with the United States Customs and Border Protection to ensure that imported vehicles and engines are certified. In addition, light-duty vehicle emissions are checked periodically through state-implemented “inspection and maintenance” programs in most ozone nonattainment areas. EPA conducts inspections of:

  • vehicle and engine manufacturing facilities,
  • emission laboratories,
  • dealers of vehicles and mobile engines and
  • suppliers and installers of vehicle and engine parts.

EPA conducts fuels inspections primarily at:

  • retail outlets
  • terminals
  • refiners
  • importers
  • fuels testing laboratories

Refiners and importers are required to test all their gasoline and submit reports to EPA. In addition, refiners and importers are required to use independent laboratories to conduct quality assurance testing of reformulated gasoline when it is produced and quality surveys of reformulated gasoline when it is sold at retail outlets, and to submit reports to EPA of this testing.