Emissions inspections for diesel-powered vehicles


We regulate diesel exhaust smoke by means of two diesel inspection and maintenance programs, one for fleets of nine or more heavy-duty vehicles and another for smaller fleets and privately-owned vehicles.


Large fleets (nine or more vehicles)

  • If you own or operate a larger diesel fleet,(gross vehicle weight rating > 14,000 lbs), you must take part in a Diesel Fleet Self-Certification Program, which gives fleet owners and operators the option to self-inspect and certify their vehicles annually to maintain compliance with state smoke opacity standards.
  • Fleets subject to self-inspection and certification are those within the Automobile Inspection and Readjustment (AIR) Program area with nine or more diesel vehicles of more than 14,000 lbs gross vehicle weight rating.
  • New heavy-duty diesel vehicles under 26,000 lbs gross vehicle weight rating are exempt from inspections for four years. New heavy-duty diesel vehicles over 26,000 lbs gross vehicle weight rating are exempt from inspections for six years. 

Privately-owned and small fleets (eight or fewer vehicles)

  • If you own a small fleet or a private diesel vehicle, you must take part in the Diesel Opacity Inspection Program.
  • This program is for all light-duty diesel vehicles, as well as heavy-duty diesel vehicles not subject to the large-fleet self-certification program.
  • New diesel vehicles are exempt from testing for four years.
  • The Diesel Opacity Inspection Program requires eligible vehicles newer than ten model years to be inspected every two years. Vehicles that are ten model years and older must be inspected annually.
  • The program applies only to the Automobile Inspection and Readjustment (AIR) Program area and uses a loaded-mode dynamometer-based test. All 1991 and newer diesel vehicles are inspected for the presence and operability of manufacturer-required emissions control equipment. All inspections are performed by private, state-licensed diesel inspection stations.