Diesel-Powered Vehicles

Exemption & Groupings

Diesel vehicles receive a *four-year exemption (from model year) and are categorized in two groups (Light Duty / Heavy Duty) for emission-testing purposes.

Light Duty (GVWR 14,000 or Less)

Once the exemption period expired, an opacity test is valid for 2 years until the vehicle is 10 model years old.  Starting with the 11th model year, the test is valid for 1 year.

Heavy Duty (GVWR above 14,000)

Once the exemption period expires, an opacity test is valid for 2 years until the vehicle is 10 model years old and then the test is valid for 1 year.

*2014 and newer Heavy Duty diesels with a GVWR of 26,000 lbs or more have a 6 year exemption (from model year).

Newly Purchased

Newly purchased vehicles require a new diesel opacity test unless more than 12 months remains on the vehicle’s four-year exemption period.

Diesel Testing Locations

The Colorado Department of Public Health and Environment maintains a listing of diesel testing locations.  Click for Diesel Testing Locations (PDF).