Diesel vehicles receive a *four-year exemption (from model year) and are categorized in two groups (Light Duty / Heavy Duty) for emission-testing purposes.
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.
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 vehicles require a new diesel opacity test unless more than 12 months remains on the vehicle’s four-year exemption period.
The Colorado Department of Public Health and Environment maintains a listing of diesel testing locations. Click for Diesel Testing Locations (PDF).