Diesel Vehicles
Diesel Emissions Program
Diesel Opacity Pass/Fail Limit Update: The allowable smoke opacity standard for all light-duty and heavy-duty naturally aspirated diesel vehicles has changed to 20% (for 5 seconds). All diesel vehicles, including heavy-duty turbocharged vehicles, which remain unchanged, must now meet this 20% opacity limit or they will fail the emissions test.
Which counties require a passing emissions test to register a vehicle?
- Boulder
- Jefferson
- Broomfield
- Denver
- Douglas
- Portions of Adams
- Portions of Arapahoe
- Portions of Larimer
- Portions of Weld
- Portions of El Paso
See our map for testing locations and diesel emissions area boundaries. For hours of operation, please contact the diesel testing station. If you are unsure if a diesel test is required in your area, please contact your local county motor vehicle office.
Frequently Asked Questions (FAQs)
Click here to see the 2025 Diesel Emissions Requirements.
- Obtain an emissions test if the statement “Emissions Test is Required” appears on the vehicle registration renewal notice. Diesel emissions areas are as follows: Boulder, Jefferson, Broomfield, Denver and Douglas Counties, and portions of Adams, Arapahoe, Larimer, Weld and El Paso counties.
- Submit the Certificate of Emissions Control (the bottom third of your passing emissions test) with your registration fee to your county motor vehicle office. Check with your county or the Requirements page for additional information.
- If you choose to renew your vehicle online, you can do so through mydmv.colorado.gov, Vehicle Services tab, “Renew a vehicle registration”. If your county participates in the kiosk program you can also renew at any kiosk location. Your emissions test information from Air Care Colorado should be uploaded into our system within 3 days for a diesel vehicle.
Diesel emission testing facilities charge up to one-hour of the posted labor rates, so fees will vary. Contact the specific station for fees.