What Denver's emissions test requires
Denver requires an emissions test every two years for most vehicles, and every year for vehicles model year 1981 and older. The test measures what comes out of your tailpipe — specifically nitrogen oxides, particulate matter, and hydrocarbons — to make sure your vehicle meets Colorado air quality standards. You cannot renew your vehicle registration without a passing test result.
The actual test takes about 10 minutes. A technician plugs a diagnostic machine into your vehicle's onboard computer port (located under the steering wheel on most cars made after 1996) and runs your engine through a short cycle. For older vehicles without that port, the technician uses a probe inserted into the tailpipe. You do not need to do anything except show up with your vehicle running and your registration documents.
The test costs between $25 and $35 at most Denver testing stations, though prices vary slightly by location. You pay whether you pass or fail. If you fail, you have 60 days to fix the problem and retest at no additional charge at the same station.
Key Takeaways
- Denver emissions tests are required every two years for most vehicles and every year for vehicles older than 1981.
- The test plugs into your vehicle's computer or tailpipe and takes about 10 minutes to complete.
- You must pass before you can renew your registration, and the test costs $25 to $35.
- If you fail, you have 60 days to repair your vehicle and retest at the same station without paying again.
- Testing stations are located throughout Denver and the surrounding metro area, and you can find them through the Colorado Department of Public Health and Environment website.
Finding a testing station in the Denver area
The Colorado Department of Public Health and Environment maintains a searchable list of all licensed emissions testing stations on its website. You can search by zip code or city name to find stations near your home or workplace. Most stations are independent repair shops, tire shops, or dedicated testing facilities rather than dealerships.
Testing stations are open during regular business hours, typically 8 a.m. to 5 p.m. on weekdays and sometimes Saturday mornings. You do not need an appointment at most stations — you can walk in or drive in and wait your turn. During peak times (late afternoon and Saturdays), wait times can stretch to 30 minutes or longer, so arriving early in the day or midweek usually means a shorter wait.
Bring your vehicle registration and a valid ID. Some stations accept cash only, while others take credit cards, so calling ahead to confirm payment methods can save a trip back to the ATM.
What happens if your vehicle fails the test
A failing result does not mean your vehicle is unsafe to drive — it means your emissions are above the legal limit for Denver's air quality standards. Common reasons for failure include a faulty oxygen sensor, a loose gas cap, a clogged air filter, or an engine that is running too rich (burning too much fuel). Some of these are inexpensive fixes; others can cost several hundred dollars.
After you fail, you have 60 days to repair your vehicle and return to the same testing station for a retest. The retest is free. You do not need to pay the testing fee again, and you do not need to wait for a new appointment — just bring your vehicle back and tell the technician you are retesting. If you pass the retest within the 60-day window, your registration can be renewed.
If you cannot afford the repair, some nonprofits and community programs in the Denver area offer low-cost vehicle repair information or can point you toward resources. The Colorado Department of Public Health and Environment website lists these programs by county.
Timing your test before registration renewal
Your emissions test is valid for 30 days before your registration expires and remains valid for 30 days after expiration. This means you can test up to a month early without losing the result. Testing early gives you time to fix any problems and retest if needed before your registration important date.
You can check your registration expiration date on your vehicle registration card or by logging into the Colorado Department of Revenue website with your driver's license number. Plan to test at least two weeks before that date so you have time to address any failures.
If your registration expires before you pass the test, you cannot legally drive your vehicle except to and from a testing station or repair shop. If you are caught driving with expired registration, you face a fine.
Vehicles exempt from Denver emissions testing
Some vehicles do not require an emissions test in Denver. These include vehicles that are model year 2025 and newer (they are exempt for their first eight years), vehicles registered as classic or antique (usually model year 1967 and older), and vehicles registered as off-road only. Electric vehicles and hydrogen fuel cell vehicles are also exempt.
If your vehicle falls into one of these categories, you still need to renew your registration, but you do not need to submit an emissions test result. When you renew, you will see a note on your registration paperwork indicating that emissions testing is not required.
What to do if you disagree with your test result
If you believe your vehicle failed unfairly or the test was conducted incorrectly, you can request a retest at a different station. Your original test result is valid for 30 days, so you have that window to visit another licensed testing station and have them run the test again. You will pay the full testing fee at the second station.
If the second test also fails, both results stand and you will need to repair your vehicle. If the second test passes, you can use that passing result to renew your registration. Keep both test results in case the Colorado Department of Public Health and Environment questions the discrepancy.
You cannot dispute the test result directly with the state — the testing stations are responsible for the accuracy of their equipment, which is calibrated and inspected regularly by the state. If you believe a station's equipment is faulty, you can file a complaint with the Colorado Department of Public Health and Environment, but this does not change your test result.
Frequently Asked Questions
Do I need an emissions test if I just moved to Denver?
If you are registering a vehicle in Colorado for the first time, you need an emissions test before you can complete the registration. The test must be done at a Colorado testing station, so you cannot use a test from another state. Once registered, you follow the normal two-year cycle.
What if my vehicle has a check engine light on?
A check engine light does not automatically mean you will fail the emissions test, but it often does. Many testing stations will still run the test even with the light on, and you will see the result. If you fail, the light is usually related to the reason for failure. Have the code read at a repair shop before you retest so you know what to fix.
Can I test my vehicle in a different Colorado county instead of Denver?
Yes, you can test anywhere in Colorado as long as the station is licensed. However, your vehicle must meet the emissions standards for the county where it is registered. Denver has stricter standards than some rural counties, so a vehicle that passes in another county might fail in Denver. Test in Denver if your vehicle is registered in Denver.
What if I cannot get to a testing station before my registration expires?
You can renew your registration online or by mail without the emissions test result, but your registration will be marked as conditional and will expire in 30 days instead of two years. You then have 30 days to submit the test result. If you do not, your registration will be suspended and you cannot legally drive the vehicle.
Is there a way to test my vehicle at home or have someone come to me?
No, emissions testing must be done at a licensed testing station with calibrated equipment. Mobile testing services do not exist in Colorado. You must bring your vehicle to a station during their business hours.