What Colorado requires and who has to test

Colorado requires emissions testing for most vehicles registered in the state, but the rules depend on where you live and what you drive. If you register a car in the Denver metro area — which includes Denver, Boulder, Jefferson, Adams, Arapahoe, Douglas, and Broomfield counties — you must test every two years. Outside that region, testing is required every three years. Diesel vehicles, motorcycles, and vehicles older than model year 1968 are exempt.

The state runs this program through the Department of Public Health and Environment's Air Pollution Control Division. When you renew your vehicle registration, you cannot complete the renewal without proof of a passing emissions test (unless your vehicle is exempt). The test itself is not done by the state — it happens at private testing stations licensed by Colorado.

If you buy a used vehicle in Colorado, you have 60 days to get it tested before you can register it in the state. New vehicles are exempt from testing for the first four model years after purchase.

Key Takeaways

  • Denver metro counties require testing every two years; all other Colorado counties require it every three years.
  • You cannot renew your registration without a passing test result, so plan to test before your registration expires.
  • Testing costs between $25 and $35 per vehicle at any licensed station, and the test takes about 10 minutes.
  • If your vehicle fails, you have 60 days to fix the problem and retest at no additional charge at the same station.
  • Vehicles older than 1968, motorcycles, and diesel vehicles do not require testing in Colorado.

Finding a testing station and scheduling

Colorado publishes a searchable list of licensed emissions testing stations on the Department of Public Health and Environment website. You can search by county or city to find stations near you. Most stations are independent repair shops, tire shops, or quick-lube facilities — not dealerships. Many stations accept walk-ins, but calling ahead to confirm hours and current wait times is worth doing, especially during peak months like September and October.

You do not need an appointment at most stations, but some require one. When you arrive, bring your vehicle registration and proof of insurance. The test itself takes about 10 minutes. You will stay in your car while the technician connects a probe to your vehicle's emissions system and runs the test. The station will give you a printed receipt showing whether you passed or failed.

If you pass, the station electronically reports the result to the state within 24 hours. You can then renew your registration online, by mail, or in person at your county clerk's office. If you fail, the station gives you a detailed report showing which emissions standards your vehicle did not meet.

What happens if your vehicle fails the test

A failed test does not mean you cannot drive your vehicle — it means you cannot renew your registration until you fix the problem and retest. You have 60 days from the test date to retest at no charge at the same station. During those 60 days, you can drive on your current registration while you arrange repairs.

The test report will tell you which emissions systems are out of range. Common failures include a faulty oxygen sensor, a loose gas cap, a malfunctioning catalytic converter, or an engine control light that is on. Some of these are inexpensive fixes; others are not. You are not required to use the testing station for repairs — you can take your vehicle to any mechanic or dealership.

After repairs, return to the same testing station for a retest. If you pass the second time, the station reports the passing result to the state, and you can renew your registration. If you fail again, you have another 60 days to fix the problem and test once more. If you cannot get your vehicle to pass within 60 days, you will need to contact your county clerk about registration renewal options.

Cost and timing for registration renewal

The emissions test itself costs between $25 and $35, depending on the station. This is a separate fee from your vehicle registration renewal fee, which varies by county and vehicle type. You should plan to test at least two weeks before your registration expires, because the electronic reporting to the state can take up to 24 hours, and you may need time to schedule a retest if you fail.

If your registration expires before you have a passing test on file, you cannot legally drive the vehicle. You can still test and renew after expiration, but you will owe a late renewal penalty in addition to the registration fee. The penalty amount varies by county but is typically $25 to $50.

Some counties allow you to renew your registration online through the Colorado Department of Revenue website if you have a passing test result. Others require you to visit the county clerk's office in person. Check your county clerk's website to see which method is available in your area.

Special situations and exemptions

Vehicles registered outside Colorado do not need to test in Colorado, even if you live here. If you move to Colorado from another state, you have 60 days to register your vehicle in Colorado and obtain a passing test. During those 60 days, you can drive on your out-of-state registration.

Vehicles with a salvage title, a rebuilt title, or a non-operation status do not require testing. If your vehicle is registered as non-operational (parked and not driven), you do not need to test it. Once you change the status back to operational, you will need a passing test before you can renew the registration.

If you own a vehicle that is temporarily out of service for major repairs, you can request a temporary registration extension from your county clerk. This does not exempt you from testing, but it gives you extra time to complete repairs and obtain a test result before your registration expires.

Understanding your test results

A passing test means your vehicle's emissions fall within Colorado's standards for nitrogen oxides, particulate matter, and other pollutants. The test does not measure how well your vehicle runs overall — only whether it meets the state's air quality standards. A vehicle can run fine mechanically but still fail the emissions test if the emissions control systems are not working properly.

If you pass, you will receive a passing certificate that the testing station sends to the state. You do not need to print or carry this certificate — the state's system will show the passing result when you renew your registration. If you fail, the report will list the specific emissions values that were out of range and which systems may need attention.

You can request a copy of your test results from the testing station at any time. Some stations email the results; others print them on the spot. Keep a copy for your records in case you need to show a mechanic what failed or if you dispute a result.

Retesting and dispute options

If you believe your vehicle was tested incorrectly or your results are wrong, you can request a retest at a different licensed station. The second test is not free, but if the second station's results are significantly different from the first, you can contact the Air Pollution Control Division to request a review. The Division does not overturn test results lightly, but it will investigate if there is evidence of equipment malfunction or testing error.

You cannot dispute a test result straightforward because you disagree with it or because you think your vehicle should pass. The test is objective — it measures actual emissions coming from your tailpipe. If your vehicle fails, the emissions are genuinely out of range, and repairs are necessary before registration renewal.

If you have questions about your specific test results or what repairs might be needed, the testing station can sometimes point you toward common fixes. However, they are not required to diagnose your vehicle — that is a mechanic's job. Many repair shops will diagnose the problem for free or for a small fee if you bring them the test report.

Frequently Asked Questions

Can I renew my registration without a passing emissions test?

No. Colorado law requires a passing test result on file before you can renew your registration, unless your vehicle is exempt. If your registration expires before you test, you cannot legally drive the vehicle. You can still test and renew after expiration, but you will owe a late penalty.

What if I just moved to Colorado and my vehicle has never been tested here?

You have 60 days from the date you register your vehicle in Colorado to obtain a passing test. During those 60 days, you can drive on your out-of-state registration. After 60 days, you must have a passing test on file to renew your Colorado registration.

Do I have to fix my vehicle myself, or can I take it to any mechanic?

You can take your vehicle to any mechanic or dealership for repairs. The testing station does not do repairs and cannot require you to use a specific shop. After repairs, you can retest at the same station or at any other licensed station in Colorado.

How long does it take to get my test results reported to the state?

Licensed testing stations report results electronically to the state within 24 hours. You can usually renew your registration online or by mail the next business day after a passing test. In person at the county clerk's office, you can renew when ready if you bring the printed receipt.

What if my vehicle is very old — do I still have to test?

Vehicles manufactured before 1968 are exempt from emissions testing in Colorado. If your vehicle is 1968 or newer, it must test unless it is a motorcycle or diesel vehicle. Check your vehicle's model year on the registration to confirm whether it is exempt.