What Denver requires for emissions testing

Denver requires emissions testing for most vehicles registered in the city, with a few exceptions. Your vehicle needs to pass an emissions test every two years if it was built in 1981 or later. Diesel vehicles, motorcycles, and vehicles registered outside Denver but driven there regularly have different rules — check with the Colorado Department of Revenue to confirm whether your specific vehicle is covered.

The test itself measures what comes out of your tailpipe: carbon monoxide, nitrogen oxides, and particulate matter. A technician plugs a probe into your vehicle's diagnostic port and runs it through a sequence that takes about 10 to 15 minutes. You do not have to do anything except show up with your vehicle in working order and your registration documents.

Denver's testing program is run through the Colorado Department of Public Health and Environment, but you do not contact them directly. Instead, you go to one of the licensed testing stations scattered across the Denver metro area — these are independent shops, not government offices.

Key Takeaways

  • Denver requires emissions testing every two years for vehicles built in 1981 or later, and you can find testing stations on the Colorado Department of Public Health and Environment website.
  • The test costs between $20 and $30 depending on the station, and you need your vehicle registration and a valid ID when you arrive.
  • If your vehicle fails, you have 60 days to fix the problem and retest at no additional charge at the same station.
  • You can schedule a test in advance at most stations, but many also accept walk-ins during their posted hours.

Finding a testing station near you

The Colorado Department of Public Health and Environment maintains a searchable list of licensed testing stations on their website. You can filter by location and see which stations are closest to your home or workplace. Most stations are open during standard business hours, though some offer evening or weekend appointments.

Call ahead before you go. Testing stations can get backed up, especially during peak seasons (late fall and early spring, when many people renew registrations). A quick phone call tells you whether you can walk in or whether you should book a time slot. Some stations let you schedule online; others take appointments by phone only.

What happens if you fail the test

If your vehicle does not pass, the testing station gives you a detailed report showing which emissions exceeded the limit. This report is your roadmap for repairs. Common failures involve the oxygen sensor, catalytic converter, or fuel system — these are fixable problems that a mechanic can diagnose and repair.

You have 60 days from the test date to fix the vehicle and return to the same testing station for a retest. The retest is free; you only pay the initial testing fee. Bring your repair receipts with you — the technician will want to see what was fixed. If you pass the retest, you are done. If you fail again, you have another 60 days to make additional repairs.

If you cannot afford repairs right away, do not ignore the problem. Driving without a current emissions test is a violation, and you risk a fine when you renew your registration. Some nonprofits in the Denver area offer repair information for low-income vehicle owners — ask your mechanic or contact the Colorado Department of Public Health and Environment for referrals.

Cost and timing

Testing stations charge between $20 and $30 per test. This is a set fee; you cannot negotiate it down. The test itself takes 10 to 15 minutes once you are in the bay, though wait time depends on how busy the station is. If you call ahead and book a time, you can usually get in and out in 30 minutes total.

You do not need to renew your emissions test on any particular date — it is tied to your vehicle registration renewal. When your registration is about to expire, you will receive a notice in the mail. That notice tells you whether your vehicle needs an emissions test before you can renew. If it does, you have until your registration expires to complete the test.

Documents and information to bring

Bring your vehicle registration and a valid photo ID. The testing station needs to match your registration to your vehicle's identification number (VIN), which is printed on your registration and also stamped on the driver's side of your dashboard near the windshield. If your registration is expired or your name does not match the vehicle title, the station may refuse to test you — bring proof of ownership or a current registration if you are unsure.

Your vehicle should be in working condition before you arrive. If the check engine light is on, the test may be delayed or refused until you address the underlying problem. If your vehicle will not start or has obvious mechanical problems, get it to a mechanic first.

Special situations and exemptions

New vehicles (current model year and one year older) are exempt from testing for their first few years. Vehicles registered outside Denver but driven there do not need Denver emissions testing — they follow the rules of their home state or county. If you recently moved to Denver, check whether your previous state's emissions test is still valid or whether you need a Colorado test.

Vehicles with a "gross vehicle weight rating" over 14,000 pounds (mostly commercial trucks) follow different testing rules. Motorcycles and mopeds are exempt. If you are unsure whether your vehicle is covered, the Colorado Department of Public Health and Environment website has a vehicle lookup tool, or you can call a testing station and describe your vehicle.

What to do if you move or sell your vehicle

If you move out of Denver but keep your vehicle registered in Colorado, you may no longer need Denver emissions testing — it depends on where you move. Contact the Colorado Department of Revenue to update your registration address and confirm what testing applies to your new location.

If you sell your vehicle, the new owner is responsible for any future emissions testing. You do not need to have the vehicle tested before you sell it, though some buyers may ask for proof that it passed. If the vehicle fails its next test, the new owner handles the repairs and retesting.

Frequently Asked Questions

Can I test my vehicle before my registration expires?

Yes. You can test your vehicle up to 120 days before your registration expires. This gives you time to make repairs if you fail and still renew your registration on schedule. The test date is recorded in the state system, so you do not need to bring proof to the registration office.

What if I fail the retest after repairs?

You have another 60 days to make additional repairs and test again. If you fail a second time, talk to a mechanic about whether the repairs were done correctly or whether a different problem is causing the failure. Some stations can refer you to shops that specialize in emissions repairs.

Do I need an appointment or can I just walk in?

It depends on the station. Many accept walk-ins during posted hours, but calling ahead saves you time, especially during busy seasons. Some stations only take appointments. Check the station's website or call to confirm their policy before you go.

What if my vehicle has a check engine light on?

The testing station may still test you, but the check engine light usually means there is a problem that could cause an emissions failure. Have a mechanic scan the code before you test. Fixing the underlying problem often resolves the emissions issue.

Can I test my vehicle in a different county and use that result in Denver?

No. Denver requires a test from a station licensed in Colorado. If you test in another state or at an unlicensed station, the result will not count toward your Denver registration renewal. Use only a station on the Colorado Department of Public Health and Environment's licensed list.