Who has to get an emissions test in Colorado

Colorado requires emissions testing for most vehicles registered in certain counties, but not all of the state. The Denver metro area — which includes Denver, Boulder, Jefferson, Adams, Arapahoe, Douglas, and Broomfield counties — has mandatory testing. El Paso County (Colorado Springs area) also requires it. If you register a vehicle in any other Colorado county, you do not need an emissions test.

Within those testing counties, most gasoline-powered vehicles model year 1981 and newer must pass an emissions inspection every two years. Diesel vehicles have separate requirements. Vehicles registered outside the testing counties can be driven into them without a test, but you cannot register a vehicle in a testing county without proof of a passing emissions test.

A few vehicle types are exempt even in testing counties: electric vehicles, vehicles under 8,500 pounds that are model year 2023 and newer, and vehicles that have been registered in Colorado for less than 60 days (though you will need a test before the next registration renewal).

Key Takeaways

  • Emissions testing is required only in Denver metro counties (Denver, Boulder, Jefferson, Adams, Arapahoe, Douglas, Broomfield) and El Paso County; all other Colorado counties have no testing requirement.
  • You must pass an emissions test before you can register or renew registration in a testing county, and the test is valid for two years.
  • You can find approved testing stations through the Colorado Department of Public Health and Environment website or by searching your county's air quality program.
  • The test costs between $20 and $30 at most stations and takes 10 to 15 minutes; you do not need an appointment at most locations.
  • Vehicles that fail can often be retested at no charge within 30 days if repairs are made, but you should confirm the retest policy with your testing station.

How to find a testing station and schedule

Colorado does not use a centralized appointment system for emissions tests. Instead, you find an approved testing station in your county and either walk in or call ahead. The Colorado Department of Public Health and Environment maintains a searchable list of stations on its website, organized by county. You can also search online for "emissions testing near me" and filter for your county to see which stations are closest.

Most testing stations operate on a walk-in basis and do not require an appointment. Hours vary — some are open early morning, some stay open into evening, and a few operate on weekends. Call ahead if you want to confirm wait times or if you prefer to schedule a specific time slot, since some stations do accept reservations.

Bring your vehicle registration and proof of insurance. The test itself takes 10 to 15 minutes. You will stay in the vehicle while the technician connects equipment to your car's onboard diagnostic port and runs the test. The results are printed on the spot.

What happens if your vehicle fails the test

A failed emissions test means your vehicle did not meet Colorado's standards for nitrogen oxides, particulate matter, or other pollutants. The test report will show which emissions category your vehicle failed. This does not mean your vehicle is unsafe to drive — it means it does not meet air quality standards for registration in that county.

You have options after a failure. You can have the vehicle repaired and retested. Most testing stations offer a retest at no charge within 30 days if you bring proof of repairs, though you should ask about this policy when you get your test results. Some stations charge a small retest fee. If repairs are expensive or the vehicle is old, you may decide to sell it or register it in a county that does not require testing.

If you cannot afford repairs right away, you cannot legally register the vehicle in a testing county until it passes. You can drive it in the county temporarily, but registration renewal will be blocked. Some repair shops offer payment plans or financing for emissions-related work, so ask when you get repair estimates.

Emissions testing costs and what is covered

A standard emissions test costs between $20 and $30 at most Colorado testing stations. Some stations charge slightly more or less, but the price is fairly consistent across the state. This is a one-time cost per test cycle (every two years). The test fee covers the inspection only — it does not include any repairs your vehicle might need.

If your vehicle fails and you need repairs, those costs depend entirely on what is wrong. Common emissions failures are caused by a faulty oxygen sensor, a loose gas cap, a bad catalytic converter, or issues with the fuel injection system. Repairs can range from $50 for a gas cap replacement to several hundred dollars for a catalytic converter. Get a repair estimate before committing to work.

Some testing stations also offer repair services on-site, which can be convenient. Others are inspection-only and will refer you to a repair shop. You are not required to use any particular shop — you can take your vehicle anywhere for repairs and then return to any approved testing station for a retest.

When your emissions test expires and renewal timing

An emissions test is valid for two years from the date it is issued. Your registration renewal notice will tell you when your test expires. You should plan to get a new test before your registration renewal date, not after — you cannot renew registration without a current passing test in a testing county.

Colorado sends registration renewal notices 30 to 60 days before your registration expires. If your renewal notice says your registration expires in June, and your emissions test expires in May, you need to get a new test before June. Many people get their test done at the same time they renew registration to avoid a second trip.

If your registration expires before you get a new emissions test, you cannot legally drive the vehicle in a testing county. If you let both lapse, you will need to get a new test and pay a late registration fee when you renew. Plan ahead to avoid this.

Diesel vehicles and special emissions rules

Diesel vehicles in Colorado testing counties follow different rules than gasoline vehicles. Diesel trucks and cars model year 1998 and newer must pass an emissions test, but the test is different — it measures opacity (how much smoke comes from the exhaust) rather than the chemical composition of emissions. Diesel vehicles model year 1997 and older are exempt.

Diesel testing stations are less common than gasoline stations, so you may need to drive farther to find one. The Colorado Department of Public Health and Environment website lists diesel-approved stations separately. The test cost is similar — usually $20 to $30 — and takes about the same time.

If a diesel vehicle fails the opacity test, the same retest policy usually applies: you can have it repaired and retested at no charge within 30 days. Common diesel failures are caused by a faulty fuel injector, a clogged air filter, or engine timing issues.

Vehicles registered outside testing counties

If you register your vehicle in a Colorado county that does not require emissions testing — such as Mesa, Garfield, Montrose, or most rural counties — you do not need to pass an emissions test. You can drive that vehicle into Denver or Colorado Springs without a test. However, you cannot transfer the registration to a testing county without getting a passing test first.

If you move from a non-testing county to a testing county, you will need to get an emissions test before you can register the vehicle locally. The same applies if you buy a vehicle registered in a non-testing county and want to register it in a testing county — a passing test is required before registration.

Some people register vehicles in non-testing counties specifically to avoid emissions testing, but this is only legal if that is actually where the vehicle is garaged and where the owner lives or works. Registering a vehicle in a different county to evade testing requirements is registration fraud.

Frequently Asked Questions

Can I register my vehicle online without an emissions test in Colorado?

No. In testing counties, the Colorado Division of Motor Vehicles system will not allow you to complete registration renewal without proof of a passing emissions test. You must get the test first, then renew registration. Online renewal will be blocked until the test is submitted.

What if I just bought a used car from out of state?

You have 60 days from the date you register it in Colorado to get an emissions test if you register in a testing county. After 60 days, you must have a passing test to renew registration. Plan to get the test within that window so you do not lose the grace period.

Do I need an emissions test if I only drive through Colorado occasionally?

No. You only need a test if you register a vehicle in a testing county. If your vehicle is registered elsewhere, you can drive through Colorado without a test. However, if you move to Colorado and register there, a test becomes required before registration is complete.

What should I do if the testing station says my vehicle cannot be tested?

Some vehicles cannot be tested if they have serious mechanical problems — for example, if the check engine light is on and the vehicle will not communicate with the diagnostic equipment. Ask the station what the specific issue is. You may need to have that problem fixed first, then return for testing. Some stations will note this on a report so you have documentation.

Can I get an emissions test before my current one expires?

Yes. You can get a new test up to 120 days before your current test expires, and the new test will be valid for two years from that date. This can be useful if you want to renew registration early or if you are selling the vehicle and want a fresh test for the buyer.