Colorado's emissions testing requirement and who must test

Colorado requires emissions testing for most vehicles registered in the state, but the requirement depends on where you live and what you drive. The Colorado Department of Public Health and Environment (CDPHE) administers the program through a network of certified testing stations. If you register a vehicle in any Colorado county, you will need to know whether your county is in a testing area and whether your specific vehicle is subject to the test.

The state divides Colorado into two testing regions: the Denver Metro area (which includes Denver, Boulder, and surrounding counties) and the Colorado Springs area. Vehicles in these regions must pass an emissions test before registration or renewal. Vehicles registered outside these areas are generally not required to test, though some counties have their own rules. The age of your vehicle matters too — most states exempt very old vehicles, and Colorado does the same, though the cutoff year varies by region and vehicle type.

You can find out whether your vehicle must test by entering your address and vehicle information on the CDPHE website or by calling your county clerk's office. The requirement applies to gasoline-powered vehicles, diesel vehicles, and hybrids, though the specific test procedure differs slightly by fuel type.

Key Takeaways

  • Colorado requires emissions testing in the Denver Metro and Colorado Springs areas, but not statewide, so your county determines whether you must test.
  • The test measures tailpipe emissions and checks your vehicle's onboard diagnostic system, and you must pass before you can renew your registration.
  • Testing stations are certified by the state and charge a fee that varies by location, typically between $15 and $30 per test.
  • Your vehicle must be in running condition and have a functioning check-engine light to pass; if the light is on, the vehicle will fail the test.
  • If your vehicle fails, you have options including repair, retesting at a different station, or a waiver in some cases, depending on the reason for failure.

What the emissions test actually measures

The Colorado emissions test is a two-part inspection. The first part is a visual check of your vehicle's emissions control equipment — the technician looks for the presence and condition of the catalytic converter, air filter, and other components. The second part is a tailpipe test that measures the levels of carbon monoxide, hydrocarbons, and nitrogen oxides coming from your exhaust.

For most vehicles, the test also includes a computer scan that reads your vehicle's onboard diagnostic system (OBD). This scan checks whether your vehicle's emissions control system is functioning and whether any fault codes are stored in the computer. If your check-engine light is on, the scan will detect it, and your vehicle will fail the test regardless of tailpipe readings. This is one of the most common reasons vehicles fail in Colorado.

The specific emissions standards your vehicle must meet depend on the model year and the region where you are testing. Newer vehicles have stricter standards than older ones. The CDPHE publishes the exact standards for each year and vehicle class on its website, but the testing station will know the standard for your vehicle when you arrive.

Where to find a testing station and what to bring

Colorado has hundreds of certified emissions testing stations, most of them run by independent shops, tire stores, and quick-lube facilities. You can find a station near you using the CDPHE's online station locator tool, which lists addresses, phone numbers, and hours. Not all stations are open at all times, so calling ahead to confirm hours and current wait times is a good idea, especially during peak testing periods (typically late in the month before registration expires).

When you go to test, bring your vehicle registration or renewal notice and a valid photo ID. The technician will need to know your vehicle's make, model, year, and vehicle identification number (VIN), all of which are on your registration. You do not need to bring any special documents or proof of maintenance — the test is based on what your vehicle's emissions are at the moment of testing, not on your service records.

Testing stations charge a fee for each test. The fee is set by the individual station, not by the state, so prices vary. Most stations charge between $15 and $30 per test. Some stations offer discounts if you fail and need to retest, or if you test multiple vehicles. Ask about the fee and any retest policy before the technician begins.

What happens if your vehicle fails the test

If your vehicle fails the emissions test, you will receive a detailed report showing which emissions or components failed. The report will tell you specifically what was wrong — for example, "excessive carbon monoxide" or "check-engine light on" or "catalytic converter missing." This information is what you need to take to a repair shop to fix the problem.

You have the right to retest at any certified station after repairs are made. Some stations will retest you for free or at a reduced rate within a certain time window (often 30 days), but this is the station's choice, not a state requirement. If you retest at a different station, you will pay the full testing fee again. Keep your original failure report — you may need it to show a repair shop what was wrong, and some stations want to see it before retesting.

In limited cases, Colorado offers a waiver program for vehicles that fail due to a repair cost that exceeds a certain threshold (the threshold varies by year and region). If your repair estimate is very high, you may be able to obtain a waiver that allows you to register your vehicle without passing the test. You must get a written repair estimate from a certified shop and submit it to the CDPHE or your county clerk's office. The waiver is not automatic — you have to request it, and the state will review your estimate.

Registration renewal and testing important date

Your vehicle's emissions test is valid for two years from the date you pass it. Your registration renewal notice will tell you whether you need to test before you can renew. If your registration expires in a month that requires testing, you must pass the test before the registration expiration date or you cannot legally drive the vehicle.

Colorado allows you to renew your registration online, by mail, or in person at your county clerk's office, but you cannot complete the renewal until you have passed the emissions test. The test result is reported electronically to the state by the testing station, so there is no separate form to submit. Once you pass, the station's computer sends the result to the Colorado Division of Motor Vehicles, and you can renew when ready.

If your registration expires and you have not tested, you are driving without a valid registration, which is a violation. If you know you will fail and need time to repair, contact your county clerk's office to ask about extension options. Some counties will grant a short extension if you can show proof that you have scheduled a repair appointment.

Vehicles exempt from testing and special cases

Colorado exempts certain vehicles from emissions testing. Vehicles that are more than a certain age (typically 25 years or older, though this varies by region) are usually exempt. Vehicles with a gross vehicle weight rating above a certain threshold are also exempt. Electric vehicles are exempt because they produce no tailpipe emissions. Diesel vehicles are subject to testing but use a different test procedure than gasoline vehicles.

If you own a vehicle that you believe should be exempt, check with your county clerk's office or the CDPHE website to confirm. The exemption rules can be complex, and the rules differ slightly between the Denver Metro area and the Colorado Springs area. Do not assume your vehicle is exempt based on age or type — verify it before your registration renewal is due.

Vehicles that are registered but not driven (such as collector cars or vehicles in storage) may still be subject to testing at renewal time, depending on the county. Some counties allow you to register a vehicle as "non-operational" or "off-road," which exempts it from testing, but you must request this status when you register or renew.

Frequently Asked Questions

Can I test my vehicle before my registration expires?

Yes. You can test at any time, and the test result is valid for two years. Testing early can be useful if you want to know whether your vehicle will pass before your registration renewal is due, or if you want to avoid the rush during peak testing months.

What if I move to a county that does not require testing?

If you move from a testing area to a non-testing area, you do not need to test at your next renewal. When you update your address with the county clerk's office, the system will recognize your new address and will not require a test. If you move from a non-testing area to a testing area, you will need to test before your next renewal.

Do I have to use a specific testing station?

No. You can test at any certified station in Colorado. The test result is the same regardless of which station you use, and all results are reported to the state through the same system. You can choose based on location, hours, price, or reputation.

What if my check-engine light comes on after I pass the test?

Your test result is valid for two years, so you do not need to retest when ready. However, if your check-engine light is on when your registration renewal is due, you will fail the test at that time. You should have the light diagnosed and repaired as soon as possible to avoid a failed test at renewal.

Can I get a refund if my vehicle fails the test?

No. The testing fee is non-refundable whether your vehicle passes or fails. The fee covers the cost of the test itself, not a may provide of a passing result. If you retest after repairs, you will pay the testing fee again.