What Colorado Requires and When

Colorado requires emission testing for most vehicles registered in the state, but the rules depend on where you live and what year your vehicle was made. If you live in the Denver metro area, the North Front Range (around Fort Collins), or the Pueblo area, your vehicle must pass an emissions test every two years. If you live elsewhere in Colorado, you do not need an emissions test — you only need a safety inspection.

Vehicles from 1981 and newer are subject to testing in regulated areas. Diesel vehicles, motorcycles, and vehicles over 14,000 pounds are exempt. If your vehicle is brand new (current model year), you are exempt for the first four years of registration in Colorado.

The test itself checks whether your vehicle's exhaust meets state standards for nitrogen oxides, particulate matter, and other pollutants. You cannot register your vehicle without a passing test result, and you cannot renew your registration without one.

Key Takeaways

  • Emission testing is required every two years in the Denver metro, North Front Range, and Pueblo areas, but not in most other parts of Colorado.
  • You must pass the test before you can register or renew your vehicle registration with the Colorado Division of Motor Vehicles.
  • The test costs between $20 and $30 depending on your vehicle type and which testing station you visit.
  • You can find a testing station through the Colorado Department of Public Health and Environment website, which lists all certified locations by county.
  • If your vehicle fails, you have 60 days to repair it and retest at no additional charge before you must pay the full fee again.

Finding a Testing Station and Scheduling

Colorado does not operate state-run testing stations. Instead, the Colorado Department of Public Health and Environment maintains a list of private certified testing stations on its website. You can search by county or by your city to find stations near you. Most stations are repair shops, tire shops, or dedicated emissions testing facilities.

Many stations accept walk-ins during business hours, but calling ahead is wise — some get busy during peak times, especially near the end of the two-year testing window. A few stations require appointments. The test itself takes 10 to 15 minutes once you are in the bay.

You do not need to bring anything except your vehicle keys and proof of vehicle ownership (your registration or title). The testing station will pull your vehicle information from the state database using your license plate.

What Happens During the Test

The emissions test is a computerized procedure that measures what comes out of your tailpipe. The technician will connect a probe to your exhaust system and run your engine through a series of speeds and loads. For most vehicles, this is a "two-speed idle test" — the car idles at normal speed, then at a higher RPM, and the machine records the emissions at each point.

Newer vehicles (usually 2000 and later) may undergo an "on-board diagnostic test" instead, where the technician plugs into your vehicle's computer port and reads the emissions data directly from your vehicle's systems. This test is faster and does not require the tailpipe probe.

The test does not involve driving on a road or dyno. You stay in the testing bay the entire time. If your vehicle passes, you receive a printed certificate when ready. If it fails, the technician will print a detailed report showing which pollutants exceeded the limit.

Failing the Test and What to Do Next

If your vehicle fails, you have 60 days to repair it and return for a retest. During those 60 days, you can drive your vehicle legally — the failed test does not suspend your registration. You do not pay for the retest if you return within 60 days; you only pay the original test fee once.

Common reasons for failure include a faulty oxygen sensor, a loose or missing gas cap, a malfunctioning catalytic converter, or an engine that is running too rich (burning too much fuel). A mechanic can diagnose the specific problem using the failure report the testing station gave you.

If you repair the vehicle and retest within 60 days, you will pass the second test in most cases. If you do not retest within 60 days, you must pay the full test fee again and start a new 60-day window. After two failed tests in a row, Colorado allows you to request a waiver if you have spent at least $500 on repairs — you can then register your vehicle without a passing test, though you will need to test again in two years.

Cost and Payment

The test costs between $20 and $30 depending on your vehicle type. Diesel vehicles, hybrid vehicles, and vehicles with special equipment may cost slightly more. Each testing station sets its own price within state guidelines, so calling ahead can tell you the exact cost.

Most stations accept cash, debit, and credit cards. Some accept only certain payment methods, so ask when you call to schedule or before you arrive. The fee covers one test; a retest within 60 days is included in that fee, but a test after 60 days is a new full-price test.

Timing Your Test and Registration Renewal

Your emissions test is valid for two years from the date you pass it. You can test up to 120 days before your registration expires — testing early gives you a buffer in case you fail and need time to repair. Many people test 30 to 60 days before their registration renewal date to avoid a last-minute rush.

You must have a passing test result before you can renew your registration with the Colorado Division of Motor Vehicles. You can renew online, by mail, or in person at a DMV office, but the system will not allow you to complete the renewal without a valid emissions test on file.

If your registration expires before you pass an emissions test, you cannot legally drive your vehicle. If you are in this situation, you can still test and then renew your registration, but you will likely owe a late renewal fee in addition to the test fee.

Vehicles Exempt from Testing

Motorcycles, mopeds, and vehicles over 14,000 pounds are not subject to emissions testing in Colorado. Diesel vehicles registered before 2001 are also exempt. If you own a vehicle that is exempt, you still need a safety inspection to register it, but you do not need an emissions test.

Vehicles registered outside Colorado do not need to pass a Colorado emissions test, even if you drive them in Colorado regularly. However, if you move to Colorado and register your vehicle here, it must pass an emissions test before you can complete the registration.

Frequently Asked Questions

Can I test my vehicle before my registration expires?

Yes. You can test up to 120 days before your registration expires. This gives you time to repair and retest if you fail, without rushing at the last minute. Many people test 30 to 60 days early for this reason.

What if I just moved to Colorado from out of state?

When you register your vehicle in Colorado for the first time, you must pass an emissions test before the registration is complete — unless your vehicle is brand new (current model year), in which case you are exempt for the first four years. You have 60 days from the date you register to pass the test.

Do I need an emissions test if I live in a rural part of Colorado?

No. Emissions testing is required only in the Denver metro area, the North Front Range (Fort Collins area), and the Pueblo area. If you live elsewhere in Colorado, you need a safety inspection but not an emissions test. Check the Colorado Department of Public Health and Environment website to confirm whether your county is in a regulated area.

What if my vehicle has a check engine light on?

A check engine light usually means your vehicle will fail the emissions test. The light indicates that your vehicle's on-board diagnostic system has detected a problem — often a faulty sensor or emissions system issue. Have a mechanic diagnose the problem before you test, or test and use the failure report to guide your repairs.

Can I get a waiver if my vehicle keeps failing?

Yes. After two failed tests in a row, you can request a waiver from the Colorado Department of Public Health and Environment if you have spent at least $500 on repairs. With a waiver, you can register your vehicle without a passing test, but you will still need to test again in two years.