Colorado's emissions testing map is split by county, not statewide

Colorado does not require emissions testing in most of the state. Only eight counties — Denver, Jefferson, Boulder, Broomfield, Adams, Arapahoe, Douglas, and El Paso — have active emissions testing programs. If you live anywhere else in Colorado, you do not need to test your vehicle for emissions, regardless of its age or engine type.

The reason these eight counties test is air quality. The Denver metropolitan area sits in a valley where pollution can concentrate, especially in winter. The Colorado Department of Public Health and Environment monitors air quality in these counties and requires testing when the region fails to meet federal air quality standards. Counties outside this area have air quality that consistently meets federal requirements, so testing is not mandated.

If you move to or from one of these eight counties, your testing requirement changes. A vehicle registered in a non-testing county does not need to pass emissions to renew its registration. A vehicle registered in one of the eight testing counties must pass before registration renewal, even if you recently moved there.

Key Takeaways

  • Eight Colorado counties require emissions testing: Denver, Jefferson, Boulder, Broomfield, Adams, Arapahoe, Douglas, and El Paso.
  • All other Colorado counties have no emissions testing requirement for vehicle registration.
  • Testing is required in these eight counties because air quality monitoring shows they need it to meet federal standards.
  • Your registration county determines whether you must test, not where you currently drive or where you work.

The eight counties that test and why

Denver, Jefferson, Boulder, Broomfield, Adams, Arapahoe, Douglas, and El Paso counties all fall within or near the Denver metropolitan area. This region has historically struggled to meet the National Ambient Air Quality Standards (NAAQS) set by the Environmental Protection Agency, particularly for ozone and particulate matter. Vehicle emissions are a significant source of both pollutants.

The Colorado Department of Public Health and Environment reviews air quality data each year. If a county's air quality falls short of federal standards, emissions testing remains required. If air quality improves enough to consistently meet standards, the state can remove the testing requirement — but this has not happened in any of these eight counties since testing began in the 1980s.

El Paso County, which includes Colorado Springs, was added to the testing requirement more recently than the others. The county's growing population and vehicle traffic led to air quality concerns, and testing has been required there since 2020.

Counties with no emissions testing requirement

Every Colorado county outside the eight listed above has no emissions testing requirement. This includes rural counties like Montrose, Gunnison, and Rio Blanco, as well as smaller metro areas like Fort Collins (Larimer County), Grand Junction (Mesa County), and Pueblo (Pueblo County).

These counties either have air quality that consistently meets federal standards or have such low vehicle density that emissions testing would not meaningfully improve air quality. The state does not require testing in areas where it is not needed to meet federal air quality goals.

What happens if you register a vehicle in a non-testing county

If your vehicle is registered in a county with no emissions testing requirement, you do not need to pass an emissions test to renew your registration. The Colorado Division of Motor Vehicles will not ask for test results, and you cannot be cited for failing to test.

You still must pass a safety inspection in most counties — that is a separate requirement from emissions testing. Safety inspections check brakes, lights, windshield wipers, and other equipment. Emissions testing checks what comes out of your tailpipe. Do not confuse the two.

What happens if you register a vehicle in one of the eight testing counties

If your vehicle is registered in Denver, Jefferson, Boulder, Broomfield, Adams, Arapahoe, Douglas, or El Paso County, you must pass an emissions test before you can renew your registration. The test must be completed within a certain window — usually 90 days before your registration expires through the expiration date itself.

You take your vehicle to a Colorado Department of Revenue-certified emissions testing station. The test takes about 10 minutes and costs between $25 and $35, depending on the station. Your vehicle's model year, engine type, and transmission determine which test protocol is used.

If your vehicle passes, the test station sends the results to the state electronically, and you can renew your registration online, by mail, or in person. If your vehicle fails, you have the option to repair it and retest, or to request a waiver if repairs would cost more than a certain amount (the threshold varies by vehicle age and type).

Moving between testing and non-testing counties

If you move from a non-testing county to one of the eight testing counties, your new registration will require emissions testing. When you update your address with the Colorado Division of Motor Vehicles, your vehicle will be subject to testing at the next registration renewal.

If you move from one of the eight testing counties to a non-testing county, you will no longer need to test. Your new registration will not require it. However, you must update your address with the Division of Motor Vehicles to change your registration county.

If you move within one of the eight testing counties — for example, from Denver to Adams County — you still need to test because both counties require it. The testing requirement does not change.

Vehicles that may be exempt even in testing counties

Even in the eight counties that require testing, some vehicles are exempt. New vehicles (typically those fewer than 4 model years old) are exempt from testing for their first few years of registration. Vehicles that are 25 years old or older are also exempt in most cases.

Vehicles with a salvage title, a rebuilt title, or a manufacturer's defect recall that has not been repaired may also be exempt or may have different testing requirements. Check with your local emissions testing station or the Colorado Division of Motor Vehicles if your vehicle has an unusual title status.

Frequently Asked Questions

Do I need emissions testing if I live in Fort Collins or Pueblo?

No. Fort Collins is in Larimer County and Pueblo is in Pueblo County — neither requires emissions testing. Only the eight counties listed above have testing requirements. You will need a safety inspection, but not an emissions test.

What if I work in Denver but my vehicle is registered in a non-testing county?

You do not need to test. The requirement is based on where your vehicle is registered, not where you work or drive. If your registration is in a non-testing county, you are not required to pass emissions testing, even if you commute to Denver every day.

Can I get an emissions test in a non-testing county if I want to?

Yes. Many testing stations in non-testing counties offer emissions tests even though they are not required. Some people test voluntarily to check their vehicle's condition or to prepare for a move to a testing county. You would pay the same fee as in a testing county.

If my vehicle fails emissions in a testing county, can I still drive it?

Yes, you can drive a failed vehicle. You cannot renew your registration without passing the test or receiving a waiver, but you can continue driving on your current registration until it expires. You have time to repair the vehicle and retest before your registration renewal important date.

Will Colorado add more counties to the testing requirement?

It is possible, but it depends on air quality. The state reviews air quality data annually. If another county's air quality falls below federal standards, testing could be added there. Conversely, if one of the eight counties' air quality improves enough, testing could be removed — though this has not happened since the program began.