What Denver County requires for emissions testing
Denver County requires emissions testing for most vehicles registered in the county, with the test happening every two years for gasoline vehicles and every three years for diesel vehicles. The test measures what comes out of your tailpipe — carbon monoxide, nitrogen oxides, and particulate matter — to confirm your vehicle meets state air quality standards. You'll need to pass this test before you can renew your vehicle registration.
The requirement applies to vehicles model year 1981 and newer. Vehicles registered outside Denver County but driven there regularly are not subject to Denver's testing requirement, though they must follow the rules of their home county. Electric vehicles and plug-in hybrids are exempt from emissions testing.
You can take your test at any Emissions Testing Program facility in Denver County. The Colorado Department of Transportation (CDOT) operates the program, and testing stations are spread across the county — you can find the full list and hours on the CDOT website under "Emissions Testing Program Locations."
Key Takeaways
- Gasoline vehicles in Denver County need emissions testing every two years; diesel vehicles every three years.
- The test costs between $20 and $30 depending on the testing station, and you pay at the time of your visit.
- You can take the test at any CDOT-approved facility in Denver County — no appointment is required at most locations.
- A passing test is valid for two or three years and is required before you can renew your vehicle registration with the Colorado Division of Motor Vehicles (DMV).
- If your vehicle fails, you have 60 days to repair it and retest at no additional charge at the same facility.
How to prepare your vehicle for the test
Before you go to a testing station, make sure your vehicle's engine is in normal operating condition. Bring your vehicle registration and proof of insurance — the testing station will ask for these. Your vehicle's odometer reading will be recorded, so the station can verify you're the registered owner.
If your check engine light is on, your vehicle will fail the test. Have the code read at a repair shop or auto parts store (many do this for free) and address the issue before testing. A vehicle that has been driven fewer than 20 miles since the engine was started may not pass, so drive it for at least 20 minutes before arriving at the testing station.
You do not need to schedule an appointment at most Denver County testing stations. Walk-in service is available during posted hours, though wait times vary by location and time of day. Some stations may have longer lines during peak hours like early mornings or late afternoons.
What happens during the test
The test itself takes about 10 to 15 minutes. A technician will connect a probe to your vehicle's tailpipe and run your engine through a series of idle and acceleration cycles while measuring emissions. The entire process is automated — the equipment records the data and produces a pass or fail result on the spot.
You'll receive a printed receipt showing whether your vehicle passed or failed. A passing result is valid for two years (or three years for diesel vehicles) and is automatically linked to your vehicle's registration record. You do not need to bring the receipt to the DMV — the testing station reports the result directly to the Colorado Division of Motor Vehicles.
If your vehicle fails, the receipt will show which emissions standards it did not meet. You have 60 days to repair your vehicle and return to the same testing station for a retest at no additional charge. After 60 days, you would need to pay the full testing fee again if you want to retest.
What to do if your vehicle fails
A failed test does not mean you cannot drive your vehicle — it means you cannot renew your registration until you pass. You have 60 days from the test date to make repairs and retest. During those 60 days, you can drive on your current registration.
Common reasons for failure include a faulty oxygen sensor, a malfunctioning catalytic converter, or a problem with the fuel injection system. A repair shop can diagnose the specific issue using the emissions test results. Some repairs are inexpensive (under $100), while others — like catalytic converter replacement — can cost several hundred dollars.
If repair costs are high, you may want to get a second opinion from another shop. Some repair facilities specialize in emissions-related work and may offer lower prices than general mechanics. After repairs, return to the same testing station within 60 days for your retest.
Testing station locations and hours
Denver County has multiple testing stations operated by CDOT. The main locations include facilities in central Denver, northeast Denver, and northwest Denver. Hours vary by location but typically run from early morning through early evening on weekdays, with limited weekend hours at some locations.
You can find the complete list of testing stations, their addresses, phone numbers, and hours on the CDOT website under "Emissions Testing Program." Call ahead if you want to confirm current hours or ask about wait times, though most stations do not require appointments.
Testing fees range from $20 to $30 depending on the station. Payment is accepted at the time of your test — most stations take cash and card. If you fail and need to retest within 60 days, there is no additional charge for the retest at the same location.
Connecting your test result to vehicle registration renewal
Once you pass your emissions test, the testing station sends the result to the Colorado Division of Motor Vehicles automatically. You do not need to do anything else — your registration record is updated within one to two business days. When you renew your registration online, by mail, or in person at a DMV office, the system will show that your vehicle has passed.
If you renew your registration before your test result appears in the system, you may see a hold on your renewal. Contact the testing station to confirm the result was submitted, or wait one to two business days and try renewing again. If there is still a problem, call the Colorado DMV at 303-205-5600 to verify the result was recorded.
Your registration renewal important date is based on your vehicle's license plate number, not on when you test. You can test at any time during the two-year (or three-year) testing cycle, but you must pass before your registration expires or you cannot legally drive the vehicle.
Frequently Asked Questions
Can I test my vehicle outside Denver County and still register it there?
No. If your vehicle is registered in Denver County, it must pass a Denver County emissions test. You cannot use a test result from another county. However, if your vehicle is registered in a different county, you follow that county's testing rules even if you drive in Denver.
What if I just bought a used car and it failed the test?
You have 60 days from the test date to repair and retest at no charge. If you bought the car from a dealer, check your purchase agreement — some dealers offer a warranty that covers emissions-related repairs. If you bought from a private seller, you are responsible for repairs. Get a diagnostic at a repair shop to find out what needs fixing.
Do I need to test my vehicle if I'm only moving to Denver County temporarily?
If you register your vehicle in Denver County, you must test it. If you keep your registration in another state or county and are only visiting or working in Denver temporarily, you follow your home county's or state's testing rules. Check with your home state's DMV if you're unsure.
What happens if my registration expires before I pass the test?
You cannot legally drive a vehicle with an expired registration. If your test fails and you cannot repair it in time, your registration will expire. You would need to renew your registration at a DMV office in person and explain the situation — they may be able to issue a temporary permit while you complete repairs and retesting.
Can I test a vehicle I'm about to sell?
Yes, but the test result is tied to the vehicle's odometer reading and VIN, not to the owner. If you sell the vehicle, the new owner will need to pass their own test before renewing the registration in their name. A passing test from you does not transfer to the new owner.