Where to get your emissions test in Longmont
Longmont is in Boulder County, which requires emissions testing for most vehicles registered there. You can take your car to any Colorado Department of Revenue-certified emissions testing station in the county — you do not have to go to a specific location. The state maintains a searchable list of certified stations on its website, and many are independent repair shops, not just dealerships.
The test itself takes about 10 to 15 minutes. The technician will connect your vehicle to a dynamometer (a machine that measures what comes out of your tailpipe) and run it through a standardized cycle. You will get a pass or fail result on the spot, and the results are sent electronically to the Colorado Division of Motor Vehicles.
You do not need an appointment at most stations, but calling ahead can save you a wait, especially during peak testing months (August through October and January through March). Some stations are busier than others, so if one has a long line, you can drive to another certified station in the same county.
Key Takeaways
- Any Colorado Department of Revenue-certified emissions testing station in Boulder County will perform your test, and results go directly to the state.
- The test takes 10 to 15 minutes and costs between $20 and $35 depending on the station.
- Your vehicle must be registered in Boulder County and pass a basic safety inspection (lights, horn, wipers) before the emissions test can run.
- A failed test means your vehicle has an emissions problem that must be repaired before you can register it, but you can retest at any certified station after repairs.
- Longmont residents can find certified stations and check their vehicle's test history on the Colorado Division of Motor Vehicles website.
When your vehicle needs an emissions test
Boulder County requires emissions testing for all gasoline-powered vehicles that are at least 6 years old. Diesel vehicles, motorcycles, and vehicles registered as antiques or classic cars are exempt. If your vehicle is newer than 6 years, you do not need to test it.
You must test your vehicle every two years when you renew your registration. The test is due by the expiration date on your registration card. If your registration expires in June, your emissions test must be completed by June — you cannot test early and extend the important date. The state will not let you renew your registration online or by mail without a passing test result on file.
If you move to Longmont from another county or state, you will need an emissions test before you can register your vehicle in Boulder County, even if it was recently tested elsewhere. Colorado recognizes test results from other states, but only if the vehicle was tested within the past 60 days.
What happens if your vehicle fails the test
A failed test means your vehicle's emissions are above the legal limit for Colorado. The test report will tell you which emissions are too high — usually nitrogen oxides (NOx), hydrocarbons, or carbon monoxide. This information helps a mechanic diagnose the problem.
Common causes of failure include a faulty oxygen sensor, a malfunctioning catalytic converter, a clogged air filter, or an engine that is running too rich (burning too much fuel). Some of these repairs are inexpensive; others are not. An oxygen sensor might cost $200 to $400, while a catalytic converter can run $800 to $2,000 or more depending on your vehicle.
After you repair the problem, you can retest at any certified station. There is no waiting period — you can test the same day as your repair if the station has availability. You will pay the testing fee again (typically $20 to $35). If you fail a second time, you may be able to get a waiver in some cases, but that requires a failed repair attempt documented by a mechanic and approval from the state.
Cost and what to bring
Emissions testing costs between $20 and $35 per test, depending on which station you choose. This is the only fee — there is no state surcharge or hidden cost. Some stations may charge slightly more if they perform additional services like a safety inspection at the same time.
Bring your vehicle registration card or a photo ID and proof of residency (a utility bill or lease works). You do not need your title or insurance card, though having your insurance information handy is always a good idea. The technician will look up your vehicle in the state system using your license plate number.
Your vehicle must pass a basic safety inspection before the emissions test can run. The technician will check that your headlights, brake lights, turn signals, horn, and windshield wipers all work. If any of these fail, you cannot test until they are fixed. This is not a full safety inspection — it is just a quick check of the items that affect emissions testing.
How to find a certified testing station
The Colorado Division of Motor Vehicles website has a searchable map of all certified emissions testing stations. You can filter by county and city, so you can find stations near your home or workplace in Longmont. The map shows the station's address, phone number, and hours of operation.
Many independent repair shops, tire shops, and quick-lube facilities are certified to perform emissions testing. You do not have to go to a dealership. Some stations specialize in emissions testing and can often get you in quickly; others do it as a side service. Calling ahead to ask about wait times is worth the effort during busy months.
If you have already tested your vehicle, you can check your test history on the Colorado Division of Motor Vehicles website using your license plate number. This shows you when your last test was, whether it passed or failed, and when your next test is due.
What the test measures and why it matters
The emissions test measures three main pollutants: nitrogen oxides (NOx), hydrocarbons, and carbon monoxide. These are the byproducts of burning gasoline in your engine. When these pollutants are too high, they contribute to smog and poor air quality, which affects everyone in the Front Range.
Colorado's emissions standards are set by the Colorado Air Quality Control Commission and are based on federal Clean Air Act standards. Longmont and Boulder County are in a non-attainment area for ozone, which means the air quality does not consistently meet federal standards. Emissions testing is one of the tools the state uses to keep older, higher-polluting vehicles off the road.
A vehicle that passes the test is still producing emissions — it is just producing them within the legal limit. A newer vehicle with a functioning catalytic converter and oxygen sensor will almost always pass. An older vehicle with worn components or a check engine light on is more likely to fail.
Frequently Asked Questions
Can I test my vehicle before my registration expires?
Yes, but the test result is only valid for 60 days before your registration expires. If you test too early, the result will expire before your registration does, and you will have to test again. The safest window is 60 days before your registration expiration date.
What if I just moved to Longmont and my vehicle was tested in another state?
Colorado recognizes emissions test results from other states if the test was performed within the past 60 days. Bring proof of the out-of-state test (usually a printed report or receipt) when you register your vehicle in Boulder County. If the test is older than 60 days, you will need a new test in Colorado.
Do I have to test my vehicle if I have a check engine light on?
You can still take the test, but you will almost certainly fail. The check engine light means your vehicle's onboard diagnostic system has detected a problem — usually related to emissions. Get the code read by a mechanic first, repair the problem, and then test.
What if I cannot afford to fix my vehicle after it fails?
If you have made a good-faith repair attempt and the vehicle still fails, you may be able to get a waiver from the Colorado Division of Motor Vehicles. This requires documentation from a mechanic showing what was repaired and that the vehicle still does not pass. Waivers are not may provide and depend on the specific situation.
Can I register my vehicle without an emissions test?
No. If your vehicle is 6 years old or older and registered in Boulder County, you cannot renew your registration without a passing emissions test result. The state system will not allow online or mail renewal without the test on file. You must test before your registration expires.