What Denver requires and when you need to test
Denver requires emissions testing for most vehicles registered in the city, and the test happens every two years. You'll need to pass before you can renew your vehicle registration. The Colorado Department of Revenue runs the program, and testing stations are scattered across Denver and the surrounding metro area — you pick which one to visit.
Your vehicle is exempt if it's a motorcycle, a vehicle registered outside Colorado, a vehicle that's fewer than four model years old, or a vehicle that weighs more than 14,000 pounds. Electric vehicles and some hybrids are also exempt. If you're unsure whether your car needs testing, the Colorado Division of Air Quality website lets you search by your vehicle's year and type.
The test itself checks whether your vehicle's emissions fall within Colorado's limits. A technician will plug a device into your car's diagnostic port, run it through a short driving cycle on a dynamometer (a machine that simulates driving), and measure what comes out of your tailpipe. The whole process takes about 30 minutes.
Key Takeaways
- Denver requires emissions testing every two years for most vehicles before you can renew registration, and you choose which testing station to visit.
- The test costs between $25 and $35 depending on the station, and you pay at the time of testing — there's no separate fee to the state.
- If your vehicle fails, you have 60 days to fix the problem and retest at no additional charge at the same station.
- You can schedule a test online through the Colorado Department of Revenue's website or walk in to most stations during business hours.
- A passing test result is sent directly to the Colorado Department of Revenue, so you don't need to bring paperwork to the DMV.
Finding a testing station and scheduling in Denver
The Colorado Department of Revenue maintains a searchable map of all testing stations across the state. You can filter by location and see which ones have online scheduling. Most stations in Denver are open Monday through Friday during business hours, and some offer Saturday appointments. A few stations accept walk-ins, but scheduling ahead usually means a shorter wait.
When you schedule or arrive, have your vehicle registration handy — the station will need your license plate number or VIN to pull up your testing history. If your vehicle has failed a previous test, the station will know that and may ask what repairs you've made. You don't need to bring proof of repairs; the technician will run the test and see the results.
What happens if you pass or fail
A passing result is automatically sent to the Colorado Department of Revenue within 24 hours. You can then renew your registration online, by mail, or in person at a DMV office. You don't need to print or carry the test result — the state has it on file.
If your vehicle fails, you'll receive a written report showing which emissions standards it didn't meet. Common reasons for failure include a faulty oxygen sensor, a bad catalytic converter, or an engine that's running too rich (burning too much fuel). The report will tell you what the problem is, though it won't tell you exactly how to fix it — that's between you and a mechanic.
You have 60 days from the test date to fix the problem and retest. The retest is free at the same station where you failed, but if you go to a different station, you'll pay the full fee again. Many people take their car to a mechanic, have the repair done, and then return to the testing station within a few days to confirm the fix worked.
Cost and what's included in the test fee
Testing costs between $25 and $35 depending on which station you choose. This is the only fee — there's no separate state charge or hidden cost. You pay at the time of testing, usually by cash, card, or check depending on the station's policy.
The fee covers the diagnostic scan, the dynamometer test, and the report. It does not cover any repairs your vehicle might need. If you fail and need to retest at the same station, the retest is free. If you go to a different station for the retest, you'll pay the full fee again.
What to do if your vehicle fails and you need repairs
Once you have the failure report, take it to a mechanic you trust. The report tells the mechanic what emissions standard your vehicle didn't meet, which narrows down the likely causes. Some repairs are straightforward and inexpensive — replacing an oxygen sensor might cost $100 to $300. Others, like catalytic converter replacement, can run $500 to $1,500 or more depending on your vehicle.
A few repair shops in Denver specialize in emissions work and may charge less than a dealership. You can also ask your mechanic whether they've seen this particular failure before and what the typical fix costs. After the repair, drive the vehicle for a few days to let the engine computer relearn normal operation, then return to the testing station for the retest.
If the repair is expensive and your vehicle is old, it's worth doing the math: the cost of the repair versus the value of the car. Colorado has a program called the Vehicle Emissions Inspection Program that can help with repair costs in some cases, though may be able to access is limited. Your mechanic or the testing station can point you toward current programs if you may have access to.
Renewing your registration after a passing test
Once your vehicle passes, the test result goes to the Colorado Department of Revenue automatically. You can renew your registration online through the state's website, by mail, or in person at a DMV office. You don't need to bring the test result or any paperwork from the testing station — the state already has the information.
Registration renewal costs vary by vehicle type and weight, but the emissions test fee is separate and is not part of the registration cost. You can renew your registration anytime after you pass the test, up until your current registration expires. If your registration expires before you pass the test, you can't legally drive the vehicle, so it's worth scheduling the test a few weeks before your registration renewal date.
What to bring and what to expect on test day
Bring your vehicle registration or a photo ID with your current address. The testing station will use this to look up your vehicle's history and confirm you're the registered owner. You don't need to bring maintenance records, proof of repairs, or anything else — just your ID and your vehicle.
Plan to spend 30 to 45 minutes at the station, depending on how busy it is. The technician will ask you to sit in the vehicle while they run the test, or they may ask you to wait in the lobby. The test itself is non-invasive — the technician plugs a device into your car's diagnostic port under the dashboard, and that's it. No fluids are removed, nothing is taken apart, and your vehicle is not damaged by the test.
Frequently Asked Questions
Can I test my vehicle before my registration expires?
Yes. You can test anytime, and the result is valid for two years from the test date. Many people test a few weeks before their registration expires to avoid any rush. The test result is sent to the state automatically, so you can renew your registration as soon as you pass.
What if I move out of Denver but my vehicle is still registered here?
You still need to pass an emissions test to renew your registration in Colorado, even if you've moved. You can test at any station in the state, not just in Denver. If you move to another state, you'll follow that state's rules once you register your vehicle there.
Do I need to make an appointment or can I just walk in?
Most stations accept both appointments and walk-ins, but wait times vary. Scheduling online usually means you'll be seen faster. Check the Colorado Department of Revenue's station map to see which locations near you offer online scheduling and what their current wait times are.
What if my check engine light is on?
A check engine light usually means your vehicle will fail the emissions test. The light indicates a problem with the engine or emissions system, which is exactly what the test measures. Have a mechanic diagnose the problem before you test, or test first to get the official failure report and then take that to a mechanic.
Can someone else take my vehicle to be tested?
Yes, as long as they have your vehicle registration or a signed note from you authorizing the test. The testing station needs to confirm the vehicle is registered and look up its history, but they don't require the registered owner to be present during the test itself.