Emissions Testing in Colorado

Testing Requirements

Current Testing Requirements in Colorado

Colorado operates the Air Care Colorado Inspection and Maintenance Program across nine counties on the Front Range. The program has been in place since 1995 and applies to most gasoline, hybrid, and alternative-fuel vehicles once they exceed seven model years from the date of manufacture. The test type depends on the vehicle's model year. Vehicles 8 to 11 model years old receive an OBD-II plug-in test. Vehicles 12 model years and older through 1982 receive an I/M 240 dynamometer test. Vehicles from 1981 and older receive a two-speed idle tailpipe test. Diesel vehicles are tested at separate independent licensed facilities using an opacity test. Starting in 2026, self-service kiosks will be available 24/7 for vehicles requiring the OBD-II test.

Who Needs an Emissions Test

Most gasoline-powered, hybrid, and alternative-fuel vehicles more than seven model years old and registered in the program area must pass an emissions test. The seven-year exemption is based on the model year, not the purchase date. If a vehicle changes ownership during the final year of its exemption, an emissions test is required at the time of sale. Diesel vehicles more than four model years old and registered in the program area also require testing. Electric vehicles, motorcycles, kit cars, horseless carriages, and vehicles registered as street rods are exempt. Vehicles 1975 and older may qualify for collector plates and be exempt from testing entirely. Vehicles with collector plates from model years 1976 and newer that were registered as collector items before September 1, 2009, are also exempt, provided the registration has never lapsed.

How Often Tests Are Required

Gasoline, hybrid, and alternative-fuel vehicles from model year 1982 and newer are tested every two years. Vehicles from 1981 and older without collector plates are tested every year. Diesel vehicles are tested every two years once they exceed the four-year exemption. The registration renewal postcard from the DMV will indicate whether an emissions test is required. Testing must be completed before registration can be renewed. Additionally, a seller must provide a passing emissions test to the buyer at the time of sale if the vehicle is in the program area and requires testing.

Where Emissions Testing Is Required

Emissions testing is required in nine counties along Colorado's Front Range. Full-county requirements apply in Boulder, Broomfield, Denver, Douglas, and Jefferson counties. Partial-county requirements apply in Adams, Arapahoe, Larimer, and Weld counties, where only certain areas within the county fall inside the program boundary. El Paso County requires diesel opacity testing only in certain areas but does not require gasoline vehicle testing. Vehicles registered outside the program area are exempt unless the driver commutes into the area at least 90 days per year for work or school.

What Happens During the Test

For vehicles 8 to 11 model years old, a technician connects to the OBD-II port and checks for diagnostic trouble codes, readiness monitor status, and the malfunction indicator lamp. A lit check engine light results in a failure. For vehicles 12 model years and older through 1982, the I/M 240 dynamometer test measures hydrocarbons, carbon monoxide, and nitrogen oxides while the vehicle is driven on rollers at varying speeds. Vehicles from 1981 and older receive a two-speed idle tailpipe test. All gasoline vehicles also receive a gas cap pressure test. A missing or malfunctioning gas cap causes an automatic failure. Diesel vehicles undergo an opacity test that measures exhaust smoke density, with a pass/fail limit of 20 percent opacity for five seconds. The test typically takes 10 to 20 minutes at Air Care Colorado stations.

Areas in Colorado That Require Emissions Testing

Within the program area, cities and communities that require emissions testing include Denver, Boulder, Lakewood, Arvada, Westminster, Thornton, Broomfield, Centennial, Littleton, Highlands Ranch, Castle Rock, Golden, Longmont, Loveland, Fort Collins, Greeley, and parts of Aurora. Cities and areas outside the program boundary are exempt. Colorado Springs, Pueblo, Grand Junction, Durango, Steamboat Springs, Glenwood Springs, Montrose, and Alamosa do not require emissions testing for gasoline vehicles. Air Care Colorado operates 18 testing stations throughout the Denver metro and North Front Range areas. Real-time wait times are posted on the Air Care Colorado website.

How the Emissions Test Works in Colorado

Drivers take their vehicle to an Air Care Colorado station or an independent licensed facility. No appointment is needed at Air Care Colorado stations. Stations are open Monday through Friday 8 a.m. to 5:30 p.m. and Saturday 8 a.m. to 1 p.m. Bring your vehicle registration. The fee is $35 for 1982 and newer vehicles, effective March 2026. Vehicles from 1981 and older pay $15 at independent stations. Diesel testing fees vary by facility. Payment methods include cash, check, and credit or debit cards. If the vehicle passes, the results are uploaded to the state's motor vehicle system and registration can be renewed online. Clean vehicles may also qualify through the RapidScreen program, which uses roadside remote sensing to measure emissions as vehicles drive past monitoring units. Vehicles that record two clean readings within a 10-month period receive a notification that they can skip a station visit, with the $25 RapidScreen fee added to their registration renewal. If the vehicle fails, the owner must complete repairs and return for a free retest within the same test cycle. The Regional Air Quality Council offers a Clean Air Auto Repair program that provides no-cost repairs for eligible drivers. A repair waiver may be available if qualifying repairs have been completed and the cost exceeds $715 for gas vehicles model year 1968 and newer.