Make sure your vehicle does not smoke. Visible smoke is a sure sign of excess pollution and will cause your vehicle to fail the test.

Ensure the integrity of your exhaust system. Excessive exhaust leaks can cause your vehicle to be rejected from testing. Exhaust leaks are also dangerous to the vehicle's occupants.

Fully warm up your vehicle before testing. Until your vehicle is at normal operating temperature, it emits excess pollution. Run your vehicle at highway speed for at least 15 minutes prior to undergoing an emissions test. Limit use of air conditioning and defroster if possible.

Don't overfill your gas tank. When filling your tank, resist the impulse to get just a little bit more into the tank after the nozzle clicks off. This excess gasoline has nowhere to expand so it saturates a part of the emissions control system resulting in increased emissions.

Check to see you have a gas cap in place. This is required equipment. It must be the correct type for your vehicle, and it must have a tight seal. A missing or leaky gas cap will cause your vehicle to fail the test.

Follow recommended maintenance schedules for your vehicle. Read your owner's manual, and follow maintenance guidelines. Your vehicle will perform more efficiently.

Your vehicle's emissions control equipment must be intact and functioning. Missing or tampered emissions control equipment will cause your vehicle to fail the test.

Make sure your brakes are in good condition. Poor brakes can make the vehicle difficult to test on the dynamometer, and may cause the vehicle to be rejected from testing.

Make sure your tires are properly inflated. Tires that are unevenly inflated, under-inflated or mismatched make the vehicle difficult to test on the dynamometer, and may cause the vehicle to be rejected from testing.

Front-wheel drive vehicles: Make sure the front suspension is properly aligned. Poor front-end alignment will make the vehicle difficult to test on the dynamometer, and may cause the vehicle to be rejected from testing.

Complaints & Consumer Feedback Options

Have a comment, question, suggestion or complaint about the vehicle emissions program? All consumer concerns are taken seriously, and will be addressed promptly.

There are several options for providing feedback.

Complaint forms may be requested and filled out at any emissions test station. These forms are forwarded to the customer service dept. for prompt attention.
You can call the Air Care Colorado hotline at 303-456-7090, 970-247-8378 in the NFR
You can fax us at 303-420-4066.
Send a letter to Air Care Colorado, 5175 Marshall St., Arvada, CO 80002
Use our online form (below).

In all correspondence, please include your name, street address and a daytime phone number. If you have a complaint regarding an emissions test you obtained on your vehicle, please include your vehicle's VIN number and date of test as well.

Alternatively, complaints may be made to the Emissions Program office at the Colorado Division of Motor Vehicles, Emissions Office, by phone at 303-205-5603 or by e-mail. If you have a complaint about ineffective emissions repairs or about a vehicle you purchased without a valid emissions sticker that subsequently failed its emissions test, call this state office.