Air Care Colorado

1982 and Newer Model Year Vehicles

1982 and newer gasoline-powered passenger cars and light duty trucks must be tested every other year as a condition of obtaining a vehicle registration. These vehicles are tested with the enhanced I/M 240 emissions test and can be likened to a treadmill test for your vehicle.

New vehicles do not require an emissions test until the fourth model year. For example, a 2007 model year vehicle is not due for an emissions inspections until 2011.

Pursuant to House Bill 1214, a vehicle being registered in the program area for the first time may be registered without an inspection or certification if the vehicle has not yet reached its fourth model year.

I/M 240 Emissions Test

The I/M 240 tests for carbon monoxide (CO), hydrocarbons (HC) and oxides of nitrogen (NOx) during a simulated driving cycle on a treadmill-like device called a dynamometer; typical driving activities such as idling, cruising, acceleration and deceleration are performed while pollution is collected from the tailpipe.

The name of the I/M 240 test means "Inspection and Maintenance, " with 240 representing the length of the treadmill test in seconds (240 seconds, or four minutes). Pollutants are measured in grams per mile (gpm), and emissions limits are set by vehicle type and model year.

1981 and older vehicles are tested annually with the Two-Speed Idle Test.

Test Process

  1. An inspector guides the vehicle into the inspection lane and performs a brief safety check, enters the vehicle identification number (VIN) into the computer and makes a visual inspection of required emissions equipment. Customers go to an enclosed waiting area from which they can observe the inspection.
  2. The vehicle is positioned with its drive wheels on the dynamome
    ter, allowing it to be tested under actual driving conditions. A fan is positioned in front of the vehicle to simulate wind and keep the engine cool throughout the test. During the driving simulation, emissions are collected from the tailpipe and analyzed. On the basis of emissions data, some very clean vehicles receive a "fast pass" while others have to be tested for the full four-minute cycle. 

    An automatic "second chance" test is provided for vehicles that fail by a small margin. If the vehicle fails within 200% of a pollution limit, the computer will instruct the inspector to run a second test. This is done to minimize the chance that a vehicle might fail simply because of an anomalous situation. For example, the vehicle may fail because it was not sufficiently warmed up.
  3. The vehicle is moved off the dynamometer and the gas cap seal test is performed. The customer is given a Vehicle Inspection Report detailing the test results and the inspection fee is collected. If the vehicle passes (and most do) you will be given a "Vehicle Inspection Report" when the emissions fee is collected. If the vehicle fails, you will be provided with a list of local repair facilities ranked by emissions repair success and a computer report providing useful information to assist the repair technician.

All-Wheel Drive/Traction Control Vehicles

Vehicles that are full-time four wheel drive, all-wheel drive or are equipped with non disengagable traction control are tested using specially-designed dynamometers -- one set for the front wheels and an adjustable set (adjusted based on length of wheel base) under the rear wheels. Each staion contains at least one all wheel driver dynamometer and the aforementioned vehicles are tested in this lane. Vehicles that can be shifted from four-wheel drive to two-wheel drive must be tested in two-wheel drive rather than using the four-wheel dynamometers.

Possible reasons a vehicle could be rejected from testing:

  • One or more dashboard warning lights illuminated, such as brake light warning, oil light warning, or low coolant warning.
  • Defective tires, such as cord showing, uneven wear or temporary spare tire.
  • Driver's side door unable to open.
  • Inadequate braking power.
  • Vehicle unstable on dynomometer/possible alignment problem.
  • Vehicle overheating.
  • Fluid leak of any kind.
  • Clutch or transmission slipping.

This is not an all inclusive list.

Review I/M 240 Exceptions


The following Colorado motor vehicles are exempt from emissions testing:

  • Newly-manufactured vehicles, for the first 4 model years, or until a change of ownership (click here for requirements regarding vehicles being brought into the program area from another state or from another part of Colorado);
  • Pre-1975 collector-plated vehicles
  • Pre-1942 horseless carriage-plated vehicles
  • Vehicles with a two-stroke engine manufactured prior to 1980
  • Vehicle registered as "kit" cars
  • Motorcycles
  • Farm-plated vehicles
  • Electric powered vehicles

** Hybrid electric vehicles, such as the Toyota Prius and Honda Insight, do not currently require emissions inspections.For further information on exemptions, call your county motor vehicle office, or the Colorado Division of Motor Vehicles' Emissions Program Office at 303-205-5603. Also see information regarding vehicles manufactured outside the U.S. and kit cars.