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Motor vehicle emissions

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Update: The Air Pollution Control Division has completed the initial public input process for the rulemaking to update Colorado’s vehicle inspection program. Next, the Air Quality Control Commission will consider adopting the proposed rule. You can find the rulemaking hearing date and schedule on the commission’s calendar.

There are several ways to stay engaged in the rulemaking process:

  • Submit written comments or questions about the proposed rule to the commission directly: cdphe.aqcc@state.co.us. These written comments will be included in the hearing record if submitted after the notice is published. 
  • Participate in the rulemaking hearing, which is open to the public. The commission typically posts a meeting registration link, with optional public comment registration on its website about two weeks before a rulemaking hearing. Hearing documents are available on the commission’s website 3-4 months prior to the hearing.
  • Become a party to the rulemaking hearing. More information is available on the commission’s web page on what party status means and how the process works.
  • Sign-up for email updates from the Air Pollution Control Division for information on future air quality rulemakings and public participation opportunities.

Overview

The CDPHE Air Pollution Control Division works to reduce air pollution from mobile sources through a variety of innovative programs. Emissions from motor vehicles are a major contributor to air pollution in Colorado. In 2024, the division proposed changes to Colorado’s regulations regarding vehicle inspection programs. These include Colorado Air Quality Control Commission Regulations 11 and 12.

In October 2024, the division requested rulemakings on updates for both regulations. The Air Quality Control Commission approved the request during its October 2024 meeting and set the hearings for its January 2025 meeting.

 

Proposals for regulatory changes

Regulation 11, Automobile Inspection and Readjustment (AIR) program

The division proposes changes to Regulation 11 that would impact owners of gasoline-powered vehicles in the Front Range area of Colorado that includes all or portions of Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, Jefferson, Larimer, and Weld counties. Those owners would have access to self-service kiosks for On-Board Diagnostics (OBD) emissions tests that would be available 24/7 at convenient locations. The goal is to ensure that the state's vehicle emissions program remains effective in reducing air pollution and protecting public health. Heavy-duty trucks from model year 2008 and newer would switch from the Two-Speed Idle (TSI) test to the OBD test, ensuring a more accurate evaluation of nitrogen oxides (NOx) emissions. This is important because NOx emissions are a major contributor to ground-level ozone pollution in Colorado. 

If Colorado adopts the changes in January 2025, the division would then establish a new online technical library. The library would provide detailed specifications and resources related to the Motor Vehicle Emissions Inspection Program.

The division proposes changes including:

  • Enhanced and modernized vehicle emissions testing process in Colorado. 
  • New technology that improves testing efficiency, procedures, accessibility, and accuracy of testing.

Regulation 12: Reduction of Diesel Vehicle Emissions

The division proposes changes to Regulation 12 that would impact owners of diesel-powered vehicles in the Diesel Program Area which includes all or portions of Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, El Paso, Jefferson, Larimer, and Weld counties. Regulation 12 Parts A and B require operators of diesel fleets with nine or more vehicles that self-test and certify compliance to use certain procedures and meet requirements for private testing stations. 

The proposed changes to Part A would add: 

  • A visual inspection for emission control components for self-certification test vehicles.
  • Training and qualification requirements for self-certification inspectors consistent with the requirements in Part B. 

The division also proposes:

  • New, more stringent opacity requirements in Parts A, B, and C to reflect the performance capabilities of newer diesel vehicles. 
  • Additional procedures designed to identify tampering as a result of engine replacements. 
  • Various clean-up of existing provisions to improve readability and clarity of the requirements.
  • The division’s goal with proposing changes to Regulation 12 is to modernize and enhance the diesel vehicle emissions testing process in Colorado.

Public meetings

In September 2024, the division hosted public meetings to discuss proposed changes to Regulations 11 and 12. The division considers feedback received during these meetings while preparing rule proposals.

Language interpretation services are available upon request. Registration is required.

Resources

Contact us

Questions? Email cdphe_mobile@state.co.us.