An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Vehicle Emissions Inspection and Maintenance (I/M): Regulations

You will need Free Viewers and Adobe Reader to view some of the files on this page. See EPA’s About PDF page to learn more.

Vehicle inspection and maintenance (I/M) programs help improve air quality by identifying cars and truck with high emissions and that may need repairs.  Owners or operators of vehicles with high emissions are notified to make any repairs so that emissions are within legal limits.  The 1990 Amendments to the Clean Air Act (CAA) made I/M mandatory for several areas across the country.  This page contains regulations promulgated by EPA to facilitate the states implementation of this CAA mandate.

Amendments to Vehicle Inspection Maintenance Program Requirements to Address the 8-Hour National Ambient Air Quality Standard for Ozone

Amendments to Vehicle Inspection Maintenance Program Requirements Incorporating the On-Board Diagnostic Check

Additional Flexibility Amendments to Vehicle Inspection Maintenance Program Requirements.

I/M Program Requirement - On-Board Diagnostic Checks Amendment to the Final Rule

Minor Amendments to Inspection Maintenance Program Evaluation Requirements; Amendment to the Final Rule

I/M Program Requirements Minor Amendments

I/M Requirement for On-Board Diagnostic Checks

Inspection/Maintenance Ozone Transport Region (OTR) Flexibility Amendments.

July 1996, Full list of I/M regulations and guidance (TXT)(1 pg, 7 K)  

I/M Flexibility

December 12, 1995, Guidance on Interim Approval of I/M Plans

I/M Redesignation

Full 1992 I/M Regulations

1992 Enhanced Inspection and Maintenance Technical Support Document

Top of Page