Vehicle Emissions Inspection and Maintenance (I/M): General Information and Regulations
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Vehicle inspection and maintenance (I/M) programs help improve air quality by identifying cars and trucks 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) established I/M requirements for several areas across the country. This page contains general information on I/M, the current I/M regulations, and the chronological list of rulemakings promulgated by EPA to facilitate state implementation of this CAA requirement.
- Overview of Vehicle Inspection and Maintenance (I/M) Programs (pdf) (EPA-420-F-21-067, October 2021)
This document provides information on I/M programs such as where I/M programs are required and an overview of I/M testing.
The current I/M regulations may be found at 40 CFR part 51, Subpart S.
Amendment to Align I/M Program and Attainment SIP Due Dates
- In 2015, the I/M regulations were amended as part of the Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State Implementation Plan Requirements rulemaking. In this final rule, EPA aligned the due date for the I/M program state implementation plans (SIP) with the due date of the attainment demonstration SIP.
- Final Rule (pdf) (80 FR 12264, March 6, 2015)
- Proposed Rule (pdf) (78 FR 34964, June 11, 2013)
Amendments to Vehicle Inspection Maintenance Program Requirements to Address the 8-Hour National Ambient Air Quality Standard for Ozone
- Final Rule (pdf) (published April 7, 2006)
- Fact Sheet (pdf) (EPA420-F-06-028, March 2006)
- Proposed Rule (pdf) (published January 6, 2005)
- Fact Sheet (pdf) (EPA420-F-04-059, December 2004)
Amendments to Vehicle Inspection Maintenance Program Requirements Incorporating the Onboard Diagnostic Check
Additional Flexibility Amendments to Vehicle Inspection Maintenance Program Requirements; Amendment to Final Rule
I/M Program Requirement - On-Board Diagnostic Checks Amendment to the Final Rule
- Final Rule (pdf) (published May 4, 1998)
- Final Rule Fact Sheet (PDF) (EPA420-F-98-017, April 1998)
- Proposed Rule Fact Sheet (PDF) (EPA420-F-98-002, January 1998)
- Proposed Rule (PDF) (published December 22, 1997)
Minor Amendments to Inspection Maintenance Program Evaluation Requirements; Amendment to the Final Rule
Minor Amendments to Inspection/Maintenance Program Requirements/M Program Requirements Minor Amendments
- Direct Final Rule (pdf) (published September 23, 1996)
I/M Program Requirement for On-Board Diagnostic Checks
- Correction of Final Rule (pdf) (published August 27, 1996)
- Final Rule (pdf) (published August 6, 1996)
- Proposed Rule (pdf) (published August 18, 1995)
Inspection/Maintenance Flexibility Amendments (Ozone Transport Region)
Inspection/Maintenance / Flexibility Amendments
Inspection/Maintenance Program Requirements -- Provisions for Redesignation
Inspection/Maintenance Program Requirements