California Smog Check Performance Standard Modeling (PSM) and Program Certification for the 70 parts per billion (ppb) 8-hour Ozone Standard

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In 2015, U.S. EPA lowered the 8-hour ozone standard from 75 to 70 parts per billion (ppb). Effective on August 3, 2018, U.S. EPA designated nineteen areas in California as nonattainment for this standard. Each nonattainment area must develop and implement State Implementation Plan (SIP) elements specific to their classification, which ranges from Marginal to Extreme. Based on U.S. EPA guidance, nonattainment areas that are classified as Moderate or above and meet a prescribed population threshold must demonstrate through performance standard modeling (PSM) that they meet federal Inspection and Maintenance (I/M, or “Smog Check”) Program requirements. States must submit a SIP revision either (1) demonstrating and certifying that their existing program meets the I/M program requirements; or (2) amending their Smog Check Program requirements.

In October 2022, U.S. EPA released technical guidance for conducting PSM of I/M programs in affected ozone nonattainment areas. CARB staff’s analysis following U.S. EPA guidance demonstrates that California’s Smog Check Program meets federal I/M requirements for all applicable California nonattainment areas. 

The Smog Check Certification establishes that the California Smog Check Program continues to meet I/M program requirements as applicable under the 70 ppb ozone standard for the following eight ozone nonattainment areas: 

  • South Coast Air Basin 
  • San Joaquin Valley 
  • Coachella Valley 
  • Western Mojave Desert 
  • San Diego County
  • Sacramento Metro
  • Eastern Kern
  • Ventura County 

Further, the Smog Check Certification establishes that the California Smog Check Program continues to meet the I/M program requirements as applicable under the 75 ppb ozone standard for the Eastern Kern and San Diego County nonattainment areas.  

The Board will consider the adoption of the California Smog Check Certification for the 70 and 75 ppb ozone standards on March 23, 2023. If adopted, CARB will submit the Smog Check Certification to the U.S. EPA as a revision to the California SIP.

CARB Documents: