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  1. Home
  2. EPA in California
  3. Moss Landing Vistra Battery Fire
  4. Frequently Asked Questions

Moss Landing Air: What particulate sizes did EPA monitor during the initial response in January?

Return to: Frequently Asked Questions

EPA monitored for all of the particulate sizes listed below. If we say we are monitoring for PM2.5, this includes monitoring for particles 2.5 micrometers (μm) and smaller, down to the detection limit of the instrument (in this case 0.1 micrometers).

The equipment EPA used (see product specifics: TSI DustTraks) collected data for:

  • PM1 (size fraction from 0.1 to 1 μm)
  • PM2.5
  • PM4
  • PM10
  • “Total Particulates”

PM2.5 is the smallest unit we regulate under the Clean Air Act. There is no federal air standard for less than PM2.5.

During the fires and since, regional air quality has been consistent with the air quality index (AQI) in the Monterey Bay and San Francisco Bay regions. The data shows air quality did not exceed the “moderate level” on the AQI for the Monterey area.

Related Questions

  • Moss Landing Air: What air monitoring activities did you do during the January fire response?
  • Moss Landing Air: What were the results of EPA's air monitoring from January 17 to 20?
  • Moss Landing Air: What did you test for during the fire?
  • Moss Landing Air: What air monitoring technology did you use?
  • Moss Landing Air: Are you requiring any air monitoring or sampling during Vistra’s battery removal work?
  • Moss Landing Air: Is there a difference between air monitoring and air sampling?
  • Moss Landing Air: Can you detect nanoparticles in the air with the instrumentation you used during the initial response?

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Last updated on September 22, 2025
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