Marathon Refinery Fire

On February 25, 2020, at approximately 11:00 p.m., the South Coast Air Quality Management District (South Coast AQMD) was notified of a fire taking place at the Marathon Refinery in Carson, Calif. South Coast AQMD dispatched inspectors to the scene. Los Angeles County Fire and Los Angeles County Hazmat did not request air monitoring support.

South Coast AQMD collected two grab samples on February 26 at approximately 1:20 a.m. and 2:14 a.m. (see below Map). The samples were analyzed for gaseous air toxics such as benzene, toluene, styrene and tetrachloroethylene (perc). Overall, the results did not show any levels above what is normal in ambient air in the South Coast Air Basin. For example, benzene levels from both samples show levels at 0.8 parts per billion (ppb) and 0.7 ppb. Background levels for benzene in the South Coast Basin range from 0.1 ppb to 1.8 ppb. Results for toluene from both samples show 3 ppb and 6 ppb. Background levels for toluene in the Basin range from 0.01 ppb to 6.15 ppb.

South Coast AQMD also deployed its mobile monitor on February 26th in the morning and afternoon to measure for particulate matter (PM) in the nearby community. Analysis of that data shows that PM levels were within typical range for urban areas.

During and after the fire, the agency also continued to monitor air quality. As part of the Rule 1180 fenceline air monitoring program, the Marathon facility has installed monitors around the perimeter of the facility to provide real-time data for a variety of air pollutants ( The data from these monitors show no elevated levels of gaseous air toxics.

 The investigation is ongoing, and the agency will evaluate whether any regulatory violations occurred.

View Lab Report

South Coast Air Quality Management District

21865 Copley Dr, Diamond Bar, CA 91765


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