Exceptional Events

Every year, some air quality events occur that are not feasible to control or prevent. The Federal Clean Air Act allows for special treatment of events that are naturally caused, or events that are the result of human activity and are unlikely to occur again at a particular location. These events may be designated as “exceptional events” if the resulting emissions clearly cause high air pollutant concentrations. The National Ambient Air Quality Standards specify a set of air quality levels that air districts must meet by specific deadlines. Since these standards are designed to guide regulatory decision-making, it may not be appropriate to include monitoring data influenced by exceptional events. If an air quality event meets the exceptional event criteria, South Coast AQMD may prepare an exceptional event demonstration and submit it to the U.S. EPA for consideration. If the U.S. EPA approves the demonstration, South Coast AQMD may exclude the air quality monitoring data measured during the event for determining attainment of the National Ambient Air Quality Standards.

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South Coast Air Quality Management District

21865 Copley Dr, Diamond Bar, CA 91765



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