Exceptional Events

Contact

Exceptional Events (EE) are natural or unusual events that can overwhelm existing strategies designed to control man-made pollution. If such an event occurs, data that would cause an exceedance of a federal or state standard can be excluded when determining compliance with that standard.

Data from a concurred event is not used for area designation purposes or other select regulatory determinations. The data, however, remains in both the State and federal databases.

Examples of exceptional events include, but are not limited to, wildfires (and resulting smoke), high winds and dust, volcanic activities, stratospheric ozone intrusions, and fireworks.

Exceptional Events must meet the following criteria, as specified in the federal Exceptional Events Rule (80 FR 68216), before being approved by either CARB or U.S. EPA:

  1. The event meets the statutory definition of an exceptional event;
  2. There is a clear causal relationship between the event and the measured exceedance(s);
  3. The event was not reasonably controllable or preventable;
  4. The event was a human activity that is unlikely to recur at a particular location OR was a natural event; and
  5. The public comment process and review procedures were followed.

Air districts may work both individually and cooperatively with other districts, CARB, and U.S. EPA to document events that have occurred within and across their boundaries. Final documentation is then submitted to CARB after completion of a 30-day public comment period. 

  • If the event impacts a federal standard, and CARB concurs with the district(s) assessment, CARB will forward the documentation to U.S. EPA for further review and concurrence. 
  • If the event only impacts a State standard, CARB will conduct the final review.

Additional Information

U.S. EPA Website - Treatment of Air Quality Data Influenced by Exceptional Events