Exceptional Events

Exceptional events are unusual or naturally occurring events that can affect air quality but are not reasonably controllable using techniques that agencies implement in order to attain and maintain the National Ambient Air Quality Standards. Exceptional events are events for which the normal planning and regulatory process established by the Clean Air Act (CAA) is not appropriate.

One type of exceptional event is a natural event. EPA defines a ‘‘natural event’’ as an event in which human activity plays little or no direct causal role to the event in question. For example, a natural event could include such things as high winds, wild fires, and seismic/volcanic activity. The Natural Events Action Plan describes the actions and programs to mitigate effects of high winds.

Federal regulations (40 Code of Federal Regulations Part 50.14 (b)(2)) also allow states to exclude data from regulatory determinations on a case-by-case basis for monitoring stations whose exceedances or violations are caused by emissions from fireworks displays.  DAQ submits Exceptional Event Demonstrations to EPA when ambient air monitoring data is affected by exceptional events.

For more information or questions about exceptional events that are out for public comment contact:
Particulate Matter: Rodney Langston (702)455-1661
Ozone: Jean-Paul Huys (702)455-1684