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Treatment of Air Quality Data Influenced by Exceptional Events

Exceptional events are unusual or naturally occurring events that can affect air quality but are not reasonably controllable using techniques that tribal, state or local air agencies may implement in order to attain and maintain the National Ambient Air Quality Standards. Exceptional events include wildfires, stratospheric ozone intrusions and volcanic and seismic activities.

Contact:      Mark Evangelista
                    (919) 541-2803

The Exceptional Events Rule

In September of 2016, the Environmental Protection Agency (EPA) finalized revisions to the Exceptional Events Rule to establish criteria and procedures for use in determining if air quality monitoring data has been influenced by exceptional events. The rule:

  • applies to all exceptional event types and all national ambient air quality standards (NAAQS),
  • ensures that air quality measurements are properly evaluated and characterized with regard to their causes,
  • identifies reasonable actions that state, local and tribal air quality agencies should take to address the air quality and public health impacts caused by these types of events,
  • avoids imposing unreasonable planning requirements on air quality agencies related to violations of the NAAQS due to exceptional events, and
  • ensures that the use of air quality data, whether afforded special treatment or not, is subject to full public disclosure and review.

The 2016 Exceptional Events Rule revises the 2007 Exceptional Events Rule to address issues raised by stakeholders and to increase the administrative efficiency of the Exceptional Events Rule criteria and process.

Exceptional Events Rule and Guidance (Posted: 9/16/16)

  • Federal Register Notice – Final Revisions to the Exceptional Events Rule
  • Final Guidance on the Preparation of Exceptional Events Demonstrations for Wildfire Events that May Influence Ozone Concentrations
  • Response to Comments Document for 2016 rule revisions 
  • Fact Sheet – Final Revisions to the 2007 Exceptional Events Rule and Notice of Availability for Related Draft Guidance

Additional Resources