Treatment of 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  • Fact Sheet – Final Revisions to the 2007 Exceptional Events Rule and Notice of Availability for Related Draft Guidance

Informational Public Webinar to Discuss Rule Revisions and Final Guidance

EPA hosted an informational public webinar on September 21, 2016 from 2:00-3:30 pm EDT to provide an overview of the final Exceptional Events Rule revisions and the final wildfire/ozone implementation guidance. Webinar materials are available here:

Quick-Reference Guide for Exceptional Events Demonstrations

This user-friendly quick-reference guide for exceptional events demonstrations is intended to direct air agency staff and other interested persons to specific information and guidance related to exceptional events demonstrations. The matrix pairs event and pollutant combinations (x-axis) with current Exceptional Events Rule criteria (y-axis). Each cell contains links that direct the user to specific example analyses or language that may be used in Exceptional Events Demonstrations. EPA expects to update this matrix as additional information (rule revisions, guidance, demonstrations) become available.

Examples of Reviewed Exceptional Event Submissions

This exceptional events submissions table provides examples of air agency-submitted and EPA concurred exceptional events demonstration packages along with the accompanying EPA concurrence letters and supporting analyses. EPA expects to update this table as additional demonstrations become available.

Best Communication Practices for Preparation of Exceptional Events Demonstrations

Because of the passage of time between issuing the 2013 Interim Exceptional Events Implementation Guidance and the EPA’s anticipated 2015 proposed revisions to the Exceptional Events Rule, the EPA hosted conference calls with some air agencies between September 2014 and March 2015 to ask whether any new exceptional events implementation concerns had arisen and to better understand currently employed exceptional events implementation processes and practices. As a result of these discussions, the EPA developed a list of best practices for communication and collaboration between the EPA and air agencies. The EPA will update this document, if needed, to reflect promulgated changes to the Exceptional Events Rule (if needed, revisions anticipated summer 2016).

Publicly Available Support Information and Tools

EPA provides no endorsement of specific publicly available tools, nor does EPA mandate their use. EPA believes that publicly available tools can provide supporting documentation for one or several of the exceptional event criteria within an air agency exceptional event demonstration, but EPA generally does not believe that links and/or references to these tools constitute a complete demonstration submittal.