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Related Topics: Air Quality Analysis

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.

Contact: Mark Evangelista

Evangelista.Mark@epa.gov

 (919) 541-2803

Background

The Environmental Protection Agency (EPA) finalized a rule to establish criteria and procedures 

for use in determining if air quality monitoring data has been influenced by exceptional events. The 

rule:

• ensures that air quality measurements are properly evaluated and characterized with regard to 

their causes,

• identifies reasonable actions that should be taken to address the air quality and public health 

impacts caused by these types of events,

• avoids imposing unreasonable planning requirements on state, local, and tribal 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.

In July 2012, EPA issued a Federal Register Notice of Availability announcing the release of draft 

exceptional events implementation guidance developed to clarify key provisions of the 2007 

Exceptional Events Rule (EER), respond to questions and issues that arose after the EER was 

promulgated, and reduce the burden associated with the demonstration preparation and review 

process. After considering the feedback received during the public comment period, EPA has 

decided to resolve a number of commenter-identified issues and needed clarifications in a more 

formal rulemaking process. Because the notice and comment rulemaking process is expected to 

take up to two years to conclude, EPA is issuing the interim guidance.

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Interim Exceptional Events Guidance Documents (Posted: 05/13/13)

• Interim Exceptional Events Guidance Documents

◦ Fact Sheet

◦ Interim Guidance to Implement Requirements for the Treatment of Air Quality 

Monitoring Data Influenced by Exceptional Events 

◾ Attachment 1, Interim Exceptional Events Rule Frequently Asked Questions

◾ Attachment 2, Interim Guidance on the Preparation of Demonstrations in 

Support of Requests to Exclude Ambient Air Quality Data Affected by High 

Winds under the Exceptional Events Rule

For guidance-related questions, please contact Beth W. Palma at 919-541-5432 or 

palma.elizabeth@epa.gov

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

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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.

• Technical Support Document (TSD) Preparation - “best practices and components” 

presentation

• Remote Sensing Information Gateway

• Wildland Fire Air Quality Tools Portal

• University of Utah MESOWEST

• DataFed: Web-based software providing atmospheric data and tools

Last updated on September 22, 2015

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