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Draft Guidance to Implement Requirements for the Treatment of Air Quality 

Monitoring Data Influenced by Exceptional Events 

This summary document and its attachments1 clarify key provisions of the 2007 Exceptional 

Events Rule (EER) to respond to questions and issues that have arisen since the rule was 

promulgated. The draft guidance in this document and the attachments, along with examples of 

approved demonstrations on the EPA’s website2

, are provided to help ensure that the EPA’s final 

guidance provides an efficient and effective process to make determinations regarding air quality 

data affected by events. The EPA notes that we released a previous version of these draft 

guidance documents to state, local, and tribal agencies, and to other parties as requested in May 

of 2011. The EPA incorporated some of the commenters’ feedback into these revised draft 

guidance documents. An accounting of the preliminary comment and response process is 

documented in the docketed response to comments document.3

 The EPA notes that these draft 

guidance documents and the exceptional events website present examples to illustrate specific 

points. The example analyses and level of rigor are not necessarily required for all 

demonstrations. Please direct comments on these draft guidance documents to Docket ID No. 

EPA-HQ-OAR-2011-0887 by the comment deadline indicated in the Federal Register Notice of 

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

These draft guidance materials identify the four independent criteria on which exclusion of 

event-affected data depends, describe the administrative process and associated timing for 

submittal and review of demonstrations, provide answers to frequently asked questions, and 

provide previously reviewed demonstrations and best practice components. The EPA recognizes 

the challenges that air agencies4 face in preparing exceptional event demonstration packages. 

The EPA also recognizes the limited resources of the air agencies that prepare and submit 

exceptional event demonstration packages and of the EPA regional offices that review these 

demonstration packages. One of the EPA’s goals in developing exceptional event 

implementation guidance is to establish clear expectations to enable affected agencies to better 

manage resources as they prepare the documentation required under the EER. The EPA expects 

submitters to prepare and submit the appropriate level of supporting documentation, which will 

vary on a case-by-case basis using the weight-of-evidence approach. The EPA expects the 

resources required to prepare (and review) packages to decrease as we continue to identify ways 

to streamline the process and continue to build our database of example demonstrations and 

analyses. In addition, the EPA acknowledges that certain extreme exceptional event cases may 

require more limited demonstration packages. This necessary case-by-case approach, however, 

makes the development of general guidance with bright lines difficult. 

 

1

 Attachment 1, “Draft Exceptional Events Rule Frequently Asked Questions” (the draft Q&A document), 

Attachment 2, “Draft 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” (the draft High Winds Guidance 

document), and Attachment 3, “Request for Comments on the Draft Guidance Documents on the Implementation of 

the Exceptional Events Rule” (the Request for Comments document). 

2

 Additional information and examples of exceptional event submissions and best practice components can be found 

at the EPA’s Exceptional Events website located at http://www.epa.gov/ttn/analysis/exevents.htm. 

3

 Response to Comment document entitled, “Responses to Significant First-Round Comments on the Draft Guidance 

Documents on the Implementation of the Exceptional Events Rule.” 

4

 References to “air agencies” are meant to include state, local, and tribal air agencies responsible for implementing 

the EER. 
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This draft guidance overview document and its attachments are based on the following 

principles: 

1. Air agencies should not be held accountable for exceedances due to events that were 

beyond their control at the time of the event. 

2. It is desirable to implement reasonable controls to protect public health.5

3. Clear expectations will enable the EPA and other air agencies to better manage resources 

related to the exceptional events process. 

Exceptional Event Rule Provisions 

On March 22, 2007, the EPA promulgated the “Treatment of Data Influenced by Exceptional 

Events; Final Rule” (72 FR at 13560) pursuant to the 2005 amendment of Clean Air Act (CAA) 

Section 319. This rule, known as the Exceptional Events Rule, superseded the EPA’s previous 

natural events guidance and those sections of the interim fire policy document that address 

exceptional events.6

 The EER created a regulatory process codified at 40 CFR parts 50 and 51 

(50.1, 50.14 and 51.930). These regulatory sections contain definitions, procedural requirements, 

requirements for air agency demonstrations, and criteria for EPA approval for the exclusion of 

air quality data from regulatory decisions under the EER. 

 

The definition of an exceptional event at 40 CFR §50.1(j) repeats the CAA definition which 

provides that an exceptional event is one that affects air quality, is not reasonably controllable or 

preventable, and is caused by human activity that is unlikely to recur at a particular location or a 

natural event. Additional requirements in 40 CFR §50.14(a)(2) and (b)(1) identify that an air 

agency must demonstrate “a clear causal relationship between the measured exceedance or 

violation of such standard and the event” and that “an exceptional event caused a specific air 

pollution concentration in excess of one or more national ambient air quality standards.” The rule 

further requires at 40 CFR §50.14(c)(3)(iv) that the demonstration to justify data exclusion shall 

provide evidence that the event is associated with a measured concentration in excess of normal 

historical fluctuations, including background, and evidence that there would have been no 

exceedance or violation but for the event. 

 

5

 With respect to exceptional events, Section 319 of the Clean Air Act states the following guiding principles 

(among others); 

(i) the principle that protection of public health is the highest priority 

*** 

(iv) the principle that each State must take necessary measures to safeguard public health regardless of the 

source of the air pollution 6

Previous guidance and policy documents that either implied or documented the need for identifying data affected 

by an exceptional event include: 

i) “Guideline for Interpretation of Air Quality Standards,” U.S. EPA, OAQPS No. 1.2-008, Revised February 1977. 

ii) “Guideline On the Identification and Use of Air Quality Data Affected by Exceptional Events” (the Exceptional 

Events Policy), U.S. EPA, OAQPS, July 1986. 

iii) “Areas Affected by PM10 Natural Events” (the PM10 Natural Events Policy), memorandum from Mary D. 

Nichols, Assistant Administrator for Air and Radiation, to the EPA regional offices, May 30, 1996. 

iv) “The Interim Air Quality Policy on Wildland and Prescribed Fires” (the Interim Fire Policy), memorandum 

from Richard D. Wilson, Acting Assistant Administrator for Air and Radiation, to the EPA regional administrators, 

May 15, 1998. 

v) “Guideline on Data Handling Conventions for the PM NAAQS,” U.S. EPA, OAQPS, EPA-454/R-98-017, 

December 1998. 
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Treatment of Technical Criteria for Exclusion of Data Affected by Events 

When considered together, the EER provisions summarized above identify the following six 

elements that air agencies must address when requesting that the EPA exclude event-related 

concentrations from regulatory determinations: 

 the event affected air quality 

 the event was not reasonably controllable or preventable 

 the event was caused by human activity that is unlikely to recur at a particular location, or 

was a natural event 

 there exists a clear causal relationship between the specific event and the monitored 

concentration 

 the event is associated with a measured concentration in excess of normal historical 

fluctuations including background 

 there would have been no exceedance or violation but for the event 

In reviewing exceptional events demonstration packages, the EPA has found that the 

following EER elements, along with historical fluctuations, play a significant role in the air 

agencies’ supporting documentation: 

1. not reasonably controllable or preventable 

2. if the event was caused by human activity, that human activity is unlikely to recur at a 

particular location7

3. clear causal relationship between specific event and monitored concentration 

4. no exceedance or violation but for the event8 

As described in the draft guidance documents, the EPA’s technical review of a demonstration 

package would therefore focus on these elements. While the EER requires and the EPA expects 

complete demonstration packages to contain narrative and evidence supporting all six elements, 

the EPA’s position is that these four elements represent distinct facts that air agencies must 

demonstrate for the EPA to concur on an event claim.9 Note that if an event is natural, then the 

second element is not considered in a demonstration review. In the case of an event that is 

initiated by a natural process, such as a volcano or high wind dust event, the event would be 

considered a natural event if sources are entirely natural or contributing anthropogenic sources 

are reasonably controlled.10 This concept is explained in more detail in Attachment 2, the draft 

High Winds Guidance document. 

 

7

 The remaining part of this criterion, “or a natural event” is intentionally omitted here. 8

 Criteria 1, 3, and 4 on this list, along with historical fluctuations, are considered “independent elements” in the 

draft High Winds Guidance document. 

9

 While the “historical fluctuations element” is considered an independent element, it also plays an important role in 

the “clear causal relationship” and “no exceedance but for” demonstrations. The EPA will review agency 

submissions using a weight-of-evidence approach. The state’s role in satisfying this element is to provide 

appropriate analyses and statistics comparing the event-affected concentration to normal historical fluctuations and 

conclude that the provided data show that the event was in excess of normal historical fluctuations. The EPA will 

review the information provided by the air agency. “Normal historical fluctuations” will generally be defined by 

those days without events for the previous years. The EPA acknowledges that natural events can recur and still be 

eligible for exclusion under the EER; therefore, events do not necessarily have to be rare to satisfy this element. 

However, in most cases, the EPA expects that failure of the “historical fluctuations” element indicates likely failure 

for “clear causal relationship” and/or “no exceedance but for” as well. 10 Human activity would be considered to have played little or no direct causal role in causing the entrainment of the 

dust by high wind if contributing anthropogenic sources of dust are reasonably controlled, and thus the event would 
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The EPA recognizes the inherent links between all six elements and expects that some 

sections of a demonstration package (e.g., affects air quality, natural event) may repeat or refer to 

other sections of the demonstration package (e.g., clear causal relationship, but for). Further, 

each potential event can have varied and differing characteristics, and thus would usually require 

a case-specific demonstration and evaluation. Therefore, the EPA would use a “weight-ofevidence” approach in evaluating each element within an exceptional event demonstration 

package. 

In the draft guidance documents, the requirement that the event was not reasonably 

controllable or preventable, which is part of the definition of an exceptional event in both the 

Clean Air Act and the EER, would mean that if a set of control measures could reasonably have 

been in place for contributing sources at the time of the event, then they must have been in place 

for the event to qualify as an exceptional event under the EER. This EER requirement applies to 

all events but is more complicated for high wind dust events because the event typically includes 

both natural and anthropogenic sources of dust. In contrast, an event such as a lightning-induced 

wildfire does not include an anthropogenic contribution to the event. Among other factors to 

consider, reasonableness would need to be judged in light of the technical information available 

to the air agency at the time the event occurred. The EPA would expect for nonattainment areas 

to already have the technical information needed to reasonably control anthropogenic sources in 

their jurisdiction. It would be important that each demonstration package address the question of 

reasonable controls. As with the other elements, whether an event was not reasonably 

controllable or preventable would be evaluated on a case-by-case basis. In general, reasonable 

controls would not include any control on emissions-generating activity outside of the state or 

tribal boundaries of the state (or tribal lands) within which the concentration at issue was 

monitored. 

Timing of EER Demonstration Package Submittal and Review 

The EPA understands that the initial identification of data affected by exceptional events and 

the subsequent preparation, submittal, and review of demonstration packages is a resource 

intensive process. Delays in processing and making decisions on submitted packages create 

regulatory uncertainty and potentially increase the workload for both the submitting agency and 

the EPA. In addition, the backlog of pending actions makes retrieval of data to support new 

submittals potentially more difficult. Further, air agencies and the EPA often face timelines by 

which they must make regulatory decisions that can be affected by the inclusion or exclusion of 

event-affected data. 

The EPA will work with air agencies as they prepare complete demonstration packages that 

meet the requirements of the EER. In an effort to streamline this identification, preparation, 

submittal, and review process, the EPA has developed the following draft guidelines. 

 be considered a natural event. If anthropogenic sources contributed significantly to a measured concentration (or if 

emissions from anthropogenic sources alone would have resulted in an exceedance or violation of the NAAQS) and 

these same emissions from anthropogenic sources are affected by an event and are reasonably controllable but did 

not have those reasonable controls applied at the time of the event, then the event would not be considered a natural 

event. 
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1. Identification of data affected by exceptional events in AQS – The EPA is aware that 

air agencies routinely review their air quality monitoring data, which may result in the 

identification of certain data being affected by an exceptional event. Although air 

agencies may flag any data in AQS that they wish to flag, the EPA encourages air 

agencies to flag only data that might have a regulatory consequence and for which an 

approvable demonstration is likely.11 Should air agencies wish to flag values for 

informational purposes, the EPA prefers that they use the AQS flags intended for this 

purpose. 

2a. Air agency submittal of letter of intent to submit a package (optional) – To promote 

early communication, the EPA suggests that air agencies provide a letter of intent to 

submit a demonstration package for flagged data in AQS as soon as possible, if possible 

within 12 months from the event occurrence, after the agency identifies the event(s) as 

being significant.12 This initial notification can assist both the air agency and the EPA in 

the planning and prioritization process. 

2b. Air agency notification of intent to submit a package (optional) - Air agencies 

choosing not to submit a letter of intent are still encouraged to contact their EPA regional 

office more informally to alert it of the forthcoming demonstration submittal. 

3. EPA response to air agency letter of intent – The EPA anticipates responding to the air 

agency’s letter of intent within 60 days of receipt. The EPA response will provide the 

regional office’s best assessment of the priority that can be given to the submission once 

received and any case-specific advice the EPA may have to offer for the preparation of 

the demonstration. 

4. Air agency submittal of exceptional event demonstration packages13 – Air agencies 

should prepare a technical demonstration package, taking into account the information in 

the EPA’s guidance documents, which shows that a particular air quality monitored 

value(s) is influenced by an exceptional event. The EPA acknowledges that certain 

extreme exceptional event cases may lessen the technical burden associated with 

demonstration packages. Air agencies that believe their demonstration packages are tied 

to near-term regulatory actions should submit their demonstration packages well in 

advance of the regulatory deadline. Air agencies should also identify the relationship 

between the exceptional event-related flagged data and the anticipated regulatory action 

 

11 States should place flags and an initial event description in AQS in accordance with the AQS data submission 

schedules (i.e., within 90 days of the end of the previous quarter) but not later than July 1st of the calendar year 

following the event in which the flagged measurement occurred. Note that for data certification purposes, it is 

recommended to flag data prior to submittal of data certification (May 1st). 12 The Letter of Intent is an optional step and the EPA recognizes that states may need additional time to prepare and 

submit demonstration packages particularly where the basis of the exclusion is violating an annual standard or a 3-

year design value. Similarly, a state could consider submitting an annual letter of intent if annual submittal makes 

sense for resource planning or for historically seasonal events. If a state decides to submit a letter of intent, the EPA 

recommends that it be submitted as expeditiously as possible after the state identifies the event or events as having 

significance. 

13 The EER allows states to submit packages up to 3 years following the end of the calendar quarter in which the 

event occurred, or 12 months prior to the date that a regulatory decision must be made by the EPA. 
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in the cover letter that accompanies their initial submittal package to the reviewing EPA 

regional office. 

5. EPA prioritization of submitted demonstration packages – The EPA will generally 

give priority to exceptional event determinations that may affect near-term regulatory 

decisions, such as SIP submittal actions, National Ambient Air Quality Standards 

(NAAQS) designations, and clean data findings. 

6. EPA review of prioritized demonstration packages – The EPA generally intends to 

conduct its initial review of a submitted exceptional event demonstration package within 

120 days of receipt. Following this initial review, the EPA will generally send a letter to 

the submitting agency that includes a completeness determination and/or a request for 

additional information, a date by which the supplemental information should be 

submitted (if applicable), and an indicator of the timing of the EPA’s final review. The 

EPA encourages air agencies to provide supplemental information if needed and 

requested by the EPA. The EPA anticipates a 60-day response time for states to provide 

additional requested information.14 The EPA intends to make a decision regarding event 

concurrence within 18 months of submittal of a complete package, or sooner if required 

by a near-term regulatory action. Determinations on Exceptional Event demonstrations 

do not constitute final agency action until they are relied upon in a regulatory decision 

such as a finding of attainment or nonattainment which will be conducted through noticeand-comment rulemaking procedures. 

Exceptional Events Rule Frequently Asked Questions Document (Attachment 1) 

The “Draft Exceptional Events Rule Frequently Asked Questions” document (the draft Q&A 

document) provides draft responses to questions that have arisen since the EER was 

promulgated. The questions are grouped into six broad areas. The EPA encourages those 

involved in flagging data and preparing demonstration packages to review the draft questions 

and answers, and to provide input regarding their usefulness and appropriateness and regarding 

additional questions which need answers. The following bullets identify key points of interest in 

the draft Q&A document: 

 Natural events, such as volcanic eruptions, do not have to be infrequent to qualify as 

exceptional events under the EER. Frequent events with natural triggers that have a 

contribution from anthropogenic activities that are reasonably controlled could be eligible 

“exceptional” events, provided the events meet the demonstration requirements for the 

technical criteria. 

 The EER does not prohibit air agencies from flagging individual concentration values 

below the level of the NAAQS. However, in general, only such data that contribute to a 

violation of the NAAQS are excludable. Questions 29-31 of the draft Q&A document 

describe the few, limited situations in which concentration values below the level of the 

NAAQS contribute to violations of the NAAQS. 

 

14The EPA recognizes that states may need more than 60 days to prepare and submit some types of supplemental 

information. The EPA is willing to work with agencies on supplemental timeframes; however, the mandatory timing 

of EPA actions may limit the response time the EPA allows. 
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 An event that an air agency has concluded is associated with a measured concentration 

“in excess of normal historical fluctuations” will be reviewed using a weight-of-evidence 

approach. The comparison of the measured concentration to normal historical 

concentrations will also influence how much information is needed to successfully meet 

other technical elements. For example, when the observed concentration is high 

compared to historical concentrations, the EPA may require less additional evidence to 

demonstrate the “but for” finding. The draft Q&A document provides recommendations 

for showing how the observed concentration compares to the distribution of historical 

concentrations. 

 Question 6 in the draft Q&A document describes types of evidence that could be 

submitted as part of a demonstration showing that an ozone exceedance would not have 

occurred but for the effect of a fire event. In particular, statistical or photochemical 

dispersion model predictions of the ozone concentration that would have occurred in the 

absence of the fire would be a relevant type of evidence, provided the demonstration 

package is transparent about the technical basis for the model and its uncertainties. Also, 

as noted below, the EPA intends to develop a separate draft guidance document for firerelated events. 

 Not every natural or infrequent anthropogenic event that affects air quality is a true 

"exceptional event" under the definition of that term in the Exceptional Event Rule. 

Ambient data affected by an event that does not meet the "but for" criterion cannot be 

excluded under the authority of the Exceptional Events Rule even if in all other respects 

the event meets the definition of an exceptional event. The Exceptional Events Rule does 

not address data handling associated with events that are not considered “exceptional” 

under the EER, and does not provide the EPA with authority to exclude such data. Yet, 

the event-related concentration could still impact design values. An air agency 

incorporating the event-related concentration in a design value used for a prospective 

attainment demonstration might seem to need more emission reductions to attain the 

NAAQS by its attainment deadline than is actually the case. The EPA plans to more 

formally address this topic on a pollutant/NAAQS basis, the first of which will be ozone 

guidance in the preamble of a soon-to-be-proposed rulemaking on SIP requirements for 

areas designated nonattainment for the 2008 ozone NAAQS. Until the planned guidance 

for a pollutant and NAAQS of interest is issued, air agencies should consult with their 

EPA regional office if they face this situation. EPA further discusses this issue in 

Question 13 in the draft Q&A document. 

 To remove any possible confusion, the passages of the preamble that were declared to be 

a legal nullity by the court that reviewed the EER are specifically identified in Question 

20 in the draft Q&A document.15 While air agencies cannot rely solely on these passages 

as the EPA guidance on interpretation of the EER, this draft guidance overview document 

and its attachments are consistent with those sections. 

 

15 See NRDC v. EPA, No. 07-1151 (D.C. Cir. 3/20/09). 
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 The EPA identifies in Question 28a of the Q&A document currently existing mechanisms 

that air agencies can use at various points in the exceptional events process to resolve 

disagreements regarding non-concurrence on submittal packages. 

High Winds Guidance Document (Attachment 2) 

The attached “Draft 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” (the High Winds Guidance document) when finalized will be a resource for air agencies 

when flagging data and preparing demonstrations packages for high wind dust events that have 

affected PM10 and PM2.5 concentrations. The draft document applies the provisions of the EER 

and the general guidance conveyed in this draft guidance overview document and in the draft 

Q&A document to the particular situation of a high wind dust event. While the document is 

specific to high wind dust events, it outlines how the EPA intends to implement the preparation 

and review process for exceptional events and, therefore, may have relevance for other types of 

exceptional events. The following are some of the highlights of the draft High Winds Guidance 

document: 

 In nonattainment areas, a reference point for considering what constitutes reasonable 

control of wind-blown dust during high wind events would be the set of measures that are 

identified as RACM or BACM in the approved SIPs of other areas with similar windblown dust conditions, depending on area classification. USDA best management 

practices designed to effectively reduce fugitive dust air emissions and prevent loss of 

soil during high winds could also be considered if applicable to the dust source. Also, 

RACM or BACM measures in an area’s own approved SIP should be considered part of 

the reasonable set of controls. The assessment of whether an event was not reasonably 

controllable will be made on a case-by-case basis considering all the facts. 

 Reasonable controls generally would not need to be implemented for wind-blown dust 

from undisturbed natural landscapes or previously disturbed landscapes that are being 

allowed to return to natural conditions. 

 For purposes of qualifying for the exclusion of data affected by wind events with 

sustained wind speeds above 25 miles per hour (or above another threshold determined to 

be appropriate for a particular area), the demonstration of reasonable controls applied to 

disturbed landscapes and other anthropogenic sources of dust could be less rigorous 

because: (1) the contribution from natural undisturbed lands is likely to be high and, (2) 

at such high wind speeds many available controls would have been ineffective in 

significantly reducing wind-generated dust emissions. 

 In response to commenter feedback, the EPA has developed and added the optional

prospective controls analysis as a means of documenting existing controls and reaching 

up-front agreement as to what constitutes “reasonable” controls. In the prospective 

controls analysis, the air agency would provide information on attainment status, identify 

natural and anthropogenic windblown dust sources and emissions, provide the status of 

SIP submittals (if applicable), and identify the wind speed up to which the collective 

windblown dust controls are expected to be effective. Air agencies would submit their 
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prospective controls analysis in advance of an agency submittal and the EPA review of 

any specific demonstration submittal, with a letter of intent, or with their demonstration 

package submittal. The EPA review and approval of controls and an appropriate high 

wind threshold would also typically be effective for a minimum of three years. 

 If the EPA has approved a SIP containing wind-blown dust controls within the past three 

years, then the submitting air agency has the option of using their current, implemented 

SIP-approved controls and specifying a high wind threshold to which the controls are 

expected to be effective to constitute the set of controls that would have been reasonable 

to implement. 

 The EPA would further encourage air agencies to work with the EPA regional offices to 

develop High Wind Action Plans, which need not be incorporated into the SIP, as a way 

to develop a mutual understanding of what additional controls are reasonable to 

implement in light of foreseeable high wind conditions. Similar to a Natural Events 

Action Plan16, the optional High Wind Action Plan is a mechanism to implement 

necessary controls on newly-identified sources needing reasonable controls such that the 

EPA could consider future high wind events not reasonably controllable or preventable. 

Requests for Comments (Attachment 3) 

As part of the public comment process, the EPA is soliciting feedback on a series of 

questions that address the following topics: 

 specific, broadly applicable, streamlining mechanisms 

 available web-based information, links, tools, or methodologies 

 available sources of wind data and their applicability in informing local high wind 

thresholds 

 additional feedback and tools to convert 1-5 minute wind speed data to hourly averages 

 the anticipated use and functionality of the prospective controls analysis and the high 

wind action plan 

 technical analyses that can be used to demonstrate that the wind exceeded an identified 

high wind threshold and that the exceedance was caused by emissions that were not 

reasonably controllable 

 the utility and functionality of “Informational Only” (“I”) flags in AQS 

 characterizing “extreme” events 

 

On-line Availability of Exceptional Event Packages and Best Practice Components 

To assist air agencies in deciding what type and how much evidence/technical analysis to 

include in their demonstration packages, the EPA has developed a public website at 

http://www.epa.gov/ttn/analysis/exevents.htm that contains EPA-approved demonstration 

 

16On May 30, 1996, Mary D. Nichols, Assistant Administrator for Air and Radiation issued a memorandum to EPA 

regional offices entitled, “Areas Affected by PM10 Natural Events.” The policy, known as the PM10 Natural Events 

Policy, or simply the Natural Events Policy, set forth procedures for protecting public health through the 

development of a Natural Events Action Plan (NEAP), which implements Best Available Control Measures 

(BACM) for human-generated particulate emissions in areas that could violate the PM10 NAAQS due to natural 

events. Promulgation of the Exceptional Events Rule superseded the Natural Events Policy. 
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packages and links to best-practice components. The EPA developed this website to provide 

examples to illustrate specific points; the example analyses and level of rigor are not necessarily 

required for all demonstrations. The website will continue to evolve as agencies submit and the 

EPA reviews additional demonstration packages. 

Draft Guidance Documents Still under Development 

The EPA intends to develop a separate draft guidance document addressing the preparation 

of demonstrations to support wildfire-related event claims, including events that may have 

affected ozone concentrations. We also intend to develop a draft document that when finalized 

would replace the Interim Fire Policy and would contain additional guidance on basic smoke 

management practices for prescribed fires. The EPA has not established a schedule for 

developing these documents. We expect to provide opportunities for stakeholder input on these 

draft documents. 

Conclusion 

The EPA intends to follow the draft guidance provided in this overview document and its 

attachments during the public comment period and document finalization process, because we 

believe it is consistent with the Exceptional Events Rule and the guidance already provided in 

the preamble to the rule. Although the EPA hopes to formalize the concepts in these guidance 

documents by issuing final guidance, the EPA has not excluded the possibility of issuing rule 

revisions. The EPA is deferring a decision on whether to revise the Exceptional Events Rule. 

 

The EPA’s Office of Air Quality Planning and Standards and the EPA regional offices are 

available for assistance and consultation. Interested parties may direct comments on this 

guidance to Docket ID No. EPA-HQ-OAR-2011-0887. For guidance-related questions, please 

contact Beth W. Palma at 919-541-5432. 

Attachments: 

1. Draft Exceptional Events Rule Frequently Asked Questions 

2. Draft 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 

3. Request for Comments on the Draft Guidance Documents on the Implementation of the 

Exceptional Events Rule