EPA

Office of Air Quality

Pla nnin g a nd S ta nd a rds

C Air

lean

United States Office of Air Quality EPA-454/R-98-017

Environmental Protection Planning and Standards December 1998

Agency Research Triangle Park, NC 27711

Air

GUIDELINE ON DATA HANDLING

CONVENTIONS FOR THE 8-HOUR

OZONE NAAQS
EPA-454/R-98-017

December 1998

GUIDELINE ON DATA HANDLING

CONVENTIONS FOR THE 8-HOUR

OZONE NAAQS

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Research Triangle Park, North Carolina 27711

December 1998
ii

Disclaimer

This draft has been reviewed and approved for publication by the U.S. Environmental

Protection Agency’s Office of Air Quality Planning and Standards. Mention of trade

names or commercial products are not intended to constitute endorsement or

recommendation for use. 
iii

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Data Handling Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

What monitors does this guidance cover? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

How do I compute the daily maximum 8-hour average ozone concentration? . . . . . . . . . . . 2

What is a valid ozone monitoring day? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

How many monitoring days are required? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

What is a complete data year? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Can I exclude ozone monitoring data affected by natural events such as stratospheric ozone

intrusion from computations used to determine compliance with the 

NAAQS? ................................................3

Is any credit given toward meeting the 75% minimum data completeness requirement for 

days with missing monitoring data that would have had low ozone

concentrations? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

How do I find the 4th highest daily maximum 8-hour average ozone concentration at an 

ambient air quality monitoring site? . . . . . . . . . . . . . . . . . . . . . . . . . . 4

How many significant figures must I carry in the computations? . . . . . . . . . . . . . . . . . . . . . 4

What is the attainment test? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

What is the minimum number of years of data needed to demonstrate attainment with the 

8-hour ozone NAAQS? .....................................4

How do I compute the average annual 4th highest 8-hour daily maximum ozone 

concentration at an ambient air quality monitoring site? . . . . . . . . . . 4

What is the ozone air quality design value? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

What if only 1 or 2 years of data are available at the site? ..........................5

How do I judge the air quality status of ozone monitoring sites that have stopped 

monitoring? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

What if 3 years of ozone monitoring data are available but some years do not meet the data

completeness requirements? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

How do I judge the air quality status of an area that has more than one ozone monitoring 

site? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

How do I compute the area’s design value? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Appendix I to 40CFR, Part 50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1

Guideline on Data Handling Conventions for the 8-Hour Ozone

National Ambient Air Quality Standard (NAAQS)

Introduction

This guideline covers the data handling and ambient air quality monitoring data

completeness requirements for the 8-hour ozone NAAQS as given in Appendix I. As background

for the discussion that follows, the 8-hour primary and secondary ambient ozone air quality

standards (40CFR50.10) are:

(a) The level of the national 8-hour primary and secondary ambient air quality

standards for ozone, measured by a reference method based on Appendix D to this

part and designated in accordance with part 53 of this chapter, is 0.08 parts per

million (ppm), daily maximum 8-hour average. 

(b) The 8-hour primary and secondary ozone ambient air quality standards are met

at an ambient air quality monitoring site when the average of the annual

fourth-highest daily maximum 8-hour average ozone concentration is less than or

equal to 0.08 ppm, as determined in accordance with Appendix I to this part.

For completeness, the full text of Appendix I (40CFR50.10, Appendix I) is provided as an

attachment to this guideline. This guideline uses the ‘plain English’ question and answer (Q & A)

format to present the data handling and data completeness issues of concern.

Data Handling Conventions

Q: What monitors does this guidance cover?

This guidance on data handling and data completeness requirements of the 8-hour ozone

NAAQS is intended for all ozone monitors that are designated as either National Air

Monitoring Stations (NAMS) or State and Local Air Monitoring Stations (SLAMS). All

NAMS and SLAMS sites must meet uniform monitor siting and quality assurance

requirements established in the monitoring regulations (40CFR58). This guidance also

applies to all other ozone monitoring sites, including special purpose monitors (SPM), 

that have recorded at least three years of ambient ozone data and meet all the monitoring

and quality assurance requirements for NAMS and SLAMS. 
2

Q: How do I compute the daily maximum 8-hour average ozone concentration?

The new Aerometric Information Retrieval System (AIRS) will do this computation for

you. First, running 8-hour averages are computed from the hourly ozone concentration

data for each hour of the year and the result is stored in the first, or start, hour of the

8-hour period. In the event that only 6 (or 7) hourly averages are available, the 8-hour

average is computed using 6 (or 7) as the divisor. Generally, if fewer than 6 hours of

ozone concentration data are available, then the 8-hour daily maximum concentration for

the day is assigned the value of ‘ missing.’ However, just because we are missing more

than 2 hours of monitoring data, we do not want to ignore 8-hour concentrations that

clearly exceed the level of the standard. When more than 2 hours of monitoring data are

missing, we compute the 8-hour average concentration by substituting one-half the

minimum detectable limit for the missing hourly concentrations and using 8 as the divisor. 

In this case, if the computed 8-hour average concentration is greater than 0.08 ppm, it is

retained, otherwise the 8-hour concentration for this 8-hour period is assigned the value of 

‘missing.’ In all cases, the computed 8-hour average ozone concentration is reported in

parts per million (ppm) to three decimal places (the insignificant digits to the right of the

third decimal place are truncated). 

Q: What is a valid ozone monitoring day?

An ozone monitoring day is counted as a valid ozone monitoring day if 8-hour averages

are available for at least 18 of the 24 possible 8-hour average periods that start within the

day, or the daily maximum 8-hour average concentration for the day is greater than 0.08

ppm. The new AIRS automatically computes the number of valid ozone monitoring days.

Q: How many monitoring days are required?

Ozone monitoring seasons vary by state. The designated ozone monitoring seasons for

the National Air Monitoring Stations (NAMS) and State and Local Air Monitoring

Stations (SLAMS) are listed in the ambient monitoring rule (40CFR58, Appendix D) and

are also included in AIRS. These same ozone seasons are used to compute the data

completeness requirements for special purpose monitors (SPM) used to demonstrate

compliance with the standard. 

Q: What is a complete data year?

For the purpose of judging compliance with the standard, a valid year must have valid 8-

hour daily maximum ozone concentrations for at least 75 percent (74.5 % rounds up) of

the required monitoring days in the ozone season designated for NAMS or SLAMS

monitoring sites. All three years must average at least 90 percent data completeness
3

(89.5% rounds up) to demonstrate attainment. 

Q: Can I exclude ozone monitoring data affected by natural events such as

stratospheric ozone intrusion from computations used to determine compliance with the

NAAQS?

Yes, monitoring data affected by natural events, such as stratospheric ozone intrusion, can

be excluded when determining compliance with the 8-hour ozone NAAQS under certain

conditions. One of these conditions is that the requesting agency must document that this

rare natural event had a significant impact on ozone levels and must submit the request to

the appropriate EPA Regional Office. Another is that the decision to exclude or make

adjustments to the monitoring data affected by stratospheric ozone intrusion, or other

exceptional natural events, is subject to the approval of the appropriate Regional

Administrator. Upon EPA Regional Office concurrence, the data must be appropriately

flagged in AIRS as an exceptional event if the annual 4th highest daily maximum

concentration is to be computed correctly. In the case of stratospheric ozone intrusion,

although this event is exceptional, the circumstances or the criteria under which it occurs

are difficult to measure and document given generally available meteorological data. 

Stratospheric ozone intrusions are infrequent and very localized events of short duration,

and this fact makes it difficult to use currently available airport meteorological data to

determine whether a stratospheric ozone intrusion has occurred. Therefore, determining

whether a stratospheric ozone intrusion, or any other natural event, has significantly

affected measured ozone concentrations should be a case-by-case decision based on

reasonable judgment regarding the season of the year, time of day, and accompanying

meteorological conditions associated with the ozone measurement in question. (see EPA,

1986)

Q: Is any credit given toward meeting the 75% minimum data completeness

requirement for days with missing monitoring data that would have had low ozone

concentrations?

Yes, days with missing monitoring data may be counted toward meeting the minimum 75

percent data completeness requirement, but only if there is no clear pattern to the timing

of the missing measurements and the missing measurements can be assumed to be less

than the level of the NAAQS. Meteorological data, or ambient measurements from nearby

monitoring sites, may be sufficient to demonstrate that missing ozone data at a particular

monitoring location would not likely have exceeded the level of the standard. For

example, if you can demonstrate that meteorological conditions on days with missing

ozone measurements at a site were not conducive to concentrations above the level of the

ozone standard, then you may be able to count the day toward meeting the minimum data

completeness requirements. The demonstration must follow EPA guidance on the use of

statistical analyses of air quality and meteorological data (EPA, 1998) and the results of
4

the analyses must be submitted to the appropriate Regional Administrator for approval. 

Once approved, days with missing monitoring data that are assumed to be less than the

level of the NAAQS must be appropriately flagged in AIRS to ensure that the percent data

completeness calculations are computed correctly.

Q: How do I find the 4th highest daily maximum 8-hour average ozone concentration

at an ambient air quality monitoring site?

The simplest way is to look at the annual 4th highest 8-hour daily maximum ozone

concentration in a standard AIRS summary report. Otherwise, you simply rank the 8-hour

daily maximum ozone concentrations from highest to lowest and identify the 4th highest

value. 

Q: How many significant figures must I carry in the computations?

Three. The remaining right-most digits are truncated. The units for all computations are

parts per million (ppm). AIRS sets this automatically when it computes the daily

maximum 8-hour concentrations and for all subsequent computations.

Q: What is the attainment test?

The 8-hour primary and secondary ozone ambient air quality standards are met at an

ambient air quality monitoring site when the 3-year average of the annual fourth-highest

daily maximum 8-hour average ozone concentration is less than or equal to 0.08 ppm (i.e.,

the site is said to be in attainment). Because the third decimal digit, in ppm, is rounded,

0.084 ppm is the largest concentration that is less than, or equal to, 0.08 ppm.

Q: What is the minimum number of years of data needed to demonstrate attainment

with the 8-hour ozone NAAQS?

Three complete years of ozone monitoring data are required to demonstrate attainment at

a monitoring site.

Q: How do I compute the average annual 4th highest 8-hour daily maximum ozone

concentration at an ambient air quality monitoring site?

The average annual 4th highest 8-hour daily maximum concentration is simply the average

of the annual 4th highest 8-hour daily maximum concentrations from each of the last 3

years. For example,
5

Year Valid Days (ppm)

Percent 8-hour Daily Maximum Concentrations

1st 2nd 3rd 4th

1993 100% 0.092 0.091 0.090 0.089

1994 96% 0.090 0.089 0.086 0.084

1995 98% 0.087 0.085 0.083 0.081

the average annual 4th maximum ozone concentration is,

Avg 4th max = (0.089 + 0.084 + 0.081)/3 = 0.08466... = 0.084 ppm

which rounds to 0.08 ppm and the site meets the standard.

Q: What is the ozone air quality design value?

For a concentration-based standard, the air quality design value for a site is defined as the

standard-related test statistic. Thus, the 3-year average annual fourth-highest daily

maximum 8-hour average ozone concentration (e.g., the 0.084 ppm value calculated in the

previous question) is the air quality design value for a site.

Q: What if only 1 or 2 years of data are available at the site?

If only 2 years of data are available at a NAMS or SLAMS monitoring site that is still

operating, then you must wait until the 3rd year of data is available before you can

determine the air quality status of this monitoring site. Because the form of the standard is

an average concentration, the air quality status of a monitoring site cannot be determined

using only one year of ambient data. Monitoring sites with only 1 or 2 years of data that

indicate a potential to violate the ozone NAAQS should continue to operate so that their

air quality status can be determined based on three complete years of data.

Q: How do I judge the air quality status of ozone monitoring sites that have stopped

monitoring?

The appropriate EPA Regional Office must be notified prior to shutting down a NAMS
6

site, or a SLAMS site that has exceeded the level of the ozone NAAQS. The air quality

status at a NAMS or SLAMS site that has stopped monitoring after two years must be

handled on a case by case basis. Factors to consider are the reasons that the site stopped

monitoring, the magnitude of the ozone concentrations measured, and the likelihood that

additional monitoring data may be available in future years.

Q: What if 3 years of ozone monitoring data are available but some years do not meet

the data completeness requirements?

While three complete years of ozone monitoring data are required to demonstrate

attainment at a monitoring site, fewer than 3 complete years of data may be sufficient to

demonstrate nonattainment. Incomplete data may not be used to excuse a clear

nonattainment situation. In a year with missing monitoring data, the true annual 4th

highest 8-hour daily maximum concentration will always be at least as high, or higher, than

the observed annual 4th highest daily maximum 8-hour average ozone concentration. 

Thus, calendar years with less than 75% data completeness must be included in the

attainment analysis computation if the 3-year average of the annual fourth highest daily

maximum 8-hour average ozone concentration is greater than 0.08 ppm. For example,

Year Valid Days (ppm)

Percent 8-hour Daily Maximum Ozone Concentrations

1st 2nd 3rd 4th

1993 96% 0.105 0.103 0.103 0.102

1994 74% 0.090 0.085 0.082 0.080

1995 89% 0.103 0.101 1.101 0.097

the 3-year average annual 4th highest daily maximum 8-hour ozone concentration is,

Avg 4th max = (0.102 + 0.080 + 0.097)/3 = 0.093 ppm

which rounds to 0.09 ppm and the site has failed the attainment test, even though the

1994 ozone monitoring data do not meet the 75% data completeness requirement.
7

Q: How do I judge the air quality status of an area that has more than one ozone

monitoring site?

The data handling procedures described in this guidance are applied on an individual basis

at each monitor in the area. An area is in compliance with the 8-hour ozone NAAQS if,

and only if, every monitoring site in the area meets the NAAQS. 

Q: How do I compute the area’s design value?

The air quality design value for a site is the 3-year average annual fourth-highest daily

maximum 8-hour average ozone concentration. The air quality design value for the area is

the highest design value among all sites in the area.

References

1. “Guideline on the Identification and Use of Air Quality Data Affected by Exceptional Events”,

EPA-450/4-86-007, U.S. Environmental Protection Agency, Research Triangle Park, N.C., July

1986.

2. “Guideline on Accounting for Missing Data to Meet the Data Completeness Requirements of

the 8-Hour Ozone NAAQS”, U.S. Environmental Protection Agency, Research Triangle Park,

N.C., in preparation.
8

Appendix I to 40CFR, Part 50

Interpretation of the 8-Hour Primary and Secondary National

Ambient Air Quality Standards for Ozone
9

Appendix I to Part 50--Interpretation of the 8-Hour standard.) The computed 8-hour average ozone

Primary and Secondary National Ambient Air concentrations shall be reported to three decimal

Quality Standards for Ozone places (the insignificant digits to the right of the

 1. General. data handling procedures for the reported data.) 

 This appendix explains the data handling

conventions and computations necessary for 2.1.2 Daily maximum 8-hour average

determining whether the national 8-hour primary and concentrations.

secondary ambient air quality standards for ozone (a) There are 24 possible running 8-hour average

specified in Sec. 50.10 are met at an ambient ozone ozone concentrations for each calendar day during

air quality monitoring site. Ozone is measured in the the ozone monitoring season. (Ozone monitoring

ambient air by a reference method based on seasons vary by geographic location as designated in

Appendix D of this part. Data reporting, data part 58, Appendix D to this chapter.) The daily

handling, and computation procedures to be used in maximum 8-hour concentration for a given calendar

making comparisons between reported ozone day is the highest of the 24 possible 8-hour average

concentrations and the level of the ozone standard concentrations computed for that day. This process

are specified in the following sections. Whether to is repeated, yielding a daily maximum 8-hour

exclude, retain, or make adjustments to the data average ozone concentration for each calendar day

affected by stratospheric ozone intrusion or other with ambient ozone monitoring data. Because the

natural events is subject to the approval of the 8-hour averages are recorded in the start hour, the

appropriate Regional Administrator. daily maximum 8-hour concentrations from two

 2. Primary and Secondary Ambient Air Quality concentrations in common. Generally, overlapping

Standards for Ozone. daily maximum 8-hour averages are not likely,

 2.1 Data Reporting and Handling Conventions. less pronounced diurnal variation in hourly

 2.1.1 Computing 8-hour averages. Hourly average (b) An ozone monitoring day shall be counted as

concentrations shall be reported in parts per million a valid day if valid 8-hour averages are available for

(ppm) to the third decimal place, with additional at least 75% of possible hours in the day (i.e., at

digits to the right being truncated. Running 8-hour least 18 of the 24 averages). In the event that less

averages shall be computed from the hourly ozone than 75% of the 8-hour averages are available, a day

concentration data for each hour of the year and the shall also be counted as a valid day if the daily

result shall be stored in the first, or start, hour of the maximum 8-hour average concentration for that day

8-hour period. An 8-hour average shall be is greater than the level of the ambient standard.

considered valid if at least 75% of the hourly

averages for the 8-hour period are available. In the 2.2 Primary and Secondary Standard-related

event that only 6 (or 7) hourly averages are Summary Statistic.

available, the 8-hour average shall be computed on

the basis of the hours available using 6 (or 7) as the The standard-related summary statistic is the

divisor. (8-hour periods with three or more missing annual fourth-highest daily maximum 8-hour ozone

hours shall not be ignored if, after substituting concentration, expressed in parts per million,

one-half the minimum detectable limit for the averaged over three years. The 3-year average shall

missing hourly concentrations, the 8-hour average be computed using the three most recent, consecutive

concentration is greater than the level of the calendar years of monitoring data meeting the data

third decimal place are truncated, consistent with the

consecutive days may have some hourly

except in those non-urban monitoring locations with

concentrations. 
10

completeness requirements described in this level of the standard shall not be ignored on the

appendix. The computed 3-year average of the ground that they have less than complete data. Thus,

annual fourth-highest daily maximum 8-hour in computing the 3-year average fourth maximum

average ozone concentrations shall be expressed to concentration, calendar years with less than 75%

three decimal places (the remaining digits to the right data completeness shall be included in the

are truncated.) computation if the average annual fourth maximum

 8-hour concentration is greater than the level of the

 2.3 Comparisons with the Primary and Secondary standard.

Ozone Standards. (d) Comparisons with the primary and secondary

 (a) The primary and secondary ozone ambient air 2 in paragraphs (d)(1) and (d) (2) respectively as

quality standards are met at an ambient air quality follows:

monitoring site when the 3-year average of the

annual fourth-highest daily maximum 8-hour (1) As shown in example 1, the primary and

average ozone concentration is less than or equal to secondary standards are met at this monitoring site

0.08 ppm. The number of significant figures in the because the 3-year average of the annual

level of the standard dictates the rounding fourth-highest daily maximum 8-hour average ozone

convention for comparing the computed 3-year concentrations (i.e., 0.084 ppm) is less than or equal

average annual fourth-highest daily maximum to 0.08 ppm. The data completeness requirement is

8-hour average ozone concentration with the level of also met because the average percent of days with

the standard. The third decimal place of the valid ambient monitoring data is greater than 90%,

computed value is rounded, with values equal to or and no single year has less than 75% data

greater than 5 rounding up. Thus, a computed 3-year completeness.

average ozone concentration of 0.085 ppm is the

smallest value that is greater than 0.08 ppm.

 (b) This comparison shall be based on three

consecutive, complete calendar years of air quality

monitoring data. This requirement is met for the

three year period at a monitoring site if daily

maximum 8-hour average concentrations are

available for at least 90%, on average, of the days

during the designated ozone monitoring season, with

a minimum data completeness in any one year of at

least 75% of the designated sampling days. When

computing whether the minimum data completeness

requirements have been met, meteorological or

ambient data may be sufficient to demonstrate that

meteorological conditions on missing days were not

conducive to concentrations above the level of the

standard. Missing days assumed less than the level

of the standard are counted for the purpose of

meeting the data completeness requirement, subject

to the approval of the appropriate Regional

Administrator.

 (c) Years with concentrations greater than the

ozone standards are demonstrated by examples 1 and
11

Example 1. Ambient monitoring site attaining the primary and secondary O standards. 3

Year Percent 1st 2nd Highest 3rd Highest 4th Highest 5th Highest

Valid Days Highest Daily Max Daily Max Daily Max Daily Max

Daily Max 8-hour 8-hour 8-hour 8-hour

8-hour Conc. Conc. Conc. Conc.

Conc. (ppm) (ppm) (ppm) (ppm)

(ppm)

1993 100% 0.092 0.091 0.090 0.088 0.085

1994 96% 0.090 0.089 0.086 0.084 0.080

1995 98% 0.087 0.085 0.083 0.080 0.075

Average 98% 0.084

 (2) As shown in example 2, the primary and than 0.08 ppm. Note that the ozone concentration

secondary standards are not met at this monitoring data for 1994 is used in these computations, even

site because the 3-year average of the fourth-highest though the data capture is less than 75%, because the

daily maximum 8-hour average ozone concentrations average fourth-highest daily maximum 8-hour

(i.e., 0.093 ppm) is greater average concentration is greater than 0.08 ppm.

Example 2. Ambient monitoring site failing to meet the primary and secondary O standards. 3

Year Percent 1st 2nd Highest 3rd Highest 4th Highest 5th Highest

Valid Days Highest Daily Max Daily Max Daily Max Daily Max

Daily Max 8-hour 8-hour 8-hour 8-hour

8-hour Conc. Conc. Conc. Conc.

Conc. (ppm) (ppm) (ppm) (ppm)

(ppm)

1993 96% 0.105 0.103 0.103 0.102 0.102

1994 74% 0.090 0.085 0.082 0.080 0.078

1995 98% 0.103 0.101 0.101 0.097 0.095

Average 89% 0.093
12

 3. Design Values for Primary and Secondary

Ambient Air Quality Standards for Ozone.

 The air quality design value at a monitoring site is

defined as that concentration that when reduced to

the level of the standard ensures that the site meets

the standard. For a concentration-based standard,

the air quality design value is simply the

standard-related test statistic. Thus, for the primary

and secondary ozone standards, the 3-year average

annual fourth-highest daily maximum 8-hour

average ozone concentration is also the air quality

design value for the site.
TECHNICAL REPORT DATA

(Please read Instructions on reverse before completing)

1. REPORT NO. 2. 3. RECIPIENT'S ACCESSION NO.

 EPA-454/R-98-017

4. TITLE AND SUBTITLE 5. REPORT DATE

Guideline on Data handling Conventions for the 8-Hour Ozone December 1998

NAAQS

 6. PERFORMING ORGANIZATION CODE

7. AUTHOR(S) 8. PERFORMING ORGANIZATION REPORT NO.

 Warren P. Freas

 

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT NO.

 Air Quality Trends Analysis Group (MD-14)

 U.S. Environmental Protection Agency

 Office of Air Quality Planning and Standards

 Research Triangle Park, NC 27711

11. CONTRACT/GRANT NO.

 

12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED

 Director

 Office of Air Quality Planning and Standards

 Office of Air and Radiation

 U.S. Environmental Protection Agency

 Research Triangle Park, NC 27711

14. SPONSORING AGENCY CODE

EPA/200/04

15. SUPPLEMENTARY NOTES

Document is available electronically at “http://www.epa.gov/ttn/oarpg/”

16. ABSTRACT

This report provides technical guidance on the data handling conventions for the 8-hour ozone National

Ambient Air Quality Standards (NAAQS). The report is written in the “plain English” question and answer

(Q&A) style. The following data handling issues are addressed:

1) Rounding conventions

2) Missing data

3) Treatment of exceptional natural events

4) Data completeness requirements for computing averages

5) Minimum years of data required to demonstrate compliance with the NAAQS

6) Use of data from Special Purpose Monitors (SPM)

7) The attainment test used to judge compliance with the NAAQS

17. KEY WORDS AND DOCUMENT ANALYSIS

a. DESCRIPTORS b. IDENTIFIERS/OPEN ENDED TERMS c. COSATI Field/Group

 Ozone Compliance Air Pollution Control

 Ozone Standard 

 Ambient Air Quality Standards (NAAQS) 

18. DISTRIBUTION STATEMENT 21. NO. OF PAGES

 Release Unlimited

19. SECURITY CLASS (Report)

 Unclassified 16

20. SECURITY CLASS (Page)

 Unclassified

22. PRICE

EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION IS OBSOLETE