California Code of Regulations › Title 17 - Public Health › Division 3 - Air Resources › Chapter 1 - Air Resources Board › Subchapter 1.5 - Air Basins and Air Quality Standards › Article 3 - Criteria for Determining Area Designations › Appendix 1 - Criteria for Determining Data Representativeness

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
This Appendix describes the criteria to be used in
						determining the representativeness of individual air quality measurements and
						statistics for the purpose of designating areas as described in this article.
						Data representativeness, as that term is used herein, relates to the
						determination of whether the amount of data reflected in an individual air
						quality measurement or statistic is sufficient to characterize reliably air
						quality during the respective averaging time of a state standard. The criteria
						for determining data representativeness are summarized in the accompanying
						table and discussed further, below.
Air quality measurements and statistics are usually
						computed from short term observed values. If all the short term values for the
						statistical time period are available, the calculated statistic is
						representative. However, because all the short term values for a given period
						often are not available, a minimum number of observations are needed to provide
						reasonable assurance that the calculated measurement or statistic is a reliable
						estimate for the averaging time specified in the state standard.
In general, air quality measurements and statistics are
						considered representative if a minimum of 75 percent of all the potential short
						term values are included and are distributed throughout the entire statistical
						time period. This 75 percent criteria must be met from the averaging time of
						the initial measurement, up to and including, the final averaging time
						reflected by the air quality measurement or statistic. For example, a maximum
						daily statistic must meet the representativeness criteria specified for a
						"Day." Because a daily statistic reflects a single day, it does not need to
						meet the representativeness criteria for any other level (Month, Quarter, or
						Year). In evaluating data representativeness, all measurements are considered,
						including those identified as affected by a highly irregular or infrequent
						event under the "Air Resources Board Procedure for Reviewing Air Quality Data
						Possibly Affected by a Highly Irregular or Infrequent Event," set forth in
						Appendix 2 to this article.
Individual air quality measurements and statistics used
						for designating an area as attainment, nonattainment-transitional, or
						nonattainment must be representative. Furthermore, to ensure that the group of
						air quality measurements or statistics used for designating an area as
						attainment or nonattainment-transitional reflect the time of day and the season
						of expected high concentrations, these data must also be complete under the
						"Criteria for Determining Data Completeness" set forth in Appendix 3 to this
						article. In contrast, the air quality measurements or statistics used for
						designating an area as nonattainment are not required to be complete.Criteria
						for Representativeness of Air Quality Measurements and Statistics
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1.
						Amendment of first two paragraphs filed 8-20-96; operative 9-19-96 (Register
						96, No. 34).
2. Amendment of first and third paragraphs filed
						8-26-99; operative 9-25-99 (Register 99, No. 35).
3. Amendment filed
						6-7-2004; operative 7-7-2004 (Register 2004, No.
						24).