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Ozone (O3) Standards -

Table of Historical Ozone NAAQS

History of the National Ambient Air Quality Standards for Ozone
During the Period 1971-2008

Final Rule/Decision Primary/ Secondary Indicator (1) Averaging Time Level (2) Form
1971

36 FR 8186
Apr 30, 1971
Primary and Secondary Total photochemical oxidants 1-hour 0.08 ppm Not to be exceeded more than one hour per year
1979

44 FR 8202
Feb 8, 1979
Primary and Secondary O3 1-hour 0.12 ppm Attainment is defined when the expected number of days per calendar year, with maximum hourly average concentration greater than 0.12 ppm, is equal to or less than 1
1993

58 FR 13008
Mar 9, 1993
EPA decided that revisions to the standards were not warranted at the time
1997

62 FR 38856
Jul 18, 1997
Primary and Secondary O3 8-hour 0.08 ppm Annual fourth-highest daily maximum 8-hr concentration, averaged over 3 years
2008

73 FR 16483
Mar 27, 2008
Primary and Secondary O3 8-hour 0.075 ppm Annual fourth-highest daily maximum 8-hr concentration, averaged over 3 years

(1) O3 = ozone

(2) Units of measure are in parts per million (ppm).

 

 

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