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Green Book

Ozone Designation and Classification Information


Nonattainment: Any area that does not meet (or that contributes to ambient air quality in a nearby area that does not meet) the national primary or secondary ambient air quality standard for a NAAQS.
 
Attainment: Any area (other than an area identified in clause (i)) that meets the national primary or secondary ambient air quality standard for a NAAQS.
 

8-Hour Ozone (2015 Standard) Classifications

Extreme
Area has a design value of 0.163 ppm and above.
Severe-17
Area has a design value of 0.111 up to but not including 0.163 ppm
Severe-15
Area has a design value of 0.105 up to but not including 0.111 ppm
Serious
Area has a design value of 0.093 up to but not including 0.105 ppm.
Moderate
Area has a design value of 0.081 up to but not including 0.093 ppm.
Marginal
Area has a design value of 0.071 up to but not including 0.081 ppm.

8-Hour Ozone (2008 Standard) Classifications

Extreme
Area has a design value of 0.175 ppm and above.
Severe 17
Area has a design value of 0.119 up to but not including 0.175 ppm
Severe 15
Area has a design value of 0.113 up to but not including 0.119 ppm
Serious
Area has a design value of 0.100 up to but not including 0.113 ppm.
Moderate
Area has a design value of 0.086 up to but not including 0.100 ppm.
Marginal
Area has a design value of 0.076 up to but not including 0.086 ppm.

8-Hour Ozone (1997 Standard) Classifications

Extreme
Area has a design value of 0.187 ppm and above.
Severe 17
Area has a design value of 0.127 up to but not including 0.187 ppm
Severe 15
Area has a design value of 0.120 up to but not including 0.127 ppm
Serious
Area has a design value of 0.107 up to but not including 0.120 ppm.
Moderate
Area has a design value of 0.092 up to but not including 0.107 ppm.
Marginal
Area has a design value of 0.085 up to but not including 0.092 ppm.

1-Hour Ozone (1979 Standard) Classifications

Extreme
Area has a design value of 0.280 ppm and above.
Severe 17
Area has a design value of 0.190 up to 0.280 ppm and has 17 years to attain.
Severe 15
Area has a design value of 0.180 up to 0.190 ppm and has 15 years to attain.
Serious
Area has a design value of 0.160 up to 0.180 ppm.
Moderate
Area has a design value of 0.138 up to 0.160 ppm.
Marginal
Area has a design value of 0.121 up to 0.138 ppm.
Submarginal
Kansas City was the only area classified submarginal, but it has been redesignated attainment. This category includes areas that violate the Ozone standard and have a design value of less than 0.121 parts per million. This occurs when there is not a complete set of data so that the estimated design value is higher than the Ozone standard exceedance rate of 1.0 per year even though the estimated design value is less than the level of the standard.
Section 185A (Previously called Transitional)
An area designated as an Ozone nonattainment area as of the date of enactment of the Clean Air Act Amendments of 1990 has not violated the national primary ambient air quality standard for Ozone for the 36-month period commencing on January 1, 1987, and ending on December 31, 1989. Twelve areas were classified transitional in 1991.  
See: Section 185A of the Clean Air Act
Incomplete (or No) Data
An area designated as an Ozone nonattainment area as of the date of enactment of the Clean Air Act Amendments of 1990 and did not have sufficient data to determine if it is meeting or is not meeting the Ozone standard.
See: Section 181 of the Clean Air Act