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Electronic Code of Federal Regulations
Title 40: Protection of Environment
§50.10 National 8-hour primary and secondary ambient air quality standards for ozone.
(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.
(c) The 1997 ozone NAAQS set forth in paragraph (a) of this section will no longer apply to an area for transportation conformity purposes 1 year after the effective date of the designation of the area for the 2008 ozone NAAQS pursuant to section 107 of the CAA. The 1997 ozone NAAQS set forth in this section will continue to remain applicable to all areas for all other purposes notwithstanding the promulgation of the 2008 ozone NAAQS under §50.15 or the designation of areas for the 2008 ozone NAAQS. Area designations and classifications with respect to the 1997 ozone NAAQS are codified in 40 CFR part 81.
[62 FR 38894, July 18, 1997, as amended at 77 FR 30170, May 21, 2012]