{"data":{"id":"us/40-cfr-50.15","jurisdiction":"us","citation":"40 CFR 50.15","heading":"National primary and secondary ambient air quality standards for ozone.","body":"(a) The level of the national 8-hour primary and secondary ambient air quality standards for ozone (O3) is 0.075 parts per million (ppm), daily maximum 8-hour average, measured by a reference method based on appendix D to this part and designated in accordance with part 53 of this chapter or an equivalent method designated in accordance with part 53 of this chapter.\n(b) The 8-hour primary and secondary O3 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 O3 concentration is less than or equal to 0.075 ppm, as determined in accordance with appendix P to this part.","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER C—AIR PROGRAMS","PART 50—NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-40.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:04Z","sha256":"ae1927965986013bafe74ab4f31c08f4dc6af8b8befd0870e0d0925f0a1e6feb","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-50.14","next":"us/40-cfr-50.16"},"notice":"GroundRules: Original legal text. Not legal advice."}