{"data":{"id":"us/40-cfr-51.1400","jurisdiction":"us","citation":"40 CFR 51.1400","heading":"Definitions.","body":"The following definitions apply for purposes of this subpart. Any term not defined herein shall have the meaning as defined in § 51.100.\nAttainment year means the calendar year in which the attainment year ozone season occurs.\nAttainment year ozone season means the full ozone season immediately preceding a nonattainment area's maximum attainment date.\nCAA means the Clean Air Act as codified at 42 U.S.C. 7401-7671q (2010).\nFormer attainment date means any attainment date associated with the classification under subpart 2 of part D of title I of the CAA preceding reclassification from a lower classification to a higher classification.\nFormer classification means any classification under subpart 2 of part D of title I of the CAA preceding reclassification from a lower classification to a higher classification.\nHigher classification/lower classification means for purposes of determining which classifications are higher or lower, the classifications are ranked from lowest to highest as follows: Marginal; Moderate; Serious; Severe-15; Severe-17; and Extreme.\nI/M refers to the inspection and maintenance programs for in-use vehicles required under the 1990 CAA Amendments and defined by subpart S of 40 CFR part 51.\nInitially classified means the first nonattainment classification that becomes effective for an area for a specific ozone NAAQS and does not include reclassification to another classification for that specific NAAQS.\nInitially designated means the first designation to nonattainment that becomes effective for an area for a specific ozone NAAQS.\nOzone season means for each state (or portion of a state), the ozone monitoring season as defined in 40 CFR part 58, appendix D, section 4.1(i) for that state (or portion of a state).","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER C—AIR PROGRAMS","PART 51—REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTATION PLANS","Subpart DD-Requirements for Reclassified Ozone Nonattainment Areas"],"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":"d1e500395f6379aff7d9a3326744c702a47a119f32bc6ac4420f48be1c9b8a14","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-51.1319","next":"us/40-cfr-51.1401"},"notice":"GroundRules: Original legal text. Not legal advice."}