{"data":{"id":"us/30-cfr-57.22221","jurisdiction":"us","citation":"30 CFR 57.22221","heading":"Overcast and undercast construction (I-A, II-A, III, and V-A mines).","body":"Overcasts and undercasts shall be—\n(a) Of substantial construction;\n(b)(1) Constructed of noncombustible materials; or\n(2) Where constructed of combustible materials, the outside surfaces shall be coated with at least one inch of construction plaster containing perlite and gypsum; at least one inch of expanded vermiculite, Portland cement and limestone; or other coatings with equivalent fire resistance;\n(c) Kept clear of obstructions.","path":["Title 30—Mineral Resources","CHAPTER I—MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR","SUBCHAPTER K—METAL AND NONMETAL MINE SAFETY AND HEALTH","PART 57—SAFETY AND HEALTH STANDARDS—UNDERGROUND METAL AND NONMETAL MINES","Subpart T—Safety Standards for Methane in Metal and Nonmetal Mines"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-30.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:25:24Z","sha256":"2c80d2bce53f4887bab83694cf1e97b90fd79dde73fd99188011809a5643a3e0","source_id":"us-cfr","stale":true,"prev":"us/30-cfr-57.22220","next":"us/30-cfr-57.22222"},"notice":"GroundRules: Original legal text. Not legal advice."}