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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
: Ventilation
57.22221 - Overcast and undercast construction (I-A, II-A, III, and V-A mines).
Overcasts and undercasts shall be?
(a) Of substantial construction;
(b)(1) Constructed of noncombustible materials; or
(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;
(c) Kept clear of obstructions.
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