30 CFR Part 57Public Domain
§ 57.22221 — Overcast and undercast construction (I-A, II-A, III, and V-A mines)
Subpart T — Safety Standards for Methane in Metal and Nonmetal 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.
Public Domain: 30 CFR Part 57 (MSHA Safety and Health Standards — Underground Metal and Nonmetal Mines) is a U.S. government publication and is not subject to copyright. Text extracted from the official source ↗. Figures are served from the eCFR; if one does not load, use the link in its place.