30 CFR Part 57Public Domain
§ 57.22217 — Seals and stoppings (I-A, I-B, and I-C mines)
Subpart T — Safety Standards for Methane in Metal and Nonmetal Mines
All seals, and those stoppings that separate main intake from main return airways, shall be of substantial construction and constructed of noncombustible materials, except that stoppings constructed of brattice materials may be used in face areas.
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.