30 C.F.R. § 57.22205 Doors on main fans (I-A, II-A, III, and V-A mines).
Title 30 - Mineral Resources
In mines ventilated by multiple main fans, each main fan installation shall be equipped with noncombustible doors. Such doors shall automatically close to prevent air reversal through the fan. The doors shall be located so that they are not in direct line with explosive forces which could come out of the mine.
Title 30: Mineral Resources
PART 57—SAFETY AND HEALTH STANDARDS—UNDERGROUND METAL AND NONMETAL MINES
Subpart T—Safety Standards for Methane in Metal and Nonmetal Mines
Ventilation
§ 57.22205 Doors on main fans (I-A, II-A, III, and V-A mines).
