30 C.F.R. § 57.6403 Branch circuits.
Title 30 - Mineral Resources
(a) If electric blasting includes the use of branch circuits, each branch shall be equipped with a safety switch or equivalent method to isolate the circuits to be used. (b) At least one safety switch or equivalent method of protection shall be located outside the blast area and shall be in the open position until persons are withdrawn.
Title 30: Mineral Resources
PART 57—SAFETY AND HEALTH STANDARDS—UNDERGROUND METAL AND NONMETAL MINES
Subpart E—Explosives
Electric Blasting—Surface and Underground
§ 57.6403 Branch circuits.