30 CFR § 57.6402
Deenergized circuits near detonators.
Electrical distribution circuits within 50 feet of electric detonators at the
blast site shall be deenergized. Such circuits need not be deenergized between
25 to 50 feet of the electric detonators if stray current tests, conducted as
frequently as necessary, indicate a maximum stray current of less than 0.05
amperes through a 1-ohm resistor as measured at the blast site.
[58 FR 69596, Dec. 30, 1993]