30 CFR § 57.12006
Distribution boxes.
Distribution boxes shall be provided with a disconnecting device for each
branch circuit. Such disconnecting devices shall be equipped or designed in
such a manner that it can be determined by visual observation when such a
device is open and that the circuit is deenergized, and the distribution box
shall be labeled to show which circuit each device controls.
For more information: See MSHA'S Program Policy Manual