30 CFR § 56.4503
Conveyor belt slippage.
Belt conveyors within confined areas where evacuation would be restricted in
the event of a fire resulting from belt-slippage shall be equipped with a
detection system capable of automatically stopping the drive pulley. A person
shall attend the belt at the drive pulley when it is necessary to operate the
conveyor while temporarily bypassing the automatic function.
For further information: See MSHA's Program Policy Manual