467. No person may leave a shelter to return to a blasting area before 10 minutes have elapsed since the closing of the firing circuit, where the firing has been done by electric detonators and the explosion has been heard.
Where no explosion has been heard following the firing and a defect in the electrical circuit has been observed, the circuit shall be repaired after the blaster has seen personally that the blasting line wires are short-circuited and disconnected from the power source and, where a firing switch is used, it shall be in the open position and the door of the box shall be locked.