Abstract: Three maintenance workers were replacing a circuit breaker on a 480-volt, 800-ampere circuit. The job had been scheduled for a Sunday, with all equipment shut down. However, no one called the electric utility to deenergize the service drop from the utility pole. The crew was aware that the circuit was still energized, but decided to perform the job anyway. The two employees who were performing the work were standing on a wooden pallet for insulation from ground. Neither of them was wearing rubber insulating gloves or eye protection. They disconnected the load-side conductors and pulled the circuit breaker out of the panelboard while it was still attached to the energized supply-side conductors. As they were removing the screws for the supply-side conductors, they caused an electrical fault. The ensuing electric arc seriously burned all three employees, killing one of them and hospitalizing the other two.