Abstract: At 7:45 am on April 5, 2001, a supervisor at a department store was installing a new switch in a 480-volt, 1600-ampere main switchboard. The employee did not want to disrupt other store employees by deenergizing the switchboard, so he decided to work it energized. The supervisor was not wearing safety glasses or a face shield, rubber insulating gloves, or a long sleeve shirt. Using a DeWALT Type 4, 18-volt dc, battery-powered drill, he began drilling and tapping holes in the energized vertical bus so that he could mount the new switch. Some of the shavings from the drill contacted an energized part and ground, causing an electrical fault. The ensuing electric arc burned the employee on his arms, hands, and face. He was hospitalized for 6 days for treatment of second-degree burns.