Abstract: At 7:40 a.m. on August 6, 2002, Employees #1 through #4, all subcontract electrians, were preparing to remove and replace a 12-kilovolt electrical bus at a public sanitation waste water treatment facility. Employee #1, a journeyman electrician and also the foreman, opened the circuit leading to the bus being removed, and locked out that system with two locks. He then instructed Employee #2 to open the back of the equipment so that they could get at the bus. Employees #1 through #3 together opened the compartment, after which Employees #2 and #3 left the area to get additional equipment. Upon their return, they observed that Employee #1 had already attached one end of a grounding strap to the cabinet. When the other end of the grounding strap contacted the 12-kilovolt circuit, there was an electrical explosion and fire ball. Seconds later, as the public electrical utility system tried to come back on line, a second explosion and fire ball occurred. Employee #1 was directly in front of both explosions and suffered third-degree burns over 90 percent of his body; he was transported to the hospital, where he died 23 days later. Employees #2 and #3, who had been watching the attachment of the grounding strap, were hospitalized with second- and third-degree burns to their faces and arms. Employee #4 and Employee #5, the safety inspector for the general contractor, were also observing the process and received minor singeing and contusions, for which they were treated and released that same day. Subsequent investigation revealed that Employee #1 apparently told Employee #2 the wrong compartment number to open so they were actually working on energized lines. Employee #1 had available a SB Touch Tester, serial #10493, which Employees #1 and #3 had checked was operating before entering the building. Employee #4 stated Employee #1 had not used it before attaching the grounding strap. After the accident, the tester was checked at a lab and found to be functioning properly.