Abstract: On April 11, 2003, Employee #1, an electrician with Adock's Electric, Alarms & Controls, LLC, had de-energized the circuit that controlled the building's HVAC system to service an individual breaker. After finishing the job, he tried to close a device known as a Pringle Switch to restore power to the circuit breakers. According to Employee #2, the Building Engineer, he and Employee #1 were discussing what the next step should be when there was an electrical arc blast. Employee #1 suffered second- and third-degree burns and was transported to Washington Hospital Center, where he later died. The Building Engineer suffered first- and second-degree burns on both hands and on his face. He was treated and released that same day. This job involved a three-phase, four-wire, 277/480-volt AC system that serviced only the perimeter HVAC system in the building. The switchboard was rated at 3,000 amps and was fused at 2,500 amps. This unit was last serviced by Adcock's Electric on August 25, 2001, according to the service decals on the unit.