Abstract: An electrical contractor was hired by an industrial plant to replace and clean two switchgear enclosures. The two enclosures were located on a mezzanine above the shop floor. The site owner left the system energized to provide power to subcontractors working at the site. The electrical contractor was aware that the switchgear was energized. The contractor had racked out one circuit breaker and had cleaned the switchgear and cabinet with a vacuum provided by the site owner. After replacing the panel, he racked out the second breaker and rigged it so that it could be lowered from the mezzanine. An electrical fault occurred, and the ensuing electric arc severely burned the contractor's arms and face. He was hospitalized for his injuries. The fault was caused either by dust kicked up by a ventilating fan or by a brush used by the contractor to clean around the busbars. (The brush had a metal band holding its bristles.) After the accident, a brush with burn marks was found on the mezzanine deck next to a melted pair of safety glasses.