Abstract: Employee #1, working at a steam-powered electricity generating plant, was using a vacuum system to extract metal discs from a Stretford chemical reaction chamber, a device used to clean steam and reduce sulfur dioxide emissions. Employee #1 and two coworkers were on a 50 ft high catwalk when an explosion occurred in the reactor chamber. The explosion expelled metal discs from the chamber at high velocity; Employee #1 sustained deep lacerations when he was struck in the face. The explosion was likely caused by the ignition of dust and fine metal particles in the overpressurized reaction chamber by a static electric spark. The flame continued down the vacuum line to a collection chamber, and from there into the vacuum truck. The system was not grounded. A second possibility may have been an endothermic reaction occurred involving oxygen, the moisture from the rain, sulfur residues, and rust particles.