Abstract: At 10:06 p.m. on September 11, 2005, Employees #1, #2, and #3 were working at a steel service center where aluminum coated steel tubing is manufactured for use by the HVAC industry as heat exchangers. This manufacturing process occurs on a steel tube mill line, where rolls of aluminum coated steel strips are loaded into the mill and the edges are bent together and formed into a tube. After the strip are welded together to form the tube, aluminum is sprayed on the tube to replace the coating that was damaged during the welding process. The aluminum coating is applied by Praxair arc spray equipment, Model Number BP 400, which is contained in a steel box. The box measures approximately 2-feet long by 2-feet wide by 2-feet tall and has an exhaust system installed to remove aluminum dust particles. Employees #1, #2, and #3 were working to clean the components of the steel tube line. Employee #1 was cleaning out the spraying enclosure, while Employees #2 and #3 were changing the spools of aluminum wire on the spray gun. While they were cleaning the equipment, an explosion occurred. Employee #1 received burns on his face, arms, and chest. Employees #2 and #3, who were about 5 feet away, were burned on their arms and torso. All three employee's cloths caught fire, as well, increasing the severity of their injuries. Emergency services were contacted and the local fire department responded, finding the outdoor dust collector of the facility on fire, which they extinguished. Although the duct work was damaged, the fire did not spread to the inside of the building. Employees #1, #2, and #3 were taken to a local burn unit, where they were hospitalized and treated for their injuries. The accident investigation revealed that the explosion was caused by ignition of aluminum dust that had escaped the spraying enclosure, while Employee #1 was cleaning, and ignited the wire feeder device of the spray gun. Also, although the exhaust system was shut down during the cleaning operation, the wire feeder was not locked out. In addition, Employee #1 was using a steel scraper that was not spark resistant, to clean the steel spray box, and no provisions for dissipating static generation were used.