Abstract: At approximately 1:00 p.m. on May 16, 1990, Employee #1 started welding cable tray brackets and conduit pipe supports with a Lincoln arc welder #6251. Welding was taking place on the inside wall of the building and Employee #1 was standing on top of an exhaust duct leading to the outside of the building. This exhaust duct came from a wet type dust collection machine called a Type N Roto-Clone. The duct carried aluminum fines and dust. Due to a gap in this duct, aluminum fines were dispersed into open air. Welding sparks ignited the dust and fines, which created a fireball. Employee #1 was engulfed in flames and sustained second- and third-degree burns to his legs, back, and chest. Employees #2 through #7 helped in fighting the fire and rescuing Employee #1. They were checked over at the hospital; none sustained burns. Contributing factors may have been the failure to implement and train employees on hazard communication standards and that the welding was allowed to take place where combustibles or dust concentrations created a hazard.