Abstract: At approximately 4:00 p.m. on September 24, 1996, Employees #1 through #3 were hydroblasting a series of 1 in. diameter E-201 finned fan tubes located in the vinyl chloride monomer unit of a Georgia Gulf plaquemine plant. This was done by inserting a wand that fired water at 10,000 psi into the tubes; the water removed deposits of sludge. Employees #4 through #7 were working in close proximity to this operation. At approximately 7:00 p.m., Employee #1 left the plant, and at 1:15 a.m. on September 25, 1996, he began to experience symptoms of exposure to mustard agents. On September 27, 1996, Employees #1 through #4 were admitted to the Baton Rouge Burn Unit, where a chemical analysis revealed that the substance responsible was tris-2-chloroethylamine. Employees #5 through #8 also suffered symptoms of exposure, but were not hospitalized. It was later learned that this mustard agent was in the finned fan tubes prior to their being cleaned. A total of 148 workers--most of them involved in a scheduled turnaround at the vinyl chloride monomer unit--were exposed to this agent. Injuries ranged from second-degree burns that required hospitalization to cold-like upper respiratory problems that failed to respond to symptomatic treatment.