Abstract: Employees #1, #2, #3 and #4 were working for a subcontractor in a chemical plant. They were working on a scaffold, fitting pipe, directly above a chemical tank where phosphorus tri-chloride was being transferred. A chemical spill occurred when a chemical operator transferred phosphorus tri-chloride from one chemical tank to another. A low point drain valve on the second tank was open allowing the spilled phosphorus tri-chloride to react with ground water. This reaction formed hydrochloric acid vapor and also causing an explosion. Employees #1, #2, #3 and #4 were exposed to chemical vapor and suffered from lung irritation. Employees #1, #2, #3 and #4 required medical assistance and were examined and evaluated by paramedics on site. Employee #3 was hospitalized. The other employees were treated but not hospitalized. The subcontracting employer of did not provide escape respirators or a written emergency procedures covering use of such respirators. (This accident is the same as #000674101.)