Abstract: At approximately 10:05 p.m. on July 29, 1993, a fitting connecting flexible hose to a make-up tank (st-1) broke, releasing what was initially reported to be hydrogen chloride, although it was subsequently determined that other materials such as chloroform, hydrogen fluoride, antimony, and lithium were also in the tank. Employee #1 had been working in the general area and was overcome by the release on the way to the freon administrative/control building. Employee #2 went to check on the release and also was overcome on his way to the administrative/control building. Employee #3 was overcome by a vapor cloud as he entered the maintenance shop to obtain ppe. Employees #4, #5, and #6 responded to the release in chemical suits and were sent to the hospital due to heat stress from working in the encapsulated suits.