Abstract: At about 2:10 p.m. on March 11, 1990, Employees #1, #2, and #3 had been using electric Skilsaws to cut and remove a damaged interior vapor barrier from a 55,000 barrel crude oil tank. They had just returned from a break, during which time the coppus ventilator had been turned off. Temperatures reached the mid-80s during the day, increasing the vapor concentration within the tank. An explosion fire occurred in which Employees #1, #2, and #3 suffered second- and third-degree burns, smoke inhalation, and concussions. All three died. The model #5125 Skilsaws were not approved for use in a class I atmosphere. The owner of the tank tested the atmosphere only once per day for percent lower exposure limit and oxygen. The accident was the result of using unapproved (for the location) equipment in a potentially flammable atmosphere.