Abstract: On April 17, 1990, Employees #1 and #2 were removing a 10,000 gallon underground storage tank (UST) that previously contained gasoline. The UST was 10 feet in diameter and 17 feet 3 inches long. One 251 cubic ft cylinder of nitrogen had been used to inert the tank. An explosimeter gas monitor had been used at least once to monitor the interior of the UST. Around 3:45 p.m., Employee #2 held an air eductor against one of the tank's top openings. Employee #1, using a gasoline-powered saw, began to cut a shot window in one end of the UST. When the saw blade pierced the UST shell, a fire and explosion occurred. One end of the UST blew out, striking and killing Employee #1. Employee #2 was burned on his right arm. The company did not have procedures for inerting and/or purging tanks before hot work was done. The explosimeter was not calibrated according to the manufacturer's recommendation. The employees were not trained on the fire and explosion hazards of USTs, how to use and interpret explosimeters, and how to inert and/or purge USTs.