Abstract: At 3:20 p.m. on April 21, 1993, Employee #1 was using a Quadco-Wisconsin gas-powered concrete cutting machine, engine number W4-1770, to cut a concrete floor around an underground tank #17 in compounding room #2. The cutting machine hit a vent pipe 6 in. below the floor and flammable vapors of toluene that had been in the tank exploded. Employee #1 suffered severe burns over 85 percent of his body and was taken to San Bernadino County Medical Center. On April 28, 1993, he was airlifted to Sherman Oaks Medical Center, where he died at 7:00 a.m. on May 4, 1993. Employee #1 had worked at his position for three years, and was by himself at the job site. His employer had not visited the site prior to the accident. Openings on the manway of the underground tank had not been properly secured, allowing flammable vapors to escape.