Abstract: At approximately 8:00 a.m. on January 20, 1997, Employee #1 and a coworker, both asbestos field technicians for CST Environmental, were working on the roof of a vacant 25 ft tall building in Lakewood, CA. The house was being demolished and first had to undergo asbestos removal. On the previous afternoon, the coworker had cut a 38 in. square hole in the roof to install a chute, covering it with a 3/4 in. piece of plywood cut to the appropriate size and held in place with a sandbag. He also erected two, 5 ft tall scaffold sections on opposite sides of the hole; the remaining sides had crossbraces tied to the scaffold sections. On the morning of January 20, the coworker removed the sandbag and asked Employee #1, who had not seen the hole preparations the previous day, to remove the cover. He picked up the plywood and walked straight into the hole. Employee #1 was transported to Long Beach Memorial Medical Center. When the DOSH compliance officer visited him in the hospital, he was not able to talk and he did not seem to remember things. Causal factors in this accident include (1) the hole opening not being guarded by a standard railing and the cover not being well-secured and clearly labeled OPENING--DO NOT REMOVE; and (2) failure to use approved safety belts and lanyards. The supervisor who had been overseeing operations at the site, was on the ground at the time of the accident.