Abstract: On June 21,1990, Employee #1 and coworkers were installing ducts in a newly erected dust collection system. Employee #1, a journeyman sheet metal worker, was installing a piece of 17 in. by 35 in. sheet metal over an opening on the south side of the dust collector. The opening was directly behind the deck of the third catwalk and directly above an elbow in a stack for the dust collector. Employee #1 had installed the sheet metal plate from atop the stack and the top bolts on the plate from the third catwalk. He could not reach the bottom bolts, so he descended to the second catwalk. The distance between the deck of the 24 in. wide second catwalk and the bottom bolts was 13 ft 2 in. Employee #1 wanted to use a 12 ft portable metal ladder to install the bolts, but a coworker was using it to burn the flange off the opening so the sheet metal plate could be installed. Employee #1 held the ladder while the coworker completed this task. The coworker then left the catwalk to go to another task. At 12:55 p.m., Employee #1 was using the ladder to install the bottom bolts when he fell 22 ft 5 in. onto concrete slate on the ground and was killed. The 5 ft 9 in. tall, 220 lb employee had over 20 years of experience as a sheet metal worker. He had been hired for this job on June 11, 1990.