Abstract: Employee #1, a formwork carpenter, and a coworker, were removing overhead forms in a five-story building that had twin floor openings for air handling equipment. Concrete beams ran over each opening. At the start of the day, the west opening was covered but the east opening was not. The removal crew "borrowed" two or three sheets of plywood from the west opening, placed them on the east opening, and proceeded to strip the east overhead beam. The crew then worked its way to the west end of the building. When they reached the west floor opening, they did not replace the recently removed plywood decking. Both crew members were directing their attention to the overhead ceiling. The coworker was working from a rolling scaffold while Employee #1 worked from the floor using a long 2 by 4 as a prybar. Employee #1 either stumbled or stepped into the opening, which was about 4 feet long by 18 feet in wide. He fell 30 feet to an air conditioning duct and was killed.