Abstract: On July 21, 2005, Employee #1 was demolishing a stairway between a basement-level garage and the first floor of a three-story building owned by the Port of Los Angeles. The concrete on the steel steps of the stair had been removed the day before. On the day of the accident, the steel portion of the stair, including a 6-ft by 10-ft first floor landing, was torch-cut. The first floor slab already had an opening approximately 22 ft by 13.5 ft with guard rails protecting a portion of the opening. A segment of the stair between first floor and basement was suspended from a crane, ready to be lowered to the basement. A supervisor, who was cutting steel with an oxy-acetylene torch, asked Employee #1 to use a pneumatic hammer to loosen/dislodge the concrete in the southwest corner of the stair landing. While Employee #1 was standing in a semi-kneeling position and leaning forward to begin that operation, the suspended stair segment unexpectedly swung away from him. Employee #1 then lost his balance and fell off the unguarded edge of the floor opening, 11 ft 4 in. to the basement floor. He was hospitalized at Little Company of Mary Hospital for a compression fracture of his L3 vertebra. Employee #1 was not using personal fall arrest/restraint equipment.