Abstract: Employee #1 was assigned by his job site superintendent to relocate a roof storm drain system in a new school. The storm drain system ran down the wall, alongside and over the top of an unguarded triangular open duct chase. The chase measured 7 ft. 6 in. long on the inside wall (left side) and was 8 ft long on the outside wall (the right side) and its width varied from 5 in. wide at one end to 3 ft 3 in. wide at the far end. The employee went up to this location without fall protection and stood on top of concrete cinder blocks that measured 12 in. long by 8 in. high (standard sized blocks). One block broke, and the face of the block, which was on the duct chase side, gave way under the employee's weight. He fell into the duct chase and fell 27 ft to the 1st floor gymnasium. He sustained separated and torn muscles to his left shoulder joint and a mild closed head injury (concussion).