Abstract: Employee #1 and a coworker, both iron workers, were positioning steel rebar mats at the northeast wall of a stairway vault. They climbed down the rebar mat structure beside the floor without incident. After this mat was positioned, the two employees began to again descend the rebar mat structure toward the first level. Employee #1 was positioned over the stairwell to the basement when for some reason he fell. He dropped 20 feet through the stairwell to the concrete basement floor, fracturing his neck. An emergency medical crew responded and administered CPR prior to transporting the employee by ambulance to a local hospital. He died 36 days later at this same hospital.