Two employees were removing a 4-foot long piece of 14-inch diameter ventilation duct work, which supported a second piece of 10- to 11-foot long duct work. When the employees removed the 4-foot long piece, the 10 to 11-foot long piece fell and struck one of the employees, who suffered abdominal and intestinal injuries, a head contusion, and a fractured hip. The employee was hospitalized.