Abstract: On March 3, 2003, an employee and a coworker were installing a door frame in a second floor hallway in a commercial building. The second floor was completely decked at the time. They had set up a 42-in.-high scaffold. The coworker was working on the scaffold, installing pieces of lumber using a Hitachi pneumatic nail gun, Model Number NR83A. The employee was working from the ground as a support to his coworker. The coworker was standing on the scaffold with the nail gun pointing down. The employee needed to get to the other side of the scaffold, so he walked under the scaffold. When he stood up on the other side, his hard hat came in contact with the tip of the nail gun, which fired a nail. The nail went through the hard hat. The employee was transported to UCI Medical Center in Orange County and underwent brain surgery for the puncture wound he received. He was hospitalized and in a rehabilitation center for several weeks following this accident.