A temporary employee was on a scissor lift, using a nail gun to secure HVAC duct strapping on a steel beam. The employee shot a concrete nail through the strapping and into the beam, resulting in an arc flash that ignited the employee's clothes, the insulation, and the ducting. The employee sustained an electric shock (480 volts); he also received third-degree burns to his neck and second-degree burns to his arms, face, and the back of his head, resulting in hospitalization.