An employee was blasting angles inside the cargo tank on the upper level of a scaffold. A 6-inch pipe approximately 24 inches above the scaffold deck was running horizontally behind him. During the process, he stepped backwards, lost his balance and fell backwards over the pipe as pressure remained on the hose. His legs went in the air during the fall the blaster blasted his right leg below the knee. The employee suffered a deep laceration and injection injury to his lower right leg.