EMPLOYEE WAS WORKING APPROXIMATELY 3 FEET FROM THE GROUND ON A LADDER. HE WAS ATTEMPTING TO UNPLUG AN AIRSLIDE. WHEN THE MATERIAL BEGAN TO FLOW, HE WAS OVERCOME BY DUST AND IN AN EFFORT TO GET AWAY, HE JUMPED DOWN AND AWAY FROM THE LADDER. IN DOING SO, HE STRUCK HIS UPPER BODY AGAINST SOME WATER PIPES.