EMPLOYEE WAS WORKING 5' OFF GROUND LEVEL USING 10' STEP LADDER. HE WAS INSPECTING A SERIES OF THREE SHUT OFF VALVES ON A KILN FEED AIRSLIDE BY INSPECTION HATCHES. WHEN HE OPENED THE SECOND INS PECTION HATCH KILN FEED BLEW OUT CAUSING EMPLOYEE TO FALL CUTTING HIS LEFT ELBOW. KILN FEED HAD TO BE WASHED FROM RIGHT EYE AND CUT, REQUIRED 17 STAPLES.