EMPLOYEE WAS ATTEMPTING TO CLEAN CARDOX TUBE IN CARDOX ROOM UNDER #1 KILN. THE CARDOX TUBE WAS STILL PARTIALLY PRESSURIZED AND WHEN THE EMPLOYEEUSED PNEUMATIC WRENCH TO REMOVE HEAD, THE UNRELE ASED PRESSURE CAUSED THE HEAD TO COME OFF AND PULLED AT EMPLOYEE'S LEFT ARM AND TWISTED HIM AROUND.