EMPLOYEE WAS CLEARING A PLUG IN THE PRE-HEATER BUILDING THROUGH A POKE HOLE. HE WAS NOT WEARING THE PROTECTIVE COAT, FACE SHIELD & USING A SHORT AIR LANCE. THESE ITEMS WERE AVAILABLE FOR USE. HOT FEED BLEW OUT THE POKE HOLE & CAUSED SECOND DEGREE BURNS ON ARMS, BACK & FACE.