PROPER SAFETY PROCEDURES WERE FOLLOWED AND THE HYDRAULIC SYSTEM WAS DEPRESSURIZED PRIOR TO REMOVING TWO HYDRAULIC HOSES. THE FIRST HOSE WAS REMOVED WITH NO PROBLEM. HOWEVER THE SECOND HOSE HAD AN UNKNOWN INTERNAL BLOCKAGE HOLDING HIGH PRESSURE IN IT. THIS WAS UNKNOWN AND UNSUSPECTED TO THE PERSON REMOVING THE HOSE. WHEN FASTENER WAS LOOSENED, HYDRAULIC OIL SPRAY IN FACE CUTTING LIP