EMP TURNED OFF VALVE ON CAUSTIC DELIVERY SYSTEM CAUSING PRESSURE TO BUILD UP BEHIND VALVE AND CAUSTIC HOSE TO BURST. EMP WAS SPRAYED WITH CAUSTIC. HE HAD ON SAFETY GLASSES BUT NOT MANDATORY FA CE SHIELD. EE WAS TAKEN TO E.R. AND HIS EYES WERE FLUSHED WITH NO APPARENT DAMAGE MAKING IT A FIRST AID CASE.