EMPLOYEE WAS USING AIR PRESSURE TO CLEAN OUT DRILL HOLES. MUCK BLEW OUT OF DRILL HOLE AND HIT ENMPLOYEE IN THE FACE, WITH SOME MATERIAL GOING UNDER SAFETY GLASSES INTO EMPLOYEE'S EYES. NO IMME DIATE DISCOMFORT NOTICED. LATER IN THE EVENING, HIS EYE BECAME VERY IRRITATED. EMPLOYEE WENT TO E.R. AND A SMALL PIECE OF PARTICLE DUST WAS REMOVED. ANTIBIOTIC DROPS PRESCRIBED.