AS EMPLOYEE COMPLETED HIS WORKPLACE INSPECTION PRIOR TO ENTERING THE TUNNEL TO POWDER, HE NOTICED SCALE ON THE RIB. HE THEN ATTEMPTED TO REMOVE THE 4' BY 4' SCALE BY HAND SCALING WITH SCALING BAR. DURING THE REMOVAL OF THE SCALE, THE SCALE CAME LOOSE. AS THE SCALE FELL, IT KNOCKED THE SCALING BAR OUT OF HIS HAND AND THE SCALING BAR STRUCK THE EMPLOYEE BEHIND THE LEFT EAR.