EMPLOYEE WAS WORKING ON THE STEEL RACK ON OVERBURDEN DRILL WITH ANOTHER EMPLOYEE. 1ST EMPLOYEE WENT TO THE MECHANIC'S TRUCK AND OPENED THE DOOR ON THE COMPARTMENT THAT HELD THE TOOLBOX. HE REA CHED IN FOR A WRENCH AND A GUST OF WIND BLEW THEDOOR SHUT. THE DOOR STRUCK HIS LEFT ELBOW, FRACTURING THE BONE. HE WAS TREATED IN THE EMERGENCY ROOM AND RETURNED TO WORK.