EMPLOYEES HAD REMOVED 3 DOOR SECTIONS FROM THE TOP OF THE BAGHOUSE IN PREPARATION TO PERFORM MAINTENANCE. ONE DOOR SECTION WAS PLACED VERTICALLY AGAINST A HANDRAIL AND NOT TIED DOWN. A WIND GUST BLEW AGAINST THE DOOR CAUSING IT TO FALL, INJURING THE EMPLOYEE. MEDICAL CARE WAS GIVEN AND DIAGNOSIS WAS CERVICAL STRAIN TO NECK. EMPLOYEE RETURNED TO MODIFIED DUTY STATUS ON 4/14.