As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APPROACHING FL180 CREW STARTED SMELLING FUMES IN THE COCKPIT AS FLIGHT ATTENDANTS REPORTED A BURNING SMELL GETTING STRONGER AT THE BACK OF THE CABIN. TURNED OFF RECIRCULATION FAN. RETURNED TO DFW AND LANDED WITHOUT INCIDENT. PERFORMED AIR CONDITIONING PACK BURN OUT AND REPLACED COALESCER BAGS. SYSTEM GROUND CHECKED NORMAL OPERATION.