As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAH - DURING FLIGHT 3941 - THE CREW REPORTED A PUNGENT ODOR IN THE COCKPIT AND CABIN. THE AIRCRAFT RETURNED TO IAH WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED THE AIRCRAFT AND FOUND THE NR 1 RECIRCULATION FAN TO BE INOPERATIVE. MAINTENANCE REMOVED AND REPLACED THE AFFECTED RECIRCULATION FAN, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE. (M)