As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EN ROUTE FROM RMS TO DAN, THE FLIGHT CREW SENSED FUMES IN THE COCKPIT DURING CLIMB. THE FLIGHT RETURNED TO RMS FOR AN UNEVENTFUL LANDING. MAINTENANCE INSPECTED THE AIRCRAFT LOCATING A PIECE OF INSULATION LYING ON THE AIR CONDITIONING DISTRIBUTION DUCT. MAINTENANCE REMOVED THE INSULATION, PERFORMED A SUCCESSFUL OPERATIONAL CHECK ON THE AIR CONDITIOINING SYSTEM. THE AIRCRAFT WAS RETURNED TO SERVICE.