As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE ENROUTE AT 41000 FT HEAVY ACRID BLACK SMOKE THE INUNDATED CABIN. OXYGEN MASKS WERE DEPLOYED AND AN EMERGENCY DESCENT WAS INITIATED. ACFT WAS LANDED AT THE NEAREST SUITABLE AIRPORT WITHOUT INCIDENT. ON FEB 21ST, MX IDENTIFIED THE MALFUCTION AS A OVERHEAD BLOWER FAN AND REPLACED WITH NEW FAN ASSY. THE ACFT WAS SUBSQUENTLY RETURNED TO ITS HOME BASE FOR CLEANING AND INTERIOR RESTORATION.