As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURNBACK, CREW SENT A CARS MESSAGE REPORTING BLOWER FAN FAULT AND FUMES IN THE COCKPIT. CAPTAIN DONNED O2 MASK AND DECLARED AN EMERGENCY. ACFT RETURNED TO DEPARTURE AND LANDED WITHOUT INCIDENT. MAINT REMOVED AND REPLACED THE AVIONICS VENT BLOWER FAN IAW MM 21-26-51. (K)