As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - FLT 5055 - SMELLED FUMES IN COCKPIT IN-FLIGHT. SMELL PERSISTED FOR TWO TO THREE MINUTES. DECLARED AN EMERGENCY AND RETURNED TO DFW. PERFORMED GROUND RUN FOR 30 MINUTES. FOUND NO SMOKE OR FUMES DURING THIS TIME WITH AIR CONDITIONING PACKS AND BLEEDS IN USE. AIRCRAFT RETURNED TO SERVICE. (X)