As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: DURING THE ARRIVAL INTO DCA BOTH PILOTS AND FLIGHT ATTENDANT SMELLED AN ELECTRICAL BURING SMELL. NO ELECTRONIC CENTRALIZED AIRCRAFT MONITOR. DISCOVERED CIRCRUIT BREAKER W18 (RECIRCULATING FAN SUPPLY) POPPED. SMELL QUICKLY DISSIPATED. REMOVED AND REPLACED RIGHT HAND CABIN RECIRCULATION FAN PER AMM 21-21-51.