As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMOKE ALARM SOUNDED IN RIGHT AFT LAVATORY. CREW REPORTED NO VISIBLE SMOKE, SDCU AND FDU SHOW NO FAULTS. NO OBVIOUS FAULTS LAV ELECTRIC COMPONENTS, LIGHTS OR WATER HEATER. CLEANED EXCESSIVE DUST FROM LAV VENT/SMOKE DETECTOR AREA. UNABLE TO DUPLICATE SMOKE ALARM. REMOVED AND REPLACED HOT AIR VALVE.