As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: FORWARD LAVATORY SMOKE DETECTOR ALARMED FOR ABOUT 10 SEC IN CRUISE. NO SIGN OF SMOKE. THERE APPEARS TO BE EXCESSIVE DUST BUILD UP ON THE DETECTOR. MAINTENANCE CLEANED FORWARD LAVATORY DETECTOR FILTER SCREEN AND ACCOMPLISHED A SATISFACTORY OPERATIONAL TEST PER AMM 26-17-00.