What was found
ON DESCENT, FLIGHT ATTENDANT RELEASED HALON EXTINGUISHER IN AFT LAV DUE TO LIGHT HAZE/SMOKE AND HEAT. EMERGENCY PROCEDURES WERE PUT INTO EFFECT. SMOKE/HEAT HAD DISSIPATED ON LANDING. RAN ENGINES AND APU. CHECKED AFT FWD LAV FOR SIGNS OF SMOKE, ELECTRICAL SMELL NONE NOTED. CHECKED LAV WATER HEATER, OPEN UP PANEL IN AFT PIT AND CHECK APU DUCTING FOR POSSIBLE LEAK, NONE NOTED. REPLACED BOTH THE LEFT AND RIGHT PACK OZONE FILTERS. RAN PACKS FOR FIVE HOURS. ALSO RAN GALLEY CHILLERS, OVENS, COFFEEPOT, HEATERS AND COFFEEMAKERS. CHECKED THE HOT WATER HEATERS UNDER SINK CHECKED GOOD. UNABLE TO POSITIVELY IDENTIFY HAZE/SMOKE/HEAT SOURCE.