What was found
SMOKE IN THE CABIN AFTER TAKE OFF, MOST CONCENTRATED IN AREA OF ROW 5, FOLLOWED COM AND ISOLATED THE SOURCE TO BE PACK 2 AIR SUPPLY. DECLARED AN EMERGENCY AND RETURNED TO PEK AND LANDING WAS UNEVENTFUL. INSPECTED CABIN OVERHEAD CEILING AREA, LIGHTING BALLAST, IN FLIGHT ENTERTAINMENT SYSTEM, PACK VALVES, APU AND ENGINE FOR OIL LEAK AND THE HP VALVE AND HYDRAULIC LINE THAT HAD JUST BEEN REPLACED, NO DISCREPANCIES FOUND. THE 4 FORWARD RECIRCULATION FILTERS WERE REPLACED AND RAN THE ENGINES AND COULD NOT DUPLICATE DISCREPANCY. SUBSEQUENT MX REPLACED THE OZONE CONVERTER.