What was found
NOXIOUS ODOR IS EMANATING FROM THE AIR DUCTS. THE AIR IS DIFFICULT TO BREATHE WHILE THE PLANE IS ON THE GROUND AND WAS NOTICEABLE TO THE PASSENGER. IN THE AIR THE ODOR GOT MUCH BETTER BUT RETURNED BRIEFLY ON DECENT CLEANED WATER SEPARATORS AND BOTH COALECERS INSPECTED APU AND APU EXHAUST NO LEAKS FOUND INSPECTED ENVIROMENTAL CONTROL UNITS DUCTS NO FAULTS NOTED PERFORMED ENVIRONMENTAL CONTROL SYS DUCT BURN OUT WITH NR 1 AND 2 ENGINES AND APU SYS OPS CK GOOD NO BAD ODORS IAW AMM 21-51-00