What was found
(LOG 5034594) AFTER TAKEOFF FAINT SMELL OF JET FUEL IN COCKPIT. IT WAS INTERMITTENT THROUGH FLIGHT. RAN TO FULL POWER, RECIRC FILTERS NEED CHANGED + DUCTS CHECKED FOR OIL. ALSO C/W NO GO ODI PREVENTION 21-72 STEPS 1-9. NO FINDINGS ON RUN-UP/ SMELL OK. REMOVED + REPLACED BOTH RECIRC FILTERS INSPECTED DUCTING DOWNSTREAM OF BOTH ENGS PRV PER B737 MM 36-11 FOR OILING, NO OIL FOUND. INSPECTED APU DUCTING FOR OILING, PER B737 MM 49-52. NO OIL FOUND.