What was found
AIRCRAFT WAS GROUNDED: AT CRUZE FL400 APPROX 1 HOUR INTO THE FLIGHT, CA AND FO VOCALIZED UNKNOWN ODOR IN FLIGHT. MAINTENANCE PERFORMED GROUND TEST OF FLIGHT DECK HUMIDIFIER, AMM 21-71-02, HAD A SLIGHT ODER. REMOVED AND REPLACED HUMIDIFIER PAD, RAN TEST-NO ODERS, REF AMM 21-71-04. C/W SOF JC 78L00021001. ODER WAS CONTAINED TO FD ONLY.