What was found
HOT PLASTIC ODOR NOTED THROUGHOUT ACFT. OVENS CHECKED AND NOT THE SOURCE. DEBRIEFED CREW, & FLIGHT ATTENDANTS, REPORTED ODOR STARTING AROUND ROW 35 , EMINATING FROM UPPER CABIN AND MOVING FORWARD UNTIL FLT CREW SMELLED IT. REPORTED ODOR WAS MORE OF A PLASTIC SMELL VERSUS ELECTRICAL INSULATION. PAX DEPLANED & NO EVIDENCE OF ODOR BY MAINTENCE. TROUBLESHOT IAW FIM TASK21-00 TASK 830. SOURCE UNKNOWN, FOUND NO FUME NOR BURNT PLASTIC SMELL. FLT CREW REPORTED THE AIRCRAFT WAS PARKED BEHIND ANOTHER AIRCRAFT RUNNING. SUSPECTED INTERMITTENT FAULT IAW FIM. R & R BOTH CABIN AIR RECIRCULATION FILTERS IAW MM 21-25-01/401.