What was found
(LP# 5147974) MUSTY ODOR DESCENDING THROUGH 1600 AND REMAINED AFTER ENGINE SHUTDOWN. ODOR WAS STRONGER ON APU POWER. COMING BACK TO JFK EVERYTHING WAS NORMAL BUT ODOR WAS PRESENT. MAINTENANCE INSPECTED APU PER NO GO ODI PREVENTION PROGRAM. NO CONTAMINATION FOUND. REPLACED RECIRC FILTERS PRECAUTIONARY. AFTER OPERATING APU, MINOR MUSTY SMELL NOTED. ISOLATED CAUSE TO APU BLEED. REMOVED AND REPLACED APU ON LP 0841315.