What was found
SECOND HALF OF FLT NOTICED AN ACCRID OR SMELLY GYM SOCKS WITH PACKS ON. NO SMOKE PRESENT. PER CREW ODOR CONTINOUS WITH APU RUNNING & IN FLIGHT DECK, REF TSM 05-50-810-831-A. APU NEEDS INSPECTION IAW AMM 49-00-00-200-816. NOTED BY MAINT. NO PRIOR HISTORY. INSPECTED APU AREA IAW AMM 49-00-00-200-816. RAN BOTH PACKS ON HIGH FOR A SIGNIFICANT PERIOD. COULD NOT DUPLICATE ANY ODOR. SATISFIED AND AMM REF 05-51-10-200-801-C1. R & R TWO RECIRCULATING FILTERS (4012HM , 4013HM) IAW AMM 21-21-41-400-001-A.