What was found
AT 15000 FEET ON DESCENT DIRTY SOCK SMELL ALL WAY UNTIL SHUTDOWN. FLIGHT ATTENDANT SMELLED IT. FO PUT MASK ON AS PRECAUTION. EMERGENCY DECLARED. C/A: INSPECTED. OIL PRESENT IN APU COMPARTMENT. APU DEFERRED ON LOG 8423667. C/W MSI PREVENTION 2172. A- CREW NOT AVAIL. B- C/W. C- FORM NOT COMPLETED. D- N/A. E/F - APU BELIEVED TO BE CULPRIT. NO PTRACK SPIKES DURING ENGINE RUNS. G/H - N/A. I - C/W. J/K/L - C /W. FILTERS REPLACED. REF A320 AMM 21-21-. LEVEL B CONTAMINATION REMOVAL C/W. REF AMM 21-00. AIRCRAFT WAS GROUNDED