What was found
FUMES - DESCENDING THRU FL190, CREW NOTICED A DIRTY SOCKS SMELL. O2 MASKS WERE DONNED AND AN EMERGENCY DECLARED. CORRECTIVE ACTION: INITIAL T/S FOUND OIL BEHIND NR 1 ENGINE SPINNER. NR 1 ENGINE FOAM WASH PERFORMED. FOLLOW UP BORESCOPE WAS GOOD. LEVEL C DECONTAMINATION PERFORMED. POST DECONTAMINATION ENGINE RUNS PERFORMED. P-TRAK RESULTS DEEMED APU AS SOURCE OF ODOR. APU BLEED DEFERRED TO MEL. INSPECTED APU COMPARTMENT FOUND CLEAN NO SIGN OF FLUID LEAKING PER AMM 49-00-00. LATER, REPLACED NR 1 ENGINE. A/C RTS. (LP 7995595, 8319604 - AIRCRAFT WAS GROUNDED)