What was found
AIRCRAFT 5014, DESCENDING THROUGH 5K' MSL ON APPROACH, WE HAD THE DIRTY SOCK SMELL. CABIN CREW SAID THEY DID NOT SMELL ANYTHING IN THE CABIN. ENGINES WERE NORMAL FOR APPROACH, APU WAS OFF, NO INDICATIONS ON ECAM. SMELL SEEMED TO GET STRONGER AS WE DESCENDED AND AS ENGINES WERE AT IDLE. CREW DONNED THEIR OXYGEN MASKS DUE TO FUME AND EMERGENCY WAS DECLARED BY ATC. FLIGHT LANDED WITHOUT INCIDENT. CORRECTIVE ACTION: PERFORMED LEVEL B ECS DECONTAMINATION REVERSE DUCT BURN REF ERA 568923-14TR. (LP 6960250, 0779859)