What was found
FLT 545, ISP-PBI. LEVEL 2 FUMES EVENT ON DESCENT START AS A MILD DIRTY SOCK SMELL THEN AS A ALT GOT LOWER AND PACKS WHERE ON HP VALVES IN SWITCH TO A STRONG DIRTY SOCK SMELL BOTH PACKS TRIED TOO ISOLATE WHICH PACK BUT SEEMS TO BE BOTH PACKS O2 MASK WERE USED ; PERFORMED INSPECTION PER TSM 05-50-00-810-831-A. NO ACTIVE HYDRAULIC OR APU OIL LEAKS NOTED. COMPLIED W/ INFO NOTICE 2017-T015, STEPS 1 AND 2. IDENTIFIED ODOR TYPE 5 - PACK 1. DECONTAMINATION LEVEL A WAS C/W PER AMM 21-00-00-615-802. AND REPLACED RECIRC FILTERS IAW AMM 21-21-41.