What was found
A STINKY SOCK SMELL IN CABIN & COCKPIT WITH APU RUNNING. ACFT WAS PARKED AT GATE. TROUBLE SHOT CABIN AIR QUALITY IAW JOB CARD 26L00021001, CHECKED OK. PERFORMED JOB CARD 26L00021002, APU SMELL IN CABIN, CHECKED OK. PERFORMED DECONTAMINATION OF THE ENVIRONMENTAL CONTROL SYS IAW JOB CARD 26L00021004, CHECKED OK.