As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE DESCENDING THROUGH FL320, A LOUD DULL THUD WAS HEARD, FOLLOWED CLOSELY BY AN ACRID ODOR AND A GREYISH HAZE . THE HAZE AND ODOR RETURNED ON THE GROUND WITH APU POWER AND CABIN PAC SELECTED ON. INSPECTED AND FOUND THE FWD ACM LOCKED UP. REMOVED AND REPLACED WITH A REPAIRED UNIT. WORK PERFORMED IN REFERENCE TO THE MM 25-51-00. OPS CHECK GOOD. ALSO REMOVED AN REPLACED BOTH OF THE SOCKS.