As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ACM SEIZED AND SENT SMOKE INTO THE CABIN, CAPTAIN'S RESPONSE WAS TO SHUT OFF BOTH PACKS, SMOKE DISSIPATED. RETURNED TO BWI AFTER DECLARING AN EMERGENCY. CONFIRMED ACM WAS CAUSE OF SMOKE AND PLACED ITEM ON MEL 80007. PACK NOT USABLE. REMOVED AND REPLACED ACM.