As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
COLD BLACK SMOKE OR MIST CAME OUT OF THE FLOOR VENTS AT ROWS 2 AND 3 ON BOTH SIDES OF THE AIRCRAFT. MAINTENANCE INSPECTED BELOW THE FLOOR PANELS IN THE SUSPECTED AREA AND FOUND NO DEFECTS. GROUND RAN ENGINES, WITH AIR CONDITIONING SYSTEM ON BOTH HOT AND COLD. NO DEFECTS NOTED. NO PARTS REPLACED.