What was found
ON THE GROUND IN DFW, WHEN NR 1 PACK WAS TURNED ON USING ONLY THE APU, A VISIBLE HAZE AND FUMES WERE NOTICED IN THE COCKPIT AND LOWER GALLEY. REMOVED AND REPLACED COALESCER BAG IAW MM 21-54. RAN PACKS FOR 30 MINUTES AT VARIOUS TEMP SETTINGS, NO ODOR OR FUMES NOTED.