As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER ENGINE START AND PACK BROUGHT ON LINE, CABIN AND COCKPIT RAPIDLY FILLED WITH SMOKE. THE CAPTAIN SHUT AIRCRAFT DOWN AND DEPLANED NORMALLY AT THE GATE. ATLANTA MAINTENANCE REMOVED AND REPLACED THE PRESSURE REGULATING SHUT OFF VALVE. OPERATIONAL CHECKS WERE GOOD. AIRCRAFT RETURNED TO SERVICE. (M)