As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, UNABLE TO PRESSURIZE AIRCRAFT. CONTINUED TO ATL AT LOWER ALTITUDE AND DECLARED AN EMERGENCY. FOUND LEFT PACK CONDITIONED AIR CHECK VALVE FLEXIBLE SLEEVE DAMAGED. REPLACED SAME. OPS CHECK GOOD. (LOG 8313806 - AIRCRAFT WAS GROUNDED).