As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SFO - CREW REPORTED LEFT PACK FAILED WITH RIGHT PACK ON PLACARD. CAPTAIN INITIATED EMERGENCY DESCENT. NO OXYGEN MASKS WERE DEPLOYED. EMERGENCY DECLARED LANDED SFO WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED LEFT AND RIGHT AIR CYCLE MACHINE. SYSTEM GROUND CHECK NORMAL OPERATION.