As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EXTREME SULPHUR FUMES IN COCKPIT AND CABIN AT FL390, BOTH PACS IN NORM, BOTH TEMP SELECT IN AUTO, ENROUTE TIME 60 MINUTES. FUMES DISIPATED DURING DESCENT. DECLARED AN EMERGENCY. NORMAL APPROACH AND LANDING. REMOVED AND REPLACED AFT ACM IAW MM 21-51-00. OPS CHECK AND LEAK CHECK GOOD.