As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT FL 310 DURING CRUISE, RECEIVED A STRONG ODOR. ISOLATED THE NR 1 PACK AND FOLLOWED COM PROCEDURE. THE ODOR WENT AWAY. FLYING THROUGH MOISTURE AT THE TIME. THEN DURING DESCENT, THE ODOR RETURNED ON THE NR 2 PACK ONLY THROUGH FL200. DONNED OXYGEN MASKS AND CONTINUED FOR LANDING.