As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
COMING THROUGH 31K FEET. STRONG ODER NOTICED IN COCK PIT/CABIN. DISSIPATED GOING BACK THROUGH 31K FEET. OCCURRING INTERMITTENTLY ON DESCENT. COULD DUPLICATE ON GROUND WITH PACKS. INSPECTED RELAY AND DISTRIBUTION BOX PANELS, NO DEFECTS NOTED. R/R'D #2 RE-CIRCULATION FAN. OPS CHECKS GOOD IAW 221-24-01-04.