As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON DESCENT FUME EVENT IN COCKPIT, VERY NOTICEABLE WHEN HP VALVES OPEN. ISOLATED PACK 1 AND SMELL IMMEDIATELY WENT AWAY. -REF TSM 05-50-00-810-831-A DECISION TABLE LEAD TO APU. EXAMINED APU PER AMM 49-00-00 NO LEAKS OR DEFECTS NOTED AT THIS TIME. SECOND CAUSE IS PACK 1. REF L/P 3607976-2 FOR CORRECTIVE ACTION ON PACK 1