What was found
CREW REPORTED THE AIRCRAFT RETURNED TO GATE FOR ODOR COMING FROM AIR CONDITIONING IT SEEMS. ODOR WAS ISOLATED TO APU. THE NEXT DAY DURING FLIGHT 1649 (DCA TO TPA), FLIGHT ATTENDANT REPORTED AN ODOR IN CABIN DURING DESCENT BETWEEN APPROXIMATELY 16,000 FEET AND 8,000 FEET. FLIGHT ATTENDANT DESCRIBED ODOR AS SMELLING LIKE "SCORCHED DEICING FLUID". MAINTENANCE PLACED NR 1 PACK ON MEL 21-52-01A AND INSPECTED AIRCRAFT AND FOUND SAFE FOR MAINTENANCE FERRY FLIGHT FROM TPA TO CLT. MAINTENANCE REMOVED AND REPLACED THE APU. OPS CHECK GOOD. NO LEAKS NOTED. DECONTAMINATION OF THE ENVIRONMENTAL CONTROL SYSTEM. NO ODOR NOTED. ALSO, REPLACED LEFT AND RIGHT CABIN AIR FILTER PER AMM 21-21-41.