As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHIP 3922 -ATB/FUMES- RETURNED TO ATL DUE TO A CHEMICAL SMELL IN THE COCKPIT AND CABIN. PEFORMED BOROSCOPE OF NUMBERS 1 AND 2 HPC, NO DEFECTS NOTED. C/W ENGINE WASH OF NUMBER 1 AND 2 ENGINES PER WORK CARD 7200-1425. RAN BOTH ENGINES AT 80% FOR 5 MINS NO ODOR DETECTED. REPLACED BOTH RECIRC FILTERS PER B 737 AMM 21-15.