What was found
DURING CLIMBOUT WE NOTICED A SMELL (LIKE BURNT BAGELS). NO SMOKE WAS VISIBLE. THE FLIGHT ATTENDANTS REPORTED THE SAME CONDTIONS IN THE CABIN. WE DECLARED AN EMERGENCY, COMPLIED WITH CHECKLISTS AND RETURNED TO DEN. THE CONDITIONS MAY HAVE IMPROVED SLIGHTLY WHEN WE TURNED OFF THE RECIRC FAN. COMPLIED WITH FIM 21-00 TASK 806 R&R RECIRCULATION AIR FILTER IN REF TO AMM 21-25-01, R&R R AND L COALESCER BAGS IN REF TO AMM 21-51-05, PERFORMED SUCCESSFUL ENGINE RUN IN REF TO AMM 71-00-00. NO ODORS OR DISCREPENCIES NOTED.