As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DESCENDING THROUGH FL210 STRONG BURNING SMELL. NO SMOKE NOTED. SMELL LASTED ABOUT 45 SECONDS-1MINUTE. (IN COCKPIT) INSPECTED THE COCKPIT AND AVIONIC BAY FOR SMOKE SMELLING AND NO SMOKE SMELLING NOTED AT THIS TIME. FOR PRECAUTION UNDER MOC REQUEST DEFERRED RECIRCULATION FANS#1,#2 IAW MEL 21-22-1. PLACARD INSTALLED, MX PROCEDURES COMPLIED WITH AND MOC#14332 NOTIFIED.