As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE ENROUTE AT FL190, THE PILOT SMELLED SOMETHING BURNING. THE CO-PILOT CONFIRMED. A TRACE OF SMOKE WAS NOTED IN THE COCKPIT. THE FLIGHT CREW THEN DONNED EMERGENCY EQUIPMENT. LANDED WITH NO FURTHER ISSUES. DETERMINED THE COCKPIT AIR CYCLE MACHINE HAD FAILED.