As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN CRUISE RECEIVED A LT BLEED DUCT WARNING MESSAGE THAT CHANGED TO A LT BLEED DUCT CAUTION MESSAGE. RAN THE QRH AND RECEIVED A RT BLEED DUCT WARNING MESSAGE. PERFORMED AN EMERGENCY DESCENT AND DECLARED AN EMERGENCY, RETURNED TO FIELD. (FLT 5218) FO: 06/28/2018 CLOSED REMOVED AND REPLACED CLAMP FOR TOPS DUCT OF PRECOOLER IAW AMM. OPS AND LEAK CHECKS GOOD.