As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - CREW REPORTED FUMES AND SMOKE IN CABIN. EMERGENCY DECLARED RETURNED DFW LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED LEFT PRESSURE REGULATOR AND ACCOMPLISHED BURN OUT OF HIGH PRESSURE PNEUMATIC DUCTING. SYSTEM GROUND CHECKED NORMAL OPERATION.