As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - CREW REPORTED ELECTRICAL/PLASTIC ODOR IN CABIN. EMERGENCY DECLARED FLIGHT RETURNED DFW LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED LEFT AND RIGHT PRESSURE REGULATING AND SHUT-OFF VALVES. SYSTEM GROUND CHECK NORMAL OPERATION.