As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - CREW REPORTED STRONG BURNING RUBBER SMELL THROUGHOUT CABIN DURING TAKEOFF AND LIGHT SMOKE IN REAR CABIN. EMERGENCY DECLARED FLIGHT RETURNED DFW LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED BOTH AIR CONDITIONING PRESSURE REGULATOR VALVES. SYSTEM GROUND CHECK NORMAL OPERATION.