As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR VALVE STUCK IN OPEN POSITION CAUSING FULL HOT AIR TO CABIN. SMOKE STARTED TO FLOW INTO CABIN AFTER TAKEOFF. AIRCRAFT RETURNED TO AIRPORT WITHOUT INCIDENT. MAINTENANCE CLEANED VALVES AND OPS CHECKED OK. BOTH BYPASS VALVES WILL BE REPLACED.