As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFT LAVATORY SMOKE WARNING ILLUMINATED AFTER TAKEOFF. FUMES PRESENT THROUGHOUT AIRCRAFT. REPLACED LT AND RT RECIRCULATION FAN FILTERS. REPLACED LAVATORY SMOKE DETECTOR. GROUND RAN AIRCRAFT AT SEVERAL POWER SETTINGS WITH NO LAVATORY SMOKE DETECTED OR SMELL NOTED. ACCOMPLISHED SATISFACTORY FUNCTIONAL CHECK FLIGHT. AIRCRAFT RETURNED TO SERVICE. LAVATORY RECIRCULATION FILTER PN CA01131B UNSERIALIZED. (K)