What was found
ON CLIMB-OUT, AIRCRAFT FILLED WITH SMOKE. AIRCRAFT WAS DEPRESSURIZED AND BLEED AIR SHUT OFF. LANDING WAS UNEVENTFUL. PROBLEM COULD NOT BE DUPLICATED UNLESS AIRCONDITIONING SYSTEM WAS INTENTIONALLY OVERHEATED AND ALLOWED TO SATURATE AT WHICH POINT A HAZE WAS NOTED IN THE CABIN. THE DUCT OVERHEAT LIGHT WAS ON DURING THIS OVERHEAT CONDITION. AFTER INSPECTING THE ACM, THE AIRCRAFT WAS TEST FLOWN AND AN ADDITION 6 HOURS OF REVENUE FLIGHT, WITH NO FAULTS FOUND.