What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Narrative: this was a flight made for pilot training with a CFI. The owner was flying the aircraft and the flight instruction area was not reached. At aprox. 900' on climb-out and on the first flight following an annual inspection the pilot noticed smoke coming into the cabin from the cabin heat inlet. He checked cabin heat secured closed and called the twr for emergency return. On the landing approach the smoke dissipated and the landing was uneventful. The investigation found the aircraft had made the flight immediately following an annual inspection. It was found a small amount of engine cleaning solvent had remained in the heat muff and had not completely drained or evaporated prior to the flight. The ground runup following the annual inspection and the ground runup prior to the flight did not produce any smoke. Only after flying speed was gained and air pressure pushed air through the heat muff did the smoke develop.
As the FAA filed it
NARRATIVE: THIS WAS A FLIGHT MADE FOR PILOT TRAINING WITH A CFI. THE OWNER WAS FLYING THE AIRCRAFT AND THE FLIGHT INSTRUCTION AREA WAS NOT REACHED. AT APROX. 900' ON CLIMB-OUT AND ON THE FIRST FLIGHT FOLLOWING AN ANNUAL INSPECTION THE PILOT NOTICED SMOKE COMING INTO THE CABIN FROM THE CABIN HEAT INLET. HE CHECKED CABIN HEAT SECURED CLOSED AND CALLED THE TWR FOR EMERGENCY RETURN. ON THE LANDING APPROACH THE SMOKE DISSIPATED AND THE LANDING WAS UNEVENTFUL. THE INVESTIGATION FOUND THE AIRCRAFT HAD MADE THE FLIGHT IMMEDIATELY FOLLOWING AN ANNUAL INSPECTION. IT WAS FOUND A SMALL AMOUNT OF ENGINE CLEANING SOLVENT HAD REMAINED IN THE HEAT MUFF AND HAD NOT COMPLETELY DRAINED OR EVAPORATED PRIOR TO THE FLIGHT. THE GROUND RUNUP FOLLOWING THE ANNUAL INSPECTION AND THE GROUND RUNUP PRIOR TO THE FLIGHT DID NOT PRODUCE ANY SMOKE. ONLY AFTER FLYING SPEED WAS GAINED AND AIR PRESSURE PUSHED AIR THROUGH THE HEAT MUFF DID THE SMOKE DEVELOP.