An R44 cabin heater was selected ON and shortly thereafter an odor followed by smoke filled the cabin. The heater was selected OFF; the aircraft returned to the departure airport.

Narrative

My student and I had just departed to begin our IFR cross country flight. We established a climb at 70 KTS direct to the first VOR at about 1 1/2 miles out from the airport. The aircraft was vibrating more than usual at a 70 KT climb attitude. This did not raise any red flags at this time because the helicopter was fully loaded with fuel. I than turned on the heater because the cabin was cold. My student and I both made a comment that there was an unusual smell coming into the cabin. About 30 seconds later; what appeared to be smoke started coming into the cabin of the helicopter. I immediately turned the heater off; took the controls; and we opened the vents to clear the cabin out. I then turned the helicopter 180 degrees back to the airport to return for a landing. By shutting off the heater and turning around the smoke cleared out of the cabin. I contacted Tower and requested to land on the numbers of 12 and back to base. Tower approved us as requested so we performed a normal approach; and taxied back to the FBO to have maintenance look at the helicopter.