A supply air terminal device (10) has a supply air chamber (12), into which fresh air is conducted from out of doors and further from it through a nozzle gap or nozzles (12a1, 12a2 . . . ) into a mixing chamber (14). The fresh supply air (L1) induces a circulated airflow (L2) from a room (H) to flow through a heat exchanger (13) into the mixing chamber (14). The combined airflow (L1+L2) combined in the device solution of the fresh supply air (L1) and the room air (L2) flow is made to flow from the mixing chamber (14) into a room space (H) or other such. The mixing chamber (14) of the supply air terminal device (10) has in the mixing chamber (14) or in connection with this in a flow passage (14′) a film element (15), preferably a film-like electric resistance.