Smoke smells different than steam. You can also hold your hand above the pot, if it's steam, your hand will feel moist after a couple of seconds or so.

The boiling point of water is 100 C (212 F). The smoke point of most oils is above 325 F (I don't know the conversion to C off the top of my head). If your mixture is boiling and giving off steam/smoke and its around 100 C, it's steam. If it's significantly higer, it might be smoke.

Good luck.