My daughter moved in to a fairly new apartment with heat & air that comes from an electrical unit at the front of the apartment. The unit is similar to something you would see in a hotel room. There is black soot that is on her things. When you rub your finger through it it smears. Does anyone know what could be causing this? It doesn't appear to be regular dust.

Is she burning allot of candles without trimming the wick first?

Could it be drawing it in from the outside? Does it have filters? It is possible the soot is so fine it is going through the filters.

My daughter moved in to a fairly new apartment with heat & air that comes from an electrical unit at the front of the apartment. The unit is similar to something you would see in a hotel room. There is black soot that is on her things. When you rub your finger through it it smears. Does anyone know what could be causing this? It doesn't appear to be regular dust.
She is not burning candles, I had that same thought.

Somehow tape a white cover over the incoming air from the furnace/air conditioner run it for a few minutes and then look to see if you see any of the soot on the white cover, this does not mean it is coming from the outside but at least it will let her know if she needs a better filter.