Where is all this coming from?

I am losing the battle with dust. The final tile has been cut, the last board sawn and nailed, and the floor sanding is done. Why then is everything covered with dust! Within hours after dusting every flat surface looks as though it hasn't been touched for a month. I might understand if we had heating ducts that would constantly recirculate the air, but we don't. Our heat is in-floor radiant. Oh, I do know where the dog hair is coming from. Don't wear black to this house!