It can be more complicated, yes. I assert that it usually isn't. You don't spend time worrying as much about what the contaminants are, you just drive them to

It can be more complicated, yes. I assert that it usually isn't. You don't spend time worrying as much about what the contaminants are, you just drive them to zero. I grant the point that you don't want to just stir up the air. Which is why you don't just run a fan, necessarily.