Fresh air is vital. We can't waste it. But you need clean air in the place where you spend the most time, right? If that place is on top of a mountain, well, good for you. But if that place is in your home, you need your home air to be as fresh as an eagle's cry at the cusp of a golden dawn. SKREEEEEEE! That's your air after you run it through an HEPA purifier like this one.