I'm sure this topic has been hit on many times, but I know opinions change. So, I have an opportunity to buy a very expensive Nikken air purifier. My son is 7 months with CF and even though he has no lung issues, I want to make sure our home is clean. They some the air inside homes is often more polluted than the outside, so I really want to get it right while he is young and healthy. Any opinions on air purifiers in general, or this one specifically?