Air Cleaner Filter

And in that order. Those are the 3 tactics to dramatically improving the quality of the air you breathe in your home.

1. Source control. This is the "ounce of prevention" tactic. Keep the nasty stuff out to begin with. Better to not smoke than to try to rid your house (or lungs) of smoke. Dust mites thrive in carpets. Get rid of the carpet! Keep humidity levels in check so your house doesn't become a breeding ground for mold.

2. Ventilation - Air cleaners can trap a lot of particles but have a heck of a time with VOC's, or fumes that might be toxic. Nothing like opening a window for some fresh air. There are also mechanical ventilation systems that can provide controlled fresh air without significantly adding to your energy usage.

3. Air Cleaners - even larger, fan-operated room units - can take contaminants out of the air. OK THERE, I SAID IT! Use a portable air purifier! But if you decide to go this route, do your homework. There are tons of small portable purifiers that just don't work at all. Use a larger room air cleaner; one with a fan and a high efficiency HEPA filter - as high efficiency as you can find - But don't expect it to work in more than one room. It's just like a portable room fan. It's only going to circulate air in one room. It can't work through walls.

If you have a forced air heating/cooling system with ductwork, you can install a whole-house unit and every time your blower runs, you're cleaning your air. Every room that has return air ducts is being cleaned.