Clean Air. We all crave cleaner air. Most everyone has some form of sinus troubles or allergies. Even our pets do these days. Winter is bad enough when the windows are shut, and recirculated air is blowing dust around. but then again, open windows in the summer, invite pollen to enter our home. Why most people go for central Air, to keep those Micro invaders from entering our space. The big question here is, which air purifier do I use? The choice is mainly between, the Ionic type and the Hepa type.  Ionic Purifier have been the rage for some time now, because it is very quiet, vs the circulating fan of a air filter type, and no expensive filters to replace, just wipe clean the metal plates. Yes, the air you breath will be cleaner however the particles do not always end up on the plate and after being "charged", end up clinging very stubbornly to your carpet and furniture and curtains. So the immediate air might feel better, anyone, say down on the floor, like your pets and tiny children are getting bombarded! Every time you sit on your furniture you are surrounded by the particles, even more so densely than before. Who has time to sweep carpets, furniture and drapery several times a day? Plus, Ionic purifier do not remove very well, gases, chemical and odors. One major manufacturer of Ionic Purifiers was involved in a class action law suit, after testing their purifier, that it infact recirculate dirty patches of air, and air quality was very little improved. Ozone generators, another new air filtration idea, has proved to be extremely hazardous to allergy sufferers and those with asthma. Hepa air purifiers can remove irritants like dust, smoke, chemicals, asbestos, pollen, and pet dander. Now there is a difference between Hepa LIKE-Type and True Hepa. Not all filters are alike. If you do not wish to waste your money and not achieve the air quality of your goal, look for the TRUE  HEPA, words on the label. There are even IQ purifiers that combine Hepa technology with an ultra violet light that kills Viruses and Bacteria! Before you shop for one, be sure to know the size of your room. If you feel you cannot afford one large one or have a central enough location for it, buy two smaller units that will be adequate for that room. This will also help to save money, as in the evening, you can then relocate these smaller units into your and your children's bedroom for comfortable night breathing. Remember to also change you furnace and AC filter regularly. Be sure to check with your manufacturer to see if these units can "handle" a Hepa replacement filter. Some heating and cooling  systems do not have the powerful draw needed to run with these tightly woven filters. My husband and I were tired of the sinus attacks in the evenings, and my poor dog was a mess with allergies. The vet was blaming it on her food and we were popping too many sinus pills. We decided to go the Hepa air purifiers.In just two days, we noticed a huge difference, and our dog was much more comfortable, and uncongested.  Yes, fan noise can be a nuisance, I usually run them on high when I am not in the room, and then turn on low when we are in the room. At night however, the "white noise" does help drown out any outside racket. My only problem with the Fan driven True Hepa systems, are the "breeze" it makes. It can be a bit chilly in winter. I try to locate them away from chairs. There are many great deals on air Purifiers on Ebay. I hope this info helps you and your family,  2 and 4 legged, feel better, I know we are!