Both of these previous answers are simply untrue!
For the ultimate in air filtration, a true HEPA filter (one that passes all of the air in the house through it by installing inline to your HVAC system) is the best choice. It uses the type of filtration technology required in hospitals and operating rooms. HEPA filters are the most efficient mechanical filters for removing small particles which can be breathed deep into the lungs. HEPA filters have a 99.97% efficiency for particle sizes all the way down to 0.30 microns.
The vast majority of the odor and unhealthy particles in the air are smaller than 5 microns, and these smaller ones are generally more detrimental to your health, so it’s important to remove those by using devices like a HEPA filter
When talking about odors, almost all major odors in a house are 0.30 microns and above. These contaminants include:
Pollen, mold, plant spores 7 - 70 microns
Dust mites 3 - 10 microns
Hairspray 3 - 10 microns
Large bacteria 1 - 20 microns
Auto emissions 1 - 3 microns
Lead dust 1 - 3 microns
Fungal spores 0.50 - 7 microns
Cooking smoke/odors 0.30 - 1 microns
Paint pigments 0.30 - 1 microns
Pet dander 0.15 - 8 microns
Small bacteria 0.08 - 1 microns
Tobacco smoke 0.008 - 0.6 microns
So as you can see, The HEPA filter removes almost all of the major casues of odors in a house.
As far as "Ionic Air Cleaners," you need to know recent studies Studies by the scientiﬁc community and a leading consumer publication have demonstrated that these devices do a poor job of ﬁltering and cleaning the air, and even worse, they can generate possibly unhealthy levels of ozone!
Independent studies have shown that ionizing air cleaners are not effective in cleaning the air and improving indoor air quality. Despite the manufacturer’s claims, all the models tested received ratings of “Poor” for removal of
dust, smoke and pollen. The ionization process (which generates ozone) is often touted as the key to removing indoor air contaminants. There is considerable scientiﬁc evidence that demonstrates that ozone has little potential to remove contaminants at concentrations that do not exceed public health standards. These units also lack the ability to move adequate amounts of air for thorough ﬁltration.
While the ozone layer in the upper atmosphere is beneﬁcial and protects us from harmful ultraviolet rays, at ground level, ozone is an irritant that can cause decreased lung function and aggravate asthma. In fact, the EPA refers to ozone as “Good up high— bad nearby”.
Ozone is a toxic gas with vastly different chemical and toxicological properties from oxygen. At ground level it has another common name you may know: smog! Independent tests have conﬁrmed that ionizing air cleaners can produce levels of ozone 5-10 times higher than public health limits!!
Based on the available scientiﬁc evidence and independent reports in noted consumer publications, the ability of these devices to clean air is very low, and much less effective than other ﬁltration products on the market today. Further, the potential health risks associated with the high levels or ozone generated make these products questionable at best, and possibly even detrimental to human health. The American Lung Association suggests that ozone generators should not be used.