Our friends at the Asthma and Allergy Foundation of America (AAFA) have a nice website that among other things, explores air filters. It correctly communicates that the HEALTH benefits of using an air cleaner are of a dubious nature; that there are conflicting viewpoints and studies out there. But then, the website goes on to quote that the EPA recommends air filtration.

 

It also compares various methods for air cleaning. In particular, an air cleaner installed with the heating and cooling system has the advantages of using: 

" the great force with which air will pass through the filter. And it eliminates a space-consuming appliance and an additional sound in your home. On the other hand, the filters may be more expensive and more difficult to handle; and they may need to be changed more often. Consult your doctor and your heating service on this alternative to a portable system. Applying the already-existing fan"

 

One note to clarify; these whole-house systems, once installed,  are typically LESS difficult to handle and need to be changed LESS often than portable room air cleaners. And yes, the filters are more expensive than 1" filters you buy at the hardware store. But you only change them once every 1 or 2 years. You can get two of them for about sixty bucks online. So its $15 - $30 a year for a filter.

They also provide the added benefits of keeping your expensive heating/cooling system cleaner and running more efficiently.

Back to the HEALTH benefit - it's totally true that the jury is still out on that as it relates to air cleaners. It's also totally true that high efficiency air cleaners installed in your HVAC system capture alot more crap than any portable device or regular furnace filter. Just look at a dirty filter coming out of one some time. All that crap is airborne before it's trapped in the filter.

It's also totally true that I know allergy sufferers who swear by them.