There was an item in New Scientist, perhaps last century, of an experiment done at a hospital's ICU ( UK, iirc, the hospital had some kind of religious name, like St (somethingorother) ),
and that experiment tested whether patient-to-patient infections were affected by ionizers ( which charge the air, making particles in the air stick to surfaces, like walls, objects, whatever )...
That experiment had no effect in the control condition, but the ionizer-test condition reduced those infections down to ZERO.
No hospital with any reputation would dare use such "New Age woo", of course, no matter that evidence, combined with the Hippocratic Oath ( 1st do no harm! ), should oblige its use.
Bah.
I couldn't find much of anything through DuckDuckGo.com
and Scholar.Google.com had stuff that wasn't what I was trying to find,
and normal google had this
Anyways, according to the NO cases of inter-patient infection that was reported in the study I remember, it should have been made globally normal.
Notice that the things are called, by many, "air cleaners".
I'm disputing that air cleaners have no effect on health ( put a box-fan with a 20"-square furnace-filter on the suction-side of it, and it'll reduce the amount of dust, without any expensive products, and in some areas, in industrial or desert zones, e.g. it'll likely reduce the harm done to one's lungs by that air ), and pointing-out that different definitions of "air cleaner" are valid, though not about the same thing.