I could see business campuses installing these on their grounds for their own personal benefit. And unlike a lot of technologies that benefit the installers locally while hurting everyone else just a little, this is a net positive to everyone. If you make them cheap and efficient, they'll start showing up by hospitals, in malls, on hotels and apartment buildings, etc, and pretty soon the air everywhere looks cleaner.
Sure, game theory would say that there's less and less benefit for future adopters as the overall air gets cleaner, but if they become a status symbol people will still install them.
I'm having trouble believing that it's nearly as effective as they say though, so it probably doesn't matter.