Not OP, but thanks for the comment! In my research for cleaner indoor air custom fan-mounted purifiers came up as a cheaper and much more effective alternative to commercial air purifiers, but I haven't seen the Airfanta before.

Regarding humidifiers, do you have any links for further reading on the pollution aspect? I assumed that the distilled water ones wouldn't pollute the air, but I'm now realising I haven't actually checked.

I guess that most of the humidifiers sold on e.g. Amazon are the types you mentioned, do you have any recommendations in terms of brands/models?