I really hate that medically-certified HEPA filters are my only choice for cleaning the air.
Every time I try to google and search, I get blog and web articles that say, "air purifiers that use water aren't as effective as HEPA filters." Which is great and I'm sure it's true, but for my purposes inside my own home I don't care about catching viruses, bacteria, or even VOCs out of the air. I don't even care about funky smells. I JUST want an air filter that will scrub out particulates like dust, pollen, mold.
I really don't like having to use up and discard medically-certified HEPA filters for that purpose. It's wasteful. I do not need medical-grade air. I just want cleaner air.
And I've seen a Rainbow vacuum in use, so I know from experience that it's theoretically possible to make an air filter that filters the air through water, but all of the consumer products that I can find simply do not look like serious products intended to clean the air. They look like essential oil diffusers.