Those would be more similar to hot steam humidifiers, which tend to leave any minerals or impurities behind as deposits inside the machine. That said, I'm not buying the original premise here that water-soluble minerals are in inhalation hazard. Our lungs have robust systems for cleaning out stuff we inhale, it's the exceptions where this doesn't work that get a lot of attention.
If anyone else is wondering, I checked: yes, there is such a thing as an ultrasonic vape pen.
(2021) At the time (24 points, 22 comments) https://news.ycombinator.com/item?id=29559021
I wonder how steam baths, saunas etc compare.
Those would be more similar to hot steam humidifiers, which tend to leave any minerals or impurities behind as deposits inside the machine. That said, I'm not buying the original premise here that water-soluble minerals are in inhalation hazard. Our lungs have robust systems for cleaning out stuff we inhale, it's the exceptions where this doesn't work that get a lot of attention.