I installed a HRV system in my (well insulated) house, and I love it - air quality indoors is noticeably improved.
Only downside is that there’s lots of wood burning in my particular (and densely populated) area of Europe, so I was quickly drawn into the rabbit hole of particulate matter sensors and how to automatically shut the ventilation system off when the neighbors turn on their fireplace.
And when it comes to mold, our bathroom used to have black spots on the walls after a while, but with improved ventilation it stays amazingly clean and everything dries much more quickly. Almost no condensation on surfaces like mirrors and walls anymore either.
I see that they're saying 24% of the population, not the 1-in-6 I recall reading from some other source. Also, I seem to have been wrong about the test's needed to be ordered by a doctor (except in Pennsylvania).
Also, for whatever its worth house molds (black molds) are not the same as the fungi that infect us (like candida sp.), and if you somehow did get infected with a fungus that usually isn't part of our flora (like aspergillus does), you have a very severe underlying medical condition and need medical attention immediately.
I don't believe I am infected but mold spores did 'something' and MB helps. I wasn't trying to use it for candida but it was just scraping my tongue as usual and noticing there was nothing there.
I wish there was a good intermediate class of doctor that knew about non patent medicines more besides YouTube. They're not taught "yesterday's" medicine that might have worked better.
If someone doesn't mind the winter air, I also practice the German way of airing my house too, twice a day. It's called lüften.
https://www.politico.eu/article/germanys-energy-efficiency-o...
It's super cheap, no patent, and yes I'm paid by big blue!