[DantesKite]

I once saw a video of someone attaching one of those HEPA filters to a box fan with tape and it works more or less just as decently.

Alternatively, have you done maintenance on your air ventilation system in your house? They should have HEPA filters as well. That should help.

You can also do a mold test. A simple one is leaving a cup of water near a wall and wait a couple days to see if mold grows on it from a free-floating spore.

[WalterGR]

> I once saw a video

There have been several submissions of (various? or the same?) DIY air filters.

The trick to finding them on hn.algolia.com appears to be to use 'air purifier' rather 'air filter' (which kind of suggests that they're submissions about the same one):

https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...

Or using Google site search (the trick here being to search for "points by" to limit results to the toplevel submissions (and incidentally submissions with not exactly 1 point :)): https://www.google.com/search?q=site%3Anews.ycombinator.com+... - «site:news.ycombinator.com fan filter "points by"»

[muzani]

I tried doing the DIY HEPA filter because I was poor. It's not much better than just buying a cheap filter that's basically the two put together. It was okay but not too effective.

Getting rid of moss cleared up most of the trouble. And antihistamine (Vitamin E) shots.