I have a Riccar vacuum cleaner. It does a pretty good job. But dang, it's expensive to have it serviced or buy parts/filters from the local store.

One of the filters it has needs to be replaced. I ordered one, but now I'm thinking I could easily make the next one. It's just about 2"x3" at most. It's a soft material that has crushed charcoal in it. I'm sure I'd have to find the right kind of material to use.......or just cut this one open and re-fill it, then sew it back up. (I just thought of that last possibility). This is the filter that keeps the yukky smells from your vacuum from being blown back out into your air.
Anyone make their own? I couldn't make my own HEPA bags or the other intake filter, but I could do this one.

Speaking of filters..........I just saw a You Tube video of a guy who bought a cheap-ish furnace filter and taped it to the front of a box fan to have a home-made air filter. He had a particulate matter meter and this system brought down gunk in the air 90%. I think I'll try that.