In college, I encountered a list of improvised filters that could be used to guard against inhaling radioactive contamination. I haven’t been able to find that list, but here’s something from the Wall Street Journal: Will homemade filters protect against the coronavirus?
A coronavirus particle is about 0.12 microns, or an eight millionth of a meter. Different materials have been tested for their ability to screen out virus particles.
- Furnace filters — 98%
- Automotive filter — 95%
- Vacuum bag — 90%
- Swiffer dry sweeping cloth (five layers) 60%
- T-shirt fabric (five layers) 60%
- Bed sheets (five layers) 50%
- Paper towels (five layers) 40%
- Coffee filters (two layers) 10%