[dragontamer]

> At that point it’s like putting your shirt over your nose: looks like you are protected but there are giant gaps that let in air.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3373043/

A cut t-shirt over your nose is actually quite good, so long as the pattern is somewhat tested. No, its no where close to an N95 mask, but even aerosol sprays can be somewhat mitigated with a simple cut t-shirt.

There are some internet studies suggesting an efficacy of 70% for T-shirts against 1-micron (bacteria) and 0.02 micron (viruses) particles. That's 6x worse than an N95 mask, but much better than unprotected.

EDIT: It seems like the flu (also a 0.02 micron virus) is primarily on water-droplets 5 microns in size. So we don't actually have to reach N95 mask levels for a major amount of protection, aiming at the 5 micron sized moisture bubbles is already going to help us severely.