A Google search result for droplet sizes: https://www.pnas.org/content/115/10/E2386
A Google search result for effectiveness of various masks related to particle size: https://blogs.cdc.gov/niosh-science-blog/2009/10/14/n95/
People seem to have a huge misunderstanding about how viruses travel through air (which is how you get stupid memes like this[1]). There aren't isolated viruses floating around passing through spaces 1/10th of a micron or larger. They need a medium of which to travel upon (such as saliva droplets) that are much larger than the virus itself[2] (usually 5-10 microns)
1. https://starecat.com/content/wp-content/uploads/im-wearing-t...
2. https://www.npr.org/sections/goatsandsoda/2020/04/03/8256393...
Example: measles is spread airborne and the R value is > 10. Coronavirus R value is < 3
Bad ventilation and dry air keeps the airosols floating around making it easier for people to inhale them. The spread in meat factories is one example.
But a mask still can prevent a lot of airosols. While also being limited. There was research that shows a lot of air escapes above and below the mask if someone coughs or sneezes.
If you are hanging around and talking to someone at a fairly close distance, masks simply won't do anything other than visually signal distance is required to others. And, in the unlikely event someone sneezes or coughs, it probably prevents widespread contamination of the surrounding area.
The Seattle choir episode and some studies out of China in restaurant air handling systems seems to indicate the virus is airborne and can be spread to others within a fairly large area, with time and proper airflow. This will happen with or without a mask in place, in my opinion.
I'm super nervous about sharing indoor space with people I don't know, so I don't. The more time we can buy ourselves, the better the outcome.