Create your own face mask to protect yourself, protect your community, and learn about sewing! This is called the Olson Mask, and it was designed by a hospital system in Cedar Rapids, Iowa.
This mask was originally designed to help supply hospitals with surgical masks in case they were unable to purchase commercially-produced masks. With that in mind, they are NOT AS GOOD as purchased masks, but a whole lot better than nothing at all. You can use these yourself when you need to go out in public, and you can add filter material to the pocket to make it even better.
Sewing Instructions and Pattern (PDF)
The YouTube video mentions several possibilities for filter materials; the best materials block particles down to 0.3 microns.