There are various masks, alot of them cloth, and I have heard that any type will at least cut down about 50-70% of virus and other germs. But, if you need more protection, nursing someone at home who is sick with this, or if the medical personell get so desperate in a few weeks/next month they will take un-verified homemade -- well, if you have any HEPA vacuum bags or can get hold of a few, it would be good to make some of these to have on hand
Here are instructions for making a mask that comes the closest to replacing an N95 mask, so better face fit ( wire over nose) and using a filter fabric. This uses HEPA filter vacuum bags. An "insert" into a cloth mask does not work the same as you can easily end up breathing around it, those are not the same as a mask entirely made of the filter medium.
Mask pattern to cut out here:
Pictures of mask process so you dont have to keep rewatching the You tube: