Why Should I Wear a Mask?
From the popular press:
From the professional literature and health agencies:
Fabric and Filtration
Not all fabrics will filter equally well. Some fabrics are more porous, some increase in efficacy with prolonged wear. The following scientific studies give some evaluation of the comparative filtration effectiveness of fabrics in home-made masks.
Fabric isn't, of course, everything. Using a pattern that includes a pocket for an extra filter will mitigate some risk. Likewise, mask fit is remarkably important in increasing efficacy. But using the recommended fabrics as much as possible is recommended. Note, however, that a mask that is up to the highest standard of filtration may not be appropriate for someone who has breathing troubles and may inhibit use. Make choices that fit your needs.
All this aside, though, seal is as important as fabric!
Wearing a mask does not absolve one of practicing recommended vector mitigation strategies, like remaining home, maintaining distance with others, sanitizing or quarantining item brought into your space, and washing hands. Each of these practices helps to reduce risk alongside wearing a mask in public.
Who is it for?
What do you have at your disposal?
Patterns 1&2 use curvilinear seams and require piecing of individual fabric pieces. Pattern 3 is a much simpler style for production, but much less well fitting.