[sbnsd]

Here is a simple mask, no sewing, and if you have a filter to add, I think it’d easily fit in there, and at this link, it shows what each fabric’s effectiveness is:

(https://smartairfilters.com/en/blog/best-materials-make-diy-face-mask-virus/ )

https://youtu.be/hBVtkX0yJ4Y

[sbnsd]

Here’s another one with a filter compartment for those who sew:

https://www.youtube.com/watch?v=e-vIyLMgUhg

[MayflowerMadam]

This is a serious (but weird) question. I wonder how thin panty liners would work as a filter.