Mean penetration profile as a function of aerodynamic particle diameter for the material of seven fabric masks with an internal layer to augment filtration.

Note, the penetration range is 0 to 100%. Multi-layer material systems included: i) cotton/electret furnace filter/cotton, ii) cotton/procedure mask/cotton, iii) cotton/electret filter membrane/cotton, iv) cotton/quilt batting/cotton, v) cotton/polypropylene shopping bag/cotton, vi) cotton/polypropylene craft 1/cotton, and vii) cotton/polypropylene craft 2/cotton.