
DIY face masks with nylon stocking on top can work better than surgical masks - gregwebs
https://www.medrxiv.org/content/10.1101/2020.04.17.20069567v1
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gregwebs
> As has been previously observed by Cooper et al. (1983), adding a layer of
> nylon stocking over the masks minimized the flow of air around the edges of
> the masks and improved particle filtration efficiency for all masks,
> including all commercial products tested. Use of a nylon stocking overlayer
> brought the particle filtration efficiency for five of the ten fabric masks
> above the 3M surgical mask baseline.

> When compared to commercial baseline masks, the addition of the stocking
> layer improved particle removal efficiency of many masks to match or exceed
> the baseline; the masks that achieved this level of filtration using the
> stocking layer each included a filter layer (organic cotton batting, Pellon,
> or loosely-woven cotton muslin) in addition to two layers of cotton fabric.

I think we now have a basic recipe for producing good home-made masks!

Also, some sewers did tests with the same machines used in this article. Their
design claimed 50% efficiency without any filtration media. Adding filtration
media achieved up to 87%, equivalent to the best results in this study, by
using particular brands of blue shop towels. I think their good results are
because their design also emphasizes creating a better seal to the face.
[https://suayla.com/pages/suay-community-mask-
coalition](https://suayla.com/pages/suay-community-mask-coalition)

