Mask Material --Think Out of the Box: How about HEPA Home Air Conditioning Unit Filters?

[KY_EnviroGuy]

19. No. Not proven fit for purpose.

We should not be suggesting or recommending any material or product for other people's protection against contracting a potentially fatal disease unless it has been approved and tested under the Federal code linked here:

42 CFR Part 84 Respiratory Protective Devices: https://www.ecfr.gov/cgi-bin/retrieveECFR?gp=&SID=c9c15fd462ffe5c4f4e85b73f161b2e0&r=PART&n=42y1.0.1.7.67#se42.1.84_11143

Filtration materials are carefully selected and tested under the worse case conditions of use for each application, including particulate or gas capture rate and breathing air flow rate, and production of assembled devices is carefully controlled and monitored. Pleated or flat HEPA filter material for furnaces and air purifiers is tested only for their specific intended use.

Of course, we are free to use anything we like for our own personal protection. Just please be aware that you may be creating a false sense of security for yourself and others around you by using anything not scientifically proven fit for purpose by a certified testing lab.