This blog is not intended as advice. It is for educational and research purposes only. Read this disclaimer first if you want to read this post.
There is an international movement for home made face masks, but it is worth looking at the evidence as to whether they actually help.
Lisa Broussea is a retired Industrial Hygienist and Professor at the University of Illinois at Chicago with a wealth of expertise. She has been giving timely advice on face masks. Read her recent commentaries and the associated references and make up your own mind. The articles give depth on filter efficiencies for different fabrics and the importance of fit. P2 (Australia) is similar to N95 (US).
Wearing a face mask that is uncertified (P2/N95) appears very unlikely to give much protection. People also tend to touch their faces more to adjust the mask and may reduce Social Isolation in the belief the mask is giving them all the protection they need.
It appears there is a lot of work being done on decontamination of face masks, particularly by the larger US manufacturers. Protective face masks are not like a fine sieve, but tend to be “depth filters” and often use the mask’s electrostatic properties to filter fine particles. The commentaries above discusses some of the approaches to decontamination. Making masks sterile without degrading their filtration or fit is one thing. Cleaning them so you are not wearing another person’s armpit is another.
Decontamination strategies are becoming more important as stocks of face masks run down and reuse becomes the only alternative, despite decontamination not being officially approved.
When I researched the service life of heavy chemical gloves (another form of PPE or personal protective equipment), I found that one of the main reasons that the gloves got replaced was they stank from the smelly products from skin bacteria after a week or so. Physical failure – fingers poking though the glove when the glove degraded was a secondary reason. The gloves had failed to protect well before visible failure due to invisible diffusion of chemicals through the glove polymer. Once that occurred the glove served to increase the chemical exposure -“a poultice of poison”. The soggy skin inside the glove also allowed ten times the chemical though the skin and the increase in skin temperature from 33 to 36C inside the glove roughly doubled skin permeation. I suspect similar problems are occurring with face masks, where the face masks get smelly after repeated use and the filtration of the fabric and importance of fit are poorly understood.
