"Penetration of cloth masks by particles was almost 97% and medical masks 44%."
How do you test particle penetration in a 'maskless' group?
Isn't it implied that the 'maskless' group would have 100% particle penetration?
How do you test particle penetration in a 'maskless' group?
Isn't it implied that the 'maskless' group would have 100% particle penetration?
https://bmjopen.bmj.com/content/bmjopen/5/4/e006577/F2.large...
The evidence shows that changing masks frequently combined with using medical grade material is effective.
The current mask recommendations for the USA though... is folk science akin to using leeches or trepanation.
And no one demands any scientific rigour they just follow along blindly trusting whoever is on the T.V.
Masks need to be changed constantly.