Although adding a procedure mask (mean [SD] FFE, 61% [13%]) over the cloth masks provided modest increases in their FFE (mean [SD] range, 55% [10%] to 60% [14%]), the overall performance was no different than wearing the procedure mask by itself. In contrast, wearing a procedure mask under the cloth face covering produced marked improvements in overall FFE (mean [SD] range, 66% [5%] to 81% [6%]).
Source: Fitted Filtration Efficiency of Double Masking During the COVID-19 Pandemic | Otolaryngology | JAMA Internal Medicine | JAMA Network
Researchers used the Fugaku supercomputer to model the flow of virus particles from people wearing different types and combinations of masks, according to the study released by research giant Riken and Kobe University on Thursday.A single surgical-type mask, made of non-woven material, had 85 per cent effectiveness in blocking particles when worn tightly around the nose and face.But adding a polyurethane mask on top increased the effectiveness to just 89 per cent.
Source: Two face masks no better than one at blocking viral spread, Japanese supercomputer shows