Japanese supercomputer simulations showed that wearing two masks gave little benefit in blocking viral spread compared with one properly fitted mask.
Researchers used the Fugaku supercomputer to model the flow of virus particles from people wearing different types and combinations of masks, according to a study released on Thursday by research giant Riken and Kobe University.
Using one surgical-type mask, made of non-woven material, had 85% effectiveness in blocking particles when worn tightly around the nose and face.
Adding a polyurethane mask on top boosted the effectiveness to just 89%.
Professional grade N95 masks were the best in protecting against infection, followed by non-woven masks, cloth masks, and finally polyurethane types, the study showed.
