Two face masks no better than one at blocking viral spread, Japanese supercomputer shows

Findings contract recommendation given by US Centers of Disease Control and Prevention

A woman wearing a face mask crosses a road on in Tokyo, Japan (Yuichi Yamazaki/Getty Images)

Wearing two face masks provides limited benefits in blocking viral spread compared to one properly fitted mask, simulations from a Japanese supercomputer have showed.

The findings contradicts recent recommendations given by the US Centers of Disease Control and Prevention (CDC) which said two masks were better than one at reducing a person’s exposure to coronavirus.

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.

Wearing two non-woven masks is not useful because air resistance builds up and causes leakage around the edges.

"The performance of double masking simply does not add up," wrote the researchers, led by Makoto Tsubokura.

Professional grade N95 masks were found to be the best in protecting against infection, followed by non-woven masks, cloth masks and finally polyurethane types, the study showed.

The Riken research team previously used the Fugaku supercomputer to model how humidity can affect viral contagion to study the infection risks in trains, work spaces, and other environments.

As the Covid-19 epidemic has progressed, scientific consensus has grown that the virus is spread through the air and masks are effective in controlling the spread of the disease.

Additional reporting by Reuters