• Jiji, Kyodo, staff report


Simulations by Japan’s Fugaku supercomputer have shown that wearing two face masks has more or less the same effects as wearing one well-fitting nonwoven mask in reducing the spread of droplets, a team led by researchers at government-affiliated institute Riken said Thursday.

“It’s important to wear a single mask made of nonwoven fabric appropriately,” said the team, led by Makoto Tsubokura, professor at Kobe University.

The team simulated effects to curb the spread of droplets when a nonwoven mask is worn tightly by using a nose bridge wire or when it is used without a wire.

When a mask fits well, 85% of droplets were curbed, with the effects falling to 69% for an ill-fitting mask, the team said.

When an ill-fitting nonwoven mask is covered by a urethane mask, the reduction effects came to 89%, almost equivalent to a single unwoven mask with a good fit, according to the simulations.

“Masks have limits in their effects to curb the spread of droplets,” Tsubokura said. “It’s important to take measures against infectious diseases comprehensively, including washing hands, ensuring ventilation, keeping social distancing and limiting the duration of contacts with others,” he said.

For people who want to wear two masks to avoid damage to their skin, Tsubokura recommended they wear a tighter fitting mask inside.

Tsubokura also said that droplets spread widely behind a person when he or she is moving, such as walking or jogging. He added that if an infected person speaks while on an escalator, there will be a higher risk of people behind getting infected.

The U.S. Centers for Disease Control and Prevention said last month that fitting a cloth mask over a medical procedure mask — and knotting the ear loops of a medical procedure mask and then tucking in and flattening the extra material close to the face — substantially reduced exposure from infected wearers and exposure of uninfected wearers, highlighting the importance of good fit to maximize mask effectiveness.

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