Health officials from the U.S Centers for Disease Control and Prevention are making the case for wearing two well-fitting masks. Scientists at the center conducted experiments last month to see how well wearing a cloth mask over a three-ply medical procedure mask and knotting the ear loops of a surgical mask and then tucking the excess material close to the face, protects against COVID-19. The tests found that combining the procedures is likely to significantly reduce a person’s exposure to the coronavirus.

The tests showed that both these methods helped reduce the exposure to potentially infected aerosols by more than 90 percent in laboratory simulations. The data also showed that wearing a mask helped reduce exposure to aerosol particles that were the size of droplets that spread COVID-19, when compared to wearing no mask at all.

The experiments highlight that “masks work, and they work best when they have a good fit and are worn correctly,” CDC Director Rochelle Walensky said. Walensky added that re-useable devices known as mask-fitters were also an option to improve a mask’s fit.

Results from one experiment demonstrated that the un-knotted medical procedure mask alone blocked 42 percent of the particles from a simulated cough and the cloth mask alone blocked 44.3 percent. The double mask combination blocked 92.5 percent of the cough particles.

In another experiment, the CDC tried to simulate the spread of COVID-19 during breathing when one or both people are properly masked. In the first scenario with only the source of the aerosols wearing a mask, they found coronavirus exposure was reduced by 82.2 percent when double-masking and 62.9 percent with a snug-fitting, knotted and tucked surgical mask. When the source and receiver of simulated breathing aerosols were both fitted with double masks, or knotted and tucked medical masks, the exposure of the receiver was reduced 96.4 percent and 95.9 percent, respectively, the experiments found.

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