The Right Mask for the Task: According to Johns Hopkins School of Public Health

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The Right Mask for the Task: According to Johns Hopkins School of Public Health


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Surgical masks, homemade masks, and respirators have become symbolic of protection during the COVID-19 crisis. How much protection do these masks and respirators really offer, can they be reused, and what are their limits?

N95 respirators [as well as KN95 masks, depending on their quality and ability to seal around the face] are made of special material that removes at least 95% of even the small droplets. They’re also manufactured to fit with a tight seal around the nose and mouth so air and viral particles can’t get around the side of the respirator.

Surgical masks are also made of special material, but they don’t provide a seal around the nose and mouth, meaning that smaller droplets may still be inhaled. Surgical masks are good, however, to protect the nose and mouth from larger droplets from coughs or sneezes, and for preventing infected people from spreading droplets.

Homemade [and other] cloth masks may remove some large droplets but will not remove small ones. They cannot provide a seal around the nose and mouth. If surgical masks are not available, cloth masks worn by infected people may reduce the spread of large droplets.

Can masks be reused?
Yes—and it’s important to note that reused N95 [and KN95] respirators will provide better protection than homemade masks. We can extend the [useful life of] supplies if we reuse them until they are visibly soiled or structurally damaged.

When should masks be discarded?
Discard a mask when it is contaminated with bodily fluids, when you can no longer obtain a good seal at the nose or around the mouth [for N95/KN95 types], or when it is visibly damaged or dirty or hard to breathe through.

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