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What types of masks to avoid

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The big flaw in some N95 masks that wearers will want to avoid

You found an N95 respirator mask left over from your home remodeling project. Should you wear it to lower your risk of getting or giving someone COVID-19?

That depends, say BJC infectious disease experts. If the mask has a little plastic valve in the middle of it, wearing it may actually do more harm than good to those around you.

News coverage of potential personal protective equipment (PPE) shortages earlier in the pandemic taught the general public that the N95 respirator mask is the gold standard for protecting health care workers from being infected with COVID-19 in some high-risk situations. The N95 designation means the respirator blocks 95 percent of very small airborne particles that may be able to carry the virus that causes COVID-19. The virus is also carried in larger droplets that are easily blocked by cloth masks and standard isolation masks.

When the Centers for Disease Control and most public health experts began advising the public to wear face coverings (as well as maintaining at least six feet of distance from others) some people turned to the N95 respirator masks commonly used by remodelers and construction workers. Some of those masks are made with plastic “exhalation valves.”

“Valved masks don’t filter exhaled air when people breathe out; they only filter the inhaled air when people breathe in,” says Dr. Babcock. “All other masks, including cloth masks, provide ‘source control,’ meaning they contain any exhaled droplets that can carry COVID-19 or other viruses out to other people. The masks with exhalation valves don’t provide that source control and might allow viral particles to spread.”

Hilary Babcock, MD, Washington University and BJC infectious disease specialist.

So, while valved masks might give wearers some protection against COVID-19, BJC discourages their use because of their lack of source control, says BJC infection prevention specialist Casey Sherman.

"Our goal [in requiring non-valved masks] is protecting others from potentially asymptomatic carriers, so it’s important that we all wear masks that provide some sort of barrier to the air we exhale, which one-way valves don’t provide."

Casey Sherman, BJC infection prevention specialist.

For this reason, screeners at the entrances to all BJC facilities make sure that those entering have a cloth mask or isolation mask or an N95 mask without an exhalation valve. Those without a mask or who prefer to keep on their valved N95 mask for their own protection are given a disposable, medical-grade isolation mask to wear or place over their valved mask, says Sherman.

While some visitors may find wearing a mask a little inconvenient or even uncomfortable, it’s part of BJC’s commitment to keeping its patients, visitors, employees and the communities it serves as healthy and safe as possible.

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