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The US government sent out a shipment of expired face masks to health workers. Here's how face masks can expire, and when they're still usable.

Business Insider logo Business Insider 3/18/2020 Gabby Landsverk
© Romeo Ranoco/Reuters

Healthcare workers responding to the rise of COVID-19 cases across the U.S. are facing an unprecedented shortage of equipment, particularly the specialized face masks used to protect medical staff from infection while working with patients.

The federal government recently shipped out thousands of the masks to help - but many of them are past their expiration date for effective use, according to new reporting from the New York Times.

Still, the masks - called N95 filtering facepiece respirators - may still offer protection against the coronavirus even after their expiration date, according to experts.

"N95 masks really don't expire in terms of their functionality. The only part that is subject to damage over time are the elastic bands that attach the mask to the user's face, which can be damaged by sunlight," Dr. John Balmes, professor of environmental health science at Berkeley Public Health, told Business Insider in an email.

The specialized masks create a seal to protect wearers, but that can be damaged over time as materials degrade

The key to figuring out whether the masks are still usable is the special seal that distinguishes filtering respirators from other protective face wear.

A surgical mask can block large particles, including saliva, to protect both the wearer and surrounding people. However, the loose fit can leave room for smaller particles to get through.

The seal on the N95 prevents this if worn properly, which is why even small variables such as facial hair can prevent the masks from working correctly.

Over time, parts of the mask can wear out depending on how it is stored. The straps are made from a plastic and rubber polymer, which can expand or contract when exposed to heat or cold. This can affect the fit of the mask and prevent proper sealing, according to the CDC.

Expired masks can still provide protection

If properly stored, masks should still be safe to use, according to Balmes.

"If the masks are stored in a dark, dry place, they should be OK to use. The filter material is inert," he said. "At this critical time, N95 masks should definitely be used past the expiration date."

The CDC has tested samples of masks past their expiration date and found many of them were still effective at providing better protection than surgical masks, improvised face coverings like bandanas, or nothing at all.

In response to widespread shortages of medical supplies, the CDC issued new guidelines to help prevent infection as efficiently as possible with limited supplies.

According to the guidelines, users should manually check expired masks for any visible damage to the straps, nose piece or other pieces, and check the seal. If any problems are found, the respirator should be thrown away. If not, the mask can offer some protection, but should only be used in emergencies.

Healthcare workers are already being asked to reuse the masks or use them for long periods of times in some cases, Business Insider previously reported, which the CDC has noted can be risky.

The CDC and other government agencies have also said that N95 masks are not for use by the general public, as they're in high demand by medical professionals who routinely face close contacted with infected individuals. Instead, it is more effective for the public to prevent the spread of the virus by avoiding crowds and practicing good hygiene habits like frequent hand-washing when it is necessary to be in public spaces.

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