Face Mask or Face Shield?: Which Offers Better Protection Against Coronavirus?


Face Mask or Face Shield?: Which Offers Better Protection Against Coronavirus?

People are using either or both of these devices to try and stay safe. But what does the science say?

More the nine months into the ongoing pandemic, most medical experts are now on board with the idea that face masks and coverings are key to limiting the further spread of the novel coronavirus.

For some individuals, however, wearing masks can be highly uncomfortable and affect their breathing. Therefore, many have ventured into trying another type of personal protective gear—face shields.

But are they really effective in protecting you from the virus?

Face shields—simply a curved plastic or plexiglass panel attached to a headband—have long been used in health-care settings. They are often worn during medical procedures and surgeries in which bone fragments, blood, or other bodily fluids could get into the eyes, nose, and mouth.

A study in 2014 revealed that when tested against an influenza-infused aerosol from a distance of eighteen inches away, face shields were able to reduce the exposure by 96 percent during the time period immediately after a cough. These shields also were shown to lower the surface contamination of a respirator by 97 percent.

Despite these positive findings, the U.S. Centers for Disease Control and Prevention still does not recommend wearing face shields for normal everyday activities or as a substitute for cloth face masks and coverings.

“At this time, it is not known what level of protection a face shield provides to people nearby from the spray of respiratory droplets from the wearer,” the CDC states.

“There is currently not enough evidence to support the effectiveness of face shields for source control. Therefore, CDC does not currently recommend use of face shields as a substitute for masks.”

The agency, however, is okay with individuals wearing a regular mask underneath the face shield, which would help minimize the risk of infection as these shields have rather large openings at the bottom. If face shields are used without a mask, they should wrap around the sides of the wearer’s face and extend to below the chin, it added.

The CDC’s stance is seemingly supported by a recent study out of Florida Atlantic University, in which face shields and valved masks have been shown to be less effective at blocking viral particles than regular face masks.

The research, published in the journal Physics of Fluids, determined that these two particular protective-gear options allow ejected viral particles to escape, putting individuals nearby in danger of being infected by the virus.

“We observe that face shields are able to block the initial forward motion of the exhaled jet; however, aerosolized droplets expelled with the jet are able to move around the visor with relative ease,” the study said.

“There is a possibility that widespread public adoption of the alternatives, in lieu of regular masks, could have an adverse effect on ongoing mitigation efforts against COVID-19.”

The researchers posted a visual demonstration that uses lasers to illuminate the path of coughs—showing how large plumes of particles can escape from behind a face shield or vented mask.

“Overall, the visuals presented here indicate that face shields and masks with exhale valves may not be as effective as regular face masks in restricting the spread of aerosolized droplets,” the study added.

Ethen Kim Lieser is a Minneapolis-based Science and Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek, and Arirang TV. Follow or contact him on LinkedIn.

Image: Reuters