Study Gives Video Evidence That Face Shields, Valved Masks Offer Less Coronavirus Protection
There is currently not enough evidence to support the effectiveness of face shields for source control.
Face shields and valved masks have been shown to be less effective at blocking viral particles than regular face masks, according to a new study out of Florida Atlantic University.
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 coronavirus, also known as COVID-19.
“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.
The U.S. Centers for Disease Control and Prevention had already stated that clear plastic face shields and masks equipped with vents or exhalation valves are not recommended.
“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 agency said.
“There is currently not enough evidence to support the effectiveness of face shields for source control.”
The CDC, though, is okay with individuals wearing a mask underneath the face shield, which would help minimize the risk of infection.
If face shields are used without a mask, then they should wrap around the sides of the wearer’s face and extend to below the chin, the agency added.
As for masks with vents or exhalation valves, they could still allow the virus to escape and pose a threat to others nearby.
“Masks with one-way valves or vents allow exhaled air to be expelled out through holes in the material,” the CDC said.
“This can allow exhaled respiratory droplets to reach others and potentially spread the COVID-19 virus.”
Last month, White House coronavirus advisor Dr. Anthony Fauci suggested that wearing goggles or an eye shield, along with a face mask or covering, would provide better protection against the coronavirus.
The nation’s top infectious disease expert called the use of goggles and eye shields as “perfect protection” from the virus, but also said that it’s not “universally recommended.”
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.