People donning plastic face shields or masks accompanied by a valve could spray droplets over a broad area through coughing or sneezing. Therefore, masks with valves and face shields could still spread the virus as the devices are not effectual in the prevention of the spread of COVID-19 when used on their own.
Limitation of Face Shields
According to a simulation, face shields are limited in order to protect against the novel coronavirus.
In Boca Raton, scientists at Florida Atlantic University used laser light to display how face shields are able to bar the initial advancing movement of a simulated cough. However, fine droplets were in motion around the visor.
Plastic Face Shields, Masks, Exhalation Valves
As numerous people opt to use clear plastic face shields and masks with exhalation valves instead of surgical masks or cloth for comfort, the aforementioned researchers caution that they may not be as efficient to combat the prevalence of the coronavirus, reported Dentistry Today.
Upon moving around the visor with relative ease as mentioned earlier, they could prevail over a large area dependent on light ambient interference.
Students' Return to Classes
Students from college, high school, and elementary are returning to classes, occasionally donning face shields with a cloth mask and at times without such.
For instance, in California, the Orange County Health Care Agency, the Orange County Department of Education and school districts nationwide have created precautionary measures for returning to classes. According to their guide, "A face shield is an acceptable alternative for children in this cohort who cannot wear them properly," reported MarketWatch.
Florida Atlantic University Study
The study was published on the 1st of September in the peer-reviewed scientific journal "Physics of Fluids."
According to the researchers, they initiated the study to help the public surmise the effectiveness of face shields and masks equipped with exhalation valves which are their increasingly popular alternatives.
Warning
The scientists cautioned that widespread use of alternatives to medical and cloth masks could have a probable adverse effect on mitigating the pandemic.
CDC Advisory
According to The Centers for Disease Control and Prevention (CDC), they do not recommend using face shields in place of masks in efforts to flatten the curve of the pandemic.
The aforementioned university visualized invisible droplets from a mannequin's mouth while simulating sneezing and coughing.
Face Shields
Easier to breathe in, face shields lessen humidity and fogging when worn with glasses. They safeguard the eyes from sprays of infected droplets, enable visual communication for the hearing-impaired, and could be conveniently disinfected and cleaned.
Unfavorably, tiny aerosolized droplets could penetrate under the face shield's bottom and from the visor's sides. The scientists discovered that over exposure in a span from one minute to half an hour, it was only 23 percent successful in reducing the droplets' inhalation.
Mask With a Valve
For the mask with a valve fitted for easy breathing, "a large number of droplets pass through the exhale valve unfiltered, which make it ineffective in stopping the spread the COVID-19 virus if the person wearing the mask is infected," reported Manila Bulletin.
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