Study: Face Shields and Masks With Valves Ineffective Against Coronavirus



Face coverings are effective ways to stop the spread of the coronavirus, according to the Centers for Disease Control and Prevention. But a new study found that two popular options, the face shield and the N95 respirator mask that has one or two exhale ports or valves, still release infectious droplets into the air.

According to Study Finds, researchers at Florida Atlantic University used laser light to illuminate the flow of aerosols released when people coughed or sneezed. In a university news release, the scientists at FAU’s College of Engineering and Computer Science said they used a mannequin to simulate coughing and sneezing while wearing both types of face coverings.

Their visualizations showed that a large number of potentially infectious droplets were able to escape from the exhale valve on N95s and around the edges of the face shields or visors.

“There is an increasing trend of people substituting regular cloth or surgical masks with clear plastic face shields as well as using masks that are equipped with exhalation valves,” said Sid Verma, Ph.D., the lead author of the study. “A driving force for this increased adoption is better comfort compared to regular masks. However, face shields have noticeable gaps along the bottom and sides, and masks with exhalation ports include a one-way valve, which restricts airflow when breathing in, but allows free outflow of air. The inhaled air gets filtered through the mask material, but the exhaled breath passes through the valve unfiltered.”

According to Fox News, the San Francisco Department of Public Health has already warned residents that N95 masks with valves or openings in the front aren’t safe. In California’s Bay Area, there is a stipulation that you can wear any style mask you want, as long as it doesn’t have a valve in it.

San Francisco city officials followed up with advice on how to make these masks safer. They suggested wearing them with a surgical mask or other cloth covering over them or covering the valve with tape.

According to Fast Company, even the CDC does not recommend that hospitals use the N95s with valves because “the exhalation valve allows unfiltered air to escape within a sterile field.”


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