Do face shields stop the spread of COVID-19?

Fact Finders: Face shield effectiveness

TUCSON, Ariz. (KOLD News 13) - The Centers for Disease Control and Prevention does not recommend using face shields instead of masks in efforts to slow the spread of the coronavirus.

If you still needed convincing on the effectiveness of certain face coverings, a new study may sway your opinion.

Researchers from Florida Atlantic University’s College of Engineering and Computer Science used lasers to show how well face shields and masks with exhalation valves were in stopping the spread of aerosol-sized droplets.

Results showed face shields block the initial forward motion of the jet, but the expelled droplets move around the visor with relative ease and spread out over a large area depending on light ambient disturbances. They visualized droplets from a mannequin’s mouth while simulating coughing and sneezing.

According to the study:

“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. Thus, despite the increased comfort that these alternatives offer, it may be preferable to use well-constructed plain masks. 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.”

According to the CDC, a face shield is primarily used for eye protection for the person wearing it.

“My biggest concern is the lack of awareness,” said Dr. Madhu Murthy, who was not involved in the study. “There is no real protection from the face shields, in that current CDC guidelines do not recommend substituting face masks with the face shields.”

The CDC does not recommend using masks for source control if they have an exhalation valve or vent.

Visualizations for the face mask equipped with an exhalation port indicate that a large number of droplets pass through the exhale valve unfiltered, which significantly reduces its effectiveness as a means of source control.

To see read the study, click here.

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