While the Center for Disease Control and Prevention has found double masking to improve protection by about 50%, wearing a surgical mask over a fabric mask is pointless, according to a new study.
Researchers at the University of North Carolina at Chapel Hill tested several mask combinations on volunteers, from a single cloth mask to doubled-up surgical masks. They found that wearing a full-coverage mask, such as a bandanna or gaiter, over a surgical mask provided the best filtration.
Layering a cloth mask over a surgical mask also improved the fit and filtration, the study found. However, the same combination with the surgical mask on top provided no additional benefit than wearing a single surgical mask alone.
"[This] leads us to understand that double masking is most effective because of the improved fit that it offers, not because of the additional layers," lead author Emily Sickbert-Bennett wrote in an email to Insider.
The CDC study and the recent Chapel Hill research found that mask-wearing works best when both people are wearing well-fitted masks.
"The best form of double masking is when you and the person you are interacting with both have a mask on," Sickbert-Bennett said, according to Insider.