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Penn's new indoor masking policy requires all community members to either double-mask or wear a KN95 or N95 mask. Credit: Alvin Yu

Penn is set to begin in-person classes Monday, with a revised indoor masking policy as part of the University's spring semester COVID-19 mitigation efforts.

In an interview with The Daily Pennsylvanian, Chief Wellness Officer Benoit Dubé explained the University's new masking strategy, defined what it means to "double-mask," and the negligible difference in efficacy rates among allowed masking types.

Here are Penn's mask rules, explained.

What is allowed?

Community members are allowed to wear a KN95 or N95 mask or double masking combination — defined as a cloth mask layered on top of a surgical mask. Following the new policy, community members are not allowed to wear a single surgical mask or a single cloth mask by itself indoors.

What is more protective?

The protection rates between N95 and KN95 masks and double-masking are quite similar. 

In a study cited by the Centers for Disease Control and Prevention, scientists tested the fitted filtration efficiency of different face mask combinations.

A single cotton mask had a mean FFE protection rate of about 44%, but adding a surgical mask underneath increased the FFE rate up to 81% at the highest. By comparison, N95 and KN95 masks are designed to filter out 95% of air particulates.

When analyzing the differing effectiveness of masking, Dubé said the University looks at two key components — the amount of air leakage and the quality of the mask’s physical barrier preventing particles from entering and leaving. Dubé noted that the effectiveness of double-masking and wearing KN95 masks is "very similar," and both are incredibly safe when it comes to the classroom setting.

Dubé said the University specifically recommends using a cloth and surgical mask combination because it offers "broader and snugger coverage" compared to two identically-shaped surgical masks.

Will masks be available?

Dubé said the University has bought surgical masks in bulk and plans to distribute them at various entry points around campus buildings and facilities. Community members are encouraged to take a University-provided surgical mask and layer a self-bought cloth mask on top.

Although the University has sponsored the purchasing of masks, Dubé said each campus building will handle the distribution of masks individually, since those who work in each building know the best entry points to place a station to distribute surgical masks.

"This decision to require double-masking is not forever," Dubé said. "We wanted to keep the solution as simple and as accessible as possible."