FFP2 masks offer extremely high protection against corona infection. However, it depends on the correct way of wearing them, as researchers from the Max Planck Institute for Dynamics and Self-Organisation in Göttingen report according to a study. According to the study, if an infected person and a healthy person meet in an indoor space at a short distance, the risk of infection is a good one per thousand (0.1 percent) even after 20 minutes. The prerequisite is the correct fit of the FFP2 or KN95 mask, writes the team around Institute Director Eberhard Bodenschatz in the “Proceedings” of the US National Academy of Sciences (“PNAS”).
With poorly fitting FFP2 masks, on the other hand, the risk of infection in the same scenario is around four percent, the team calculates. For optimal protection, the nose clip must be shaped into a “rounded W” so that it presses laterally on the nostrils. With surgical masks, a good fit is still enough to reduce the risk of infection to a maximum of ten percent.
The researchers calculated the risk of infection by combining various factors such as particle sizes, physics during exhalation, various mask types, and risk of inhaling coronaviruses. “In daily life, the actual probability of infection is certainly ten to a hundred times smaller,” Bodenschatz is quoted as saying in a statement from the Institute. This is because the breathing air that flows out of the mask at the edges is diluted. However, the researchers had wanted to calculate the risk as conservatively as possible. “If even the greatest theoretical risk is small under these conditions, you are on the completely safe side under real conditions,” says Bodenschatz.
In contrast to this is the result for encounters between two people who do not wear masks: if in this case, a healthy person stands in the breathing air of an infected person for a few minutes at a distance of three meters, he or she is very likely to become infected, the researchers say. Bodenschatz emphasizes: “Our results show once again that wearing masks in schools and also, in general, is a good idea.”