Study by the Max Planck Institute: Minimal risk of infection with FFP2 mask

Danger of infection only in the per mille range: A new study shows how effective FFP2 masks are – if they are worn correctly. Without a mask and even with a lot of distance, the risk of infection is almost 100 percent.

FFP2 masks offer an extremely high level of protection against corona infection. This is the result of a study by the Max Planck Institute. If an infected and a healthy person meet in an indoor area at a short distance, the risk of infection is only 0.1 percent even after 20 minutes.

Masks have to fit properly

However, according to the researchers, it depends on the correct way of wearing the FFP2 or KN95 mask. For optimal protection, the nasal clip must therefore be shaped into a “rounded W” so that it presses laterally on the nostrils. In contrast, with poorly fitting FFP2 masks, the risk of infection in the same scenario is around four percent, writes the team around institute director Eberhard Bodenschatz in the Proceedings of the US National Academy of Sciences (PNAS).

The researchers’ analysis also shows that tightly fitting FFP2 masks protect 75 times better than well-fitting surgical masks. Nevertheless, even medical masks with a good fit reduce the risk of infection to a maximum of ten percent.

Extensive influencing factors taken into account

The researchers calculated the risk of infection by combining various factors such as particle sizes, physics when exhaling, various mask types and the risk of inhaling coronaviruses. “In daily life the actual probability of infection is certainly ten to a hundred times smaller,” Bodenschatz is quoted in a communication from the institute. Because the air that flows out of the mask at the edges is diluted. However, the researchers wanted to calculate the risk as conservatively as possible. “If even the greatest theoretical risk is small under these conditions, you are on the safe side under real conditions,” says Bodenschatz.

In contrast, the result of encounters between two people who do not wear a mask: If in this case a healthy person stands three meters away in the breath of an infected person for a few minutes, there is a 90 percent probability that they will be infected Researcher. “We would not have thought that at a distance of several meters it would go so quickly until the infectious dose was absorbed from the breath of a virus carrier,” said Bodenschatz. “Our results show once again that wearing masks in schools and in general is a good idea.”