In their calculations of the risk of contamination, the team took into account a number of factors not previously included in comparable studies. For example, the scientists investigated how the incorrect connection of the masks reduces the protection and how this can be prevented.
“The materials of FFP2 or N95 masks, as well as some surgical masks, filter the air very effectively,” Bagheri said. “The risk of contamination is then dominated by the air entering and escaping around the edges of the mask.” This occurs when the edge of the mask is not close to the face.
In extensive experiments, Bagheri, Bodenschatz and their team measured the size and number of the particles that flow along the edges of the mask if they are not positioned correctly.
“A mask adapts very well to the shape of the face if you fold the metal strap into a rounded ‘W’ before putting it on,” said Bodenschatz. “Then the infectious aerosol particles can no longer get past the mask and the glasses of your glasses no longer vaporize.”
The team also took into account the fact that droplets that people spread when they breathe or speak become drier and lighter in the air. This means that they stay in the air longer, but also that they have a greater concentration of the virus than equally sized droplets immediately after they are released. When inhaled, the particles reabsorb water and re-size, making it easier for them to settle in the respiratory tract.
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