Three meters are not enough to guarantee protection. Even at that distance, it takes less than five minutes for an unvaccinated person to stand up to the breath of a person with COVID-19 get infected with almost a 100% chance.
The good news is that if you both wear well-fitting masks or, better yet, FFP2 masks, the risk drops dramatically, as a new study by a team from the Max Planck Institute for Dynamics and Self-Organization in Göttingen suggests.
Study with the delta variant
The Göttingen study confirms that FFP2 or KN95 masks are particularly effective in filtering infectious particles from breathed air, especially if they are as tightly sealed as possible on the face.
If both the infected and the uninfected person wear tight fitting FFP2 masks, the maximum risk of infection after 20 minutes is just over one per thousand, even at the shortest distance. If your masks are not fitting properly, the chance of infection increases to about 4%. If you both wear well-fitting medical masks, the virus is likely to be transmitted within 20 minutes with a maximum probability of 10%.
In our study we found that the risk of infection without wearing masks is enormously high after only a few minutes, even at a distance of three meters, if infected people have a high viral load of the delta variant of SARS-CoV-2.
In the following video we can see how, using a mannequin, the team from the Max Planck Institute for Dynamics and Self-Organization demonstrates how the respiratory cloud, and possibly coronaviruses with it, spread in different scenarios. Without a mask, many potentially infectious particles are dispersed in the room. Surgical masks already significantly reduce the amount, even if they fit poorly: