Has anyone tried the petri dish experiment with and without mask but at the side?

Question

There are quite a few videos and experiments online that show the benefits of wearing a mask by holding a petri dish in front of their face while talking, singing, coughing etc., once with a mask and once without a mask. However, I have realised that while wearing a mask, despite the mask doing a good job blocking water droplets in the front, a lot of my breath (i.e. water droplets) goes to the sides of the mask.
Given that authorities are saying that the virus is airborne, I would think that the water droplets that come out of the side of the mask matter as well, especially in an enclosed room where many people would be spending their day. Has there been anyone who has put the petri dish at the side and did the same test as mentioned earlier? I can't seem to find any, but then again, my researching skills are not the best.

Luigi · Accepted Answer

While I'm not sure about the petri dish experiment, I will answer the main question I think you're asking: how important is the air that escapes out of the sides/top of the mask?
This question is answered with really cool visuals in this paper: Visualizing the effectiveness of face masks in obstructing respiratory jets. While the main point of the paper aims to test the effectiveness of different masks in blocking coughs, you can see the trajectory of all the air (including the air coming out of the side). This example here shows a labelled diagram of air moving through and around through a folded handkerchief mask:

Fig 3b
Looking at both the homestitched (top) and commercial masks (bottom) below, you can see that there isn't much leakage around the mask, and the leakage that does happen out of the top of the mask appears to stay close to the cougher:

My interpretation is that the leakage around the mask is likely much less of a risk, since it probably is not moving as rapidly as air expelled directly out of the mouth--since the leaking air has already bounced off the mask, it does not get as far away from the person breathing/coughing. So, while stuff may escape out of the side/top, it doesn't get very far (hence the synergy of social distancing plus masking).

Has anyone tried the petri dish experiment with and without mask but at the side?

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