Originally posted by Mooncatt What you said is true, but I'll connect the other dots.
Here in the U.S, social distancing is considered 6 feet or more spacing. If no one is moving, then coughing without a mask is potentially a greater issue (though a large number of people cough into their sleeves and such, mitigating the mask issue). In the video, they go to great lengths to show this and also make a point to show the droplets actually linger in the air for several minutes and travel much further than 6 feet. That calls into question the 6 ft recommendation.
When time to show the masked demonstration, they only show a single "cough," which lasts all of about two seconds. They refer to it as a properly worn and effective mask, glossing over the cloud of droplets that escape around it (as shown in the attached screen shot).
They don't remind you that those droplets will linger just as long as an unmasked cough. That's inconsistency 1. They dismiss it as being a less dense cloud that isn't as infective, but they caution that the less dense cloud of the unmasked cough (at the longer distances) are still dangerous. That's inconsistency 2. That means when you are following someone at 10, 15, even 20 feet back and they cough, you will still be walking through their infectious cloud regardless of if they had a mask or coughed unobstructed. That's inconsistency 3. (Side note, some stores here tried making their aisles one way to promote social distancing, but hopefully you see how that could be more risky, and the practice was largely ignored and ended.) The only way this news story can be taken at face value is if the demonstration assumes no one is moving about, and there is no air movement. Transfer these results into a real world setting, and the results change drastically.
I think all of this is covered by my comment on 'reduction, not elimination'. They do caution that cough at 9ft, despite being less dense, is still a risk and I think that's a valid point. I would rather a less dense cough not being transmitted at velocity to the extremities of a room than a similarly dense cough being static in the room. Again, risk reduction, not removal. This is where I'd normally draw a diagram to highlight that movement + greater travel of cough = greater risk of contamination/greater coverage, but can't go about that right now.
Yes, there is still going to be some contamination. Yes, there is never going to be a perfect solution.
They did comment that a proportion of the 'cough' does escape around the edges of the mask, but it is still being reduced versus an unmasked cough. Bear in mind that not all of the cough will penetrate the mask, or even be diverted and that you will have some that will simply be stopped by, or condense on, the mask. You will have less incidence of contaminated droplets as a result.
The results change in real-world versus laboratory but you're omitting the fact that you are still reducing risk and that is better than not reducing risk.
Edit: Please don't think I can't see the point you're trying to make - they're passing it as a perfect solution when it's not, and I understand that is frustrating. However, people don't often listen to 'this is an imperfect solution'.
Further edit: Missed your comment about issues with the 6ft recommendation. Risk reduction. 6ft is viable in most places and, especially when coupled with masks, does offer some reduction in potential contamination. I think it'd be worthwhile posing questions such as 'do you think being 6ft away from someone is
less risky than being 1ft away from them?'. Those sorts of questions have provided the answers and ultimately the recommendations. If 9ft isn't feasible, but 6ft is, and 6ft is significantly better than 4ft, then 6ft wins. If 9ft was feasible, then 9ft would win. 6ft is a tangible distance for most.