Slipping in here with a question that will probably seem obnoxious, but isn't intended so.
If cloth masks are effective (I'm not arguing either way) and those who wear them felt endangered by those who don't, could they simply double their mask? Particulates passing in or out, in either direction, would be subject to the same amount of material as if both were wearing a single mask.
guy with mask + guy with mask = two masks
guy with 2 masks + guy with 0 masks = two masks.
I'm not suggesting that anyone should have to bear the responsibility of another, but the effect should be the same for the wearer if non airborne contaminated surfaces are of low risk. Unless it's a matter of directionality.
Could it be tested to observe a controlled situation where group A) exhales only through cotton while inhaling without, while a seperated group B) does the opposite, exhaling without and inhaling with?
Is this absurd to consider? I'm not feeling well and might actually be absurd right now.
That's actually a good question and has to do with the physics of respiration. When you inhale, you're creating negative pressure that pulls particles closest to you into your lungs, leaving a void that other particles fill as they randomly redistribute themselves. This causes aerosolized droplets to follow the path of least resistance around the mask, as if they are pulled, rather than landing against it. That's why real N95/100 masks require a proper fit: if there's even a sliver of space between the mask and face, inhaling will simply suck air in through that space instead of through the filter, which has a higher "resistance".
When you exhale, on the other hand, you create positive pressure which violently expels the droplets regardless of what's in the way. This creates droplets with high velocity and turbulent flows within the mask that prevent them from traveling a straight path through the mask and cause most of them to collide with the fabric.
Basically, once it's exhaled it's a hazard to anyone who doesn't have a properly fitted N95/100 mask (which requires specialized equipment, though it's relatively common)
Those guys who used to say 2+2=5 might have been on to something, but more correctly, it was probably 3 for fluid dynamics here.
I remember as an OTR driver the truckstop bathrooms I survived each day. The olfactory violence was palpable enough to feel it crawling through the mask and see it grinning as it coursed through what must have been an unusual ratio of gas to air. I'd think to myself in that sometimes surreal environment where photons seemed to sweat and stagger, that even an n95 was pointless, perhaps life itself. If rona be here, every particle is riding a pale horse in a hazmat suit. I'll always consider myself a permanent petri dish for that.
The idea is that the masks filter particulates at the source, and then again at the destination. See https://www.livescience.com/face-mask-visualization-droplets... for a visualization. Reasonable. Wearing masks when having symptoms is elementary courtesy, and self quarantining is even better. Unfortunately we've embraced the 'asymptomatic spreader' idea a bit too much and now we regard anyone that doesn't take the most extreme measures at all times as a de facto murderer, because there might be a tiny chance they are infectious. Not healthy.
I think part of the benefit of everyone wearing masks is that there is more value in limiting the distribution of virus laden particulates from the source, ie the infected persons mouth or nose, at least to an extent. That is best done when an infected individual has a mask on. Additionally, if we assume that wearing a mask limits spread, then unmasked individuals overall are a higher risk for receiving infection. Therefore community risk is higher.
That's how we end up with a calculus that determines that impinging individual liberty (requiring masks) has a net benefit (limiting overall community spread).
I guess a similar analogy might be: driving half the speed limit might in a weird sense feel like you're protecting yourself from harm in an accidental if else someone drives too fast, but the better policy would be that both directions of traffic maintain speed at or under the limits. Again, this is an instance where we limit individual freedoms when there is a perceived net benefit to community safety.
Stocks vs. flows. The idea is that masks reduce the flow into a reservoir (like inside air of a building), and not just direct transmission. In your example double masking might reduce your personal intake from a large reservoir (refilled by unmasked people who happen to be sick), while everyone wearing a mask should reduce the size of the reservoir.
Solid math and reasonable general principles, with an element or two I question. He comes close to clarifying it, though not quite. And while the percentage of 50 was a disposable placeholder to illustrate valid points, I doubt cotton could be quite so effective as 50% leading to 75% (and certainly not 100%) and some assumptions are required to flow along with the logic, as was mentioned. This is still reasonable for a fast-paced video; some finicky details must be overlooked. However, it is primarily based on math and no data was shown giving any unambiguous indication for cotton efficacy. Also, he addresses directionality as nearly equal for the illustration, but later provides another resource that accounts for it in detail. Was this prefactored? Otherwise surprisingly apropos and worthwhile.
you’re welcome. i’m a bit low on sleep so i missed part of your question, and don’t think the video addresses it — that is, are two [cotton] masks more effective than one. i honestly think that this is an interesting question. for most people, their intuition would be to answer “probably,” but i suspect there are some complexities that someone smarter than i am would have to address.
wearing two masks instead of one wouldn’t make things worse, though. but better? again, good question.
I'm guessing you've hidden away a lot of meaning in the words "well done" but here's one:
https://www.preprints.org/manuscript/202004.0203/v4
These also: https://docs.google.com/document/d/1HLrm0pqBN_5bdyysOeoOBX4p...
If you don't think these are "well done", can you at least clarify what such a study would look like and point us to an example?