3 ms·

>A cotton mask has 60% filtration. An N95 mask has 95% filtration. If you "breath" in 1000 virus particles, someone with a cotton mask would only breath in 400

>A cotton mask has 60% filtration. An N95 mask has 95% filtration. If you "breath" in 1000 virus particles, someone with a cotton mask would only breath in 400 of them, while the one with N95 would breath in 50 virus particles Do you have a source for this? Because from what little I've been able to find, filtration efficiency for particulate in the aerosolized size range are practically negligible with cotton masks and even surgical masks. Which makes sense considering that aerosolized particles are around 2-3 orders of magnitude smaller than pore sizes in cotton and surgical masks, putting such masks in the realm of security theatre. I suspect studies which show cotton masks having an effect on transmission (in contrast to studies near the start of the pandemic which showed no effect) are failing to consider secondary effects of masking on behavior, namely that masks indirectly remind people of the pandemic and influence their social distancing behavior

dragontamer 5y ago
> Do you have a source for this? Because from what little I've been able to find, filtration efficiency for particulate in the aerosolized size range are practically negligible with cotton masks and even surgical masks. Which makes sense considering that aerosolized particles are around 2-3 orders of magnitude smaller than pore sizes in cotton and surgical masks, putting such masks in the realm of security theatre. Pretend that you're blowing out a candle: make a small "stream" with your lips and blow as far as you can. When I do so, my stream can go at least as far out as my arm, which I think is ~1.5 feet or ~2feet or something (longer than that, because my breath is still "strong" at the full length of my arm in front of me). Now put a cotton mask on and do the same thing. How far does the stream go? Inches, at best. Note: oxygen, nitrogen, and CO2 are all much much smaller than mask fibers. But you'll find that these things behave as a __fluid__, and thus we have a fluid-dynamics question rather than one of physical objects hitting a screen door model. ------ The distance your breath goes when talking is much reduced. Similarly, the "stream" where you draw in more air is also reduced to a smaller distance when you're masked up. ----- Or heck, _do_ blow out a candle. This experiment is like, $2. One dollar for a mask, and a second dollar for a birthday candle. Just measure it yourself: the mask grossly affects the distance that oxygen / CO2 / Nitrogen leaves the body.
- twofornone 5y ago
  >Now put a cotton mask on and do the same thing. How far does the stream go? Inches, at best. >The distance your breath goes when talking is much reduced. Similarly, the "stream" where you draw in more air is also reduced to a smaller distance when you're masked up. So instead of breath being directed downward from the nose, the aerosolized particles are redirected upward, where they linger for longer? Moreover, the difference in velocity between speech and "blowing out a candle" makes this a bit of a contrived argument. The key here is that these aerosolized particles have very long settling times - so if they are not being filtered by mask media and instead being blown higher upwards with a mask as opposed to without, then as best masks are useless, at worst they are actually counterproductive.
  - dragontamer 5y ago
    Your argument is that virus particles are too small for a mask to catch them. My counterargument: Nitrogen + Oxygen is even smaller than a virus particle, and the mask seems to redirect N2 + O2 just fine. As such, your mental understanding of how streams flow around people who breath is faulty. This physics question you're posing is one of fluid dynamics, not one of "bigger" vs "smaller" filters. This simple experiment I show proves that incredibly tiny particles (N2 / O2) behave differently than your mental model suggests. > Which makes sense considering that aerosolized particles are around 2-3 orders of magnitude smaller than pore sizes in cotton and surgical masks This statement you posted, this right here is wrong. Size has nothing to do with anything when we drop down to sub-microns.
    - twofornone 5y ago
      No, you're completely missing my point. The fact that the particles act like fluids makes masks counterproductive. Because exhaling into a mask redirects the fluidlike stream upwards where it lingers for longer. Breathing unmasked directs the stream straight ahead/down. Here's an example of what I'm describing[0]. Yes, it may be helpful for talking, but otherwise you are potentially increasing the dispersal of particulate when wearing a mask and breathing normally. In this case I am agreeing that filtration is irrelevant. 0. https://nationalfile.com/video-doctor-vapes-through-face-masks-shows-thick-clouds-escape-through-sides-bottom-and-top/ https://nationalfile.com/video-doctor-vapes-through-face-mas...

dragontamer 5y ago

> Do you have a source for this? Because from what little I've been able to find, filtration efficiency for particulate in the aerosolized size range are practically negligible with cotton masks and even surgical masks. Which makes sense considering that aerosolized particles are around 2-3 orders of magnitude smaller than pore sizes in cotton and surgical masks, putting such masks in the realm of security theatre. Pretend that you're blowing out a candle: make a small "stream" with your lips and blow as far as you can. When I do so, my stream can go at least as far out as my arm, which I think is ~1.5 feet or ~2feet or something (longer than that, because my breath is still "strong" at the full length of my arm in front of me). Now put a cotton mask on and do the same thing. How far does the stream go? Inches, at best. Note: oxygen, nitrogen, and CO2 are all much much smaller than mask fibers. But you'll find that these things behave as a __fluid__, and thus we have a fluid-dynamics question rather than one of physical objects hitting a screen door model. ------ The distance your breath goes when talking is much reduced. Similarly, the "stream" where you draw in more air is also reduced to a smaller distance when you're masked up. ----- Or heck, _do_ blow out a candle. This experiment is like, $2. One dollar for a mask, and a second dollar for a birthday candle. Just measure it yourself: the mask grossly affects the distance that oxygen / CO2 / Nitrogen leaves the body.

twofornone 5y ago
>Now put a cotton mask on and do the same thing. How far does the stream go? Inches, at best. >The distance your breath goes when talking is much reduced. Similarly, the "stream" where you draw in more air is also reduced to a smaller distance when you're masked up. So instead of breath being directed downward from the nose, the aerosolized particles are redirected upward, where they linger for longer? Moreover, the difference in velocity between speech and "blowing out a candle" makes this a bit of a contrived argument. The key here is that these aerosolized particles have very long settling times - so if they are not being filtered by mask media and instead being blown higher upwards with a mask as opposed to without, then as best masks are useless, at worst they are actually counterproductive.
- dragontamer 5y ago
  Your argument is that virus particles are too small for a mask to catch them. My counterargument: Nitrogen + Oxygen is even smaller than a virus particle, and the mask seems to redirect N2 + O2 just fine. As such, your mental understanding of how streams flow around people who breath is faulty. This physics question you're posing is one of fluid dynamics, not one of "bigger" vs "smaller" filters. This simple experiment I show proves that incredibly tiny particles (N2 / O2) behave differently than your mental model suggests. > Which makes sense considering that aerosolized particles are around 2-3 orders of magnitude smaller than pore sizes in cotton and surgical masks This statement you posted, this right here is wrong. Size has nothing to do with anything when we drop down to sub-microns.
  - twofornone 5y ago
    No, you're completely missing my point. The fact that the particles act like fluids makes masks counterproductive. Because exhaling into a mask redirects the fluidlike stream upwards where it lingers for longer. Breathing unmasked directs the stream straight ahead/down. Here's an example of what I'm describing[0]. Yes, it may be helpful for talking, but otherwise you are potentially increasing the dispersal of particulate when wearing a mask and breathing normally. In this case I am agreeing that filtration is irrelevant. 0. https://nationalfile.com/video-doctor-vapes-through-face-masks-shows-thick-clouds-escape-through-sides-bottom-and-top/ https://nationalfile.com/video-doctor-vapes-through-face-mas...