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> What a tool was being used for 2 months ago isn't relevant It is very relevant. These face shields wouldn't protect anyone from airborne/aerosol pathogens or

> What a tool was being used for 2 months ago isn't relevant It is very relevant. These face shields wouldn't protect anyone from airborne/aerosol pathogens or viruses. They have a very specific purpose and that isn't one of them. If you're talking about adapting construction grade shields (like used for painting, etc) for medical use -- sure. But you aren't going to use a face shield as a replacement for a face mask, which is what it seems like you're arguing for. If you're saying that you should wear a face shield in public to protect yourself from aerosolized virus -- that's not the point of a face shield. The particles can travel around the sides of the mask too easily. If you want to protect from small, airborne particles, you need a mask.

roenxi 7y ago
If someone is facing me and a stream of airborne particles hits a plastic shield instead of streaming out to me, it seems pretty likely that I will be protected. I'm certainly open to the idea that fluid mechanics are complicated and somehow air currents are going to do unhelpful things, but until I find someone with a paper on the topic I'd much rather be talking to someone wearing a face shield than not. Plus obviously wearing a face shield will protect against self-inflicted infections from a contaminated finger.
- mbreese 7y ago
  > it seems pretty likely that I will be protected And you'd be wrong. Sure, a face shield will protect you from liquid streaming out at you (partially). However, it isn't a liquid that you need to protect yourself from in this instance... it is aerosolized particles. And those travel in the air. So when you breathe in, that air can and will move around the face shield. The sibling comment about smoke moving is exactly right. Smoke is a great example of how small particles can move and travel in the air. If you think that a face shield will protect you from something in the air, you'd be wrong. Side note: this is how N95 masks are actually fit. (Well, not using smoke, but similar test). If you can smell the chemical used in the test, the fit is wrong. If you really want to protect yourself from other people sneezing -- stay away from other people. That's why social distancing is still the primary, and best, recommendation.
  - roenxi 7y ago
    You say that with great confidence and a lack of sources; and I'm guessing we are equally ignorant on the actual physics of how small droplets move. The details aren't clear on how the virus is spreading. The virus might have multiple modes of transmission. Closing 2 of them reliably a great deal. There are important things to do with "catching COVID" that aren't binary; starting doses likely matter as well. I'd rather not talk to you in person if you aren't going to cover your face, tyvm :)
    - seletz 7y ago
      Stop spreading FUD.
    - brirec 7y ago
      > The virus might have multiple modes of transmission. Closing 2 of them reliably a great deal. Sounds reasonable, but how is a face shield a reliable way to close a mode of transmission if people aren’t spitting liquid in your face?
      - woofie11 7y ago
        It increases the effective time large droplets need to spend in the air to get to me, and decreases the airflow around me. It's about the same reason plexiglass screens help, and keeping a 6-foot distance helps. Plus, it stops me from touching my face. No, it doesn't stop everything, but it's a buck.
        DanBC 7y ago
        > Plus, it stops me from touching my face. You would be touching your face if you had correctly fitting PPE, because it's uncomfortable. https://twitter.com/gabbyjackson95x/status/1247939178962325505 https://twitter.com/gabbyjackson95x/status/12479391789623255...
    - pertymcpert 7y ago
      This is just common sense. Aerosolized particles are not impeded by a shield. A shield is intended to obstruct ballistic projectiles. If those projectiles are aerosolized and are in the air that you breathe, then the shield will offer no protection at all. Even an N95 mask still can let in up to 5% of these particles. What efficacy is a piece of plastic in front of your face going to do against that?
- chrischen 7y ago
  Go light a cigarette or incense and and see if a face shield prevents you from inhaling any smoke.
  - roenxi 7y ago
    Yeah, that is pretty much what I'm imagining. If someone tried to smoke behind a facemask it seems pretty likely that most of the smoke will be caught behind the mask then drift out behind them like a comet trail, or move up/down. Only small wisps would end up traveling forward to where I'd be standing for conversation. The doses of virus would be diluted very rapidly which is helpful. Ideal scenario would be most of the smoke gets pushed down in a knee-wards direction, which is well within the realm of the imaginable.
    - Talanes 7y ago
      >If someone tried to smoke behind a facemask it seems pretty likely that most of the smoke will be caught behind the mask then drift out behind them like a comet trail, or move up/down. Only small wisps would end up traveling forward to where I'd be standing for conversation. You ARE the person in the faceshield (I assume you meant that instead of facemask), you don't control what other people do so assume they uncovered. The smoke is in the air, it can reach you. Will it get around that shield or not?
      - roenxi 7y ago
        How could me wearing a face shield help protect me from catching the virus? It'd be mostly useless; although obviously as mentioned it'd stop me touching my face as much as normal. This is all about containing the spread. Although I suppose in hindsight that explains why people were downvoting me.
    - rumanator 7y ago
      > it seems pretty likely that most of the smoke will be caught If your plan is to only block most of the virus then perhaps you should rethink it. It's like stating that a hole in the hull is not a problem because the rest of the ship keeps most of the water out.
dillonmckay 7y ago
Nobody is advocating for a face-shield as a replacement for an N-95 mask, but using them together, would reduce the odds of infection. According to the MIT paper, a typical sneeze will travel over 20 feet. Additionally, there is mention of the velocity of the particles may be able to penetrate the mask, so a face-shield could help with that, too.
- awaythrower 7y ago
  Yes. Defense-in-depth. In China, most hospital red zones required 3 layers of PPE, whether that's two masks and a face shield or such. One layer alone is not very good, and a face shield alone is no good. A mask and a face shield are very good, especially for confined spaces like subways and busses where there are jerks coughing and sneezing all over without hygiene or manners.
awaythrower 7y ago
Strawman and wrong.
woofie11 7y ago
What if I want to protect myself and my facemask from large droplets. I also want to protect myself from accidentally touching my face. Is a face shield okay then? And if so, why not drop $300 million to get one for everyone in the US? They're cheap, wash easily, and that's less than 0.02% of the last stimulus.

roenxi 7y ago

If someone is facing me and a stream of airborne particles hits a plastic shield instead of streaming out to me, it seems pretty likely that I will be protected. I'm certainly open to the idea that fluid mechanics are complicated and somehow air currents are going to do unhelpful things, but until I find someone with a paper on the topic I'd much rather be talking to someone wearing a face shield than not. Plus obviously wearing a face shield will protect against self-inflicted infections from a contaminated finger.

mbreese 7y ago
> it seems pretty likely that I will be protected And you'd be wrong. Sure, a face shield will protect you from liquid streaming out at you (partially). However, it isn't a liquid that you need to protect yourself from in this instance... it is aerosolized particles. And those travel in the air. So when you breathe in, that air can and will move around the face shield. The sibling comment about smoke moving is exactly right. Smoke is a great example of how small particles can move and travel in the air. If you think that a face shield will protect you from something in the air, you'd be wrong. Side note: this is how N95 masks are actually fit. (Well, not using smoke, but similar test). If you can smell the chemical used in the test, the fit is wrong. If you really want to protect yourself from other people sneezing -- stay away from other people. That's why social distancing is still the primary, and best, recommendation.
- roenxi 7y ago
  You say that with great confidence and a lack of sources; and I'm guessing we are equally ignorant on the actual physics of how small droplets move. The details aren't clear on how the virus is spreading. The virus might have multiple modes of transmission. Closing 2 of them reliably a great deal. There are important things to do with "catching COVID" that aren't binary; starting doses likely matter as well. I'd rather not talk to you in person if you aren't going to cover your face, tyvm :)
  - seletz 7y ago
    Stop spreading FUD.
  - brirec 7y ago
    > The virus might have multiple modes of transmission. Closing 2 of them reliably a great deal. Sounds reasonable, but how is a face shield a reliable way to close a mode of transmission if people aren’t spitting liquid in your face?
    - woofie11 7y ago
      It increases the effective time large droplets need to spend in the air to get to me, and decreases the airflow around me. It's about the same reason plexiglass screens help, and keeping a 6-foot distance helps. Plus, it stops me from touching my face. No, it doesn't stop everything, but it's a buck.
      - DanBC 7y ago
        > Plus, it stops me from touching my face. You would be touching your face if you had correctly fitting PPE, because it's uncomfortable. https://twitter.com/gabbyjackson95x/status/1247939178962325505 https://twitter.com/gabbyjackson95x/status/12479391789623255...
  - pertymcpert 7y ago
    This is just common sense. Aerosolized particles are not impeded by a shield. A shield is intended to obstruct ballistic projectiles. If those projectiles are aerosolized and are in the air that you breathe, then the shield will offer no protection at all. Even an N95 mask still can let in up to 5% of these particles. What efficacy is a piece of plastic in front of your face going to do against that?
chrischen 7y ago
Go light a cigarette or incense and and see if a face shield prevents you from inhaling any smoke.
- roenxi 7y ago
  Yeah, that is pretty much what I'm imagining. If someone tried to smoke behind a facemask it seems pretty likely that most of the smoke will be caught behind the mask then drift out behind them like a comet trail, or move up/down. Only small wisps would end up traveling forward to where I'd be standing for conversation. The doses of virus would be diluted very rapidly which is helpful. Ideal scenario would be most of the smoke gets pushed down in a knee-wards direction, which is well within the realm of the imaginable.
  - Talanes 7y ago
    >If someone tried to smoke behind a facemask it seems pretty likely that most of the smoke will be caught behind the mask then drift out behind them like a comet trail, or move up/down. Only small wisps would end up traveling forward to where I'd be standing for conversation. You ARE the person in the faceshield (I assume you meant that instead of facemask), you don't control what other people do so assume they uncovered. The smoke is in the air, it can reach you. Will it get around that shield or not?
    - roenxi 7y ago
      How could me wearing a face shield help protect me from catching the virus? It'd be mostly useless; although obviously as mentioned it'd stop me touching my face as much as normal. This is all about containing the spread. Although I suppose in hindsight that explains why people were downvoting me.
  - rumanator 7y ago
    > it seems pretty likely that most of the smoke will be caught If your plan is to only block most of the virus then perhaps you should rethink it. It's like stating that a hole in the hull is not a problem because the rest of the ship keeps most of the water out.

dillonmckay 7y ago

Nobody is advocating for a face-shield as a replacement for an N-95 mask, but using them together, would reduce the odds of infection. According to the MIT paper, a typical sneeze will travel over 20 feet. Additionally, there is mention of the velocity of the particles may be able to penetrate the mask, so a face-shield could help with that, too.

awaythrower 7y ago
Yes. Defense-in-depth. In China, most hospital red zones required 3 layers of PPE, whether that's two masks and a face shield or such. One layer alone is not very good, and a face shield alone is no good. A mask and a face shield are very good, especially for confined spaces like subways and busses where there are jerks coughing and sneezing all over without hygiene or manners.

awaythrower 7y ago

Strawman and wrong.

woofie11 7y ago

What if I want to protect myself and my facemask from large droplets. I also want to protect myself from accidentally touching my face. Is a face shield okay then? And if so, why not drop $300 million to get one for everyone in the US? They're cheap, wash easily, and that's less than 0.02% of the last stimulus.