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N95 masks... the masks that by definition result in a 95% reduction in viral load... you want to argue that those are "MAYBE better than nothing"? You shouldn't

N95 masks... the masks that by definition result in a 95% reduction in viral load... you want to argue that those are "MAYBE better than nothing"? You shouldn't even need a study for that one - that's just basic common sense if you understand what an N95 mask is. I can understand skepticism about cloth masks (where the effect is more a statistical one), or maybe even surgical masks, but to assert that an N95 mask is ineffective is to assert that viral load doesn't matter AT ALL. We're talking a literal 20x difference, here! https://www.epa.gov/sciencematters/epa-researchers-test-effectiveness-face-masks-disinfection-methods-against-covid-19 https://www.epa.gov/sciencematters/epa-researchers-test-effe... if you really need some sort of citation for this claim.

timr 5y ago
> N95 masks... the masks that by definition result in a 95% reduction in viral load ... you want to argue that those are "MAYBE better than nothing"? Yes. First, that's not what "N95" means. The material in an N95 mask is capable of filtering 95% of 0.3um particles. That's it. It has nothing to do with "viral load". If a virus travels in particles smaller than 0.3um? No good. If the concentration of larger particles in a space is enough that 5% can infect you? Same thing. Theoretical efficiency is not the same as real-world efficiency. But far more importantly, if you don't fit such a mask properly, then the air will leak around the gaps, and the filtration efficiency of the material is largely irrelevant. Everyone I see on the street wearing (K)N95 masks has massive gaps around their nose and chin. If I can see the gaps from 10 feet away, their fancypants masks aren't doing much of anything except deflecting the air back over their head. Can a well-fit, correctly worn N95 mask make a difference as PPI? Sure, I don't doubt it. But I guarantee that most people aren't getting close to either criterion. Illustrative anecdote: I've had really nasty hay fever for my entire life, and I went through a period of trying N95 masks to keep the pollen out whenever I did yard work. Didn't work at all. Want to guess how big pollen is?
- handoflixue 5y ago
  > If a virus travels in particles smaller than 0.3um? No good. What does that have to do with Covid? > If the concentration of larger particles in a space is enough that 5% can infect you? Same thing. There is a huge body of evidence that viral load impacts severity, so if 5% of the viral load could infect you, then 20x that was going to put you on a ventilator. > if you don't fit such a mask properly, then the air will leak around the gaps There are actual real-world tests based on "average usage". We don't just have to make up our notion of efficiency based on your anecdotes. > Illustrative anecdote: I'll admit I prefer the overkill of a P100, but I've taught people how to use one in the course of 5 minutes and their reaction is "wow, this works so well". Maybe the extra filtering makes up for the air gaps, but they're really not hard to get real-world results from.
  - timr 5y ago
    > What does that have to do with Covid? The virus travels in saliva particles. > There is a huge body of evidence that viral load impacts severity There's actually no evidence for this claim. It's a hypothesis, not a fact. It's essentially impossible to verify the initial viral load of an infectious dose without doing challenge trials, which we haven't done (yet). > There are actual real-world tests based on "average usage". We don't just have to make up our notion of efficiency based on your anecdotes. There are no real-world trials of n95 masks and Covid. There were a few studies pre-2020 with n95 masks in hospitals and influenza, SARS and MERS. Two hospital studies involved Covid. Essentially all of the research concerning masks and respiratory illnesses was summarized by the WHO here: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31142-9/fulltext https://www.thelancet.com/journals/lancet/article/PIIS0140-6... Figure 4 is the relevant figure. Any study with a 1 in the "respirator" column was conducted with an n95 mask. Overall, they're more effective than the non-respirator masks, but the confidence intervals for nearly all studies overlaps "no effect".

timr 5y ago

> N95 masks... the masks that by definition result in a 95% reduction in viral load ... you want to argue that those are "MAYBE better than nothing"? Yes. First, that's not what "N95" means. The material in an N95 mask is capable of filtering 95% of 0.3um particles. That's it. It has nothing to do with "viral load". If a virus travels in particles smaller than 0.3um? No good. If the concentration of larger particles in a space is enough that 5% can infect you? Same thing. Theoretical efficiency is not the same as real-world efficiency. But far more importantly, if you don't fit such a mask properly, then the air will leak around the gaps, and the filtration efficiency of the material is largely irrelevant. Everyone I see on the street wearing (K)N95 masks has massive gaps around their nose and chin. If I can see the gaps from 10 feet away, their fancypants masks aren't doing much of anything except deflecting the air back over their head. Can a well-fit, correctly worn N95 mask make a difference as PPI? Sure, I don't doubt it. But I guarantee that most people aren't getting close to either criterion. Illustrative anecdote: I've had really nasty hay fever for my entire life, and I went through a period of trying N95 masks to keep the pollen out whenever I did yard work. Didn't work at all. Want to guess how big pollen is?

handoflixue 5y ago
> If a virus travels in particles smaller than 0.3um? No good. What does that have to do with Covid? > If the concentration of larger particles in a space is enough that 5% can infect you? Same thing. There is a huge body of evidence that viral load impacts severity, so if 5% of the viral load could infect you, then 20x that was going to put you on a ventilator. > if you don't fit such a mask properly, then the air will leak around the gaps There are actual real-world tests based on "average usage". We don't just have to make up our notion of efficiency based on your anecdotes. > Illustrative anecdote: I'll admit I prefer the overkill of a P100, but I've taught people how to use one in the course of 5 minutes and their reaction is "wow, this works so well". Maybe the extra filtering makes up for the air gaps, but they're really not hard to get real-world results from.
- timr 5y ago
  > What does that have to do with Covid? The virus travels in saliva particles. > There is a huge body of evidence that viral load impacts severity There's actually no evidence for this claim. It's a hypothesis, not a fact. It's essentially impossible to verify the initial viral load of an infectious dose without doing challenge trials, which we haven't done (yet). > There are actual real-world tests based on "average usage". We don't just have to make up our notion of efficiency based on your anecdotes. There are no real-world trials of n95 masks and Covid. There were a few studies pre-2020 with n95 masks in hospitals and influenza, SARS and MERS. Two hospital studies involved Covid. Essentially all of the research concerning masks and respiratory illnesses was summarized by the WHO here: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31142-9/fulltext https://www.thelancet.com/journals/lancet/article/PIIS0140-6... Figure 4 is the relevant figure. Any study with a 1 in the "respirator" column was conducted with an n95 mask. Overall, they're more effective than the non-respirator masks, but the confidence intervals for nearly all studies overlaps "no effect".