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> 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

> 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

> 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".