> The "95" in N95 represents the filtration effectiveness.

> So _any_ leakage means the mask fails in it purpose of filtration.

What do you mean by that? The "95" is just a statement of its performance characteristics, which literally every well-engineered thing has quantified (and are always less than "perfect").

Now if you want an N95 to meet its specifications, it has to be tightly fitted. However it's a spectrum of effectiveness, and unless the fit is ridiculously bad, the protection factor is still going to be better than a cloth mask, e.g.:

                                                                               poorly           well-    
                       cloth or                                                fitted           fitted
    No mask            surgical mask                                           N95              N95    Perfect
   |O-------------------------O---------------------------------------------------O--------------O--------O|

Don't let the perfect be the enemy of the good.

Now add a time component of exposure to the virus.

And your graph shows 100% infection rate with every setup that has any kind of leak at some point in time.

> Don't let the perfect be the enemy of the good.

Show one study in a vaccinated population of humans, that demonstrates any real-world effectiveness of masks.

The "good" here is never quantified, nor demonstrated. It's always an inference from some mechanism.

Its 95% at the worst particle size for filtering which is 2.5 microns. Above and below that size they perform substantially better.

The minimum size of a covid19 carrying particle is 4.7 microns, resulting in at least 99.7% effectiveness at worst.

[1]https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC7579175/# [2]https://pubmed.ncbi.nlm.nih.gov/9487666/

Almost every single time someone links a paper on HN as evidence of their statement, it shows evidence of the opposite of their statement:

2nd paragraph:

In a study by Chia et al. (2020), SARS-CoV-2 genes were detected in sampled aerosol particles with diameters >4 μm and 1–4 μm [20]. In a study by Liu et al. (2020), SARS-CoV-2 was detected in submicrometer aerosol particles ranging between <0.25 and 1 μm in diameter via a droplet-digital-PCR-based detection method [21]. In a study by Liu et al. (2020), the maximum SARS-CoV-2 concentrations of 40 and 9 copies per m3 of air were measured in aerosol samples with diameters of 0.25–0.5 μm and 0.5–1.0 μm, respectively [21].

>> In a study by Chia et al. (2020), SARS-CoV-2 genes were detected in sampled aerosol particles with diameters >4 μm and 1–4 μm [20]. In a study by Liu et al. (2020), SARS-CoV-2 was detected in submicrometer aerosol particles ranging between <0.25 and 1 μm in diameter via a droplet-digital-PCR-based detection method [21]. In a study by Liu et al. (2020), the maximum SARS-CoV-2 concentrations of 40 and 9 copies per m3 of air were measured in aerosol samples with diameters of 0.25–0.5 μm and 0.5–1.0 μm, respectively [21].

Are those viable virus particles? Because that's what actually matters, not the mere presence of genes. Also, are the smaller droplets as effective at transmission as the larger ones? Scanning the paper, it looks like they get smaller as they desiccate.

Why would a virus become unviable just because it's embedded in a smaller droplet?

> Why would a virus become unviable just because it's embedded in a smaller droplet?

From my scan, it looked like some of the smaller droplet sizes were due to desiccation of larger particles. As a particle desiccates, concentrations will change, and maybe they'll change in a way that makes the virus non-viable E.g., imagine a freshwater lake that contains certain amount of salt, as you dry it out it will get saltier and saltier, to the point where freshwater fish can no longer live in it. Eventually you get a salt pan.

That's not true: leakage decreases protection, but there's a scaling relationship rather than a complete elimination of efficacy: https://pubmed.ncbi.nlm.nih.gov/24275016/

Over a long enough time the efficacy drops to zero.

So, no need to use, buy, sell, or produce sun screen. It just increases the time you can stay outside without getting a sunburn from a few minutes to hours. Totally useless. /s

All you need is a moment of infection. A single second, one breath of air through a leak in your mask. Sunburn is not even remotely similar.

This just isn't true. Viral load matters.

> Over a long enough time the efficacy drops to zero.

And in the long run, we're all dead.

Yes, so why are we stressing about this? Just focus on getting healthy and doing the best we can is our long term limit of capability.

Masks won't save us.

How long?

Good question, doesn't it depend on environment? If you are alone in the woods, the mask will always work forever.

If you are in a small room with a dozen infected people coughing...?

Hence it gives "only" a 70x boost in protection, not a 100% protection cast iron guarantee.

For how long? 10 years of exposure with a leaky mask is not 70% any more, more like .05%.

It's the minimum standard, really. Most reputable N95s seem to hit over 99% in real tests.

This was lately on HN, so you can check yourself: https://www.armbrustusa.com/pages/mask-testing