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Comment by troelsSteegin | Hacker News Reader

Simple conclusion: "Masks make a huge difference indoors and rarely matter outdoors." The 10% estimate in question is perhaps orders of magnitude too conservative. Why would the CDC employ such a weak numeric argument? They could have left it at something like we see no strong evidence for outdoor transmission. Does there have to be a number attached to public health advice?

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>Simple conclusion: "Masks make a huge difference indoors and rarely matter outdoors."

Also: For a disease that we now know is airborne/aerosol spread rather than airborne/droplet, N95 and KN95 masks are highly effective, a two layer cloth mask fit tightly over a surgical mask is moderately effective, and a cloth mask by itself is largely for show. I still see people saying you should NOT use N95 masks (they're cheaply and widely available now) while donning a neck gaiter pulled up over their mouth. It's another area where the initial messaging was terrible (in this case out of the good intention of reserving them for healthcare workers) and unfortunately has persisted.

Cloth masks are largely for show in protecting you from other people. They are still highly effective in preventing your aerosols from getting out into the air. Even though COVID is airborne, it comes out of your mouth and nose in liquid droplets that then dehydrate and become airborne. If they hit a cloth mask on the way out, they'll be trapped.

By "N95 mask", do you mean this

https://www.amazon.com/3M-8511HB1-C-PS-Sanding-Fiberglass-Re...

or this?

https://www.amazon.com/AccuMed-Respirator-Filtration-Disposa...

I've had a box of the former out in the garage for a couple of years; before 2020, if you looked for an "N95" mask, that's what you would find. But they're not terribly useful in a medical situation.

More the latter. They're both N95, but the valve in the former means outgoing air isn't being filtered.

You can wear another mask, like a surgical mask, to cover the exhale valve.

Or tape over it (securely).

> For a disease that we now know is airborne/aerosol spread rather than airborne/droplet, N95 and KN95 masks are highly effective, a two layer cloth mask fit tightly over a surgical mask is moderately effective, and a cloth mask by itself is largely for show.

I mean, who's "we"? I knew this back in January 2020.

Actually, and just for the record, a N95 properly fitted works very, very well.

But usually you cannot wear (properly) a N95 for more than two/three hours without having your face with deep signs (and of course you need to be clean shaven).

A "generic" N95 used by untrained people and loosely worn, isn't that much better a protection for the person wearing it than a surgical mask, while both are quite good at protecting other people from the "emissions" of the person wearing the mask (of course only if it is valveless).

Previous post with a link to a video of a proper "fit test" and some more info about valve and valveless: https://news.ycombinator.com/item?id=23957506

I can sympathize with that, that would probably have been much more truthful.

But the CDC recommendations have been so poorly thought out so far, it's hard to blame anyone who would say "screw your judgment of evidence, give us a number"

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