
Face Masks: Much More Than You Wanted to Know - monort
https://slatestarcodex.com/2020/03/23/face-masks-much-more-than-you-wanted-to-know/
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exabrial
Side notes: I was trying to figure out how I could "help" by developing an N95
respirator with some online communities. I was prepared to be humbled by what
I didn't know, but holy smokes, now I realize I can't even begin to know what
I don't know.

* 3d printed PLA? Deforms at autoclaving temperatures. chemical sterilization not recommended b/c there's not many good ways to "know" it's worked correctly.

* Sealing? Good luck. There are some people working on using TPU to help seal, but again, sterilization is a problem.

* Porosity? 3d printed materials can barely pass 2psi. This also creates a LOT of places for bacteria to hide.

* Filter media? DO NOT cut up a HEPA filter! They're made with micron-scale fiberglass. This keeps getting suggested, but people don't realize that HEPA filters are not made of paper.

I'm confident an open source design and process can eventually be made, but
it's much harder problem than it looks. There's a lot of people are adding a
lot of noise (I'm in "read-only" mode for now to cut down on the noise level)
so if you're thinking of contributing, the best thing you can do is just read
atm.

Producing Face Shields has some interesting and unexpected requirements (head
back leakage among other things), but is a much simpler problem to solve and
there are some good designs (Google Prusa 3d Face Shield)

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mattzito
As usual, a great write up. I think one nuance that is important is:

> Does letting a single influenza virus through mean you will get infected? If
> so, any reduction short of 100% is useless. I have a vague sense that this
> isn’t true; your immune system can fight off most viruses, and the fewer you
> get, the better the chance it will win. Also, even respirators don’t claim
> to reduce particle load by more than 99% or so, and those work, so it can’t
> be that literally a single virus will get you

I was speaking with an ER doctor yesterday who said that aside from
comorbities and age, the single biggest predictor of how severe a case may be
is the viral load exposure. The reasons that N95 respirators are so important
in a hospital setting is that when a dr or nurse are continuously exposed to
the virus, those deltas in performance might mean they pstill get sick, but
it’s mild and back to work in two weeks vs ending up in the hospital for a
month.

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malandrew
This is exactly the reason the anti-mask people in the US or so frustrating.
Yes, you might still get sick but the initial viral load is likely to be
greatly reduced and the speed and intensity at which you get sick is likely to
be milder.

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miroz
I'm trying to decide if I should wear the mask or not, but whatever I read the
only question is if a mask can protect me from getting the virus. But the
question that interests me is if the mask protects people around me if I have
the virus (and I don't have the symptoms yet). If it does, then everybody
should wear a mask.

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js2
> But the question that interests me is if the mask protects people around me
> if I have the virus (and I don't have the symptoms yet).

Possibly, for the same reason you should cough or sneeze into your elbow. It
reduces the number of droplets you spread into and around the environment
around you, and before they aerosolize.

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tcbawo
Once testing is widely available, I hope to see wearing masks in public as a
precondition for ending lock-downs/quarantines and returning to normal life.
This might be something most state governments of all stripes could sign onto.

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crazygringo
Why? And for how long?

As long as the curve has been "flattened" and the health care system is under
capacity, what are you hoping to achieve?

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maxander
"As long as the health care system is under capacity" is about a week or so at
best, in much of the U.S., and not much longer (or already past) in many other
places. And it's going to stay that way for awhile - outside China and Korea,
the best news we have so far is the rate of new cases in some places has
stopped increasing _exponentially._

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woofie11
Old-school cotton masks help a lot too. We don't know exactly how much, but
they do. They reduce viral loads by at least 30% and more likely by something
like 70%.

Cover your mouths.

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crazygringo
Citation please?

In response to a long article full of links to scientific papers and nuanced
analysis, saying a blanket statement like this isn't helpful at all unless
it's backed up.

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stuartc842
[https://smartairfilters.com/en/blog/best-materials-make-
diy-...](https://smartairfilters.com/en/blog/best-materials-make-diy-face-
mask-virus/)

not direct citation, but relevant

