
If Your Mask Has a Valve, It's Half Useless - miked85
https://vitals.lifehacker.com/if-your-mask-has-a-valve-its-half-useless-1843182019
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beerandt
This author has no business writing on this subject if she can't even get the
basic terminology correct. There's a difference between a mask and a
respirator. To over simplify, one deflects and one filters. Masks don't have
valves, respirators (sometimes) do.

A valved n95 respirator is essentially acting as a respirator (filter) while
inhaling, and as a mask (deflector) while exhaling.

Calling valved respirators half useless implies that masks are wholly useless.

Neither surgical masks or cotton/other homemade masks (or valved respirators)
are designed to _filter_ exhaled breath; in fact, most of the air goes
_around_ surgical masks, but droplets hit and stick to the mask based on the
same principles of bugs hitting a windshield.

And that's all they're designed to do- retain/deflect droplets/particles
expelled by the wearer. _Valved respirators still do this_. Even the tiny gap
in the open valve usually is filtered, just not to n95 levels.

Of course all of this presumes the user is using the PPE correctly in the
first place. If you don't know the difference between a mask and a respirator,
I can almost guarantee you're using yours wrong.

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tenken
But there's a pm2.5 filter insert that covers the Whole mouth portion between
cloths. Yes there is an airhole, but there's a filter snug up against the
whole airhole ....

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projektfu
Data or GTFO. I’m not sure if there are studies showing this to be true, but
the existence of authorities saying it is is really not enough. I’d be happy
with mechanical data, but actual droplet data would be better.

~~~
_bxg1
It's an intentional feature of the product, though? It sounds like they're
specifically designed not to obstruct exhalation. Why would you be skeptical
of that?

~~~
projektfu
Because that fact doesn’t mean it doesn’t protect against spreading.

~~~
_bxg1
"The fact that this hammer is heavy and shaped for hammering things doesn't
mean it will drive nails. Data or GTFO."

~~~
projektfu
Almost everything in medicine ends up being surprising. So much "knowledge" is
just someone's assumption being passed as gospel only to be discovered false
years later. Medicine isn't an engineering problem. There is an analogy in
software engineering where people argue about the most "efficient" way to do
something and don't bother profiling it with real world data.

There are consequences to advising people that their masks are half worthless,
if it is not true. People might not be willing to wear valveless N95 masks. Or
they take those masks off more and expose themselves more. Asking for a little
data behind a recommendation is more than reasonable.

