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Duke physics dept tests mask efficacy
Posted by: Lemon Drop
Date: August 09, 2020 06:51AM
[advances.sciencemag.org]

Some of the popular approaches are worse than no mask at all



Edited 1 time(s). Last edit at 08/09/2020 06:55AM by Lemon Drop.
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Re: Duke physics dept tests mask efficacy
Posted by: Acer
Date: August 09, 2020 09:06AM
Eight months into a global pandemic, not to mention 100 years of near-misses, and we're just now scientifically analyzing the effectiveness of non-professional masks. Of course the professionally-fitted N95 is the best, but we were never no-how going to outfit a country, much less a continent or a globe with professionally-fitted N95s.

Maybe it was hubris. No way those people in dusty 1918 wearing goofy white masks could have known anything, so why bother checking?



Edited 1 time(s). Last edit at 08/09/2020 09:06AM by Acer.
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Re: Duke physics dept tests mask efficacy
Posted by: Lemon Drop
Date: August 09, 2020 09:33AM
Quote
Acer
Eight months into a global pandemic, not to mention 100 years of near-misses, and we're just now scientifically analyzing the effectiveness of non-professional masks. Of course the professionally-fitted N95 is the best, but we were never no-how going to outfit a country, much less a continent or a globe with professionally-fitted N95s.

Maybe it was hubris. No way those people in dusty 1918 wearing goofy white masks could have known anything, so why bother checking?

I think the most helpful thing from the article is that neck gaiters and bandannas are not effective and in some cases worse than no mask at all. We're all obsessed with face coverings, which I hope are here to stay because it's going to cut down on all kinds of disease spread esp. cold and flu. It's possible we may barely have a flu season at all this year if people will wear masks at least somewhat consistently. May as well go with ones that actually work.
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Re: Duke physics dept tests mask efficacy
Posted by: Acer
Date: August 09, 2020 10:39AM
Quote
Lemon Drop
I think the most helpful thing from the article is that neck gaiters and bandannas are not effective and in some cases worse than no mask at all.

Yes, that is an important take-away from this study.

It's also important to note the study was proof of concept about a measurement method, not a definitive comparison of masks. That would be the next step and hopefully that will be expedited. Though again I'm disappointed we're still at this preliminary stage this late in the crisis.

I would conjecture that an ill-fitting N95 is worse than a cotton mask, because the air will seek the path of least resistance. The cotton mask, being more permeable is less likely to force air to the gaps, and that will give absorbency of the material the opportunity to function.
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Re: Duke physics dept tests mask efficacy
Posted by: sekker
Date: August 09, 2020 11:54AM
My conclusions: Bandanas and knitted material provide very little protection to others when used as a face covering. Most of the cotton masks have similar performances though 'cotton 3' (mask number 9) looks worse than others. 3-layer surgical mask works second best to a fitted N95.

I would guess adding a filter to a cotton mask would get close to a surgical mask in performance.
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Re: Duke physics dept tests mask efficacy
Posted by: Ammo
Date: August 09, 2020 06:24PM
I wonder if all masks that look like mask #1 are considered surgical masks or are there variables in efficacy between them.



Be kind, for everyone you meet is fighting a battle you know nothing about. —Wendy Mass

Until you make your unconscious conscious, it will direct your life and you will call it fate. - Carl Jung
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Re: Duke physics dept tests mask efficacy
Posted by: GGD
Date: August 09, 2020 07:27PM



Here's the list sorted from most effective to least effective with the number of the picture corresponding to the name. I wish the article had a simple table like this.
Mask,	Name		Description
14,	'Fitted N95'	N95 mask, no exhalation valve, fitted
1,	'Surgical' *	Surgical mask, 3-layer
5,	'Poly/Cotton'	Cotton-polypropylene-cotton mask
4,	'PolyProp'	2-layer polypropylene apron mask
	'Swath'		Swath of mask material, polypropylene
13,	'Cotton5' *	2-layer cotton, pleated style mask
7,	'Cotton2'	2-layer cotton, pleated style mask
2,	'Valved N95'	N95 mask with exhalation valve
8,	'Cotton4'	2-layer cotton, Olson style mask
6,	'MaxAT'		1-layer Maxima AT mask
10,	'Cotton1'	1-layer cotton, pleated style mask
9,	'Cotton3'	2-layer cotton, pleated style mask
3,	'Knitted'	Knitted mask
12,	'Bandana' *	Double-layer bandana
	'None'	*	Control experiment, no mask
11,	'Fleece'	Gaiter type neck fleece

Masks marked with an asterisk (*) were tested by four speakers, all others by one speaker.



Edited 1 time(s). Last edit at 08/09/2020 07:39PM by GGD.
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Re: Duke physics dept tests mask efficacy
Posted by: rgG
Date: August 09, 2020 07:50PM
Thanks for the list.
I gave up trying to figure it out.





Roswell, GA (Atlanta suburb)
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Re: Duke physics dept tests mask efficacy
Posted by: Lemon Drop
Date: August 09, 2020 08:08PM
Quote
GGD


Here's the list sorted from most effective to least effective with the number of the picture corresponding to the name. I wish the article had a simple table like this.
Mask,	Name		Description
14,	'Fitted N95'	N95 mask, no exhalation valve, fitted
1,	'Surgical' *	Surgical mask, 3-layer
5,	'Poly/Cotton'	Cotton-polypropylene-cotton mask
4,	'PolyProp'	2-layer polypropylene apron mask
	'Swath'		Swath of mask material, polypropylene
13,	'Cotton5' *	2-layer cotton, pleated style mask
7,	'Cotton2'	2-layer cotton, pleated style mask
2,	'Valved N95'	N95 mask with exhalation valve
8,	'Cotton4'	2-layer cotton, Olson style mask
6,	'MaxAT'		1-layer Maxima AT mask
10,	'Cotton1'	1-layer cotton, pleated style mask
9,	'Cotton3'	2-layer cotton, pleated style mask
3,	'Knitted'	Knitted mask
12,	'Bandana' *	Double-layer bandana
	'None'	*	Control experiment, no mask
11,	'Fleece'	Gaiter type neck fleece

Masks marked with an asterisk (*) were tested by four speakers, all others by one speaker.


Thanks for creating the table! Ugh, research articles. I first read about this in a summary article in another source, should have linked to that instead.

One consideration in favor of the cotton masks - the negative environmental impact of all these disposable, non-biodegradable masks and gloves.
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Re: Duke physics dept tests mask efficacy
Posted by: space-time
Date: August 09, 2020 10:06PM
Surgical mask, 3-layer is almost as good as a true N95? amazing.
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Re: Duke physics dept tests mask efficacy
Posted by: GGD
Date: August 09, 2020 10:13PM
Quote
space-time
Surgical mask, 3-layer is almost as good as a true N95? amazing.

Remember this is for what you EXHALE when speaking. I'd like to see similar tests for what you inhale.
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Re: Duke physics dept tests mask efficacy
Posted by: space-time
Date: August 09, 2020 10:29PM
Quote
GGD
Quote
space-time
Surgical mask, 3-layer is almost as good as a true N95? amazing.

Remember this is for what you EXHALE when speaking. I'd like to see similar tests for what you inhale.

true. If those around you do not wear good masks, then YOU need to protect yourself.
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Re: Duke physics dept tests mask efficacy
Posted by: RgrF
Date: August 09, 2020 10:48PM
So it comes down to Fitted N95 or your beard - what's more important?
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Re: Duke physics dept tests mask efficacy
Posted by: sekker
Date: August 10, 2020 08:17AM
Quote
GGD
Quote
space-time
Surgical mask, 3-layer is almost as good as a true N95? amazing.

Remember this is for what you EXHALE when speaking. I'd like to see similar tests for what you inhale.

The entire purpose of mask-wearing outside the hospital setting is to prevent you from infecting others, especially if you are COVID-positive but asymptomatic. Self-protection is far less of a consideration.
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Re: Duke physics dept tests mask efficacy
Posted by: sekker
Date: August 10, 2020 08:18AM
Quote
RgrF
So it comes down to Fitted N95 or your beard - what's more important?

Most health care locations have instructed workers to end their beards (men) and no longer regular use of make-up (mostly women) for N95 function and re-use.
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Re: Duke physics dept tests mask efficacy
Posted by: sekker
Date: August 10, 2020 08:26AM
Quote
Lemon Drop
Quote
GGD


Here's the list sorted from most effective to least effective with the number of the picture corresponding to the name. I wish the article had a simple table like this.
Mask,	Name		Description
14,	'Fitted N95'	N95 mask, no exhalation valve, fitted
1,	'Surgical' *	Surgical mask, 3-layer
5,	'Poly/Cotton'	Cotton-polypropylene-cotton mask
4,	'PolyProp'	2-layer polypropylene apron mask
	'Swath'		Swath of mask material, polypropylene
13,	'Cotton5' *	2-layer cotton, pleated style mask
7,	'Cotton2'	2-layer cotton, pleated style mask
2,	'Valved N95'	N95 mask with exhalation valve
8,	'Cotton4'	2-layer cotton, Olson style mask
6,	'MaxAT'		1-layer Maxima AT mask
10,	'Cotton1'	1-layer cotton, pleated style mask
9,	'Cotton3'	2-layer cotton, pleated style mask
3,	'Knitted'	Knitted mask
12,	'Bandana' *	Double-layer bandana
	'None'	*	Control experiment, no mask
11,	'Fleece'	Gaiter type neck fleece

Masks marked with an asterisk (*) were tested by four speakers, all others by one speaker.


Thanks for creating the table! Ugh, research articles. I first read about this in a summary article in another source, should have linked to that instead.

One consideration in favor of the cotton masks - the negative environmental impact of all these disposable, non-biodegradable masks and gloves.

Thanks for the table! Very useful.

I have a couple 'disposable' surgical masks - I use them when my cotton are unavailable (I carry one in a plastic bag in my pocket as an emergency mask). I let them sit a week between re-use rather than disposing which seems consistent with COVID half-life estimates on surfaces.
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Re: Duke physics dept tests mask efficacy
Posted by: PeterB
Date: August 10, 2020 12:08PM
Quote
sekker
Quote
GGD
Quote
space-time
Surgical mask, 3-layer is almost as good as a true N95? amazing.

Remember this is for what you EXHALE when speaking. I'd like to see similar tests for what you inhale.

The entire purpose of mask-wearing outside the hospital setting is to prevent you from infecting others, especially if you are COVID-positive but asymptomatic. Self-protection is far less of a consideration.

Reminder: this isn't true for everybody; those of us who are at higher risk (for whatever reason) have a legitimate reason to wear an N95 outside of a hospital setting.




Freya says, 'Hello from NOLA, baby!' (Laissez bon temps rouler!)
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Re: Duke physics dept tests mask efficacy
Posted by: Lew Zealand
Date: August 10, 2020 12:44PM
Note that the "N95 with valve" was bad at preventing exhalation droplets in big breaths as the valve opens for those types of breaths. Which is exactly the worst behavior for prevention of covid spread if the wearer is infected. It still protects the wearer pretty well, though.
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Re: Duke physics dept tests mask efficacy
Posted by: sekker
Date: August 10, 2020 08:20PM
Quote
PeterB
Quote
sekker
Quote
GGD
Quote
space-time
Surgical mask, 3-layer is almost as good as a true N95? amazing.

Remember this is for what you EXHALE when speaking. I'd like to see similar tests for what you inhale.

The entire purpose of mask-wearing outside the hospital setting is to prevent you from infecting others, especially if you are COVID-positive but asymptomatic. Self-protection is far less of a consideration.

Reminder: this isn't true for everybody; those of us who are at higher risk (for whatever reason) have a legitimate reason to wear an N95 outside of a hospital setting.

Thanks for that. My hope is that those at risk can find ways to WFH.
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