1/ In context of extra precautions against new COVID variants, some new questions pop up about #masks.

Article by @cwarzel @zeynep asks/answers some good questions to start. Other thoughts in a https://abs.twimg.com/emoji/v2/... draggable="false" alt="🧵" title="Thread" aria-label="Emoji: Thread">, e.g. N95s, fit (Tw7+ https://abs.twimg.com/emoji/v2/... draggable="false" alt="⬇️" title="Pfeil nach unten" aria-label="Emoji: Pfeil nach unten">), when to replace (Tw25 https://abs.twimg.com/emoji/v2/... draggable="false" alt="⬇️" title="Pfeil nach unten" aria-label="Emoji: Pfeil nach unten">), etc. https://www.nytimes.com/2021/01/29/opinion/coronavirus-masks.html">https://www.nytimes.com/2021/01/2...
Opinion | It’s Been 10 Months, and I Still Don’t Know When to Replace My Mask!

Practical pandemic guidance is still a huge problem.

https://www.nytimes.com/2021/01/29/opinion/coronavirus-masks.html
2/ Countless recent articles w/ interviews from relevant experts imploring people to still take mask-wearing & overall airborne COVID health seriously.

One of many, here by @skbaer w/ broad contribution. (Tw33 below has link to a compilation of more). https://www.buzzfeednews.com/article/skbaer/double-masking-coronavirus-variants">https://www.buzzfeednews.com/article/s...
What Is Double-Masking? Here’s How It Can Keep You Safer From The Coronavirus.

“I would prefer that somebody wore one mask properly than two masks improperly, but if you can wear two masks properly, that's great.”

https://www.buzzfeednews.com/article/skbaer/double-masking-coronavirus-variants
3/ Many good arguments recently towards motivating broader use of #bettermasks, i.e. #N95s. So if not using already, consider.

See e.g. this editorial by @j_g_allen: https://www.washingtonpost.com/opinions/2021/01/26/n95-masks-safest-next-best-options/

Or">https://www.washingtonpost.com/opinions/... this opinion-piece by a group of excellent scientists: https://twitter.com/HuffmanLabDU/status/1354129198319693825?s=20">https://twitter.com/HuffmanLa...
4/ One of the simplest overviews on practical aspects of this topic of upgraded masks/respirators (i.e. N95s, KN95s, double-masking) is a brief video interview also with @j_g_allen: https://twitter.com/j_g_allen/status/1354608059771973648">https://twitter.com/j_g_allen...
5/ Also a great overview on the importance & physical science principles behind face masks for COVID-19 protection was written recently by @MonicaGandhi9 & @linseymarr. It& #39;s a very short, easy read; worth your time. https://www.cell.com/med/fulltext/S2666-6340(20)30072-6">https://www.cell.com/med/fullt...
Uniting Infectious Disease and Physical Science Principles on the Importance of Face Masks for...

This commentary will summarize the evidence on face masks for COVID-19 from both the infectious diseases and physical science viewpoints; standardize recommendations on types of masks that afford the...

https://www.cell.com/med/fulltext/S2666-6340(20)30072-6
6/ This is one of the best videos to explain how masks work (especially focused on #N95s); by @minutephysics. https://youtu.be/Y47t9qLc9I4 ">https://youtu.be/Y47t9qLc9...
7/ To achieve adequate health benefit from masks, keep in mind that both FILTRATION & FIT are critical.

I frequently share this video that beautifully demonstrates the importance of fit. Notice what happens to the aerosol with a poorly fitting mask: https://youtu.be/mJ81IBTMvcU ">https://youtu.be/mJ81IBTMv...
8/ Scientific motivation for better mask FIT quality is deep & wide. Three of *many*:

I.e. poor fit of surgical masks = insufficient & danger to HCWs

Goldberg et al: https://twitter.com/HuffmanLabDU/status/1355580532814278661
Prof.">https://twitter.com/HuffmanLa... @CappaSnappa: https://www.researchsquare.com/article/rs-142138/v1
Rothamer">https://www.researchsquare.com/article/r... et al (https://abs.twimg.com/emoji/v2/... draggable="false" alt="⬇️" title="Pfeil nach unten" aria-label="Emoji: Pfeil nach unten">): https://www.medrxiv.org/content/10.1101/2020.12.31.20249101v1">https://www.medrxiv.org/content/1...
9/ Also *lots* of research & resources on mask/filtration quality. https://abs.twimg.com/emoji/v2/... draggable="false" alt="🧵" title="Thread" aria-label="Emoji: Thread"> not meant to be comprehensive, but e.g.:

Pan et al: https://www.medrxiv.org/content/10.1101/2020.11.18.20233353v1
Clapp">https://www.medrxiv.org/content/1... et al: https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2774266?alert=article
Interactive">https://jamanetwork.com/journals/... graphs by @smogdr: http://jv.colostate.edu/masktesting/ 
Lit:https://jv.colostate.edu/masktesti... href=" #citations">https://examine.com/topics/coronavirus-masks/research/ #citations">https://examine.com/topics/co...
Coronavirus masks: What’s the latest evidence? Research Breakdown

We analyzed over 80 studies to help answer your mask questions: efficacy of different types, storage, and more.

https://www.medrxiv.org/content/10.1101/2020.11.18.20233353v1
10/ One strategy to improve filtration/fit combo could be to double-mask. This can be effective (webinar from Sept by @Smogdr w/ test data: ).

But">https://youtu.be/lxzznIsXU... make sure that the added layers don& #39;t interfere with your ability to breath smoothly through the material.
11/ Another broad strategy to improve mask FIT is to add a #maskbrace to hold on a looser mask w/ gaps (i.e. surgical). It& #39;s usually a piece of rubber that makes sure no aerosol sneaks in or out through gaps at your face, nose, chin.

E.g. Rothamer et al.: https://www.medrxiv.org/content/10.1101/2020.12.31.20249101v1">https://www.medrxiv.org/content/1...
Strategies to minimize SARS-CoV-2 transmission in classroom settings: Combined impacts of ventila...

The impact of the COVID-19 pandemic continues to be significant and global. As the global community learns more about the novel coronavirus SARS-CoV-2, there is strong evidence that a significant...

https://www.medrxiv.org/content/10.1101/2020.12.31.20249101v1
12/ Here is a short video interview with @katherinepasem1, a designer of the @FixTheMask brace:
https://twitter.com/abc7kristensze/status/1356387694348177408
You">https://twitter.com/abc7krist... can buy these braces at https://www.fixthemask.com/ .">https://www.fixthemask.com/">...
13/ OR you can use the free template provided by @FixTheMask to make your own #maskbrace for improved fit. https://www.fixthemask.com/products/v2-diy-rubber-sheet-brace">https://www.fixthemask.com/products/...
DIY Mask Brace from Rubber Sheet Downloadable Template

V2: The rubber sheet brace. Make this Mask Fitter yourself. Cut out your own with just a pair of scissors. Video tutorial here. We're happy to offer this as a free download on our site, but if you're...

https://www.fixthemask.com/products/v2-diy-rubber-sheet-brace
14/ This is a nice video explaining by @FixTheMask filtration in general and the importance of good mask fit: https://youtu.be/Vd_5yU5uobA ">https://youtu.be/Vd_5yU5uo...
15/ @linseymarr (aerosol & mask-testing expert) recently shared her impressions after having made one of these DIY mask braces: https://twitter.com/linseymarr/status/1354099221687918592">https://twitter.com/linseymar...
16/ Another good #maskbrace option is the Badger Seal developed through @UWMadEngr, which can be purchased for ~$10 or made yourself using their linked instructions & videos. https://making.engr.wisc.edu/mask-fitter/ ">https://making.engr.wisc.edu/mask-fitt...
Badger Seal (Mask Fitter, Mask Sealer, Mask Brace)

What is the Badger Seal (mask fitter)? A soft, flexible and adjustable “frame” that significantly improves the outer seal of a mask. Why use it?  Increase filtration performance: Adding the Badger...

https://making.engr.wisc.edu/mask-fitter/
17/ No matter the mask, only as effective as it& #39;s ability to seal to face around both nose & mouth.

If hard to breath through a #mask, it is too restrictive/thick. Air (& aerosol) will always escape mask. If air exits via gaps rather than THROUGH layer(s), mask is ineffective!
18/ CDC doc gives some tips related to checking the seal of your mask/respirator:

- Make sure material sucks in or blows out sufficiently when breathing
- Fogging glasses or gaps formed are signs of poor fit

(Note: for COVID, never use a mask w/ valve!)
https://www.cdc.gov/niosh/docs/2018-130/pdfs/2018-130.pdf">https://www.cdc.gov/niosh/doc...
19/ This is a 4-min video also shows how to do a user seal-check on a #N95 mask/respirator.

Keep in mind that this was developed for occupational safety and not wrt general public health, but most principles still apply.

(HT @DavidLKeating) https://youtu.be/pGXiUyAoEd8 ">https://youtu.be/pGXiUyAoE...
20/ Some other links with various tips & hacks in terms of mask fit:

Via @NebraskaMed: https://www.nebraskamed.com/COVID/13-mask-hacks-to-make-your-mask-fit-better

O& #39;Kelly">https://www.nebraskamed.com/COVID/13-... et al: https://www.medrxiv.org/content/10.1101/2020.10.28.20221895v1.full.pdf

CDC:">https://www.medrxiv.org/content/1... https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/how-to-wear-cloth-face-coverings.html

Via">https://www.cdc.gov/coronavir... @lisa_iannattone: https://twitter.com/lisa_iannattone/status/1357513295448702984

Article">https://twitter.com/lisa_iann... by @mgodoyh: https://www.npr.org/sections/health-shots/2021/02/03/962197192/5-hacks-to-make-your-face-mask-more-protective">https://www.npr.org/sections/...
21/ Also important to note that facial hair/beards makes it very difficult/impossible to get a good fit to your face and so efficiency of the #mask is reduced.

Check out this awesome CDC/NIOSH chart.

Be a #walrus, not Dali!
https://www.cdc.gov/niosh/npptl/pdfs/facialhairwmask11282017-508.pdf">https://www.cdc.gov/niosh/npp...
22/ Related; you have probably heard of the " #candletest" for testing filtration quality (i.e. blow through mask; candle flame out = bad). I personally don& #39;t like this, b/c may just mean air/aerosol escapes through gaps. E.g.: https://twitter.com/linseymarr/status/1357365723874680832

https://twitter.com/linseymar... href=" https://www.npr.org/sections/goatsandsoda/2020/07/24/895090627/coronavirus-faq-what-does-it-mean-if-i-can-blow-out-a-candle-while-wearing-a-mas">https://www.npr.org/sections/...
23/ Mid-summary: Upgrade to best mask quality you can find (N95 if avail., KF94, possibly KN95), but FIT is always still critical. #bettermasks

If you can& #39;t breathe easily so exhaled breath goes THROUGH material, it is too restrictive and/or a bad fit.
24/ One concern is counterfeit or knock-off #N95, #KN95 respirators. I don’t think anything is fool-proof, but the CDC has this resource:
https://www.cdc.gov/niosh/npptl/usernotices/counterfeitResp.html">https://www.cdc.gov/niosh/npp...
25/ Another question that has come up a lot recently is how long you can wear your #N95-type mask. See tweet #1 for some ideas & sub-links.

First, if possible look at manufacturer recommendations for tips.

CDC/NIOSH officially lists e.g. 8-hr limit: https://www.cdc.gov/niosh/topics/hcwcontrols/recommendedguidanceextuse.html">https://www.cdc.gov/niosh/top...
26/ The next set of tweets is NOT meant to be definitive, b/c there are plenty of people who work in this space more than I do. I assembled some thoughts related to practical questions, however, and these may be helpful as you answer questions specific to your situation.
27/ Convos about practical N95 care & longevity, w/ @linseymarr @Smogdr @j_g_allen @JudahWorldChamp +

- Rotate use per day: https://twitter.com/Smogdr/status/1357120830610632704">https://twitter.com/Smogdr/st...
- Filtration likely good for months: https://twitter.com/linseymarr/status/1357103925380280321">https://twitter.com/linseymar...
- Good until straps no longer pull to seal: https://twitter.com/Smogdr/status/1357121649963720704">https://twitter.com/Smogdr/st...
28/ A few add’l #N95 tips:

- Use longer than 8-hrs likely ok if necessary: https://twitter.com/HuffmanLabDU/status/1357111817554698241
-">https://twitter.com/HuffmanLa... But best to swap when damp from use (can reduce filtration)
- N95, HEPA filtration add electrostatic properties to boost filtration; this is reduced when damp or after washing
29/ For use outside of a medical environment, it is probably best not to clean N95s but rather to rotate use. I.e. place aside in a paper bag for a couple days and then return, e.g. suggestion by @smogdr: https://twitter.com/Smogdr/status/1357120830610632704">https://twitter.com/Smogdr/st...
30/ In a medical environment, may be necessary to sterilize if not enough to dispose. Several studies have focused on break-down after rounds of cleaning, e.g.:

https://www.generalsurgerynews.com/In-the-News/Article/10-20/Fit-and-Efficacy-Deteriorate-With-Reuse-of-N95-Masks/60823">https://www.generalsurgerynews.com/In-the-Ne...

https://pubmed.ncbi.nlm.nih.gov/33279587/ 

Via">https://pubmed.ncbi.nlm.nih.gov/33279587/... @linseymarr: https://twitter.com/linseymarr/status/1341759236989214721">https://twitter.com/linseymar...
31/ One question is about shelf-life of N95 (and similar) masks. That is relatively little concern. They don& #39;t physically break down easily.

This study also supported that from an experimental perspective: https://aaqr.org/articles/aaqr-19-12-oa-0620">https://aaqr.org/articles/...
Effectiveness of N95 Facepiece Respirators in Filtering Aerosol Following Storage and Sterilization

ABSTRACT The use of electret N95 filtering facepiece respirators (N95FFRs) after prolonged storage or treatment can reduce the expense of buying non-expired N95 and thus enable developing and...

https://aaqr.org/articles/aaqr-19-12-oa-0620
32/ Summary: Masks still a critical piece of community armor against further COVID transmission. As variants of concern threaten, upgrade to #bettermasks & focus on fit.

For more general answers wrt #COVIDisAirborne, see FAQ by @jljcolorado & colleagues: https://tinyurl.com/FAQ-aerosols ">https://tinyurl.com/FAQ-aeros...
FAQs on Protecting Yourself from Aerosol Transmission

FAQs on Protecting Yourself from COVID-19 Aerosol Transmission Shortcut to this page: https://tinyurl.com/FAQ-aerosols Version: 1.87, 9-Dec-2020 Click here to jump over the scientific & historical...

https://tinyurl.com/FAQ-aerosols
33/ If you want to read still further about #bettermasks and much more, lots of articles (search "mask") compiled on both & #39;media& #39; tab (i.e. news) & & #39;science articles& #39; tab (research). #gid=1475562242&range=A1">https://docs.google.com/spreadsheets/d/1-l78z-rSodmSfsfChv7d_tubb6d1Zxst-d7YI4HZp4g/edit #gid=1475562242&range=A1">https://docs.google.com/spreadshe...
Resources on transmission & prevention of COVID-19

OVERVIEW Resources on transmission & prevention of CoVID-19,Link to this page:,https://bit.ly/3fzmB16 Contact:,@HuffmanLabDU alex.huffman@du.edu Direct Excel download:,

https://docs.google.com/spreadsheets/d/1-l78z-rSodmSfsfChv7d_tubb6d1Zxst-d7YI4HZp4g/edit#gid=1475562242&range=A1
You can follow @HuffmanLabDU.
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