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Dr. Alex Huffman Profile picture
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25 Jan, 4 tweets, 3 min read
1/2 @DrLaPook on the importance of quality face coverings (i.e. N95s or even multiple mask layers), esp. as worrying COVID variants rise (via @linseymarr).

But wrt to multiple #mask layers; mask FIT and overall BREATHABILITY also critical, because ...
cbs.com/shows/cbs_even…
2/2 ... If it's 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!

E.g. watch where/how aerosol escapes this poorly-fitting mask
3/2 (bonus) Since mask fit is so so important (even for N95s), there are various strategies to help improve air flow *through* the mask layers & improve fit. This preprint paper shows improvement in mask filtration efficiency by adding a mask brace/fitter.
4/2 (bonus) This webinar from Sept by @Smogdr is one of the best, detailed resources to learn about #mask quality & fit to apply the principles to your own choices.

Whole video is great; content towards the end covers mask-fit, multiple-layering, etc.

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More from @HuffmanLabDU

Dr. Alex Huffman Profile picture
26 Jan
1/ A really good, short read on a very important topic, providing motivation and support for mandated, high-quality #mask-wearing.

By @sri_srikrishna @MonicaGandhi9 @Don_Milton & others = These people you should trust.
hbr.org/2021/01/a-3-st…
2/ COVID19 still very serious & "widespread vaccination is expected to take multiple years globally."

Key arguments from the article above ⬆️ concerning masks.

1. Launch an awareness blitz
2. Communicate about appropriate mask types
3. Prioritize distribution to the vulnerable.
3/ A really important, practical message to emphasize:

Disposable N95s had been in short supply & "have been largely reserved for health care workers. But N95s are now available [widely]."

Should help motivate use of N95s, which have high & standardized filtration efficiency.
Read 5 tweets
Dr. Alex Huffman Profile picture
15 Jan
Important new preprint from Lednicky et al. on #aerosol transmission of COVID

*Aerosol <0.25 - 10 μm collected in car driven by COVID-patient w/ mild symptoms
*Viable virus only detected in airborne particles in size range 0.25 – 0.5 μm

HT @DavidElfstrom
medrxiv.org/content/10.110…
Paper shows: "the potential risk of SARS-CoV-2 transmission by minimally symptomatic persons in the closed space inside of a car (w/ closed windows & air conditioning running), & suggest that a substantial component of that risk is via aerosolized virus."
medrxiv.org/content/10.110…
This 👇 earlier paper by the same Lednicky et al. (published Sept. 2020) showed viable (infectious) SARS-CoV-2 was present in aerosols within the hospital room of COVID-19 patients.

Both add to growing body of evidence of real-world COVID #aerosol risk.
ijidonline.com/article/S1201-…
Read 7 tweets
Dr. Alex Huffman Profile picture
15 Jan
1/ Adding #ventilation helps reduce (but not remove!) aerosols & risk from COVID. One simple measure of ventilation is to keep #CO2 sufficiently low. Simple CO2 sensors can be <$150 and are easy to take with you.

One nice summary of consumer CO2 monitors:
bit.ly/monitorsCO2
2/ The idea is that indoor #CO2 comes primarily from people breathing out; but breathing also produces potentially infectious aerosols. So keeping #CO2 levels <800 ppm (or <600 ppm) means air is likely refreshed rapidly enough to keep aerosol risk low.
3/ There are lots of good resources & articles on improving #ventilation & for using #CO2 monitors for rough checks. This article by @B_resnick from months ago is worth a read as a broad overview on various topics related to air safety wrt COVID/aerosols.
vox.com/science-and-he…
Read 8 tweets
Dr. Alex Huffman Profile picture
13 Jan
1/ Really great article that explains common misconceptions & myths about airborne viruses. Clear & easily readable.

Led by a #multidisciplinary slew of all-star scientists. If you trust anyone in the world on these topics, these are the people you trust.
journalofhospitalinfection.com/article/S0195-…
2/ Dispelled myths:

Myth 1: #Aerosols are droplets with a diameter < 5 μm
Myth 2: All particles > 5 μm fall within 1-2 m of the source
Myth 3: If it's short range, then it can't be airborne
Myth 4: If R0 isn't as large as for #measles, then it can't be airborne
3/ Dispelled myths:

Myth 5a: If it's #airborne then surgical #masks (or cloth face coverings) won't work
Myth 5b: The virus is only 100 nm (0.1 μm) in size so filters and masks won't work
Myth 6: Unless it grows in tissue culture, it's not infectious

#COVIDisAirborne
Read 5 tweets
Dr. Alex Huffman Profile picture
17 Dec 20
1/ During July 2020 many worked quickly to scramble #COVID19 prep before the Fall classes. I helped model estimated COVID #aerosol risk as @UofDenver made plans. Not allowed then, but shared now in case it can prompt discussion for Winter prep.

Doc + 🧵:
bit.ly/3gVfMcu
2/ A key concern at the time (& still) was #music ensemble classroom activities, b/c it was obvious early on that #COVIDisAirborne and that #choir & wind instruments were likely to present high COVID #aerosol risk.

nfhs.org/articles/unpre…
3/ Using my version of an aerosol #boxmodel, I calculated probability that #SARSCoV2 could infect after breathed out by someone in specific classrooms. With this I could easily investigate best prevention bang for buck. I.e. Rehearsal duration? Wait time b/n classes? Etc.
Read 20 tweets
Dr. Alex Huffman Profile picture
17 Nov 20
1/x With #COVID19 cases skyrocketing all over the US, holiday meals are going to be very dangerous. To show the risks of meeting indoors I used an #aerosol box model to estimate relative the risks.

Maybe this can help you re-think your plans to gather.
drive.google.com/file/d/1xmN0e4…
2/x The #WellsRiley model has been used for decades, was put online recently by @jljcolorado & others as a #COVID19 viral aerosol transmission tool. In July I re-wrote the model onto a different platform @Wavemetrics #IgorPro so I could manipulate faster.
tinyurl.com/covid-estimator
3/x Modeled only room-mixed #aerosol (not droplet spray or aerosol plume; these add risk).

Results highlights:
- No matter the room size, infection for 10 people is at least 40% or much more
- If #superspreader there, everyone will be infected
- Outside, risk drops dramatically
Read 14 tweets

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