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Alex Huffman, Ph.D. Profile picture
@HuffmanLabDU
Feb 27, 2021 • 17 tweets • 11 min read • Read on X
🧵1/ The #CDC update today (2/26) on "Ventilation in Schools and Child Care Programs" looks like good progress.

Details on #ventilation, #filtration, #bettermasks, w/ helpful links. Seems they're listening to @kprather88 @j_g_allen @CorsIAQ and others?
cdc.gov/coronavirus/20…
2/ The relatively short #CDC page seems to have more succinct, yet clear #K12 guidance & connection to other pages of support.

Though I admit, I haven't digested yet fully. What are your takes? (also e.g. @jljcolorado @linseymarr @ProfCharlesHaas @Don_Milton @ShellyMBoulder)
3/ I was pleased to see early mention that "Wearing a well-fitting, multi-layer mask helps prevent virus particles from entering the air or being breathed in by the person wearing the mask."

(BTW, need for good fit implies aerosols)

Links (twice) here:
cdc.gov/coronavirus/20…
4/ The new #CDC doc then goes on to say (w/ various specific tips & links):

* bring in "as much outdoor air as possible"
* ensure HVAC settings are maximizing ventilation
* filter and/or clean the air
* use exhaust fans
* open windows in transport vehicles
5/ I was happy to see specific mention at least to "consider":

* portable air cleaners that use high efficiency particulate air (HEPA) filters, and
* ultraviolet germicidal irradiation (UVGI)

@polsiewski
BTW, if you're looking for HEPA filtration, see:
docs.google.com/spreadsheets/d…
6/ And the bit about opening windows on transportation vehicles is important too. I think this is an overlooked area & where easy measures (e.g. cracked windows) can make a huge impact (for school or any transport).

E.g. some simple modeling by @CorsIAQ:
7/ Though "recommendations" that have no teeth are still going to be met by some communities who "feel" differently or who don't seek expertise to implement changes. Need to keep advocating for communities to put *good* preventative measures into practice.
8/ For example, there are lots of well-meaning administrators who will buy products made available.

One tip: Don't rely on plexiglass barriers to prevent airborne spread. Small aerosol particles flow around like smoke.
9/ Another tip: Put more resources into cleaning the air than cleaning surfaces. Evidence suggests the spread is more strongly driven by airborne aerosols than surface contamination. Buy HEPA filters, not air foggers.

Nice article by @dyanilewis
nature.com/articles/d4158…
10/ Yet another tip: Buy & mount #CO2 sensors for ~$150 each as a real-time measure of how well ventilation is matched to the occupancy in your rooms (basically a proxy of "rebreathed" air, or how much air from someone's exhale is now in your lungs).
11/ Also lots of good data emerging on the efficacy of #HEPA filtration in settings like schools. See link above for a guide to choose the right type of air filtration for your needs. But rely on the filtration, and don't buy with extras like ionization.
12/ As far as portable, in-room portable #filtration, one option is to build relatively inexpensive #DIY options for ~$40:
13/ But along w/ ventilation & filtration, don't forget critical strategies of mandating good, tight-fitting masks and physical distancing.

Indoor lunch time is especially risky, b/c masks are off. See guidance e.g. by @j_g_allen et al via:
schools.forhealth.org/risk-reduction…
14/ Loose-fitting masks allow aerosols to flow around through gaps. High-quality, tight-fitting masks control the source of infectious aerosols.

For more motivation & basis for updating your mask see🧵 e.g.:
15/ Investing in the improvement of indoor air quality in classrooms & #K12 schools will have strong, positive benefit not just during respiratory virus pandemics, but during all other times as well. Now is the time to listen to experts and do it right.
(I meant to add in somewhere that the CDC update doc was HT @Concern14923094 & @DocJeffD, so Thx!)
16/ One addition to points above about mitigation strategies against airborne infection in schools -- see this *very* cool @nytimes aerosol emissions #visualization, also w/ windows, HEPA filtration, etc. (and an augmented reality view).

HT @Poppendieck
nytimes.com/interactive/20…

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More from @HuffmanLabDU

Alex Huffman, Ph.D. Profile picture
Oct 7, 2022
Important article by @PatriciaFabianS & @jonlevyBU: investment in improving school air quality is critical.

Adds to reminder by @IAQinGWN at #AAAR2022 yesterday that investing in filtration can realize $10-100 return per $ spent e.g. via ⬇️ absences.
theconversation.com/investing-in-i…
Well-maintained HVAC filters or portable air cleaners can “also clean the air of pollen particles, mold spores & pollution from car exhaust and industrial operations. And in areas where wildfires are common, filters reduce the concentration of smoke particles inside buildings.”
[In schools that increase ventilation rate] “For kids and school staff, particularly those with asthma, allergies and sensitivities, this can mean fewer missed days of school, less medication, and fewer asthma attacks and subsequent trips to the hospital.”
onlinelibrary.wiley.com/doi/10.1111/in…
Read 4 tweets
Alex Huffman, Ph.D. Profile picture
Aug 18, 2022
"Indoor Air Management of Airborne Pathogens: Lessons, Practices, and Innovations" eventbrite.com/e/indoor-air-m…

Workshop by @theNASEM focusing on the current state of knowledge ➡️ practical lessons learned. Session 1 starting now.

Live-tweets below
#EHMI #NASEM #EnviroHealthMatters ImageImage
2/ @Don_Milton summarizes evidence that saliva PCR much better at catching COVID positive cases than PCR from nasal swabs. ImageImage
3/ @Don_Milton: It's the *combination* of masks, ventilation, filtration that can dramatically reduce spread Image
Read 66 tweets
Alex Huffman, Ph.D. Profile picture
Jul 6, 2022
A family emergency means I’m flying today for the first time since 2019. Fortunately I’ve got my N95 to reduce my inhaled dose as much as possible + my CO2 meter to gauge air.

Short 🧵 to occupy me while on a layover.

The CO2 was nicely & low in the Shreveport, LA airport (1/x) ImageImage
2/ On this tiny United commuter flight, 45 minute flight time from Shreveport to Houston, no one with N95 masks. Maybe 2 w/ surgical masks.

Boarding & taxi process, the #AirplaneCO2 briefly peaked at 1600 ppm, but mostly in 1100 range. Obviously higher than ideal, but not bad. Image
3/ Cruising (if you call it that for just a few minutes) was still in the 1000 - 1200 ppm range. At that upper level, roughly 2% of the air is likely rebreathed from others on board. But the ventilation is also filtering resp. particles from background air relatively frequently. Image
Read 23 tweets
Alex Huffman, Ph.D. Profile picture
Apr 4, 2022
Excellent OpEd by @linseymarr & @jljcolorado on the early and persistent confusion around the word "airborne" wrt the pandemic. It's a short overview on the effects of these miscomms across medical & disciplinary boundaries.
Some salient quotes, links (1/)
time.com/6162065/covid-…
2/ “This fundamental misunderstanding of the virus disastrously shaped the response during the first few months of the pandemic & continues to this day. We still see it now in the surface cleaning protocols that many have kept in place even while walking around without masks. …”
3/ “… There is a key explanation for this early error. In hospitals, the word “airborne” is associated w/ a rigid set of protective methods, incl. the use of N95 respirators by workers and negative pressure rooms for patients. These are resource-intensive and legally required.”
Read 11 tweets
Alex Huffman, Ph.D. Profile picture
Jan 14, 2022
CDC came out with another incremental update on #mask & #respirator guidance today: cdc.gov/coronavirus/20…

Clarifies N95s aren't in short supply & can be worn again!

It's still not perfect, but it feels like we're at least inching in the right direction. Some thoughts via a🧵.
2/ New statement that most respirators (i.e. #N95s) "are disposable and should be discarded WHEN they are dirty, damaged, or difficult to breathe through."

So you CAN #ReuseN95s‼️
See, e.g.:

That's *much* better guidance than to toss after a single use!
3/ Also clearly states that:
"Loosely woven cloth products provide the least protection ... and well-fitting NIOSH-approved respirators (including #N95s) offer the highest level of protection."

YES!!
Read 15 tweets
Alex Huffman, Ph.D. Profile picture
Jan 12, 2022
Really happy to see our paper led by @DaveyRachel1 just out in the #Forefront section of @AnalBioanalChem: rdcu.be/cEJN7

Improves a procedure to expose surrogate proteins to urban air (especially NO2, O3) to quantify changes in protein nitration ➡️ allergies, etc.
1/🧵 Image
2/ @DaveyRachel1 did a great job of quantifying & improving each step of the #bioanalytical procedure; ozone loss across PM filters, extraction & detection efficiencies, even good old analytical #FiguresOfMerit sensitivity & limit of detection.
rdcu.be/cEJN7 Image
3/ Possibly the most broadly useful piece is the data showing ozone loss across several filter types. The HEPA capsule scrubbed >60% of the ozone (bad if you're trying to quantify ozone). Kynar removed only 3%.
Important if using filter to remove PM, while quantifying O3 behind. Image
Read 6 tweets

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