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Lazarus Long Profile picture
@LazarusLong13
Aug 11, 2021 • 29 tweets • 14 min read • Read on X
A mega thread on the ultimate DIY air filter known as the Corsi/Rosenthal Box (@CorsIAQ/ @JimRosenthal4).

Take it into work. Donate a couple to your school classroom if they'll let you.

Illustrations beautifully done by @ughberta, discovered through @kprather88.

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But my little angels don't transmit CoVid!?

They have ACE2 receptors, which SARS-COV-2 targets.

They get it and transmit it.

And those little bodies have a thermal plume wafting CoVid up to you.

. link.springer.com/article/10.100…
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Always a typo, no matter how many times you go over it....

Sorry - @Poppendieck has a great FAQ here - used up above!



Another classic FAQ is one maintained by about 10 aerosol scientists.


poppendieck.com/IAQ/COVID19%20…
tinyurl.com/FAQ-aerosols
Above...about 40,000 tweets ago, you mentioned 5 microns...and seemed excited about it. Why?

Respiratory aerosols (emitted when we breathe, talk, laugh, yell, sing, cough, sneeze) carry SARS-COV-2.

And 85% of them are 5 microns or smaller.

Corsi/ Rosenthal boxes in action!

Classroom








Used for wildfires:


For STEM fair





Used for Bacon. Gets it's very own tweet. Mmmmm. Bacon....

For sports palace.


For no reason given
















Pulling this up into the thread for optimum visibility.

Thank you, David!

(A great follow!)
A great resource for clean air:

Your lungs will thank you!

Next tweet...this is the hand sanitizer for the lungs you've always needed. Just without that bad smell...

This spacing is really excellent.

The one thing I would change, based on @Poppendieck's recommendation is to flip the box to be pointed up.

So any dried respiratory aerosols (carrying SC2) on the ground are not lifted off the ground (re-aerosolized).


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Would these help in a hospital with already great ventilation?
(H/T
)

Yes.

Preprint, but Dr. Marr is serious money:



Great discussion of why they still help in such already great ventilation:


And that tweet author is the lead on this study showing basically the same:


Same study, but a great tweetorial, too.

Ontario, Canada bringing in 20,000 portable air cleaners.
Someone asked how to dispose of the filters.

Put on your N100 elastomeric respirator (more comfortable than N95).



Carefully, pick up the Corsi box and gently take it outside.

Since you used painter tape, gently peel it back to get the fan off.
Separate the filters and gently place in a garbage bag. Do not shove them in as might have virus in them and don't want the garbage bag blowing the virus back on you.

Tie the bag tight. Toss into garbage.

Make new box!

Why not spray disinfectant on it?

Because by the
time the garbage bag degrades the virus will have been activated...

nejm.org/doi/full/10.10…
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Corsi/Rosenthal Thread Update:

Some folks, (mostly teachers) cannot bring in an air cleaner. But can bring in a fan.

Here's a fan that has a filter built into it! So, a stealth air cleaner.

"Lasko FF305 Air Flex 2-in-1 20-inch Box Fan and Air Purifier in One with MERV10 Image
Air Purifying Filter"

Won't be as good - but something is better than nothing!



H/T @kprather88 for this. She is NOT endorsing it - I am just thanking her for the knowledge of its existence, and I am the one suggesting it would make a great stealth one.walmart.com/ip/Lasko-FF305…
The filters here: are 13-A - so I would buy one and swap out the MERV 10 that it comes with.



No affiliation, just these are hard to find.
@Al_pha_Q2 @CorsIAQ @JimRosenthal4 @ughberta @kprather88 @CathNoakes might require slower air to do its job. Not as familiar with that tech, so happy to stand corrected if wrong.
@Debbie_Winslow_ @ManTh1ng @tafkak @CorsIAQ @JimRosenthal4 @ughberta @kprather88 @DavidElfstrom But ...I am NOT the expert here, so if any of the actual experts could "like" the above tweet, or otherwise correct my ruminations, I'd be most appreciative :). .
@Karthik07720496 @CorsIAQ @JimRosenthal4 @ughberta @kprather88 improved by implementation of 2 portable air cleaners.

Dr. Schofield's excellent study here - with an explanation of why:


And yes, it will reduce virus transmission by removing the respiratory aerosols that carry SARS-COV-2.

&

@dgurdasani1 @laineydoyle @DavidElfstrom @fischelfe @CorsIAQ @JimRosenthal4 @ughberta @kprather88 @CathNoakes @Poppendieck But round fans are addressed here with some examples:


Overall FAQ here - includes all build instructions for 5/4/2/1 filter versions. (Actually working on finishing up the 5 version).

cleanaircrew.org/boxfanfilterfa…
cleanaircrew.org/boxfanfilterfaq
Mega Corsi/Rosenthal Box Thread Update:

David Elfstrom has done a fantastic triangle filter build with estimated CADR.


It, along with everything else, is now in the FAQ:


One of the FAQ's is the Gallery - check it out!
cleanaircrew.org/boxfanfilterfa…
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Mega Corsi/Rosenthal Box Thread Update - Adding the Baskett Box (3 filter build).

Wow! An update to the Mega Corsi/Rosenthal Box Thread that kind of went a little viral.

Here's a fan that has a filter built into it! So, a stealth air cleaner.

"Lasko FF305 Air Flex 2-in-1 20-inch Box Fan and Air Purifier in One with MERV10."

Next tweet - a surprisingly Image
good performance.

I AM impressed!

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More from @LazarusLong13

Lazarus Long Profile picture
Dec 21
Oh, we are cooked. Just cooked.

"Brain Mitochondrial dysfunction, known for ~20 years is finally recognized as a central upstream driver of Alzheimer’s disease (AD), not just a downstream effect."

And SARS2's targeting of mitochondria is well-known.

Even in the brain.
/1 We identified dysregulation of mitochondrial and synaptic pathways in deep-layer excitatory neurons and upregulation of neuroinflammation in glia, consistent across both mRNA and protein. Remarkably, these alterations overlapped substantially with changes in age-related neurodegenerative diseases, including Parkinson’s disease and Alzheimer’s disease. Our work, combining multiple experimental and analytical methods, demonstrates the brain-wide impact of severe acute/subacute COVID-19, involving both cortical and subcortical regions, shedding light on potential therapeutic targets within pat...
@LauraMiers, in case you don't have it.

nature.com/articles/s4358…
@LauraMiers This is yet another reason why I N95.

Read 6 tweets
Lazarus Long Profile picture
Dec 17
@neiljshaw - — a few tips on your excellent article from a clean air advocate

"Consider Wearing a Mask" ?

No, "It is incredibly important to wear a well-fitting mask such as a N95, KN95, or KF94, for the best protection."

You two are doing Image
public health with this article.

Public health is best done with simple clear instructions.

No:
"These masks act as a barrier, reducing the spread of respiratory droplets when people talk, sneeze or cough."

Yes:
"These masks act as a HEPA air cleaner for the face,
cleaning the air of respiratory aerosols when people breathe, talk, sneeze or cough."

The barrier carries the idea of an immovable wall. Unable to be penetrated by things like oxygen and CO2 - which feeds antimaskers.

As an who debunks antimaskers, it is
Read 9 tweets
Lazarus Long Profile picture
Dec 11
As an anonymous clean air advocate, I've put a bit of thought into how to present, well, my expertise.

If someone were to say, "How do I know you know what you are talking about? Are you a doctor, or a virologist?"

To which, I would say...."No, but that's a good thing.
/1
I have focused on aerosol and masking science. Because it is those fields that give us the most information on how airborne particles, aerosols, get from Person A to Person B.

My expertise is derived from the great studies of Dr. Lindsay Marr, MacArthur recipient. Dr. Prather,
double National Academy member, Dr Milton, inventor of the Gesundheit, aerosol scientist and medical doctor; Dr Coleman whose group found that duckbill N95s captured 98% of emitted respiratory aerosols, and more excellent individual aerosol scientists.
Read 17 tweets
Lazarus Long Profile picture
Nov 22
I am not a fan of nasal sprays to stop The 'Vid, but I respect you having it as a layer in the Swiss cheese package.

But, some people have said they got bloody noses.

While at the ER yesterday, I picked up a pretty good at home technique. Let our $1,000 lay-out
Image
save you money.

Use tongue depressors to make a nose pinch clamp.

Leave it on for 30 minutes. Still a problem? Two sprays of Afrin, and re-apply nose pinch clamp. Wait 30 minutes.

Still a problem? Cotton balls sprayed with Afrin, clamp, 30 minutes

aliem.com/trick-of-trade…Image
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Afrin- in generic form is $3.32 at Walmart.

Also, put a ice compress at the back of the neck, while doing the above.

"Cooling the nape of the neck is said to induce reflex constriction of the mucosal vessels of the nose"

✅ I agree with the authors.

pubmed.ncbi.nlm.nih.gov/1568881/Image
Image
Read 6 tweets
Lazarus Long Profile picture
Nov 13
A study demonstrated 100% PERFECT protection against SARS2 w/ readily available KF94s

✅ 181 HCWs
✅ 1 got SARS2 antibodies, but an epi investigation -> the infection happened elsewhere.
😡 The final checkpoint was March 2021. N95s only became freely available 1 month later
/1 FDA: N95 masks, now plentiful, should no longer be reused By MARTHA MENDOZA and JULIET LINDERMAN (Associated Press) April 23, 2021 12:44 p.m. Medical providers may soon return to using one medical N95 mask per patient, a practice that was suspended during the pandemic due to deadly supply shortages
What is described in the tweets
in the USA.

Korean study:
jkms.org/DOIx.php?id=10…

This is in comparison to a Swiss study during the same rough time-frame. A study which did NOT show the same excellent results, but dismal results. Why?

The Swiss had the same sort of fit testing,

pubmed.ncbi.nlm.nih.gov/35123572/ Results: We enrolled 3259 participants from nine healthcare institutions, whereof 716 (22%) preferentially used FFP2. Among these, 81/716 (11%) reported a SARS-CoV-2-positive swab, compared to 352/2543 (14%) surgical mask users; seroconversion was documented in 85/656 (13%) FFP2 and 426/2255 (19%) surgical mask users. Adjusted for baseline characteristics, COVID-19 exposure, and risk behaviour, FFP2 use was non-significantly associated with decreased risk for SARS-CoV-2-positive swab (adjusted hazard ratio [aHR] 0.8, 95% CI 0.6-1.0) and seroconversion (adjusted odds ratio [aOR] 0.7, 95% CI ...
PPE monitoring.

What was the big difference?

Are N95s/FFP2s inferior to KF94s?

No, it was supply - and other reasons.
Read 10 tweets
Lazarus Long Profile picture
Nov 5
@tomhanks has just been savaged by people screaming masks don't work.

All hospitals have fiduciary responsibilities to not waste money.

Here is a light sampling of hospitals mandating masks because they work.

Proving that not only do masks work, but mask mandates work.

Thread
Health PEI
Start/End: October 14, 2025 , How many hospitals: 7, employee count: 4,967,

Public hospital,

City: Various (e.g., Charlottetown, Summerside), Province: Prince Edward Island, Country: Canada, full url: princeedwardisland.ca/en/news/health…
Horizon Health Network
Start/End: September 3, 2025 How many hospitals: 12, employee count: 15,000, public or private:

Public hospital.

City: Various (e.g., Saint John, Fredericton),
Province: New Brunswick,
Country: Canada horizonnb.ca/coronavirus-co…
Read 32 tweets

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