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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.

Image
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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…
Image
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).


Image
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
Apr 28
I have a new thing to say to why I mask.

Ronald Reagan, Michael J Fox, Robin Williams, Lou Gehrig, Bruce Willis.

Alzheimer's, Parkinsons, Lew Body Dementia, ALS, CJD

All of them are dying or are dead from - the common cold.

You see,
One of the main viruses that results in the cold is a virus called OC43.

And it turns out that it's neuroinvasive - and is strongly associated with all of those diseases.

Even though it's just a cold in the beginning. So, those are 5 really bad diseases that I am protecting
myself from.

Kind of like HIV is often just like a cold or a mild case of flu in the beginning.

So, yeah, I mask so I don't catch a cold.

Or Covid - which is also neuroinvasive, and let me tell you all about the horrible things it does to your body much quicker....

(They
Read 7 tweets
Lazarus Long Profile picture
Apr 26
Safer showering and swimming with great breathability!

Others have used a snorkel w/ N95s - but those then collapse around the snorkel, and breathability is more restricted. This new approach is w/ an internal BRACE!

I took a shower with this, and it worked perfectly. Build 🧵 Image
This is a great technique, but I was looking for something with more breathability.

Image
This is the internal brace, and how the magic happens.

My subconscious must have picked this up from surgical mask braces that go under surgical masks.

So, here's the build. Image
Image
Read 27 tweets
Lazarus Long Profile picture
Apr 24
Got bored. Let's just check out Google Scholar and E Coli. Oh my. Oh my, that's not good.

Yes, yet another episode of "that's airborne, TOO?!!!!!"

THREAD
Pigs:
"Airborne E. coli were isolated from indoor air,....and downwind air samples (10, 50, 100, 200 and 400 m away) for five swine houses" (1)

Cows:
"E. coli was isolated in both inside and outside air, even in samples taken 150 m from the farm." (2)

READY FOR THE FUN ONES?
Restaurants:
"E coli was identified as the most prevalent illness-causing bacteria in Zone A-derived aerosols (721 CFU)"
(3)
Hospital:
"The results also showed that airborne bacterial pathogens were present in all the sampled hospital wards." (4)

Ready for another fun one?
Read 6 tweets
Lazarus Long Profile picture
Apr 21
Pope Francis passed - R.I.P.

He died from not masking.

Not masking led him to getting polymicrobial respiratory infection (multiple pathogens) on 2/6/2025, leading to bronchitis, to bilateral pneumonia, a respiratory event
- leading to stroke and cardiac arrest.
Timeline here:
cbsnews.com/news/pope-fran…

History of respiratory challenges.
cbsnews.com/news/pope-fran…

And here showing every year lately having "respiratory infections."
usatoday.com/story/life/hea…
Why didn't he mask? The peer pressure must have been enormous. Even those who know better often don't mask out of fear of social castigation.

And that's why mask mandates work so well. They allow people to mask if they want to.

And those who don't want to? Won't. But...
Read 4 tweets
Lazarus Long Profile picture
Apr 20
Save this QR Code to your phone or save this tweet. Save it for the next time you get harassed by an antimasker.

This links to the article from March 27th, 2025, with Trump saying it was so nice of a reporter to be wearing a mask.

There's a video of him on this page.

/1 QR Code to https://web.archive.org/web/20250327191931/https://www.mediaite.com/news/trump-singles-out-reporter-for-wearing-mask-in-oval-office-you-feel-more-comfortable-right/
President Donald Trump stopped answering San Francisco Chronicle Washington correspondent Shira Stein, @shiramstein, to comment on her wearing a COVID mask in the Oval Office, remarking, “You’re wearing a mask! So nice of you!” SHIRA STEIN: Mr. President, you said you want to return education control to the states, how would you handle it if a state like California were to put in place education policies that you don’t agree with? PRESIDENT DONALD TRUMP: You know, I haven’t seen a mask in so long! You’re wearing a mask! So nice of you! I haven’ seen anybody wearing a mask in a long time. It’s good. You feel more comfortable, right? SHIRA STEIN: Yes. PRESIDENT DONALD TRUMP: Good. That’s good. So go ahead. SHIRA STEIN: You said you want to return education control to the states. How would you handle it if a sta...
Our faces, our health.

And we choose to mask.

Ms. Stein was later singled out by Marjorie Taylor Greene in her for wearing a mask.

Very insulting, at first. But, after Ms. Stein pointed out she was immuncompromised (also having had a stroke, higher risk), she
Read 9 tweets
Lazarus Long Profile picture
Apr 18
Trump is trying to distract from the economy. He just pumped out the Lab Leak from the official whitehouse.gov website.

Simultaneously making masking advocacy both more difficult and easier.

The Shrodinger Presidency. If only he had.... /+

whitehouse.gov/lab-leak-true-…
Of course I don't wish him dead in a box. That is against Twitter's TOS.

But, anyway, what do I mean? On the one hand, pointing out that Covid is probably a bioweapon means that you can point out the silliness of not protecting yourself against it.

On the other hand, this: Image
Which, of course, is silly as workers in BSL2-4 labs wear N95s and better to protect against bioweapons.

Heh. I can tell an antimasker wrote that because they screwed up the logic on it.

Mask mandates do NOT equate masks.
Read 6 tweets

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