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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
Image
Image
Image
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…
Image
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
Jul 27
AVERAGE CO2 in the dead space below an N95? 1-3% - or 10,000 to 30,000 ppm. Scary?

No. You see that's the average.

Humans have focused on average or peak exhalations/waveforms.

We haven't studied the LOW POINT with capnography.

We have done it with simulations. Image
There are no published experimental (human) capnography studies inside N95 dead space that show the CO₂ dropping down as low as ~0.4% within a single exhalation. Human trials typically measure peak or average values rather than full breath waveforms.
As you can see, the amount of CO2 in the N95 goes down.

Why? Because the air around us has so much less CO2. When we inhale, it mixes with that high CO2.

Dilution and diffusion both at play.
journals.plos.org/plosone/articl…Image
As all of us who has ever worn a mask/N95, which is most of the world, knows, we don't suffer the effects of inhaling 30,000 ppm all day.

Lets look at this a different way.

What if we were in a room with huge CO2? That's what antimaskers are implying is going on.
Read 11 tweets
Lazarus Long Profile picture
Jul 27
How NOT to Science. A time travel thread and magic.

This is Helmut Traindl - the engineer who devised the procedure behind Walach CO2 study that was retracted after 16 days:
jamanetwork.com/journals/jamap…

Then, republished by Dr. Domingo just 6 months later.
sciencedirect.com/science/articl… Image
@RetractionWatch had an interesting write-up on how it was republished by Dr. Domingo.

It rings of plausible deniability. Except it smells vaguely of bad faith.

retractionwatch.com/2022/08/01/one…Image
Turns out that @TecnATox was founded, and is directed by Dr. Domingo.

You'll be hearing from me, Dr. Domingo - and a rather lot more people, once I get done writing all of this up.

You see, I found the pilot video.

Read 14 tweets
Lazarus Long Profile picture
Jul 24
So, in your apartment or hotel, we saw below how its heated facade, or front, could drive your downstairs neighbor cough into your lungs.

Let's step inside your living room now, and step forward in time to winter.

What happens if your sick neighbor is seated in that living /1
room?

Where is the worst place for them to be seated if you have your heat coming from a heat register up on the wall?

Next to your cold window.

The cold air cools your sick neighbor's exhaled infectious air, and drives it to the ground.

Where it sidles along until Image
Image
you and your family's bodies' thermal plumes pick up that air, and lifts it up to your faces to be breathed in.

Or....to put this in another way....if you go to a coffee shop as I like to do, and you see someone coughing next to a cold window? Do not dawdle.

Leave.
Read 7 tweets
Lazarus Long Profile picture
Jul 21
I looked at your thread @moog77 . The reason that epidemiological didn't work (cases continued to go up)? Is the same reason the 2023 Cochrane fails, ironically, after you touted it as the "gold standard."

Not because clean air doesn't reduce cases. It empirically does. It
just doesn't do it where it's not being applied.

What do I mean?

2023 Cochrane "the gold standard" - for community masking is based on a few studies.

One is Alfelali (2020) set in the Haji season
pmc.ncbi.nlm.nih.gov/articles/PMC75…
2 to 3 million religious pilgrims crammed into a few locations, sleeping 50 to hundreds in tent, head to toe.

Respiratory disease is typically 50% in total. Perhaps the single largest mass infection in history, year after year.

A few of them given surgical masks, and told
Read 13 tweets
Lazarus Long Profile picture
Jul 21
Do you live in an apartment or stay in hotels?

Got a "oops, outside air can get you" study. Coming out of Beijing University of Technology - taking airborne transmission seriously.

They rented 50 rooms of a building. Did some very cool CFD work - then, be still my heart, Image
followed it up with tracer gas experimentation.

See room 303 above? 403 and 503 got whatever came out of 303.

With studies like these, there are so many variables. But, if I lived in an apartment, I would set have at least a PC fan CR Box next to those open windows.
Or an HRV set up in that window. And for sure a PC fan CR box next to the front door for under the door airflow.

x.com/VentiloAngel/s…

Not HRV, but equally valid
x.com/Engineer_Wong/…
Read 17 tweets
Lazarus Long Profile picture
Jul 20
Swimming and showering.

Below is the thread of collected "swimming/ showering safer in indoor shared air" solutions, so far.

You might be thinking that the chlorine smell protects you near the pool. Chlorox is great.

But you would be thinking incorrectly.

Thread. Filti media wrapped out an inside brace made out of zip ties. Laugh all you want, but it works, yo.
Have there been indoor swimming pool transmission events? Yes.

jamanetwork.com/journals/jaman…

pubmed.ncbi.nlm.nih.gov/34606662/

And more.

Were they in the swimming pool or in the more likely shower/ locker rooms or lobby? Nobody has teased that out.
You do not smell chlorine gas in the pool. If you were actually smelling real chlorine gas, you had better start running for the door.

You are smelling trichloramine - from sweat, urine, body oils when there is not enough free chlorine.

frontiersin.org/articles/10.33…“It is a common misconception that a strong chlorine odor is caused by too much chlorine in the water. The odor is actually caused by chloramines (combined chlorines) off-gassing from the pool water surface. Chloramines are formed in the pool water when there is insufficient free chlorine in the pool to address the nitrogen-containing compounds brought into the pool water by the swimmers. These nitrogen compounds are naturally occurring and contained in sweat, urine, body oils, and other proteins that get released into the pool water. If the introduction of these nitrogen compounds outpace...
Read 29 tweets

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