Coronavirus and homemade tools

N2 is a nitrogen MOLECULE, N is an atom. As you pointed out it got an affinity with bonding to something. THAT is what causes trouble, the bonding might break a molecule you need for something else, or the broken molecule may now be poisonous, or the new molecule with the N2 becomes poisonous.

A common fertilizer, KNO3 is kind of good at letting go of that O3 if something more appealing comes along and releasing pent up energy in the process. Making some of these combinations can land you in jail in the USA and probably other places.

Quote:

---

Originally Posted by old kodger

"Caveat: snip...
Now my question is: - how can a naturally occurring element (7 on the periodic table), being more than 3/4 of the atmosphere, "be irritating/ harmful to your respiratory system" ?

---

Oxygen is also a naturally occurring element that is essential for life. Oxygen can be found alone O, combined with another O atom to make O2, or combined with 2 other O atoms to make Ozone (O3). All 3 forms are Pure Oxygen. But O3 is toxic.

Sodium and Chlorine are also VERY TOXIC to our health. But you love them on your food, as long as they are combined to make SALT

Quote:

---

Originally Posted by hemmjo

Oxygen is also a naturally occurring element that is essential for life. Oxygen can be found alone O, combined with another O atom to make O2, or combined with 2 other O atoms to make Ozone (O3). All 3 forms are Pure Oxygen. But O3 is toxic.

---

And again it's the reactivity. Both O and O3 are looking for something to mate with. They REALLY want to bond. O2 will bond fairly easily, but needs a drink or two first.

Quote:

---

Originally Posted by old kodger

"Caveat: Ozone has some bad side effects to humans apart from killing viruses, too...
While producing ozone outta air with a corona-discharge unit, you also get N2 as a by-product,
which can be irritating/ harmful to your respiratory system."

As a result of this post, I did a small amount of research. Lets look at N2, N is a nitrogen atom, but is unstable and requires another N atom to pair with, because N has three unpaired electrons. Pairing with another N atom satisfies the requirement of both N2 IS nitrogen as found in the atmosphere and it's concentration in the atmosphere is 78%.
Now my question is: - how can a naturally occurring element (7 on the periodic table), being more than 3/4 of the atmosphere, "be irritating/ harmful to your respiratory system" ?
I can comprehend however, that because big pharma can't patent ozone, in keeping with their historical performance, they would "lobby" to have a scare tactic thrown into the works to inhibit people from using it. As I said in my last post, I'm sill alive and kicking.....with no signs of respitary distress.

---

I believe that the corona discharge actually produces N2O, nitrous oxide, which binds with the haemoglobin in our blood and does not release the way oxygen and carbon dioxide do. This has the effect of making those haemoglobin complexes unavailable for O2/CO2 transport.

Quote:

---

Originally Posted by Drew1966

I believe that the corona discharge actually produces N2O, nitrous oxide, which binds with the haemoglobin in our blood and does not release the way oxygen and carbon dioxide do. This has the effect of making those haemoglobin complexes unavailable for O2/CO2 transport.

---

last post on this matter.
Is that a belief system, or provable FACT?

Quote:

---

Originally Posted by Drew1966

I believe that the corona discharge actually produces N2O, nitrous oxide, which binds with the haemoglobin in our blood and does not release the way oxygen and carbon dioxide do. This has the effect of making those haemoglobin complexes unavailable for O2/CO2 transport.

---

Thanks for pointing out my initial missing "O" and bad proofreading, Drew1966. N2O/ Nitrous oxide is the released gas, of course!
N2 is already around us, just as Oldkodger stated...
Sorry - my bad!

Johan

PS: Nitrous Oxide (a k a "Laughing Gas") is no laughing matter:
https://en.wikipedia.org/wiki/Nitrous_oxide#Safety

(Moved four politically-themed posts out of this thread and into Off-Topic. This is a good discussion, and I want to preserve its value.)

Some supply chain updates. Is there a meat/dairy shortage impending for USA? We've certainly noticed that Amazon Fresh is limiting our order quantities of meat and dairy, and, for some orders, we're not getting some of the meat and milk that we ordered. On the one side, we have the issue of meat processing plants becoming COVID outbreak hotspots, which is exacerbated by the fact that farmers have limited windows of time in which they can slaughter animals for delivery to processing plants and ultimately the consumer market. On the other hand is the argument that large US meat packing companies are positioning for government bailout funds.

Fuel prices are dropping. We scheduled a propane tank fillup, and the per-gallon price was much lower than it usually is. One gas station near us had run out of gas, and a rumor was circulating in our town that another gas station had watered down its gas. Fuel stabilizer on Amazon is still available, but I had to poke around a bit to get a gallon of it from a third-party seller.

From the U.S. Coast Guard Los Angeles twitter feed, here's a short video of tanker vessels anchored off the coast:

<video controls autoplay loop>
<source src="https://diqn32j8nouaz.cloudfront.net/tanker_vessels_anchored_off_los_angeles.mp4" type="video/mp4">
Your browser does not support the video tag.
</video>

We're starting to see some proposals for changes to common objects that consumers interact with. Behold the Finnish Fortum Lever, for opening grocery store refrigerated doors with your forearm. Is this the same forearm that we're supposed to sneeze into? And also bump our elbows with people to replace handshakes? Or is that just a transitional narrative to ease us into the reality that touching is dangerous now?

https://diqn32j8nouaz.cloudfront.net...arm_handle.jpg

Similarly, here's the CleanKey. Stuff like this will be easy for our guys to make. I wouldn't mind an accompanying sleeve for it, so that it doesn't just go back in your pocket. 0:44 video:

https://www.youtube.com/watch?v=RAUyKhtNcu4

Then there's this reversed middle seat concept with droplet shields, for preventing infection on airplanes, from Italian company Avio Interiors. Is that woman holding an invisible cup?

https://diqn32j8nouaz.cloudfront.net...rline_seat.jpg

More: https://runwaygirlnetwork.com/2020/0...9-janus-seats/

Quote:

---

Originally Posted by DIYSwede

Thanks for pointing out my initial missing "O" and bad proofreading, Drew1966. N2O/ Nitrous oxide is the released gas, of course!
N2 is already around us, just as Oldkodger stated...
Sorry - my bad!

Johan

PS: Nitrous Oxide (a k a "Laughing Gas") is no laughing matter:
https://en.wikipedia.org/wiki/Nitrous_oxide#Safety

---

Aside from the omission of the "O" that is not the only error, (according to, I think it was wiki..) N2O nitrous oxide (laughing gas) has a half life of around 5 minutes and is breathed out in very short order. HOWEVER, NO2, is nitrogen dioxide, and IS dangerous in high concentrations, does have a smell (N2O is odourless), and does indeed irritate lung etc
So in regard of my original post. I stand corrected in that being in the room with an ozone generator might not be such a good idea, but I'M still not displaying adverse effects.....yet.

Quote:

---

Originally Posted by old kodger

I stand corrected in that being in the room with an ozone generator might not be such a good idea, but I'M still not displaying adverse effects.....yet.

---

AFAIK only the corona discharge ozone units (working with air input) generate N2O, not the low pressure UV discharge lamp types
(who also, due to their way of operation, cannot reach very high ozone levels in air: less than 0,5% of weight) -
but personally, I give at least half an hour after turn-off before entering a treated space.

Regarding NOx, I've not seen any reports on that being formed in any ozone producing unit,
but mostly through combustion at fairly high temperatures (cars, furnaces and the like surrounding us).

2 cents, YMMV

Johan

Quoting "Regarding NOx, I've not seen any reports on that being formed in any ozone producing unit,
but mostly through combustion at fairly high temperatures (cars, furnaces and the like surrounding us)."

Agreed, however, and this is rationalizing only, if a corona discharge unit is capable of cracking air into it's component parts, I see no reason why, if N2 can recombine with O to produce N2O, which according to all the pundits does not cause respiratory distress, that N could just as easily recombine with two O to produce NO2, which does.
I recognize that I'm arguing against my own first post, but when someone challenges my long held beliefs, I try to do unbiased research, if that research turns up evidence that my belief is incorrect, I must accept the outcome.

Quote:

---

Originally Posted by old kodger

if N2 can recombine with O to produce N2O, which according to all the pundits does not cause respiratory distress, that N could just as easily recombine with two O to produce NO2, which does.

---

I guess we would've seen some reports finding this would be the case, then?
I haven't found any studies of this coming outta any ozone generator.

Giving the hypothesis a shot:
You mean like this: 2 NO + O2 → 2 NO2?
But then this equilibrium follows : 2 NO2 ⇌ N2O4

OK - this will perhaps not "just as easily recombine" as NO2, as one might assume?

For producing NO2 (rather than "just" N2O4, dinitrogen tetroxide), the "elevated temperatures" seems to be crucial.
At room temp the equilibrium above apparently favors N2O4 in what's (eventually) being produced.

Positive oxidizer, used (with gasoline) by Crocco* in 1930 for liquid rockets,
used extensivly in the US and USSR from the late fifties.
Hypergolic with Aerozine 50, UDMH & MMH, to mention a few:
https://en.wikipedia.org/wiki/Hyperg...pellant#Common
Out of fashion today, replaced by MON because of "reasons":
https://www.youtube.com/watch?v=HOYDj769s6k

OTOH: Dinitrogen tetroxide (NTO) isn't something brought from the health store, either:
https://en.wikipedia.org/wiki/Dinitr...o-Soyuz_mishap

I abstain from derailing this thread further, as it pretty quickly would become rocket science,
but for delving further into THAT area I (again) recommend the outstanding biography of John D. Clark: "Ignition!"
(foreword by Isaac Asimov - no less.):

http://www.sciencemadness.org/librar...s/ignition.pdf

*Quote from the book on this Italian intrepid researcher (coincidentally a contemporary compatriot of the Futurists):

Attachment 34726

ATB
Johan

The rear facing seats look great, but airlines will never agree as they take up too much space and space is money.

Quote:

---

Originally Posted by Nick79

The rear facing seats look great, but airlines will never agree as they take up too much space and space is money.

---

If the seats are correctly mounted, they wouldn’t use any extra space, but it’s only a CGI concept, so no issues

Quote:

---

Originally Posted by Drew1966

If the seats are correctly mounted, they wouldn’t use any extra space, but it’s only a CGI concept, so no issues

---

Except for trying to get from the window to the isle would be still the same problem seats leaning back and folks with their feet stuck under the seat in front of them, only now you would have to negotiate folks facing in both directions I hate flying in those sardine cans in the first place and sure wouldn't want to fly in one with reversed seating

Quote:

---

Originally Posted by Frank S

Except for trying to get from the window to the isle would be still the same problem seats leaning back and folks with their feet stuck under the seat in front of them, only now you would have to negotiate folks facing in both directions I hate flying in those sardine cans in the first place and sure wouldn't want to fly in one with reversed seating

---

So get a train or ship instead Frank. That way you can enjoy hating the trip even more! LOL

Quote:

---

Originally Posted by Drew1966

So get a train or ship instead Frank. That way you can enjoy hating the trip even more! LOL

---

after arriving back in Texas from over seas in 2013 Since the USA never developed a decent rail service like there is in Europe, I decided that if I can't drive there I'm not going.

Quote:

---

Originally Posted by Frank S

after arriving back in Texas from over seas in 2013 Since the USA never developed a decent rail service like there is in Europe, I decided that if I can't drive there I'm not going.

---

��������������������

FAA would not accept rear facing due to 'crash worthy' issues. Also seats would need a whole new certification in that position as they were certified for impact in opposite direction. In my past I went thru certifying modified seats for a client. (Tests at 6G's and 9G's etc.) Also no airline will agree to intentionally fly a 1/2 loaded aircraft for the same price as they operate on a 90% or so load factor.

Attachment 34851
Rather fitting don't you think

Two quick bits today. One is a new use for a tool in the COVID age, and the other is a new tool for the COVID age.

In the U.S., we're dealing with meat supply chain issues, in great part because meat production is very fickle and time-sensitive. At the beginning of the chain, farmers are having to euthanize animals because meat processing facilities can't accept them. At the other end of the chain, large grocery chains are limiting meat purchases for consumers.

How do you dispose of thousands of head of livestock that have to be euthanized? Apparently you use a wood chipper.

Quote:

---

The Minnesota Pork Producers Association is working with the team to establish three other composting sites in the state.

“They are trying to find other areas where there are congregations of large swine operations so they can better serve those people with a centralized site,” Crusan said, adding that farmers will have the option to deliver hog carcasses to those sites or compost on their own property.

The hog carcasses delivered to the Nobles County site will be run through the chipper simultaneously with the wood material — a new concept in the hog industry.

---

More: https://www.twincities.com/2020/05/0...hington-plant/

And here we have a prototype for the CleaRing - a portable disinfection tool from @pdzethzurich on Instagram. Next step might be to use copper (Coronavirus hates copper), and I wouldn't mind seeing a greater ability to adjust the shape of the sponge disinfection surface, so that it can sponge flat surfaces too, or possibly even pull door handles open.

https://diqn32j8nouaz.cloudfront.net...isinfector.jpg


<video controls autoplay loop>
<source src="https://diqn32j8nouaz.cloudfront.net/clearing_disinfector.mp4" type="video/mp4">
Your browser does not support the video tag.
</video>

Seems like some Chinese outlets whips out loads of discount ozone generators:

Attachment 35039

Advertised as a do-all, cure-all method "for use in the home, hotel room, conference centre, karaoke bar, car, RV" etc.
Specs for this particular unit is sparse, but it seems to be of the "Corona Discharge" type*,
pulls half an amp (at 220 VAC only) that equals 110W,
and thus cranks out a hefty 24 g/h of ozone - which could be detrimental to the stuff you're curing:

I've read in another forum thread from a dude working for a fire sanitizing company,
who'd just bought a really cheap car from a chain smoker:
He got the brilliant idea to borrow one 250 W Heavy Duty ozone generator from work,
and run it overnite in the car to rid it form the smell.

He got the car free of smell, all right - but all rubber parts within the compartment had petrified,
giving him a hell of a time to even get the unit back out, as all rubber seals had fixed the doors positively shut.
I never posted asking whether he scrapped the car or tried to refit everything "rubberish" inside.

My small unit pulls a mere 15 watts and gives plentiful of ozone for my 9 cubic meter hallway.

Two cents & YMMV

Johan

*Corona discharge units also "provide" Nitrous Oxide - which could lead to respiratory problems, established earlier in this thread:
https://en.wikipedia.org/wiki/Nitrous_oxide#Safety

Ford created a software patch to kill Coronavirus in NYC police vehicles, using the cars' heaters.

https://diqn32j8nouaz.cloudfront.net...car_heater.jpg

Quote:

---

And that’s when an engineer at Ford realized: They didn’t need bleach to kill COVID-19 when the car’s own heater could do the job instead. And over the process of just 40 days, the auto company created a software patch that could upgrade the Interceptors to self-sterilize with the climate control system in just 15 minutes, no elbow grease required. (That patch is currently being installed on NYC police vehicles, and it’s offered to police officers free nationwide through dealers, though Ford is unsure how many have received the update to date.)

---

More: https://www.fastcompany.com/90510004...ar-heater-hack

https://www.youtube.com/watch?v=o7-k...ature=emb_logo

New sterilization method seems to work on N95 masks. Research paper can be found here: https://pubs.acs.org/doi/full/10.102...stlett.0c00534
and FAQ here: https://docs.google.com/document/d/1...zKI0y0ijY/edit

Quote:

---

Originally Posted by Jon

(Moved four politically-themed posts out of this thread and into Off-Topic. This is a good discussion, and I want to preserve its value.)


Similarly, here's the CleanKey. Stuff like this will be easy for our guys to make. I wouldn't mind an accompanying sleeve for it, so that it doesn't just go back in your pocket. 0:44 video:

https://www.youtube.com/watch?v=RAUyKhtNcu4

---

The cleankey is a great idea, until a Police officer realises it also makes a usable knuckle duster, so not much good it the UK (banned it country), I've been making these out of 1/4" copper pipe offcuts and it does much the same thing, but it can't be mistaken as a weapon (hopefully). The broken s-biner lets it hang easily from a pocket or belt. Grip handle is ~1911 angle, later versions are P.08.

Attachment 36515

Quote:

---

Originally Posted by NeiljohnUK

The cleankey is a great idea, until a Police officer realises it also makes a usable knuckle duster, so not much good it the UK (banned it country), I've been making these out of 1/4" copper pipe offcuts and it does much the same thing, but it can't be mistaken as a weapon (hopefully). The broken s-biner lets it hang easily from a pocket or belt. Grip handle is ~1911 angle, later versions are P.08.

Attachment 36515

---

Still wont be of much use in the land of the round door knobs
People of today's time period are becoming far too FAUX germophobic because it is trendy

Simple. Elegant. Nice for most uses, but, as mentioned, no good for round doorknobs.

Quote:

---

Originally Posted by Drew1966

Simple. Elegant. Nice for most uses, but, as mentioned, no good for round doorknobs.

---

Thankfully here we have lever type door handles, knobs are considered unsuitable for disabled users being hard to grip, and too easy to tie a ligature on.

<!-- BEGIN /var/www/html/homemadetools/protected/modules/zeus/views/tool/postUpdate.php -->
Thanks NeiljohnUK! We've added your Antimicrobial Hand Tool to our Miscellaneous category,
as well as to your builder page: NeiljohnUK's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/homemade-antimicrobial-hand-tool"> <img src="/uploads/235308/homemade-antimicrobial-hand-tool.jpeg"/> </a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="https://www.homemadetools.net/homemade-antimicrobial-hand-tool">Antimicrobial Hand Tool</a> <span> by <a href="https://www.homemadetools.net/builder/NeiljohnUK">NeiljohnUK</a></span> </div> <div class="tags">tags: <a href='https://www.homemadetools.net/tag/door'>door</a>, <a href='https://www.homemadetools.net/tag/hand-tools'>hand tools</a> </div> </div> </div> </div>
<!-- END /var/www/html/homemadetools/protected/modules/zeus/views/tool/postUpdate.php -->

The old concept of furnace filter plus box fan has evolved into a more effective variant, and been born again as a homemade tool for filtering COVID, with the backing of a group of aerosol scientists and HVAC industry leaders, the requisite COVID-era element of government conspiracy, and plenty of duct tape.

https://diqn32j8nouaz.cloudfront.net...enthal_box.jpg

This COVID air filter build is being called a Corsi-Rosenthal box. It's essentially just a box fan duct-taped to MERV 13 furnace filters. A little more on its Wikipedia page, this Encycla page, and this CleanAirCrew FAQ. COVID aside, it's an inexpensive and highly efficient air filter that you can build in under an hour. HMT forum members have been building air cleaners with box fans and filters for years.

The Corsi part of Corsi-Rosenthal filters is Richard Corsi, an environmental engineering professor. The other half is Jim Rosenthal, the CEO of the HVAC company Air Relief Technologies. Corsi is on Twitter here, and Rosenthal is on Twitter here. The Corsi-Rosenthal box also has the approval of Bill Bahnfleth (Twitter is here), who is the chair of the Epidemic Task Force of ASHRAE, the American Society of Heating, Refrigerating and Air-Conditioning Engineers.

3M has also recently come out in support of Corsi-Rosenthal boxes; they ran their own tests and concluded "This Corsi-Rosenthal box movement is legit". Underwriters Laboratories also backs up the efficacy and safety of DIY air filters; see An Evaluation of DIY Air Filtration. Plenty of aerosol scientists have also jumped on board, including: Jose-Luis Jimenez, Kimberly Prather, Linsey Marr, Lisa Brosseau, Marwa Zaatari, and Eben Cross.

This group seems to be mostly united in their position that COVID is predominantly spread via the airborne route, and not via larger expelled respiratory droplets (they call these "ballistic droplets"). Thus, air filtration is reasonable, especially in colder seasons when ventilation is less practical. Airborne aerosols can stay suspended in the air for hours, like smoke, whereas expelled respiratory droplets arc downward to the ground in about 2 meters. Government COVID messaging worldwide was initially firmly droplet-based, and is now slowly backpedaling to an airborne position. Jose-Luis Jimenez (a highly-cited chemistry professor with a doctorate in Mechanical Engineering from MIT) has a good summary here laying out the reasons why COVID is primarily transmitted by airborne particles, and it's backed up by an article in The Lancet called Ten scientific reasons in support of airborne transmission of SARS-CoV-2. There is also a large COVID airborne FAQ written by many atmospheric chemistry and aerosol science professors and scientists here. Even more aerosol scientists in support of this are listed here: https://www.covidisairborne.org/

https://diqn32j8nouaz.cloudfront.net/cr_box_army.jpg

Some caveats:

1. There is strong backing to this position, but that alone doesn't mean that it's correct, especially in full. Science has many dueling factions.

2. The Corsi-Rosenthal box movement is popular on Twitter, but Twitter is not representative of any scientific field, and most scientists don't use it at all. There are often only a handful of heavily-cited scientists (whose volume of citations also does not make them correct) on Twitter for each field.

3. There is a tendency, especially during the pandemic, for a field to want to "own" COVID by ascribing its nuances to their own area of scientific pursuit. For example, this biases neurologists to look for a COVID link in the central nervous system, immunologists to focus on T cells, and aerosol scientists to point to air sanitation.

COVID positions are usually not complete without an element of government conspiracy, and the Corsi-Rosenthal box does not disappoint. Interestingly (and rarely), this position is neither politically left nor right. If COVID spreads primarily through expelled large respiratory droplets that arc down to the ground within 2 meters - they call this belief "droplet dogma" - then this shifts responsibility to individuals (mandating social distancing, handwashing, and homemade masks), whereas airborne acknowledgement shifts it to governments and corporations (mandating filtration of indoor public spaces). Mandating filtration of air in indoor public spaces has little impact on personal liberties, and thus little value as a political football. In fact, we already do this. Large HVAC installations are regulated in some places because they can spread Legionnaire's disease, so named because it was first discovered breeding and spreading via the air conditioning system at an American Legion convention in 1976.

Some graphic examples of this government spin, from Corsi-Rosenthal box advocates:

https://diqn32j8nouaz.cloudfront.net...n_disguise.jpg

https://diqn32j8nouaz.cloudfront.net..._soap_pump.jpg

The key quantitative question is: How much reduction of COVID spread can we get from cleaning indoor air? We don't know, and it's difficult to model, but the tradeoff between reduction of spread and sacrifice of personal liberties seems like an easy win. A little more on modeling this reduction (ventilation + Corsi-Rosenthal boxes + UVGI) is here.

Furnace filter plus box fan is not a new idea, and we have plenty of entries in the homemade tool encyclopedia with early versions of it. You might have even experimented with it yourself. Here are a couple of builds by the guys on this forum:

By mr95gst:
https://diqn32j8nouaz.cloudfront.net...r_box_fan1.jpg

By markfitz:
https://diqn32j8nouaz.cloudfront.net...r_box_fan2.jpg

The cardboard-and-duct-tape construction of the Corsi-Rosenthal box is more rudimentary, and is intended to be built by people with minimal skills. The cube shape, which at first may appear gimmicky, is a reasonable way to maximize the filter surface area. It also incorporates a fan shroud to counter backflow around the edges of the box fan, which can be cut from the fan's cardboard package.

The construction of Corsi-Rosenthal boxes has recently started to shift from ad-hoc assembly to mass DIY manufacturing:

https://diqn32j8nouaz.cloudfront.net...thal_boxes.jpg

Here's a basic homemade tool for producing the fan shrouds in bulk:

<video controls loop>
<source src="https://diqn32j8nouaz.cloudfront.net/bulk_corsi_rosenthal_shroud_cutter.mp4" type="video/mp4">
Your browser does not support the video tag.
</video>


This record player concept is clever, with the printed record label in the center and the tone arm switch:

<video controls loop>
<source src="https://diqn32j8nouaz.cloudfront.net/corsi_rosenthal_record_player_box.mp4" type="video/mp4">
Your browser does not support the video tag.
</video>


Conceptually interesting, but unnecessary rotation is a red flag for gimmickiness.

<video controls loop>
<source src="https://diqn32j8nouaz.cloudfront.net/clever_but_gimmicky_cr_box.mp4" type="video/mp4">
Your browser does not support the video tag.
</video>

Probably not practical, but this is an interesting take on connecting a CR box to a CO2 reader (these are used as proxies for measuring likely concentrations of coronavirus in the air). More info here. 3:49 video:

https://www.youtube.com/watch?v=eza2Ab-YpXw

The cardboard and duct tape is endearing, but something like this would be more aesthetically acceptable to HMT members:

https://diqn32j8nouaz.cloudfront.net/wood_cr_box.jpg

Another nice one, with more details here on GrabCAD:

https://diqn32j8nouaz.cloudfront.net/grabcad_cr_box.jpg

Corsi-Rosenthal boxes use MERV 13 rated filters, which should filter out most of the aerosol drops in which coronavirus virions travel; around 1 micron in diameter. Yes, this means that you can also just filter coronavirus by putting a MERV 13 filter on your forced air furnace or air conditioner, although you should then rebalance it. They would be useful for pollen, wildfire smoke, and of course shop dust too. They're usually arranged in a cube shape, with the box fan on top, pushing air upwards, the filter flow direction arrows pointing into the cube, and some spacers on the bottom so that air can flow through the bottom filter (if it is built with a bottom filter, and not a cardboard bottom). The same concept can also be constructed with two or three sides, although the cube shape provides the greatest filter surface area, at the lowest noise level. Note how the airflow orientation pulls the sides of the cube together (the corners are also taped). Cost is under $100, and a child can build one.

https://diqn32j8nouaz.cloudfront.net...tion_steps.jpg

A detailed assembly guide using a circular fan is here.

Analyses indicate that they're at least as effective as $1,000+ filters, and the filters should last at least 6 months, depending on use. The increased airflow and filter surface area may make them superior to most HEPA filters (equivalent to MERV 17-20), because although they have comparatively lower filtration efficiency for one pass, they have a higher flow rate and filter air faster (see CADR or Clean Air Delivery Rate). There's a good preprint on HEPA vs. Corsi-Rosenthal box efficacy here: Price-performance comparison of HEPA air purifiers and lower-cost MERV 13/14 filters with box fans, and another here: Characterizing the performance of a DIY air filter. Another nice UC Davis study is here: Testing Different Configurations of Do-It-Yourself Portable Air Cleaners. More analysis from Rosenthal is here, and also here from atmospheric chemist Eben Cross.

https://diqn32j8nouaz.cloudfront.net...ter_values.jpg

Here's a comparison of PM values for air before and after the Corsi-Rosenthal box:

<video controls loop>
<source src="https://diqn32j8nouaz.cloudfront.net/pm_air_filtration_cr_box.mp4" type="video/mp4">
Your browser does not support the video tag.
</video>

Not all filters are performing equally; Rosenthal published an efficiency test here. People are making Corsi-Rosenthal boxes with the popular FilterBuy brand of filters on Amazon, but those aren't testing very well. Some more filtration test data:

https://diqn32j8nouaz.cloudfront.net...ison_chart.jpg

https://diqn32j8nouaz.cloudfront.net..._hepa_cadr.jpg

I don't know if Corsi-Rosenthal boxes will be a transitional tool used only until we develop stricter indoor air filtration practices, or whether their utility will eventually make them more ubiquitous. They're far less controversial than masking or vaccination, and they're an easily constructed homemade tool that anyone can build.

I probably won't build one but if I did I would make it blow-through instead of draw-through to keep all the badness inside...