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A paradigm shift to combat indoor respiratory infection (drive.google.com)
147 points by edward 4 months ago | hide | past | favorite | 141 comments

From the article: "It is not known exactly what fraction of infections could be prevented if all building and transport ventilation systems on the planet were ideal (in terms of controlling airborne infections), or the cost of design and retrofitting to make them ideal."

I think this is the key question. Surely better ventilation would have prevented some infections in the covid pandemic. But how many? And to decide that we need not just manifestos by civil engineers (like this article) but convincing research results, probably in collaboration with people who actually know some things about viruses as well. And without it, could organizations like the WHO or CDC have plausibly recommended building upgrades?

The WHO and CDC have had their head in the sand for 60 years when it comes to airborne pathogens. They have only acknowledged aerosol transmission of covid in the last couple weeks. It was physicists who had to figure out why they were domatically denying reality. https://www.wired.com/story/the-teeny-tiny-scientific-screwu...

> EARLY ONE MORNING, Linsey Marr tiptoed to her dining room table, slipped on a headset, and fired up Zoom. On her computer screen, dozens of familiar faces began to appear. She also saw a few people she didn’t know

It’s really hard for me to read a WIRED article for information.

I mean I realize that’s not what it’s there for but it takes forever to get into the content of the article.

> "it takes forever to get into the content of the article."

I've found this is the style of American long-format journalism in general. Just look at something like The New Yorker: not to dispute the quality of their writing, but the word counts certainly skew high. Articles in comparable British publications tend to be a lot more succinct.

I love The New Yorker. I actually read several pages of it every night to my wife to help her fall asleep. And that's not actually a joke about it being boring. (Currently reading about the evidence for UFOs, it's highly interesting.)

However, almost every article follows such a predictable format: Introductory section, full of all the interesting and tantalizing details, and stuff you actually want to find out about. Then section two: we jump back to the main subject's childhood, what clothes they were wearing when the journalist met up with them, how softly they speak. About two pages of biographical content. Section 3: we jump to the background of the story we're actually going to tell. Explain how it fits into the history of some movement or scientific question or whatever. The "point" of the article gets buried somewhere in sections 4 or 5, in between riffing on other people's dead ends and more biographical content.

I know this is going to sound crazy, but give it a try sometime.

When I lose track while reading an article, or find difficult to understand it, I stop and reading it bottom up, one paragraph at a time. First the last paragraph, then the one before that, etc...

This cuts through directly to the conclusion, then the detailed explanations form particular to general (which works better for me) and I can skip the "excitement build up" at the top of the article.

man... this is exactly the opposite of how news articles are supposed to be written.

Good news articles should tell you everything in the headline. Then tell you everything again in the first body sentence. Then tell you everything again in the first paragraph. and the first page. And so on.

It's supposed to be a fractal that unfolds additional detail as you press forward, while ensuring that even a casual reader comes away with a mostly complete and accurate understanding of the issue.

More of THAT please.

Yeah, it's called "inverted pyramid", and it's supposed to be the gold standard of journalistic writing. IIRC it's being taught as part of vocational education.

And yet, news media are the last place you're likely to find articles written in this style. Somehow, they manage to deliver the exact opposite of what they should be. A fractal of confusion, recursively unfolding noise.

(It's as if they were making a lot of money on maximizing the time a reader is engaged with any given article. It's as if - and I know this sounds crazy - the articles were there just to hold the user down, while they're being exposed to something else...)

Its 'pyramid structure', not inverted. It was used in newspapers for two reasons.

The first is because, yes it allows busy readers to access the most salient facts first. But secondly, and perhaps more importantly from the point of print newspaper production, it allowed subs to always cut from the bottom, without having to read the whole piece carefully...

Newspapers would go through several editions throughout the night as new stories came in or existing stories were expanded. What started life as a front page lead might find itself moved to page three and progressively shortened, possibly down to a 1 sentence news-in-brief NIB.

The pyramid style let subs always fit a story into the available space, simply by cutting everything progressively from the bottom.

This story in Wired is not a news story and is not written as a news story. It is a feature story and its construction follows different rules.

It's a very good feature story, in my opinion.

Wired is a magazine, not a newspaper: it doesn't exist to quickly present information every day, but to provide entertaining writing once a month; insisting it use an inverted pyramid is as strange as arguing that if only movies and books just led with the resolution, it would save you a lot of time.

Any publication still competes for attention.

Practices which show contempt for the reader's time and interest are ultimately counterproductive.

> Yeah, it's called "inverted pyramid"...

Narrow (succinct) at the top and broad (detailed) at the bottom seems like a normal pyramid to me.

An "inverted pyramid" would be like one of those poems that describes fine details first and only in the last sentence reveals what it's been describing.

I don't doubt that it's actually called that, but it seems backwards to me.

Thank you. The other replies made me worried my memory is failing me.

Yeh, it's simply called pyramid structure.

"this is exactly the opposite of how news articles are supposed to be written."

I'm not accusing you of doing this on purpose, but there's a certain amount of equivocation in the phrase "news article" there. Yes, that's a style that is recommended for factual news articles in a newspaper context, but that's not the only form of "news article".

Call this a "news essay" instead and give it its own style and it might make more sense. It's been around for a long time. Could call it the 20th-century equivalent of clickbait and probably not be far off.

"There's an exciting revolutionary change to physics coming... but first, the full life story of the thesis advisor's influential father... keep reading...."

Arguably it's more a form of entertainment than information.

Sure, but most of the content they are writing is neither entertaining or engaging, its long and wandering and I couldn't care less.

No novel is allowed to lollygag around the point its trying to achieve in the way these articles flagrantly waste your time.

It's like someone misunderstood that the act of moving your eyes along the page is not interesting in and of itself.

>No novel is allowed to lollygag around the point its trying to achieve in the way these articles flagrantly waste your time.

With barely less than a second's though: Watership Down, a hugely popular novel in the 1970s, spends untold amounts of text/paper immersed in detailed descriptions of the flora that the characters are moving through or eating.

Why not just say "I don't enjoy this style of writing", rather than trying to come up with some supposedly objective metrics for how other people should write?

There is lollygagging in irrelevancies, and luxuriating in details.

The distinction can be quite arbitrary, but it usually does stand out.

Herman Melville and Neal Stephenson also come to mind. In nonfiction, John McFee.

I suspect that doing the opposite helps trap people on the page, resulting in more money going to advertisers. If all the info is at the top, who will scroll lower (and see more ads)?

I second this.

I applied it to this[1] super long winded article in New Yorker to get the gist of the article. This article is littered with these passages and it's super frustrating. In the end from my view point it's a shallow piece with very little new insights. FWIW the article didn't age well as India is being ravaged by the 2nd wave.

[1] https://www.newyorker.com/magazine/2021/03/01/why-does-the-p...

The New Yorker is a magazine, not a newspaper: it doesn't exist to quickly present information every day, but to provide entertaining writing once a month; reading it backwards to try to get to the point as fast as possible sounds as silly as doing the same to a movie or a book.

Excellent practice.

I'll also frequently apply this to HN comment streams.

1. Collapse the top comment. It's frequently good, but also frequently is an avalanche of compounded hot takes.

2. Scroll to the bottom of the discussion. Odds are that comments are lower-quality, but not always. I collapse these as I go up, upvoting the underrated ones. Occasionally comment.

3. If there's a long stream of lower-quality / redundant comments, I'll collapse those as well.

I really wish there were some way to surface more deeply-nested, high-quality comments. There isn't. (Though occasionally an email to mods will elevate one to a top-level comment.) There used to be a periodic HN curation. That no longer occurs AFAIU.

Sounds like the recommended way to read a research paper: (1) read the abstract; (2) if you're still interested, read the conclusion; (3) if you're still interested, read the body of the paper.

> Articles in comparable British publications tend to be a lot more succinct.

Here's a counterexample literary trainwreck from the BBC. Have a go at wading through this horror show. It appears to have been written deliberately to withhold the topic of the article from the reader, for as long as possible. The wholly uninformative title is just the beginning. Those with the necessary patience will eventually realise that the title is also plainly untrue.


Again, this is a feature story, not a news story.

I agree, and if you consider Private Eye in particular, they make the New Yorker or The Atlantic look like the Proust. Having said that, the British periodical landscape is sorely lacking a good centrist/apolitical current affairs publication in the American style.

The Economist? Or do you consider that too right leaning?

The Economist hasn’t been right leaning for at least half a decade or longer now.

This is actually because of a cargo cult fetishization of longer texts. As most people moved to rapid consumption of many disjoint sound bites, knowledgeable people read more than headlines. Those who then wished to emulate these decided that anything long is meaningful leading to a fetishization of “long form” prose.

You’ll see a pretty high correlation between fans of “long form”, readers of The Atlantic and The New Yorker, and political inclination around being perceived as erudite.

It’s one of those cargo cult mixed with a measure becoming a target.

Hear hear. Maybe Wired should talk about the coffee she's sipping, made from beans harvested on the south coast of Java, where there is a legend of a queen who drowned...

The important thing was that she had an onion on her belt, which was the style at the time.

Now, to take the ferry cost a nickel, and in those days, nickels had pictures of bumblebees on 'em. Give me five bees for a quarter, you'd say.

I need more detail... what happened to the queens relatives.

Forget the relatives, where did those BUTONS on her shoes come from!

> When the call ended, Marr sat back heavily, feeling an old frustration coiling tighter in her body. She itched to go for a run, to pound it out footfall by footfall into the pavement

This style of writing is so present tense sensationalized, I cease to believe what is written simply because all this fictionalized present tense prose they dress the article up is 100% made up - so how is one to take the "facts" seriously?

The short of it is that there was some early research done in TB transmission and they found that the nose was really good at blocking particles larger than 5 microns but it showed that 100 micron particles would be suspended in the air as an aerosol and there was subsequent research that used the 5 microns as gospel for aerosol cutoff even though particles greater than that could be considered aerosol and that cutoff stuck.

This twitter thread from Jose-Luis Jimenez is far far better.


Credentials: https://www.colorado.edu/chemistry/jose-luis-jimenez

Wait, is this a Wired link? The URL seems to go to drive.google.com and... that weirded me out so I didn't click on it but figured I'd check out the comments to see what folk had learnt.

Nails on chalkboard.

Writers with frustrated literary ambitions...

I have read both now, and IMHO there's more actual content about scientific matters in the Wired piece.

I refuse to click on Wired links anymore. The signal to noise ratio is way to low to ever be worth it.

Could someone here please make a Wired auto-summarizer that cuts out the stuff about what the subject of the article had for breakfast that day and retains the insights?

This seems closely related, actually:

Wired: EARLY ONE MORNING, Linsey Marr...

OP article: A paradigm shift to combat indoor respiratory infection ... Linsey C. Marr (in the author list)

Wired: . At one point, Lidia Morawska,

OP Article: Lidia Morawska (first listed author)

Here's a fascinating Twitter thread about the history of aerosol transmission denial, going back to the early 20th century :


It's 100 tweets long, may be more readable here : https://threadreaderapp.com/thread/1391111720526024708.html

Apparently the CDC has yet to catch up to 19th century physics.

The physics of small particles moving in the air ("Brownian motion") was completely figured out by Einstein back in 1905.

Given a virus' size and weight, it should be trivial for a physics graduate student to simulate how long it will be airborne.

>> Given a virus' size and weight, it should be trivial for a physics graduate student to simulate how long it will be airborne.

How long it remains airborne is beside the point. Does that physics grad know how long/if the virus can survive once it dries up? Do they know how long it will survive exposure to light? Do then know whether the virus can cling to dust particles?

Even brownian motion is only half the story. Does the physics grad understand airflow in office spaces? Do they understand how fast air moves when a person coughs? How much turbulence is caused by opening an office door? Plenty of things can stay airborne for extended periods because of aerodynamics without regard to brownian motion (snow/rain/dust/salt etc). That physics grad better come with minors in aerodynamics, kinesiology, microbiology ... even some basic meteorology would be helpful.

As an civil / environmental engineer, I can assure you that particle size and average settling time is INCREDIBLY important to consider and will cover basically all of your supposed edge cases to the point of being statistically irrelevant. You would handle those edge cases by simply including a safety factor in the required residence time of the average particle within the system considered (or equivalently, you'd specify a certain log removal of pathogens). The end result of all your edge cases that you seem to think are so important is something like: "Ok, 1 in 100,000 may still get sick with this design. Good enough."

You can make the same arguments for drinking water, and yet, as long as you follow the rules, it is unbelievably safe, despite the fact that no one gave a shit about turbulence along the baffles in the treatment tank.

Per that Wired article, it was intentionally ignored when the first virus-related research came up in the 1940s because it was too close to the discredited miasma theory.

> Given a virus' size and weight, it should be trivial for a physics graduate student to simulate how long it will be airborne.

This is also in the article, known research from decades ago. Social distancing is in fact based on a misunderstanding and conflation of a few things in that early research.

The thing about medicine is they like to test. Theory and simulation are nice but it’s just not medicine and therefore not suitable for a doctor to tell to someone as “medical advice” with all of the legal burden of malpractice that the term entails. “What if I’m wrong?” is a question that keeps good doctors awake at night and bad doctors have forgotten to ask themselves… when this kind of question weighs on you, it’s natural human behaviour to become more cautious, to become risk averse and question the validity of newly presented information due to the potential that regardless of if their current understanding is wrong, there’s no inherent guarantee that the new information is any less wrong.

And so medicine is understandably a slow moving science, and the practice of medicine moves even slower as it represents the slow filtration of the cutting edge of medicine the science, through a complex web of human interaction. Which with a dash of “social capital” theory, makes it easy to see why we have unfortunately often ignored sound advice like this. The mistaken assumptions of people viewing a person who’s expertise bridges two disparate fields, as being unable to understand things as deeply, clearly or fully, as the people dedicated to just one of those fields.

I can see your point, but isn't the WHO tweeting “FACT: #COVID19 is NOT airborne.” an example of the opposite? They made a hard assertion without any clear proof to back it up.

Hmm? interesting. Here's the offending tweet:

  FACT: #COVID19 is NOT airborne. 
  The #coronavirus is mainly transmitted through droplets
  generated when an infected person coughs, sneezes or 

  To protect yourself:
  -keep 1m distance from others
  -disinfect surfaces frequently
  -wash/rub your hands
  -avoid touching your Eyes Nose Mouth
- https://twitter.com/who/status/1243972193169616898

The WHO gave a lot of bad advice. Some say that it was intentionally misleading. Promoting ventilation as a reasonable treatment for the initial stages of covid-19 was the worst possible advice to give front-line medical practitioners who didn't know what they were dealing with.

We now know that the fecal-aerosol route of transmission is very important. Forbes has a recent piece about the fecal-oral/aerosol route: https://www.forbes.com/sites/williamhaseltine/2021/03/22/pre... Another tweet by ... someone was about how the masks effectively aerosolize droplets.

Keeping bathrooms open but requiring face coverings was an exercise in futility.

In the case of COVID-19, the WHO seems to have implemented #PrasadsLaw [0]. "Prasad’s Law: Medical goods and services that concentrate wealth can be paid for; medical goods and services that disperse wealth are “unaffordable.”"

[0] https://news.ycombinator.com/item?id=21728864

Farts are deadly now?

Good to expose such expert arrogance.

that's fascinating, are CDC and WHO officials even practicing physicians? Would that have helped any?

I would put money on COVID not happening at all if all buildings had 10 air refreshes per hour, and that air either coming from the outdoors or going through a HEPA filter.

I would guess an analysis of workplace COVID rates would see a strong correlation between workplaces with and without filtration in their AC systems.

There’s a saying, earthquakes don’t kill people—buildings kill people when they collapse.

In the open air on a grassland, covid won’t kill a population. The design of our hermetically sealed buildings is what’s killing us.

Back in the 1970s the air outside was full of lead and smog, so the safest thing too was completely seal all office buildings.

Today the air inside probably contains more hydrocarbons (from volatile organic compounds offgassing from carpets and furniture) so the best thing to do is vent air to the outside and keep the windows open (assuming you live in a mild climate)

Of course, that flies in the face of all efforts to make things green…which involve better insulation, sealing windows against leaks, more air filtration systems and etc.

Here in Canada the temperature drops like 5 or 10 degrees when you walk into a forest. I’ve stepped into a traditional mud hut and experienced a similar cooling effect. The common denominator is that both environments have a high surface area compared to say concrete. This acts as an efficient radiator so that when water to evaporates it removes heat. In low humidity climates this is one way to reduce cooling demands. Beyond that if we cool micro zones or interstate cooling into clothing itself through hoses or something that might be the next step in efficiency…until it gives birth to the next problem.

>Of course, that flies in the face of all efforts to make things green…which involve better insulation, sealing windows against leaks, more air filtration systems and etc.

If anyone has a half-hour of time to waste, you can look into the science of "countercurrent heat exchangers".

It's fascinating to see how 2 pipes of air current switch temperatures when they're in contact and moving in opposite directions.

So if you want to be green AND have fresh air constantly circulating through a building, then forcing the warm inside air to pass by the cold outside air as they leave/enter the building can lead to somewhere around 95% energy recovery.

Add in a humidifier to the incoming air, and you'll have a comfortable room with humidity that will attach to airborne droplets, prevent evaporative release of a raw airborne virus, and help pull the droplet down to the ground via gravity.

Wikipedia claims "Heat recovery systems typically recover about 60–95% of the heat in exhaust air".

But even recovering 95% of heat isn't exactly great. If you live in Canada and have a 2600 sq ft house with 8 ft ceilings and 10 changes of air per hour, and the indoors is 70F and outdoors is 0F, thats 2600810 cubic feet of air/ per hour, or 12000 BTU/hr. That means you are more than doubling your heating costs compared to sealing the building and just having conductive losses through the walls.

This is true for most climates - even the best energy recovery systems still double heating/cooling costs compared to having barely any fresh air.

Something must be off with your math. I’ve tested opening a window a crack in my building in montreal. The co2 gets low even with two people present. Heating costs did not double.

Or maybe I had less than ten air changes?

It can’t be that hard to focus on the rooms with people in them, reduce the other rooms to eg one change an hour.

This is already done when calculating ventilation rates. It won't matter much because the majority of space in an occupied building is going to be classified as, well, occupied.

I always wonder how much I save by blocking off the vents in under-occupied rooms. They end up sitting a few degrees cooler in winter.

The problem is very seldom the house. The problem is shared spaces.

10 air changes per hour is a lot; I believe the current recommendations for average climates is 3.

And we're looking at the margins; 1 air change per hour can do wonders for preventing the spread of disease and improving air quality, compared to 0 air changes per hour.

Nevertheless, I redid your math, and found that your hypothetical home has 26,728 more BTUs of energy in its air, compared to the outside air[-1][0][1], and that the recommended furnace for such a climate should be 160,000 BTU/hr [2].

Using those numbers as a base, I find that, with an efficiency of 95%, it would require 120 (that's one hundred and twenty) air changes per hour to double heating costs.

With 60% efficiency, it would require 15 air changes per hour to double heating costs.

And it only takes a few air changes per hour to increase comfort and prevent illness.

[-1] I suddenly realized that the google search links that I used for these calculations are messy and unwieldy, so I'll summarize my calculations: (2600 ft^2) * (8 ft) represent the volume of the house; (1.225 kg / m^3) represents the density of air, (1.005 kJ/(kg * Kelvin)) represents the specific heat of air, (70 * (5/9)) represents the temperature difference you gave me, in Kelvin. Multiplying everything together, and letting Google automatically take care of unit conversions, gives me 28.2 MegaJoules of energy in the house.

[0] https://www.google.com/search?q=%282600+ft%5E2%29*%288+ft%29...

[1] https://www.google.com/search?q=convert+28199142.9+joules+to...

[2] https://www.pickhvac.com/calculator/heating-btu/

My first calculation using entirely imperial units didn't go well... I think I'll stick to metric!

It's unavoidable when discussing residential heating. Just use google for automatic unit conversions, and be grateful that we didn't need to invoke the cumbersome unit of "R-value" to measure insulation!

> "countercurrent heat exchangers"

Very interesting! The concept makes a lot of sense, and I was able to find some companies online that produce such a thing, often under the phrase "counterflow heat exchanger".

Frustratingly there's little details online for actual pricing, but you can find the bare exchange units on ebay for $200-300.

> It's fascinating to see how 2 pipes of air current switch temperatures when they're in contact and moving in opposite directions.

Shouldn't the air ideally move in the same direction?

Nope, because they will both end up at the same temperature, namely, the average temperature halfway between the two previous temperatures.

In a countercurrent heat exchanger, the hot air will get colder and colder until it is at the same temperature as the cold air, and the cold air will get hotter and hotter until it is the same temperature as the hot air.

This is because the hot air is not warming up the same air molecules that it relies on to cool down, and the cold air is not cooling down the same air molecules that it relies on to warm up. Each current of air gives up a part of their heat/coldness, becomes colder/hotter, and then moves towards a section of pipe that's even colder/hotter than the previous section of pipe.

A picture is worth a thousand words, although it takes some staring and studying before the concept finally clicks: https://en.wikipedia.org/wiki/Countercurrent_exchange#/media...

Ah ye thank you makes sense.

There is a diagram illustrating why not in the wikipedia article: https://en.wikipedia.org/wiki/Countercurrent_exchange

With a controlled ventilation system you have better indoor air than with leaky old houses and it's also more energy efficient.

People talk all the time about air changes per hour. Even a recent Nature.com article only discussed this metric. However, if you look at suppliers of heat recovery ventilation units, a different metric is liters/sec/person. About 10 liter/sec/person seems to be pretty good for commercial spaces. For home environments people can adapt to smells a little better, so the requirements can be lower.

Also: heat recovery percentages don't always include the energy required for forced air movement through the exchanger.

The highest infection rates are still short range though. This, combined with being a new virus would still be similar to today.

Short range could be explained by airflow rates in most buildings being near nil. Someone talks in one spot, and pathogens hang around that spot in the air for many minutes.

With say 10 air changes per hour (injecting at the ceiling and extraction at the floor), and a 3m high building, you can expect airflow downwards at about 1 cm per second. That means there is perhaps only a 30 second window for a particular pathogen to hit someone else's nose before being pulled to below face level.

It's not nil, but I think that would lower transmission rates by a sufficient factor for COVID (and many other diseases) to become extinct.

Well the spanish flu happened and they did not have HVACs back then and all the windows leaked.

Spanish Flu is a really bad name for this disease.

From what we know it started in Kansas. It should be called 1918 Flu Pandemic.

It's called Spanish Flu because Spain was the first country not to cover it up to avoid adverse morale effects and revealing potential weakness because of WWI.

This is the Ben Franklin / John Adams debate when they shared a small room together overnight with one window.

“When Adams explained that he didn’t want to catch an illness from the cold night air, Franklin countered that the air in their room was even worse.”


This reminds me of an argument I had with a friend in October. When the weather got cold, I only wanted to socialize with our small group of friends outside because the open air was safer, but she only wanted to socialize inside because she thought being outside in the cold would make her catch COVID.

Miasma theory rears its ugly head once again: https://en.wikipedia.org/wiki/Miasma_theory#Contagionism_ver...

The night air is dangerous, close those windows before you go to sleep!

Miasma was a perfectly good theory and if anything, is obviously true innately. Bad smelling air from urine, shit, festering corpses and the like, was often laden with viruses, bacteria, and noxious chemical fumes. Sure, plenty of diseases are not airborne but air that smells like shit isn't exactly a boon to be inhaling. There is a non zero chance of getting sick from noxious air.

Yes, it's "obviously true" because of the confounding factors: bad air tends to go hand in hand with dirty water, contaminated food, and infection-carrying insects.

Neither cholera, malaria, typhoid nor plague are airborne, and yet their causes were ascribed to miasmata.

Right but the metabolites produced by the bacteria are harmful in their own right. And let's be clear, there are many airborne contagions like the common cold that haven't been indexed through the centuries. It isn't a good idea to inhale shit air for days on end, just like it isn't a good idea to inhale car fumes for days on end.


Nonsense. The pathogens in urine, shit, and corpses are almost never airborne. And the fumes are only toxic in extremely high concentrations. The chance of getting sick is effectively zero.

Nonsense. The risk is nonzero. Turbid air takes a toll both physically and mentally, and can lead to inflammation and weakening of the body's defenses. Your definition of sick is quite narrow.


No you're just making things up. The link you posted doesn't support your statement.

> Biogenic volatile organic compounds (BVOCs) encompass VOCs emitted by plants, animals, or microorganisms,

> VOCs are produced by animals and microbes

Try to have substantiative things to say instead of spouting off false declarations and inflammatory insults.

yes, and while it might have helped at the margin, it's frankly naive to think that we'd have largely avoided this pandemic had we just had better indoor air circulation. it's an analytical solution (so irresistable to engineers, mathematicians, and physicists!) to a complicated and stochastic set of behavioral patterns, that people want to be close to each other indoors for highly complex and very substantive social reasons (not to mention the intricate contraints the virus faces to transmit). transmission happens closely face-to-face indoors, and in light of that, folks aren't going to want to sit together for very long in an airstream strong enough and comprehensive enough to deflect and capture potential virus particles everywhere just to chat and enjoy each other's company for a bit.

while most mask usage in practice has been completely useless (like double-masking or wearing them outside), the one place where masks make real sense is between two faces close to each other emitting exhaust indoors. if we had just relentlessly kept to this one crucial scenario in our mask messaging (and simply distancing everywhere else inside), we'd have had much better and more targeted mitigation, with dramatically fewer downsides to our social and economic lives. and to boot, that avoids trying to make extraordinarily costly upgrades to every hvac system in the world for marginal benefit.

It's the theoretical key question. The practical one is more like "how's the cost benefit curve looking like, especially in the beginning?".

My personal completely unscientific musings on the topic ended with buying and cutting up a couple of vacuum cleaner hepa filters, thus obtaining a shocking quantity of filter cloth, which then can simply be taped over the standard AC mesh filter. AFAIK, "hepa" ACs don't even cover the full surface - they just have a patch of hepa, which just ensures the air inside gets circulated through it eventually - being recirculated, there's not that much of a hurry. I'd recommend low-end filters, you don't want to remove virus particles but much larger clusters of virus+saliva.

So personally I'm guessing a rather high impact for very low cost / low effort changes.

A considerable number of deaths could be prevented. There are models that show that masks helped to curb spread of flu so well that excess deaths due to Covid in some places became negative.

I agree. Changing the building codes' ventilation requirements will cost time and money. And the resulting designs are potentially louder, bulkier, and less energy-efficient.

Hopefully we'll make those changes if and only if doing so brings significant health benefits.

There is a "law of unintended effects" question as well: if we were to live - and presumably grow up - in such a sanitized environment, what would happen to our immune system.

There's a sizeable chance it would be extremely weak and that'd we'd be incapable of resisting many disease on our own and therefore would become completely dependent on the air cleaning infrastructure.

You still eat fresh fruits and vegetables, touch the surfaces on your way to work etc. There’re countless pathogens everywhere. So I guess we would be fine?

You’re right that our immune system didn’t evolve to be in a sterile environment. But we also weren’t meant to be that close to that many humans.

>So I guess we would be fine?

Can you catch airborne respiratory diseases from eating fruit?

What I'm saying is: we run the risk of never being able to go outside again if we eliminate all airborne pathogens.

Are you suggesting that bringing more air from outdoors into our indoors environments will cause us to lose our ability to tolerate outdoors air?

Not to worry, people will still have children, and I assure you, they'll still go out into the world and lick the doorknobs/each other and get you sick so you can bring it to work.

> Can you catch airborne respiratory diseases from eating fruit?

I'm willing to speculate that exposing our immune system to surface pathogens helps deal with airborne pathogens.

It seems overly complicated.

Just raise the air exchange per person and or per volume by a significant factor and mandate a very fine particulate filter. You could do many measurements and lots of theory but nobody is going to engineer their buildings like cleanrooms anyway so the results of a lot of science wouldn’t be so good regardless.

I'd like to see "air quality inspection" be part of a fire safety inspection.

Just have the inspector crack out a CO2 and PM2.5 meter during the inspection. Set legal limits and have a fee for exceeding them. Make it apply to existing buildings too, so building owners can choose to trade off increased HVAC costs Vs reducing the fee Vs costs of retrofitting better ventilation.

Obviously the measured numbers vary a lot day to day, so if a building owner isn't happy with values measured on the day, let them take an average over a week or something.

Agree and love the idea about testing.. there are no other inspectors (in oz at least) as incorruptible as fire safety inspectors.

I had the experience a couple of years ago of working in an office with visible smoke from a meat smoker working downstairs. The owner and employer had 'independent' tests done with no issue found. Fuckers.

I do reckon there is a rather disgustingly unequal relationship between people that own or build a building and people that have to deal with sickness from working in a building.

Overwhelmingly, upfront costs for systems which prioritise airchange, occupant health, and energy savings are more expensive to install but cheaper in the long run.

That has significant costs on the energy efficiency of buildings and would blunt a lot of the progress we're making on combating climate change.

Not saying it shouldn't be done but it should be done in a smart way that balances between tradeoffs.

Does it? I thought energy expenditure to maintain indoor temperature is mostly due to heating/cooling, not due to moving air to or from heat exchanger. E.g. it is cheap to rotate the air in the building in a closed loop through a filter.

Yeah, I can't see how the operating cost would be much different.

I do think the initial cost to install/upgrade to such system would be substantial, though (as in, existing systems may not have the capacity to ventilate that much.)

You can use heat exchangers between outlet and inlet air to mitigate a good portion of the energy cost I believe.

If the outflow is not compressed, you can transfer at most half of the heat and that is under perfect conditions.

That's not quite right. If the airflows are in opposite directions then you can transfer more heat. Since as the hot air cools it encounters progressively colder air ensuring there is always a temperature gradient to transfer heat. These systems are about 60%-90% efficient at transfering heat.

Doing that without the ability to quantify the affect is also a nonstarter. How would you know it's even making an appreciable difference, or if a lower factor would perform just as well?

Without the groundwork theory to rely on, you'd be hard pressed to convince new buildings to do something like that on a whim.

> You could do many measurements and lots of theory but nobody is going to engineer their buildings like cleanrooms anyway so the results of a lot of science wouldn’t be so good regardless.

This is a very strange and confused sentiment.

If you have air exchange per person, but some people are in an airflow "dead zone", then that doesn't really do you any good. You need to ensure the personal area is actively ventilated, versus the entire space as a whole.

Now, who’s gonna pay for that?

I bet it's the minimum wage workers, not receiving any bump above minimum wage, as well as the lower tier of non-minimum wage workers being reclassified to be minimum wage. You know those least able to afford it will pay for it.

> Just raise the air exchange per person and or per volume by a significant factor and mandate a very fine particulate filter.

An alternative in the meantime is to use a PAPR (powered air purifying respirator), which are more efficient, last much longer (device and filter), and are much more comfortable than N95 masks. I use an Optrel Swiss Air and cover the valves of the mask with a hoodie style balaclava.

It would be a good time to get one, as it is believed that it is only a matter of time before SARS-CoV-2 mutates into a variant that is capable of evading the vaccines.

Also, the US CDC advice may not have been such a good idea. Look at these calculations:


Singapore has a comparable vaccination rate to the US and is going into lockdown to prevent further spread. They used Pfizer and Moderna vaccines. Just some food for thought:


Wasn't Singapore supposed to be one of the few success stories for eliminating Covid-19 without using vaccination, one of the countries that supposedly proved Western countries like the US could've avoided the need for economy-destroying lockdowns if only their governments were competent? Not to mention that they were and still are one of the most aggressive about mandating mask wearing, and were pointed to as a demonstration of how effective that was as well. The idea that Singapore going into lockdown proves the US CDC was wrong to advise vaccinated people don't need to wear masks seems extremely dubious.

We're locking down because of a single cluster. Slightly more lenient than the first, but our government is probably just being a bit paranoid here. With the vaccines round the corner though, that's not necessarily a bad thing.

. Singapore is at 31% one shot(from your link), US is at 47 and rising. Of course you would still be able to get spikes in cases at only 31%, that’s expected.

The mRNA vaccines are stupendously effective at stopping all variants thus far. Not sure what evidence aside from fear point to covid being able to mutate past them.

We good, and it’s ok to accept that and have hope, not everything has to be fear-for-the-worst

Is 45-47% efficacy at preventing infection against B.1.351 & P.1 “stupendously effective at stopping all variants?” http://www.healthdata.org/covid/covid-19-vaccine-efficacy-su...

I may be reading it wrong, but from your link it says 76% and 79% (pzifer & moderna) disease prevention against 351&p1. Which is still great. Note that’s just infection, the data shows the vaxxes have near 100% chance of preventing you from having more than mild/moderate symptoms. So yeah, stupendously effective, and we shouldn’t be panicking about variants.


You are using concern trolling tactics to accuse someone else of mental disorder for taking an interest in safety precautions during an uncontrolled global pandemic. This is not only rude, it is also dangerous. Please stop.

How dare you accuse me of "concern trolling". As if that was even a thing. The suggestion was completely irrational, unscientific, and not based on an interest in safety.

So the idea is to make every room a negative pressure room of sorts? I think this is probably long overdue, but I'm afraid I don't really see the paradigm shift.

Haven't all of these steps been taken on airplanes already, to some extent? From what I see, the "personalized ventilation" idea is substantially similar to what aircraft ventilation does, just adapted for a workspace/building setting.

It's more important to think about FLOW and also the quality of air exiting an air-handling system. BTW, how often are those ducts cleaned, if ever?

I would personally love a well designed slightly positive pressure dwelling with particle scrubbed inflow and egress (some kind of circulated water system like industrial sites have). Get rid of that pollen and everything else please.

There's an interesting system called "Phenomenal Aire" that I recently installed. It sort of achieves what you're talking about, but uses a very different mechanism called "Cold Plasma Generation" (caused by dielectric barrier discharge). The air smells noticeably "fresher" though that might just be due to the ozone. It does seem to have a dramatic neutralizing effect on VOCs [0].

Interesting article re: use in meat packing plants [1].

[0]: https://www.sciencedirect.com/science/article/abs/pii/S03088...

[1]: https://pubmed.ncbi.nlm.nih.gov/33876887/

Isn’t ozone supposed to be very detrimental to indoor air quality though?

It is. It's a strong oxidizer and damages your lungs. It makes the house smell better because it oxidizes volatile organic compounds in the air, but it's horrible for you.

It's an extremely strong oxidizer. It will poke holes in your lungs. But sure, it'll also oxidize the other crap in your air.

What would be the cost implications of this? I assume we're talking about a massive energy requirement/climate impact to implement this for all public indoor spaces.

Here's a fascinating Twitter thread about the history of aerosol transmission denial in the medical community, going back to the early 20th century :

https://twitter.com/jljcolorado/status/1391111720526024708?s... (It's 100 tweets long, here's a more readable version : https://threadreaderapp.com/thread/1391111720526024708.html)

The tl;dr is that 20th century health authorities went too far in their rejection of the 19th century "miasma" theory of disease transmission, and now the pendulum is swinging back again.

Overall air quality is an issue. We "consume" more air than anything else. Every day. All day. Day after day. Pathogens are a concern. But conditions and elements that have negative impact on the lungs - and help prime such tissue for invaders and disease - should be addressed as well.

I find it regrettable that the things we eat and drink get so much more attention than the air we breathe in regards to health.

It's funny (not) cause bad air is a known killer. Yet it gets crickets. I'd add noise to that list as well. Something we should be more aware of.

Sounds swell. Have we started rebuilding our stockpile of N95 masks yet?

From industrial suppliers, they are available but about 20X more expensive than pre pandemic. We used to buy boxes of 160 count 3M 8210 for 20$ CAD.

You could also use a decidedly low tech solution - putting UV bulbs in the way of air flow (like fans): https://www.cnet.com/home/smart-home/uv-light-and-the-corona...

At https://n5air.com/ we are formulating a quantitative "VIRUS INFECTION THRESHOLD" theory while fully recognizing it may already exist. Any leads? Also, is there a way to share its outline in a PDF file? Lev

I thought about something like this for the last 10 years when taking public transport.

It came again into my mind when I heard about tesla's biohazard filter system.

It's just ridiculous how we accept the status quo.

It can't be okay to be sick every year for 5-12 days and covid showed me no I don't have to be sick every year and don't get me wrong, clearly I'm not getting better in fighting this shit of if I have it every fucki g year.

What are long-term effects of being sick every year?

No more open office plans? Managers are not rational enough, sorry.

What a good read. Shame on the authors for putting such an important article behind a paywall. Thanks someone for filesharing it.

#AbolishCopyrights #AbolishPatents #EndIntellectualStupidity

dont need all this complexity to prevent airborne illness from going exponential, just masks + contact tracing. the results have spoken for themselves in asia

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