Whose breath are you breathing? | Hacker News Reader

Whose breath are you breathing?

rnz.co.nz

110 pointstigerlily76 comments

Covid aside, a reading of almost 6000 ppm in the bus is extremely high, at this level there is a clear impact on cognitive function.

See this study[1] in Nature that measured the effects of CO2 at 1000, 3000, and 5000 PPM. Quote: "For the Psychomotor Vigilance Test, the probability of achieving an accuracy score of >90% decreased in a dose–response like fashion from 79.5%, 74.7%, 73.4%, to 64.0% for 600, 1200, 2400, and 5000 ppm, respectively".

Another study[2] tried to establish the effect on response time, finding that "For every 500ppm increase, we saw response times 1.4-1.8% slower, and 2.1-2.4% lower throughput."

For a more pop-sci take on this, see this Tom Scott video where a subject is placed inside of an airtight chamber where the CO2 gradually increases, with a major impact on their brain function: https://www.youtube.com/watch?v=1Nh_vxpycEA

[1] https://www.nature.com/articles/s41526-019-0071-6

[2] https://iopscience.iop.org/article/10.1088/1748-9326/ac1bd8

6000 ppm is a normal level after 1 hour meeting in a closed conference room. Assuming non-openable windows (which is normal in modern offices).

It decidedly isn't normal unless your HVAC is supremely bad and the room's way too small for the group.

I have so far not been in a conference room even scratching the 2000 ppm level after an hour. (Well, OK, I only leave my meter behind. At 1200ppm, I consider the level excessive and leave. But I've kept measuring to see how willing people are to burn their health to be in the office with others)

I hadn't considered how bad public transport might be in terms of ventilation, but it makes sense. I wonder how bad the London tube might be on a busy day?

It's unfortunate that research on the impact of Co2 concentration on cognitive function and general wellness is so inconclusive (ie: effect size of high concentration on most tasks seems small), when subjectively it feels really high.

Some years ago I did some datascience work with a housing association wherein they installed high-frequency sensors in various rooms of housing units across the country (with the explicit consent of the inhabitants, data anonymized) with the intent on understanding how building properties and use correlated with the sensor data. In general there was (and still is) a lack of understanding how to model the relationship between things like building material, climate, occupancy, tenant behaviour and negative outcomes like mold growth, fuel poverty/health outcomes, and so on. I mean - I'm not saying there's no understanding, but it's definitely a field where more work is needed.

Anyways, one of the things I found most shocking is that in many of these flats, Co2 concentrations would get mind-bogglingly high in bedrooms during the months where tenants would likely have the windows closed (this is something you can infer by temperature gradients and heating usage). By mid-way through the night, some individuals were in rooms with 4k+ co2 ppm. A common side effect of breathing air with such a high concentration is waking up feeling groggy, disoriented, or with a headache. But what are these people supposed to do - many of these flats were low-income housing, so they're badly insulated to begin with, and they probably can't afford the heating bills of keeping windows open for ventilation.

Sorry for the long story - but the point is that there are many negative health externalities associated with poor ventilation in buildings and interior spaces, and at least we're starting to get attention on the problem now with covid. Hopefully this leads to improvements across the board.

Does the AV help?

What's AV?

I assume it's meant to be AC

Just in case, to answer the question: The vast majority of private, let alone public housing in the UK have no AC.

that does not answer the question

To make explicit: There is no AC therefore the AC doesn't help.

To be precise, there is AC in almost every home in the UK - approximately two-hundread-and-forty volts AC!

I considered the original question to mean: "Does / would the use of AC help?"

to which tangential, interesting information was provided but left the original question unanswered.

Are we to assume literally nobody has an AC nor is it possible for AC to even exist in those situations? Because if it helps, then maybe something productive can come out of this conversation where we can aim to improve some of these living conditions through use of AC's - which would kill 2 birds with one stone.

It seemed like a genuine question that should be actually answered. I want to assume "yes" they would help, but I'd be guessing.

AC alone wouldn’t make any difference whatsoever. You need a modern HVAC system that exchanges air with the outside with something like an ERV or HRV. And even before doing that you have to make sure the building is sealed and insulated properly so the air is going where you need it to go. It’s actually a fairly complicated problem that starts with the design, building materials, and construction processes of the building itself.

(Assuming you mean AC) - HVAC systems are generally designed to keep air flowing through the building optimally, which may include control systems for attenuating fans, exterior building air intake, and whatnot as a function of sensor measurements. I'm not sure how often CO2 is taken into account during building design or operation to be honest, aside from rough targets on designed occupancy rates and volumetric estimates of airflow.

In the UK, most buildings are naturally ventilated. There's no mechanical ventilation moving air around automatically, you gotta open your window if you want airflow. In the winter this generally puts people between a rock and a hard place: either you are slightly cold and sitting in a stuffy roof, or you open a window and are REALLY cold and also go broke from the energy bills :P

London’s tube is particularly bad because of its history running steam trains, of which the residue is still present on walls and ceilings. The Tube is also poorly ventilated due to its age (when this was less considered) and the fact that vent shafts open into places that also have bad air quality.

NYC performs relatively better, it sits close to the surface with frequent vents. There have been simulated bioterror attacks that show the threat in the subway would dissipate quickly due to the ventilation.

The article mentions a bus. I would expect the bus to ventilate more poorly; trains have many doors per car and they simultaneously open for the entire stop in the station, but a double decker only has two doors, the back open to let people off and closed shortly after that’s done, and the top deck has no doors at all.

I am extremely skeptical of your claims re: London.

Steam hasn't operated on the Underground in 115 years, and only ever on a small minority of lines.

I doubt it's because of steam train residue, but when I was on the Underground it turned all the mucus in my nose black for a day every time I rode it. From searching around, this seems to be a common occurrence for visitors. Air quality there is severely compromised. There's also the health and safety problem of its steadily rising temperatures, about which nothing appears to be being done or even considered.

They are trying to install cooling at several stations where they deem it possible.

The problem is that, generally speaking, Central London lacks spots where you could just punch a ventilation shaft downwards, and the stations are too tight to accommodate modern HVAC otherwise.

I'm not sure there's a significant difference between depths of most of the London and New York subway systems.

Most of the London Underground is cut-and-cover tunnels sitting just below ground level (2-6m). The Thames Tunnel is 24m below ground level. The deepest station is Bull & Bush, Hampstead, at 57m (180ft) underground:

https://londonist.com/2015/10/how-deep-does-london-go

https://londonist.com/london/transport/how-deep-is-your-comm...

The NYC subway also uses extensive cut-and-cover routes, though deeper bores exist. The deepest station, at 191st St. (LRI) is 180 ft. (54m) below ground. About the same as the London Underground.

https://untappedcities.com/2013/06/26/deepest-highest-subway...

https://www.nycsubway.org/wiki/Chapter_14:_Engineering_Featu...

There's also difference in ventilation design. A lot of the tube relies on the piston effect for ventilation.

NYC's subways are underneath major roads and nearly always features extensive sidewalk venting for the entire length, as depicted in the iconic photo of Marilyn Monroe. https://img.atlasobscura.com/EEahxLmWgG-xahr-cXyJ1_TFUKch_pn...

Where "piston effect" is the passage of trains through the tunnels forcing out air (ahead) and drawing it in (behind), correct?

AFAIU that's a major component of any subway's ventillation.

Yes.

The difference is that London relies solely on the piston effect. NYC has the subway vent grates on nearly every block where a subway runs. Modern systems generally also use HVAC.

On the public transit point: fun fact, BART (a large SF/Bay Area transit system) trains replace all of the air in each train car every 70 seconds, which is a much higher rate of airflow than most other public spaces. Since they also use MERV 14 filters, there may be a disconnect between CO2 readings on BART (or other transit systems with aggressive filtration) and the true risk of catching a respiratory virus.

Interesting, but I see two big issues that render the data nearly meaningless:

1) does CO2 correlate well to spit droplets? they mention this (alleging that places with more talking have more spit droplets than ones without) but present no data. Also, does CO2 on public transport involve any exhaust from the vehicle? Are people in gyms breathing a lot with their mouth closed, producing more CO2 but not talking (or otherwise producing spit droplets) nearly as much. Lots of ways this could be not very correlated.

2) does quantity of spit droplets really correlate to likelihood of getting infected? Viruses are replicators. It is not at all obvious to me that 1/2 the number of viruses means 1/2 the risk of getting infected. It might not even result in a significant drop at all. Theoretically one droplet containing the virus is enough to infect you, and if infected it replicates. The operative factor is how well your immune system recognizes the threat and produces antibodies, not how many virus copies were there originally. One drop was enough to infect just over half of a young, healthy experimental subject group: https://www.science.org/content/article/scientists-deliberat...

> The operative factor is how well your immune system recognizes the threat and produces antibodies, not how many virus copies were there originally.

These probably aren't independent, and are occurring at the same time. So while a very small amount of virus is replicating, the immune system is mounting a defense, slowing down that replication. The virus may never get to a significant amount (although the immune response might knock you on your ass.)

On the other hand, if you start with a ton of virus already, you'll be dealing with the immune response and the direct effects of the virus at the same time, and the virus may overwhelm or even limit the immune response.

True, but even a large number of droplets will not result in "a ton" of virus, if by "a ton" we mean "similar to what will result if you get sick". A sick person breathes out a lungful with every breath, so obviously a sick person contains far, far more copies of the virus than that.

Put it another way. If your immune system recognizes the virus already, it matters little whether you get one droplet or a thousand, it will beat it because it has a several-day head start in doing so.

If, on the other hand, your immune system does not already recognize it, then it will not begin to see the problem, and thus will not begin to react, until it has replicated up to a large amount, where "large" is some amount greater than either one droplet or one thousand will give you. So, the consequences of getting exposed to 1/2 or 1/10 of the number of copies of the virus, is basically nil, because an exponential rise will be needed in either case to get up to the level where your immune system notices a problem.

Either your immune system already recognizes the virus as a problem, or it doesn't. I neither case does the dose matter, so long as the dose is big enough to start the process. And that probably doesn't take much.

This isn't true. Even a robust immune system cannot prevent disease at large enough doses of virus because the immune system takes time to execute at any level of robustness. Similarly, a small enough dose will not necessarily cause disease, because the immune system can recognize the virus and eliminate it before it can replicate significantly. This is actually a time-based race: the speed of which the immune system can react vs the speed in which the virus can replicate in the body.

The article is focusing on ventilation and air circulation. Poor ventilation results in increased CO2 levels, and it does so in a predicatable, measurable amount.

We also know that poor ventilation increases the likelihood of catching covid from an infected individual. So measuring the level of a space's ventilation is not meaningless data, even if it doesn't translate 1-to-1 with transmission rates.

There are two scenarios in which halving the number of droplets inhaled has little effect on the risk of being infected, and two where it is moot.

The ones where it is moot is those where either you you are already infected or no-one is.

Halving the number of droplets will have no effect if droplet inhalation is not causal in transmission. In this case, there is plenty of evidence that it is, in fact, the primary mode of transmission.

It would also be the case when, even at the lower droplet count, one is likely to become infected. This is essentially the scenario in your second point.

None of the above are the case in a typical bus ride today, and for such, it is reasonable to suppose, as a first approximation absent further evidence, that risk is correlated with the degree to which one is rebreathing other people's exhalations, even though one can postulate that it is also correlated with other factors.

One can question the source of the CO2 on a bus, but the measured values reported here are significantly above those measured by busy urban roads, where 1000ppm is considered vary high. If the bus is leaking CO2 into the cabin to any significant degree, there are more immediate health concerns.

Demanding near-perfect data before considering its implications can be a way to avoid issues.

1) Spit droplets is much less of a problem than aerosols. You can solve that problem well with keeping distance. Aerosols are a bigger problem - they travel further and linger.

All the studies I've seen so far correlate CO2 with aerosol levels. If spit droplets are a concern, I have no idea.

2) Covid studies so far have shown that there's a minimum level of viral load required for an initial infection, and they have also shown that there's a correlation between initial dose and severity of infection. So, yes, how many virus copies were there originally matters very much.

In general, this has been explored in a large number of studies. I'd suggest at least a cursory research before claiming issues that "render the data near meaningless".

it would be implied. in an indoor setting most of CO2 comes from human exhaust

Title reminds me of this:

> Nowadays, at least in the population of the industrialized nations, about 40 percent of the nitrogen contained in the human body has already taken part in the Haber-Bosch synthesis.

(from the German https://en.wikipedia.org/wiki/Haber_process article)

Any recommendations for a good portable CO2 monitor?

https://aranet.com/products/aranet4/

> "Connect your device to the app to view, track and analyze your data from the last 7 days"

In a time where gigabytes are trivial (megabytes is enough for hundred thousands of measurements anyway here), why do such limitations like "7 days" still exist?

If there's a way to get a CSV or similar file you can analyze on any device you want, then we're talking

I can’t speak to why there’s a limit but you can export your history as a CSV from within the app: as long as you export at least once every 7 days, you’d have a full history through the life of the device.

The CSV contains datapoints for each recording (default to 5 mins but use configurable): Time(dd/mm/yyyy), Carbon dioxide(ppm), Temperature(°C), Relative humidity(%), Atmospheric pressure(hPa)

I’m very impressed by the device and recommend it.

That's actually pretty nice, only a shame since I still find that 7 days is a short timespan to require manual action for something otherwise nicely automated

There's several Python scripts that can pull the data over Bluetooth.

https://github.com/stijnstijn/pyaranet4

https://github.com/Anrijs/Aranet4-Python

Don’t diabetics monitors do the same thing to make sure you keep paying?

You could also get a CO2 sensor from Adafruit for $50, connect it to an Arduino, Raspberry Pi, or other controller, and roll your own solution. It's a little hacky, but this is HN after all. https://www.adafruit.com/product/5187

I can't speak to the accuracy or quality, but there's plenty of dedicated CO2 monitoring devices on amazon for under $100. A few seem to have good reviews, anyway.

I have a couple (either 2 or three, i can't remember) from amazon that were under $100. Both have built in batteries, and one is designed to be charged and then placed in a greenhouse while you're working in it, another is designed to reference between two "rooms" or whatever.

None of them log to sd card. I'd fully expect a functional solution that does logging with all of the other features to cost more than $100, but if i can be proven wrong, i'd buy one, for sure.

For example, with an SD card we now also need a clock - which ideally would have a different power supply than the sensor suite, otherwise the timestamps will overwrite if the supply is lost, or otherwise be incorrect.

I was going to comment on accuracy, but looks like this one is actually pretty good!

Definitely the same ballpark as ara4. (I mean, building the thing would subtract several hours of time one could spend commenting on HN instead, so choose accordingly :)

It looks like a product design "feature" - they sell a "pro" version that works with their $600 base station to upload data to their cloud service.

If the home device gave unlimited history, then there'd be less incentive to buy the pro version and subscribe to their cloud service.

Shameless plug.

We are maintaining an open source / open hardware indoor air quality project that measures CO2, PM2.5, temperature and humidity [1].

We use the same CO2 Sensor (Senseair S8) as the device in the article and I can confirm that it's very accurate.

[1] https://www.airgradient.com/diy/

In a related, but much more personal note: it turns out that we are breathing, on average, one molecule of Ceasar's last breath [1]. And Jesus, Buddah, and a lot of other people.

[1] https://www.irishtimes.com/news/science-asserts-we-are-all-p...

(I know, it's probably mostly BS -- I'd bet most of the last breath has been absorbed into the ocean, or plants, or whatever. But, over my lifespan, I've probably sucked down atoms of Jesuse's breath during his lifespan. With that, who needs holy relics.)

Lately I hear about more COVID cases that presumably started on an airplane. Therefore I am now wondering how great these ventilation systems on airplanes really are, compared to, say, those in restaurants and theaters.

We don't hear how great the ventilation is in all the lines one has to wait in to get on the plane. If someone got COVID after a flight, it's hard to tell if they got it while the plane was in the air, or while waiting to board in or near the jetway.

The counterintuitive thing is people stand in lineups or sit shoulder-to-shoulder in airport seating with their masks off sipping coffee or eating chips, then get on the plane and put masks on.

It's possible (but not proven) that inverting this would be much safer, since on the airplane the air gets exchanged a lot.

I'm currently dealing with a Covid infection that, given the timing involved, I'm pretty sure I got on an airplane. It could have been at the airport, I suppose, but the guy sitting in the seat next to me sniffling and coughing, and with no mask on gives me a pretty good idea where I got it.

"CO2 level on this @VirginAtlantic A330 indicates that it isn’t really safe to remove your mask shortly after the doors have closed. Hopefully this number will drop soon."

https://twitter.com/alexr/status/1523125114371719168

"Hey @united, it'd be great to see better fresh air circulation in your Austin airport Club. The box in the photo is a CO2 sensor measuring parts per million, and 1117 was pretty high for just a few people in the bar area at the time. Above 1000 cognitive function can be impaired."

https://twitter.com/brianbehlendorf/status/15407875450338181...

Once the plane is in the air? Fantastic! It’s when the plane is on the ground and the main power and filtration is off is where the danger is. On my last few flights I’ve brought a high quality co2 meter and it consistently hit 3000-5000PPM in the time between boarding and when the plane was moving.

What is the best response here, carry an emotional support plant / tree?

N95 mask and goggles....

Airlines never stopped allowing CPAP in flight even though the US Government warned it is extremely dangerous to be around because it aerosolizes and projects virus particles.

Even NPR summarized the risks. https://www.npr.org/sections/health-shots/2020/03/27/8222116...

Airlines, and the regulators, are only worried about optics, not our health.

It sounds gross. But:

i) if we all drove cars, the result would also be bad

ii) I wonder if there are benefits from this (stronger herd immunity)

You might also wonder how this applies to supposed good bacteria, and the transfer if bacteria across people. Much like the gut microbiome, social situations might be essential. After all, people have been gathering in close quarters for a variety of reasons for millenia.

Whilst in wondering mood, think about behaviour modifying organisms who want and alter host social behaviour so that they spread more.

E.g. toxoplasmosis

There's been some research done on whether the flu is an STD making people more...sociable. Perhaps asymptomatic COVID infections encourage people to mingle more? Or maybe other actual STDs do? The existing science is weak, troublesome (it's very hard to research ethically) and few but I love the idea of it.

I cannot remember if it was covid or influenza (h5n1?) where in the initial 3 days after infection it "makes" one feel like they want to be more social - more social energy or something - so that when the contagiousness increases right before the bedridden part more people get infected.

Apologies, since i read a lot of studies and only remember to save a few, and even so i have no way to catalog/tag/review the studies i have read. I just know i read it in the last 2 years so it could have been SARS-NCoV-2 or flu.

Herd immunity through infection has never worked. It's incoherent even as a concept: to prevent infections, get infected?

There are a few diseases better to get as a kid than as an adult, but we mostly have vaccines for those now. And respiratory viruses aren't included in the category of those we need exposure to for immune system development.

>In 2003 Graham Rook proposed the "old friends hypothesis" which has been described as a more rational explanation for the link between microbial exposure and inflammatory disorders.[20] The hypothesis states that the vital microbial exposures are not colds, influenza, measles and other common childhood infections which have evolved relatively recently over the last 10,000 years, but rather the microbes already present during mammalian and human evolution, that could persist in small hunter-gatherer groups as microbiota, tolerated latent infections, or carrier states. He proposed that coevolution with these species has resulted in their gaining a role in immune system development.

https://en.wikipedia.org/wiki/Hygiene_hypothesis

> It's incoherent even as a concept: to prevent infections, get infected?

What's confusing? Get infected once, avoid tens of infections. If your immune system "forgets" the immunity after 6 months (which is the case for COVID), then every 4 months get exposed, you won't get actively sick since you still have some immunity, and you'll keep your immunity high.

Being exposed every 4 months is not quite herd immunity. Herd immunity is essentially: because some 95% of people are immune to smallpox, if there is an outbreak, it will not find any new hosts and would die out. That is very different from "get a booster (or re-infected) every X months to keep immune levels high". In other words, the rapid decay of individual immunity causes for there to be a loss in herd immunity (or herd immunity never achieved at all due to decay in immunity).

From a contra-positive point of view, if there were herd immunity, then you would not be able to get re-infected every 4 months because there would be no carriers of the virus to infect you.

I think the bottom line is that 'herd immunity' is only a concept if immunity is durable and long lasting. Otherwise that herd immunity decays too quickly and you wind up in a cycle where everyone gets infected, the infection levels drops off, that immunity wears off, rinse-wash repeat.

Anecdotally, I was on a train recently and was talking to my neighbors where an elderly woman said casually that the 3rd time being infected she was in the hospital for only 7 days that time. The implication being that this part of the population could land in the hospital repeatedly every 4-6 months. I would wager that someone who is 65 to around 70 years old will survive covid related pneumonia only so many times before they don't. I think this speaks to how Covid is pretty vicious.

And all that is to say that 'natural' herd immunity is not our ticket out of this problem (just based on the math). There may be no good tickets out of this short of everyone vaccinating every 6 months and also reducing transmission rates (eg: early detection and quarantining/masking to avoid infecting others, and reducing your own risk of infection via distancing/masking).

> What's confusing? Get infected once, avoid tens of infections. If your immune system "forgets" the immunity after 6 months (which is the case for COVID), then every 4 months get exposed, you won't get actively sick since you still have some immunity

Another problem with this concept (at least for things like COVID) is that every time the virus is passed on it has a chance to mutate into something your immune system is unprepared for. Maybe you catch it and don't feel sick, or are only briefly/mildly sick, but you can still play host to it long enough for it to mutate and get passed to someone else. The more it moves from host to host the better it gets at surviving and defeating immune systems.

Entire populations passing a virus back and forth at a high rate for long periods of time seems like a disaster waiting to happen.

Is there any other option?

Vaccination would not help because it works exactly the same way.

Vaccination certainly helps for the initial response, so people don't get as sick. But after that natural immunity is superior to vaccination.

But it's not true what you say, a mutated virus can still elicit a partial response. So if people are constantly exposed to the new virus they will never get seriously sick.

> Is there any other option?

Not spreading the virus around would be the ideal. If we got people protected with vaccines and kept community spread low the number of variants wouldn't rise as quickly. Fewer variants would mean vaccines would stay effective longer and we wouldn't be rolling the dice on any new nasty features as often. I don't think we can ever hope to eradicate the virus from the earth now that it's here, but we could do a lot more to keep it from spreading at the kinds of rates it has been.

> Vaccination would not help because it works exactly the same way.

Vaccination doesn't work the same way because you gain the immunity without having the virus. No virus in you, no chance for the virus to mutate or spread and then mutate. You might still get infected by someone else later, but you aren't depending on getting infected to maintain your immune system's preparedness and if community spread is low because people are vaccinating instead of virus swapping your odds of getting the actual virus will be low as well.

> Vaccination certainly helps for the initial response, so people don't get as sick. But after that natural immunity is superior to vaccination.

From the evidence we have right now a combination of vaccine+infection gives the most robust protection, however that still involves getting infected and taking your chances with lasting heart lung and kidney problems. In my book, not having to take my chances with complications or long covid more than makes up for the difference which makes vaccines without infection superior. The odds of ending up with long covid was 1 in 5 in a recent study (https://www.cdc.gov/mmwr/volumes/71/wr/mm7121e1.htm) but different variants will carry different levels of risk. Even if you like your odds today, if you're just passing the virus around incubating new variants all the time who knows what odds you'll end up with later. There's evidence that people who get reinfected with the virus have an increase in their risks for long covid too.

> But it's not true what you say, a mutated virus can still elicit a partial response.

It all depends on what the mutations are. If a virus changes enough it may no longer be recognizable as the virus you were previously infected with. We're somewhat lucky with Covid because its structure makes it less likely to mutate to the point where we don't get some kind of response, but it's already evolved so much that our first vaccines which were 90% effective at preventing infection while at full strength are now only 30-40% effective at preventing infection.

The good news so far is that even the old vaccines are pretty effective against the most severe cases and death, but that too is subject to change. It's already looking like re-exposing your immune system has diminishing returns. That was one concern people had over recommending 4th doses of the original vaccines. The protection from infection people got from shot #4 didn't last nearly as long as it did after getting shot #3. I'm really hoping the new vaccines help with that. Right now people who get covid can get reinfected with the newest strain after just one month!

This reminded me of an undergraduate Physics professor who made us estimate the fraction of molecules in one breath that had been exhaled by Jesus. Fun times.

I remember a question that was similar in nature; suppose you (accidentally of course!) drop a full but opened bottle of vodka in the sea. That night there is a huge storm that mixes all the water in the oceans so that the vodka is distributed perfectly. How many alcohol molecules (from that original bottle, ignoring any existing alcohol, evaporation, and other chemical or biological processes that would interfere with the answer) are in a liter of seawater?

Sadly I do not recall the answer but it was way more than I expected. The Avogadro constant is a lot.

if high CO2 equals more risk of contamination then Japan should be getting large transmissions of COVID in over-saturated trains on a daily basis, but it does not. So this data seems more junk than anything else.

I think you are being hasty. Japan has amazing mask discipline which could account for the differences. Also, like many countries train travel was reduced during the pandemic as more companies began allowing telecommuting and flexible hours.

Second, I found a wealth of articles just by searching: japan train ventilation

Train operators already have good methods in place: https://www.jreast.co.jp/e/customer_support/corona-info/inde...

It looks like the frequent stops are very good at ventilating the trains: https://www.nippon.com/en/news/yjj2020112601115/

But they recognize the the problem: https://eandt.theiet.org/content/articles/2020/07/trains-and...

So I assume you at least have some data on japan trains co2?

What's the CO2 in those trains? Japan tends to have great ventilation and has CO2 meters around the place.

It isn't impossible to ventilate a train well. I've been on a train with CO2 around 600 and another around 3,000. Air system design matters

However, one train in Japan did have very high levels based on a transport ministry study: https://www.asahi.com/ajw/articles/14515055

> It isn't impossible to ventilate a train well.

Not for the trains at rush hour in Tokyo.

huh, all the places I would never go have terrible air.

Lucky you.

Some of us want to catch the bus. Some of us have to

all of it, I hope...

preferably mostly plants

Scientists estimate that 50-80% of the oxygen production on Earth comes from the ocean. So yes, phytoplancton is an MVP. Good thing we won't kill life in the ocean any time soon due to climate change, rather only some of it.

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