9 ms·

Whose breath are you breathing?

110 points by tigerlily 4y ago

ClosedPistachio 4y ago
Any recommendations for a good portable CO2 monitor?
- greyface- 4y ago
  https://aranet.com/products/aranet4/ https://aranet.com/products/aranet4/
  - Aardwolf 4y ago
    > "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
    - phphphphp 4y ago
      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.
      - Aardwolf 4y ago
        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
    - r1ch 4y ago
      There's several Python scripts that can pull the data over Bluetooth. https://github.com/stijnstijn/pyaranet4 https://github.com/stijnstijn/pyaranet4 https://github.com/Anrijs/Aranet4-Python https://github.com/Anrijs/Aranet4-Python
    - moneywoes 4y ago
      Don’t diabetics monitors do the same thing to make sure you keep paying?
    - hugs 4y ago
      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 https://www.adafruit.com/product/5187
      - zdragnar 4y ago
        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.
        genewitch 4y ago
        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.
      - groby_b 4y ago
        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 :)
    - Johnny555 4y ago
      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.
- ahaucnx 4y ago
  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/ https://www.airgradient.com/diy/
deleted 4y ago
[deleted]
cfcf14 4y ago
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.
- moneywoes 4y ago
  Does the AV help?
  - jwilk 4y ago
    What's AV?
    - 4y ago
noja 4y ago
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)
- starkd 4y ago
  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.
  - thinkingemote 4y ago
    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.
    - genewitch 4y ago
      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.
- graeme 4y ago
  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 https://en.wikipedia.org/wiki/Hygiene_hypothesis
rossdavidh 4y ago
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-deliberately-infected-people-coronavirus-here-s-what-happened https://www.science.org/content/article/scientists-deliberat...
- pessimizer 4y ago
  > 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.
  - rossdavidh 4y ago
    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.
ekianjo 4y ago
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.
- SapporoChris 4y ago
  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/index.html 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/ https://www.nippon.com/en/news/yjj2020112601115/ But they recognize the the problem: https://eandt.theiet.org/content/articles/2020/07/trains-and-crowded-areas-need-ventilation-to-prevent-covid19-spread-study-shows/ https://eandt.theiet.org/content/articles/2020/07/trains-and...
- dzhiurgis 4y ago
  So I assume you at least have some data on japan trains co2?
- graeme 4y ago
  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 https://www.asahi.com/ajw/articles/14515055
  - ekianjo 4y ago
    > It isn't impossible to ventilate a train well. Not for the trains at rush hour in Tokyo.
deleted 4y ago
[deleted]
amelius 4y ago
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.
- hugs 4y ago
  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.
  - unsupp0rted 4y ago
    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.
  - technothrasher 4y ago
    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.
- latchkey 4y ago
  "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 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/1540787545033818114 https://twitter.com/brianbehlendorf/status/15407875450338181...
thamer 4y ago
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 https://www.youtube.com/watch?v=1Nh_vxpycEA [1] https://www.nature.com/articles/s41526-019-0071-6 https://www.nature.com/articles/s41526-019-0071-6 [2] https://iopscience.iop.org/article/10.1088/1748-9326/ac1bd8 https://iopscience.iop.org/article/10.1088/1748-9326/ac1bd8
- BruiseLee 4y ago
  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).
  - groby_b 4y ago
    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)
bsedlm 4y ago
all of it, I hope... preferably mostly plants
- a3w 4y ago
  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.
7373737373 4y ago
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 https://en.wikipedia.org/wiki/Haber_process article)
flobosg 4y ago
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.
- Thiez 4y ago
  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.
whoomp12342 4y ago
huh, all the places I would never go have terrible air.
- worik 4y ago
  Lucky you. Some of us want to catch the bus. Some of us have to
webnrrd2k 4y ago
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-part-of-christ-s-body-1.255358 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.)

110 points by tigerlily 4y ago

ClosedPistachio 4y ago

Any recommendations for a good portable CO2 monitor?

greyface- 4y ago
https://aranet.com/products/aranet4/ https://aranet.com/products/aranet4/
- Aardwolf 4y ago
  > "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
  - phphphphp 4y ago
    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.
    - Aardwolf 4y ago
      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
  - r1ch 4y ago
    There's several Python scripts that can pull the data over Bluetooth. https://github.com/stijnstijn/pyaranet4 https://github.com/stijnstijn/pyaranet4 https://github.com/Anrijs/Aranet4-Python https://github.com/Anrijs/Aranet4-Python
  - moneywoes 4y ago
    Don’t diabetics monitors do the same thing to make sure you keep paying?
  - hugs 4y ago
    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 https://www.adafruit.com/product/5187
    - zdragnar 4y ago
      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.
      - genewitch 4y ago
        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.
    - groby_b 4y ago
      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 :)
  - Johnny555 4y ago
    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.
ahaucnx 4y ago
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/ https://www.airgradient.com/diy/

deleted 4y ago

[deleted]

cfcf14 4y ago

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.

moneywoes 4y ago
Does the AV help?
- jwilk 4y ago
  What's AV?
  - 4y ago

noja 4y ago

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)

starkd 4y ago
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.
- thinkingemote 4y ago
  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.
  - genewitch 4y ago
    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.
graeme 4y ago
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 https://en.wikipedia.org/wiki/Hygiene_hypothesis

rossdavidh 4y ago

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-deliberately-infected-people-coronavirus-here-s-what-happened https://www.science.org/content/article/scientists-deliberat...

pessimizer 4y ago
> 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.
- rossdavidh 4y ago
  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.

ekianjo 4y ago

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.

SapporoChris 4y ago
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/index.html 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/ https://www.nippon.com/en/news/yjj2020112601115/ But they recognize the the problem: https://eandt.theiet.org/content/articles/2020/07/trains-and-crowded-areas-need-ventilation-to-prevent-covid19-spread-study-shows/ https://eandt.theiet.org/content/articles/2020/07/trains-and...
dzhiurgis 4y ago
So I assume you at least have some data on japan trains co2?
graeme 4y ago
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 https://www.asahi.com/ajw/articles/14515055
- ekianjo 4y ago
  > It isn't impossible to ventilate a train well. Not for the trains at rush hour in Tokyo.

deleted 4y ago

[deleted]

amelius 4y ago

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.

hugs 4y ago
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.
- unsupp0rted 4y ago
  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.
- technothrasher 4y ago
  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.
latchkey 4y ago
"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 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/1540787545033818114 https://twitter.com/brianbehlendorf/status/15407875450338181...

thamer 4y ago

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 https://www.youtube.com/watch?v=1Nh_vxpycEA [1] https://www.nature.com/articles/s41526-019-0071-6 https://www.nature.com/articles/s41526-019-0071-6 [2] https://iopscience.iop.org/article/10.1088/1748-9326/ac1bd8 https://iopscience.iop.org/article/10.1088/1748-9326/ac1bd8

BruiseLee 4y ago
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).
- groby_b 4y ago
  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)

bsedlm 4y ago

all of it, I hope... preferably mostly plants

a3w 4y ago
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.

7373737373 4y ago

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 https://en.wikipedia.org/wiki/Haber_process article)

flobosg 4y ago

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.

Thiez 4y ago
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.

whoomp12342 4y ago

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

worik 4y ago
Lucky you. Some of us want to catch the bus. Some of us have to

webnrrd2k 4y ago

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-part-of-christ-s-body-1.255358 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.)