14 ms·

Indoor CO2 may reach levels harmful to cognition by the end of this century

119 points by beefield 6y ago

MichaelZuo 6y ago
My recommendation is to get an indoor CO2 monitor for your bedroom that can alarm whenever levels go above 1000 ppm. From what I understand high end office are being equipped with such systems with direct control of the ventilation systems for exactly this reason. For home use a mid-range unit is sufficiently accurate, precise, and reliable. I use the Extech CO200 personally. Don’t but a cheap unit because those have calibration drift after a few months. And recalibration is not trivial.
- smichel17 6y ago
  To set the frame of reference for the parent's "not cheap" recommendation, the model they use seems to retail for $300-$400, based on a quick search.
- beefield 6y ago
  I did some quick search end the very cheapest sensors seem to calculate something called eCO2. Like e.g. https://www.adafruit.com/product/3566 https://www.adafruit.com/product/3566 What I was not able quickly to figure out is: - What this eCO2 actually is? - What is the real world accuracy I can expect from this kind of sensor, with and without calibration? - is it enough for calibration just to go outside and assume some number between 400 and 500 (assuming outside means not just next to industrial chimney)? If not, what would be better calibration process?
  - gsich 6y ago
    Why not use a real one? MH-Z19 or Z14.
    - beefield 6y ago
      because my google-fu was not good enough to find those.... Regardless, I would be curious on the same questions about real world accuracy on those as well.
      - acidburnNSA 6y ago
        I have two of them, one inside and one outside. They both go down to roughly 400 ppm and the indoor one goes very high when it's all cooped up inside. The outdoor one fluctuates since I'm in an urban area. I believe they are accurate to within about 10%. During the smoke event, they combined with my indoor/outdoor pm2.5 sensors have been extremely useful.
        throwaway3neu94 6y ago
        They should go down to 400ppm because the periodic autocalibration which is on by default assumes the lowest level seen in 24 hours is 400ppm.
    - throwaway3neu94 6y ago
      You should be using the newer version, MH-Z19B, not MH-Z19. The protocol is compatible though. Also note they come in up-to-3000ppm and up-to-5000ppm variants. Be sure to get the latter. In case it helps anyone: a very fast way to get it working and get graphs is to connect it to a Raspberry Pi running HomeAssistant. Takes a few clicks and 3 lines of config.
      - cosmic_shame 6y ago
        For portability, you can also hook up to an ESP8266/ESP32 and configure to talk to HomeAssistant via ESPhome: https://esphome.io/components/sensor/mhz19.html https://esphome.io/components/sensor/mhz19.html
  - amdolan 6y ago
    I found this on what eCO2 is: https://ec.europa.eu/eurostat/statistics-explained/index.php/Glossary:Carbon_dioxide_equivalent https://ec.europa.eu/eurostat/statistics-explained/index.php... Re your other questions; yeah I gather there is some experimentation involved, even with out of the box commercial products. If others have suggestions on chips or products to buy for the household, I would greatly appreciate it! The MH-Z19 looks like an option for me. Commercial products seem too unreliable for the price.
    - beefield 6y ago
      I think that is CO2e, which should be a different thing to my understanding. (CO2e is used to estimate the greenhouse gas potency of other gases like methane. Whereas I think eCO2 is some kind of estimate of amount of CO2 in the air, but what, exactly, I do not know)
      - regen 6y ago
        Mine from Amazon is accurate enough to remind me of opening the window
  - raverbashing 6y ago
    > it will return a Total Volatile Organic Compound (TVOC) reading and an equivalent carbon dioxide reading (eCO2) over I2C. It's an estimated reading of CO2, so it's not a direct reading, the sensor has to do some math to estimate the CO2 It's not very precise and/or dependent on temperature, etc
  - formerly_proven 6y ago
    I'm using an NDIR-based USB-CO2-meter (~40 €, allegedly USB only for power, but it actually spits out measurement data over USB) and I think it's pretty accurate. When I put it outside it generally reflects ambient CO2 pretty accurately (440-450 ppm) and I found through blind-testing that "air staleness" correlates very well with CO2 concentration. For me, air feels noticeably stale at around ~700-800 ppm, which seems largely inline with academic results. You can actually see when the device acquires a reading, because the tube flashes.
- gsich 6y ago
  Even your unit has a trivial calibration. But in most cases you only need relative not absolute accuracy.
  - MichaelZuo 6y ago
    Yes, that’s the limitation of current technology. thankfully it’s doable with only a few minutes of attention and no tools or specialized requirements. 1000 ppm is an absolute limit, the vast majority of the population will experience measurable effects above this threshold. And it’s surprising how often that’s exceeded in normal everyday environments.
- kwhitefoot 6y ago
  Would it be sufficient to just sleep with the bedroom window open? If so how large an opening would be needed?
  - regen 6y ago
    A few cm are enough
    - MichaelZuo 6y ago
      Yes, modern buildings are really well sealed compared to before. A few cm is an enormous gap, relatively speaking.
    - throwaway3neu94 6y ago
      I agree, I've measured this as well. Window in adjacent room (with open door between rooms), window opened 5-10cm, CO2 level stays pretty much down. I've also found that when all windows are closed, an air purifier seems to help (or a fan, lowest level is fine). Obviously it doesn't remove the CO2, but it seems to prevent buildup in the one corner where you are (bed, desk). I'm sceptical it's a problem but the data shows it is.
  - martinpw 6y ago
    Even keeping the bedroom door open helps. I did some tests with a CO2 meter - with the door closed it reached 1100ppm after a nights sleep. With the door cracked open it was around 700ppm. One thing is that air diffuses out fairly effectively even with the door closed, presumably through gaps in the door frame. Quick calculation (welcome any corrections, numbers pulled from quick online searches): Resting breathing rate is ~6 liters/minute. Sleep ~8 hours = ~500 minutes = 3000 liters exhaled. CO2 exhaled is 5% concentration, so 150 liters of CO2 Room = 30 m^3 = 30000 liters Expected additional CO2 concentration in morning in perfectly sealed room = 150 / 30000 = 0.5% = 5000ppm Actual additional CO2 = 700ppm (1100 reading - baseline 400ppm)
- LargoLasskhyfv 6y ago
  I think this wasn't about compromised air quality indoors. Rather general level of CO2 in the atmosphere. What help are ventilation systems then? You'd need to have submarine scrubbers in place to do something about it, and/or cans of liquid oxygen.
  - beefield 6y ago
    I think their point was that increasing CO2 in atmosphere makes it more difficult to keep indoor levels acceptable. First, if you start from 600pm instead of 300, you reach 1000 ppm faster. Adding to the insult, it is much more difficult to ventilate the excess CO2 away, if the air you use to ventilate contains in itself already 600ppm instead of 300ppm.
    - LargoLasskhyfv 6y ago
      Couldn't have said it better!
  - tgsovlerkhgsel 6y ago
    Indoor air usually has significantly elevated CO2 levels compared to outdoor air. More ventilation cannot push the levels below the levels of outdoor air, but it can get them close. Their argument that assuming today's already inadequate ventilation systems don't change, more outdoor CO2 = more indoor CO2, pushing it above some arbitrary threshold (which is far above predicted outdoor CO2 levels).
- dotancohen 6y ago
  Can you recommend an affordable device? $100 for the Extech CO200 is just too expensive to suggest to people who have just a passing interest.
- OpticalWindows 6y ago
  I do think we should think about passing out personal CO2 alarms now and in the future. The problem would be calibration like you said and cost for a new unit.
brer 6y ago
wear your mask!!
rkwasny 6y ago
Just get one of this: https://www.amazon.co.uk/gp/product/B01DY30PG8/ https://www.amazon.co.uk/gp/product/B01DY30PG8/
- LargoLasskhyfv 6y ago
  So. What are you going to do when it shows you levels of CO2 too high? Opening a can of Perry Air, search for https://duckduckgo.com/?q=air+quality+improvement+with+plants https://duckduckgo.com/?q=air+quality+improvement+with+plant... , or what? Using it as an indicator of when to finally move elsewhere?
  - rkwasny 6y ago
    Right now? Open the window :)
    - LargoLasskhyfv 6y ago
      How is that helping when the outdoor CO2-levels are elevated too much? (Unter Schmutzatmosphäre verkackt! https://en.wikipedia.org/wiki/Packaging_gas https://en.wikipedia.org/wiki/Packaging_gas)
      - regen 6y ago
        It still takes time for outdoor normal co2 level to reach those levels. We gain 2 co2 per year. And you can have an indoor garden
  - gclawes 6y ago
    Invent a way to put a square peg in a round hole, rapidly.
  - sandworm101 6y ago
    Plants + grow lamps. Get something easy to grow quickly indoors, say some random type of weed, and start letting it absorbing co2.
awb 6y ago
A good deal is spent explaining rising CO2 levels in the atmosphere and the effects of CO2 on cognition, but it wasn't immediately obvious to me how indoor CO2 levels would be rising. Towards the end, here is their explanation: > in steady state, indoor CO2 concentration is always at least as high as the outdoor concentration (as neither generation nor ventilation rate can be negative) and simply scales with the ratio of generation to ventilation. For reasonable values of G and Q for elementary school students (0.004 L/s per student) and classrooms (10 L/s per student), respectively, a ratio G/Q equates to 400 ppm (Persily, 2018; Persily & de Jonge, 2017). Under such assumptions, then, an outdoor CO2 concentration of 477 ppm (411 ppm as in 2019, plus a 66‐ppm urban enhancement) would equate to 877 ppm inside the classroom upon reaching equilibrium. The equation and explanation can be found about 60% of the way down.
- formerly_proven 6y ago
  Most classrooms (at least here) aren't well-ventilated (windows are generally kept closed because of "draft" or alternatively "we aren't heating for the air force!", and buildings generally don't have AC/air exchange), CO2 levels are often far beyond 1000 ppm in classrooms anyway, which is obviously not good (there may be debate if going from 450 ppm to 600 pm leads to worse outcomes, but it's pretty obvious that nausea-inducing levels of CO2 and air so stale it feels like breathing water most definitely lead to worse outcomes).
  - wiz21c 6y ago
    If climate becomes warmer, then we'll open the windows more often :-)
    - klipt 6y ago
      Not if you're running AC.
      - grishka 6y ago
        I'm from a place where you only need AC one week per year so naturally no one has it except in cars, but I've heard that decent systems, especially central ones, don't recirculate the same air over and over again but take it from the outside.
ThomPete 6y ago
Correct me if I'm wrong but that graph they show compares averaged numbers over hundreds of years or even thousands of years, with year over year numbers once we started measuring this regularly the last +100 years. This seems just straight out disingenuous to say the least unless I am missing something or is this kind of misrepresentation the new standard for research papers today?
- petermcneeley 6y ago
  Perhaps but that graph has little to do with their argument. Their argument is simple. If CO2 levels go up its going to make indoor CO2 levels worse. At some point this causes cognitive impairment.
  - ThomPete 6y ago
    It actually has a lot given that they are saying IF CO2 levels goes up to a certain level at the end of the century. They are using that graph as one of the reasons for why it's likely to go up. This is their conclusion "We conclude that indoor CO2 levels may indeed reach levels harmful to cognition by the end of this century, and the best way to prevent this hidden consequence of climate change is to reduce fossil fuel emissions. Finally, we offer recommendations for a broad, interdisciplinary approach to improving such understanding and prediction." That's a big if especially since one of the reasons they believe it might increase to those levels is exactly this mix of averaged measurements and year over year. Keep in mind the IPCC models range for nothing to worry about to the world is going under. With regards to the CO2 levels having an impact on our cognitive abilities at the end of the century thats also a lot of speculation and a lot of assumptions. This is not science this is speculation. Interesting but so filled with assumptions and guesses and speculation about what might happen in 2100. And if that wasn't enough they just straight out claim the have the solution which is hindering fossil fuel. This is just activism put into research format from what I can see.
    - adrianN 6y ago
      You're confusing the effects of CO2 on climate (which you might argue are not too bad if you enjoy playing russian roulette), with the concentration of CO2, which we can measure extremely accurately and for whose increase the mechanism is very well understood: We burn carbon, it ends up in the atmosphere as CO2, increasing the concentration there for a long time. We also understand the impact of CO2 on cognition very well, because we can simply run experiments.
mrfusion 6y ago
I’m definitely on team climate change but this just feels alarmist to me.
- recursive 6y ago
  I don't think teams and feelings are useful tools for addressing physical problems.
- tpmx 6y ago
  Yeah, what happened to being solution-oriented? It's odd how on HN you're not supposed to be negative of anything technical even if it's flaming crap, but also at the same time you're also supposed be assuming certain doom when it comes to climate change. How about we try to solve the technical problem at hand?
  - adrianN 6y ago
    I don't understand what you're trying to say. The paper just observes that outdoor and indoor CO2 concentrations are related, and that high CO2 impacts cognition. Therefore increasing CO2 in the atmosphere has an impact on indoor cognition. What is the problem with that? Why is it "flaming crap"?
    - tpmx 6y ago
      > Why is it "flaming crap"? You 100% misread my post. I did not claim the article was "flaming crap". Please re-read it, this time reading every word.
      - adrianN 6y ago
        I'm sorry, English is not my first language. I did in fact read every word in your post, but still don't understand it. Can you maybe rephrase it? I am pretty sure that this discussion here is not about climate change, but about the effects of higher CO2 concentrations in the atmosphere, on CO2 concentrations indoors.
salex89 6y ago
So, we're burning fossil fuels, increasing CO2 output, don't have an idea which will reliably improve the situation and are getting stupider by the day, decreasing our chance to ever getting one. Yay...
- adrianN 6y ago
  We in fact have multiple ideas how to improve the situation. The problem is not a lack of ideas, or deployable technology, the problem is a lack of political will to implement the necessary measures.
- cbmuser 6y ago
  We do. It’s called nuclear power and it‘s fought by those who claim they are fighting for the environment. > https://www.giss.nasa.gov/research/briefs/kharecha_02/ https://www.giss.nasa.gov/research/briefs/kharecha_02/
  - hhjinks 6y ago
    Honest and good faith question here: assuming all electricity on the grid was nuclear, how much CO2 emission would remain? You can't just swap massive cargo ships to nuclear overnight. Would "just" making the power grid green be enough?
    - whatisthiseven 6y ago
      No, power generation is about a quarter: https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emis... Transportation could push that total to 50% if all ICE cars were converted or destroyed and only electric vehicles were used (ignoring ships and trains). "Industry" includes CO2 waste byproducts which are much harder to reduce as many processes may struggle to eliminate that byproduct. Instead capture and sequestration would be needed. This is another 25% The rest are small, but since we need virtually all CO2 emissions to be zero, we are left with nearly another 25% that isn't tied to electric production and is difficult to replace. So, 50% of all CO2 isn't power generation related.
GuB-42 6y ago
Their conclusion is that we should emit less CO2. Certainly a good idea, but their data clearly point to better ventilation. Better ventilation is something we can do right now, that will improve things immediately and 100 years from now. Maybe the best thing would be the mandatory installation of powerful ventilation systems with heat exchangers for new buildings, and incentives to upgrade existing installations. That would help with both problems: getting more fresh air and limiting energy expenditures which can, in turn, reduce CO2 emissions.
- fyfy18 6y ago
  > mandatory installation of powerful ventilation systems In my country that's already been a thing for the last few years. The HRV system is around €1000, so it isn't a major cost for the benefits you get. From this year all newly installed units need to be 90% efficient. Also "powerful" is probably not needed, the system I have at the lowest speed changes the air in my entire apartment every 3 hours, and is basically the same noise level as a barely audible computer fan.
  - zdragnar 6y ago
    The difference in scale between your apartment and most schools is no trivial matter. At my high school, our one building, with tall ceilings, large cafeteria and so forth, housed around 1300 people every day. Some are smaller, some much bigger. Moving all of that air at least once a day would require powerful exchangers indeed. If nothing else, it would probably be cheaper and better for students to have plants everywhere. One of my teachers' classrooms was like a tiny jungle. I can't say that it made a significant difference, but it was pleasant at least.
    - baskire 6y ago
      Plants sadly don’t make a significant impact to indoor co2. I see a future indoor co2 sequestration device being incredibly popular
      - 6y ago
hyperpape 6y ago
Gwern raised some cautions about the studies indicating that these moderate levels of CO2 have cognitive impacts. I haven’t read enough to have an opinion, but any HN readers interested in this should probably follow up on the studies he references: https://news.ycombinator.com/item?id=21569947 https://news.ycombinator.com/item?id=21569947.
dreamcompiler 6y ago
Yes, better ventilation is part of the solution. But the authors point out that in many urban areas a "dome" of increased CO2 hangs over the city. Ventilation won't solve that problem. Only reducing fossil fuel burning will.
kev009 6y ago
Has anyone experimented with supplemental oxygen for cognitive benefit?
- frank2 6y ago
  Increasing O2 has physiological effects different from the effects of decreasing CO2. It is not just the ratio or difference between the concentrations that matter. For example, a major effect of increasing CO2 is to make the blood more acidic (or to put more stress on the homeostatic mechanisms that maintain a target pH), and my guess is that no amount of increasing O2 will cancel that out.
  - matheusmoreira 6y ago
    > a major effect of increasing CO2 is to make the blood more acidic (or to put more stress on the homeostatic mechanisms that maintain a target pH), and my guess is that no amount of increasing O2 will cancel that out True. More details on this mechanism: The body uses buffer systems in order to minimize blood pH changes. For example, the bicarbonate buffer system which is catalazyed by carbonic anhydrase. CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃- + H+ It is converted back to carbon dioxide in the lungs and exhaled. The rate at which this process occurs is mainly influenced by respiratory rate. Oxygen doesn't directly influence it. O₂ enables aerobic cellular respiration, the process which produces carbon dioxide. The hydrogen ions are buffered by proteins such as hemoglobin. They are also excreted by the kidneys. https://en.wikipedia.org/wiki/Buffer_solution https://en.wikipedia.org/wiki/Buffer_solution https://en.wikipedia.org/wiki/Bicarbonate_buffer_system https://en.wikipedia.org/wiki/Bicarbonate_buffer_system https://en.wikipedia.org/wiki/Acid%E2%80%93base_homeostasis https://en.wikipedia.org/wiki/Acid%E2%80%93base_homeostasis https://opentextbc.ca/anatomyandphysiology/chapter/26-4-acid-base-balance/ https://opentextbc.ca/anatomyandphysiology/chapter/26-4-acid...
- matheusmoreira 6y ago
  I don't think anyone's studied it for every day cognitive benefit but oxygen supplementation is common in medicine. Note that increasing oxygen concentration is not the same as decreasing carbon dioxide concentration. https://en.wikipedia.org/wiki/Oxygen_therapy https://en.wikipedia.org/wiki/Oxygen_therapy https://en.wikipedia.org/wiki/Hypercapnia https://en.wikipedia.org/wiki/Hypercapnia https://en.wikipedia.org/wiki/Arterial_blood_gas_test https://en.wikipedia.org/wiki/Arterial_blood_gas_test Obese people can also experience cognitive symptoms due to hypoventilation. https://en.wikipedia.org/wiki/Obesity_hypoventilation_syndrome https://en.wikipedia.org/wiki/Obesity_hypoventilation_syndro... I suppose this could be considered analogous to breathing in air with high carbon dioxide concentrations.
bjoli 6y ago
Not just indoor. Just google what a 400ppm increase does and look at projections. The IPCC predicts that major cities might reach 1000ppm outdoors.
- trhway 6y ago
  Looks like in a few decades the AC units will be coming with CO2 scrubbers standard. Just a one more way the global warming is going to tax our economy/society.
  - calcifer 6y ago
    Wouldn't home CO2 scrubbers need fairly frequent filter replacement? I can easily imagine units being sold with a subscription, e.g $14.99/month and you get a new filter every month.
derefr 6y ago
Is there any practical way to have less indoor CO2 than outdoor CO2, without needing to buy expensive single-use scrubber chemicals? Maybe presuming you live somewhere with cheap electricity and/or a cheap fresh water supply? Basically I’m asking whether there’s a Maxwell’s Daemon-like device for separating the CO2 from the air, and venting the CO2 back outside, while bringing in the rest of the air. Like a CO2 scrubber, but without any need for CO2 sequestration, since you exist inside an open system instead of in a space station/bunker/submarine.
- beefield 6y ago
  There are these things called plants that do that kind of stuff, so maybe if you have enough of them inside your house, they eat the CO2 away... :)
  - derefr 6y ago
    I don’t think there’s any practical level of plant-having that would result in there being less CO2 in the house than in the atmosphere. IIRC, there’s some point in running an indoor grow-ops where you start needing to worry about spraying CO2-enriched air on the plants; but that’s just to accelerate growth, like a fertilizer. Or, sometimes, it’s because OPSEC requires you to not vent your smelly waste air — and because no human or animal lives in the grow-op house to convert O2 to CO2, the air becomes gradually CO2-poor. But that wouldn’t happen if even one human lived there; humans convert metabolize a lot faster than plants do.
  - quaa55 6y ago
    came here for this.
- w1 6y ago
  I don't think this exists on a small scale yet. On industrial scales, CO2 is commonly removed with reusable scrubber chemicals, referred to as a group as amines. The amine acts as a CO2 solvent, removing the CO2 from the bulk gas. The 'rich' amine is then cycled to a separate location in the process where it is heated up, causing the CO2 to bubble out of solution, regenerating the amine for reuse, etc. I don't see any reason in principal why this can't be miniaturized, but it would be a challenging engineering problem. https://en.wikipedia.org/wiki/Amine_gas_treating https://en.wikipedia.org/wiki/Amine_gas_treating
jug 6y ago
This is already a problem in classrooms etc, and shows itself by tiredness and headaches. As I understand it, this will only push harder towards better ventilation.
offsky 6y ago
A regenerative CO2 scrubber that people could install inline with existing whole house AC systems would be a big success. I would buy it in a heartbeat.

119 points by beefield 6y ago

My recommendation is to get an indoor CO2 monitor for your bedroom that can alarm whenever levels go above 1000 ppm. From what I understand high end office are being equipped with such systems with direct control of the ventilation systems for exactly this reason. For home use a mid-range unit is sufficiently accurate, precise, and reliable. I use the Extech CO200 personally. Don’t but a cheap unit because those have calibration drift after a few months. And recalibration is not trivial.

smichel17 6y ago
To set the frame of reference for the parent's "not cheap" recommendation, the model they use seems to retail for $300-$400, based on a quick search.
beefield 6y ago
I did some quick search end the very cheapest sensors seem to calculate something called eCO2. Like e.g. https://www.adafruit.com/product/3566 https://www.adafruit.com/product/3566 What I was not able quickly to figure out is: - What this eCO2 actually is? - What is the real world accuracy I can expect from this kind of sensor, with and without calibration? - is it enough for calibration just to go outside and assume some number between 400 and 500 (assuming outside means not just next to industrial chimney)? If not, what would be better calibration process?
- gsich 6y ago
  Why not use a real one? MH-Z19 or Z14.
  - beefield 6y ago
    because my google-fu was not good enough to find those.... Regardless, I would be curious on the same questions about real world accuracy on those as well.
    - acidburnNSA 6y ago
      I have two of them, one inside and one outside. They both go down to roughly 400 ppm and the indoor one goes very high when it's all cooped up inside. The outdoor one fluctuates since I'm in an urban area. I believe they are accurate to within about 10%. During the smoke event, they combined with my indoor/outdoor pm2.5 sensors have been extremely useful.
      - throwaway3neu94 6y ago
        They should go down to 400ppm because the periodic autocalibration which is on by default assumes the lowest level seen in 24 hours is 400ppm.
  - throwaway3neu94 6y ago
    You should be using the newer version, MH-Z19B, not MH-Z19. The protocol is compatible though. Also note they come in up-to-3000ppm and up-to-5000ppm variants. Be sure to get the latter. In case it helps anyone: a very fast way to get it working and get graphs is to connect it to a Raspberry Pi running HomeAssistant. Takes a few clicks and 3 lines of config.
    - cosmic_shame 6y ago
      For portability, you can also hook up to an ESP8266/ESP32 and configure to talk to HomeAssistant via ESPhome: https://esphome.io/components/sensor/mhz19.html https://esphome.io/components/sensor/mhz19.html
- amdolan 6y ago
  I found this on what eCO2 is: https://ec.europa.eu/eurostat/statistics-explained/index.php/Glossary:Carbon_dioxide_equivalent https://ec.europa.eu/eurostat/statistics-explained/index.php... Re your other questions; yeah I gather there is some experimentation involved, even with out of the box commercial products. If others have suggestions on chips or products to buy for the household, I would greatly appreciate it! The MH-Z19 looks like an option for me. Commercial products seem too unreliable for the price.
  - beefield 6y ago
    I think that is CO2e, which should be a different thing to my understanding. (CO2e is used to estimate the greenhouse gas potency of other gases like methane. Whereas I think eCO2 is some kind of estimate of amount of CO2 in the air, but what, exactly, I do not know)
    - regen 6y ago
      Mine from Amazon is accurate enough to remind me of opening the window
- raverbashing 6y ago
  > it will return a Total Volatile Organic Compound (TVOC) reading and an equivalent carbon dioxide reading (eCO2) over I2C. It's an estimated reading of CO2, so it's not a direct reading, the sensor has to do some math to estimate the CO2 It's not very precise and/or dependent on temperature, etc
- formerly_proven 6y ago
  I'm using an NDIR-based USB-CO2-meter (~40 €, allegedly USB only for power, but it actually spits out measurement data over USB) and I think it's pretty accurate. When I put it outside it generally reflects ambient CO2 pretty accurately (440-450 ppm) and I found through blind-testing that "air staleness" correlates very well with CO2 concentration. For me, air feels noticeably stale at around ~700-800 ppm, which seems largely inline with academic results. You can actually see when the device acquires a reading, because the tube flashes.
gsich 6y ago
Even your unit has a trivial calibration. But in most cases you only need relative not absolute accuracy.
- MichaelZuo 6y ago
  Yes, that’s the limitation of current technology. thankfully it’s doable with only a few minutes of attention and no tools or specialized requirements. 1000 ppm is an absolute limit, the vast majority of the population will experience measurable effects above this threshold. And it’s surprising how often that’s exceeded in normal everyday environments.
kwhitefoot 6y ago
Would it be sufficient to just sleep with the bedroom window open? If so how large an opening would be needed?
- regen 6y ago
  A few cm are enough
  - MichaelZuo 6y ago
    Yes, modern buildings are really well sealed compared to before. A few cm is an enormous gap, relatively speaking.
  - throwaway3neu94 6y ago
    I agree, I've measured this as well. Window in adjacent room (with open door between rooms), window opened 5-10cm, CO2 level stays pretty much down. I've also found that when all windows are closed, an air purifier seems to help (or a fan, lowest level is fine). Obviously it doesn't remove the CO2, but it seems to prevent buildup in the one corner where you are (bed, desk). I'm sceptical it's a problem but the data shows it is.
- martinpw 6y ago
  Even keeping the bedroom door open helps. I did some tests with a CO2 meter - with the door closed it reached 1100ppm after a nights sleep. With the door cracked open it was around 700ppm. One thing is that air diffuses out fairly effectively even with the door closed, presumably through gaps in the door frame. Quick calculation (welcome any corrections, numbers pulled from quick online searches): Resting breathing rate is ~6 liters/minute. Sleep ~8 hours = ~500 minutes = 3000 liters exhaled. CO2 exhaled is 5% concentration, so 150 liters of CO2 Room = 30 m^3 = 30000 liters Expected additional CO2 concentration in morning in perfectly sealed room = 150 / 30000 = 0.5% = 5000ppm Actual additional CO2 = 700ppm (1100 reading - baseline 400ppm)
LargoLasskhyfv 6y ago
I think this wasn't about compromised air quality indoors. Rather general level of CO2 in the atmosphere. What help are ventilation systems then? You'd need to have submarine scrubbers in place to do something about it, and/or cans of liquid oxygen.
- beefield 6y ago
  I think their point was that increasing CO2 in atmosphere makes it more difficult to keep indoor levels acceptable. First, if you start from 600pm instead of 300, you reach 1000 ppm faster. Adding to the insult, it is much more difficult to ventilate the excess CO2 away, if the air you use to ventilate contains in itself already 600ppm instead of 300ppm.
  - LargoLasskhyfv 6y ago
    Couldn't have said it better!
- tgsovlerkhgsel 6y ago
  Indoor air usually has significantly elevated CO2 levels compared to outdoor air. More ventilation cannot push the levels below the levels of outdoor air, but it can get them close. Their argument that assuming today's already inadequate ventilation systems don't change, more outdoor CO2 = more indoor CO2, pushing it above some arbitrary threshold (which is far above predicted outdoor CO2 levels).
dotancohen 6y ago
Can you recommend an affordable device? $100 for the Extech CO200 is just too expensive to suggest to people who have just a passing interest.
OpticalWindows 6y ago
I do think we should think about passing out personal CO2 alarms now and in the future. The problem would be calibration like you said and cost for a new unit.

brer 6y ago

wear your mask!!

rkwasny 6y ago

Just get one of this: https://www.amazon.co.uk/gp/product/B01DY30PG8/ https://www.amazon.co.uk/gp/product/B01DY30PG8/

LargoLasskhyfv 6y ago
So. What are you going to do when it shows you levels of CO2 too high? Opening a can of Perry Air, search for https://duckduckgo.com/?q=air+quality+improvement+with+plants https://duckduckgo.com/?q=air+quality+improvement+with+plant... , or what? Using it as an indicator of when to finally move elsewhere?
- rkwasny 6y ago
  Right now? Open the window :)
  - LargoLasskhyfv 6y ago
    How is that helping when the outdoor CO2-levels are elevated too much? (Unter Schmutzatmosphäre verkackt! https://en.wikipedia.org/wiki/Packaging_gas https://en.wikipedia.org/wiki/Packaging_gas)
    - regen 6y ago
      It still takes time for outdoor normal co2 level to reach those levels. We gain 2 co2 per year. And you can have an indoor garden
- gclawes 6y ago
  Invent a way to put a square peg in a round hole, rapidly.
- sandworm101 6y ago
  Plants + grow lamps. Get something easy to grow quickly indoors, say some random type of weed, and start letting it absorbing co2.

awb 6y ago

A good deal is spent explaining rising CO2 levels in the atmosphere and the effects of CO2 on cognition, but it wasn't immediately obvious to me how indoor CO2 levels would be rising. Towards the end, here is their explanation: > in steady state, indoor CO2 concentration is always at least as high as the outdoor concentration (as neither generation nor ventilation rate can be negative) and simply scales with the ratio of generation to ventilation. For reasonable values of G and Q for elementary school students (0.004 L/s per student) and classrooms (10 L/s per student), respectively, a ratio G/Q equates to 400 ppm (Persily, 2018; Persily & de Jonge, 2017). Under such assumptions, then, an outdoor CO2 concentration of 477 ppm (411 ppm as in 2019, plus a 66‐ppm urban enhancement) would equate to 877 ppm inside the classroom upon reaching equilibrium. The equation and explanation can be found about 60% of the way down.

formerly_proven 6y ago
Most classrooms (at least here) aren't well-ventilated (windows are generally kept closed because of "draft" or alternatively "we aren't heating for the air force!", and buildings generally don't have AC/air exchange), CO2 levels are often far beyond 1000 ppm in classrooms anyway, which is obviously not good (there may be debate if going from 450 ppm to 600 pm leads to worse outcomes, but it's pretty obvious that nausea-inducing levels of CO2 and air so stale it feels like breathing water most definitely lead to worse outcomes).
- wiz21c 6y ago
  If climate becomes warmer, then we'll open the windows more often :-)
  - klipt 6y ago
    Not if you're running AC.
    - grishka 6y ago
      I'm from a place where you only need AC one week per year so naturally no one has it except in cars, but I've heard that decent systems, especially central ones, don't recirculate the same air over and over again but take it from the outside.

ThomPete 6y ago

Correct me if I'm wrong but that graph they show compares averaged numbers over hundreds of years or even thousands of years, with year over year numbers once we started measuring this regularly the last +100 years. This seems just straight out disingenuous to say the least unless I am missing something or is this kind of misrepresentation the new standard for research papers today?

petermcneeley 6y ago
Perhaps but that graph has little to do with their argument. Their argument is simple. If CO2 levels go up its going to make indoor CO2 levels worse. At some point this causes cognitive impairment.
- ThomPete 6y ago
  It actually has a lot given that they are saying IF CO2 levels goes up to a certain level at the end of the century. They are using that graph as one of the reasons for why it's likely to go up. This is their conclusion "We conclude that indoor CO2 levels may indeed reach levels harmful to cognition by the end of this century, and the best way to prevent this hidden consequence of climate change is to reduce fossil fuel emissions. Finally, we offer recommendations for a broad, interdisciplinary approach to improving such understanding and prediction." That's a big if especially since one of the reasons they believe it might increase to those levels is exactly this mix of averaged measurements and year over year. Keep in mind the IPCC models range for nothing to worry about to the world is going under. With regards to the CO2 levels having an impact on our cognitive abilities at the end of the century thats also a lot of speculation and a lot of assumptions. This is not science this is speculation. Interesting but so filled with assumptions and guesses and speculation about what might happen in 2100. And if that wasn't enough they just straight out claim the have the solution which is hindering fossil fuel. This is just activism put into research format from what I can see.
  - adrianN 6y ago
    You're confusing the effects of CO2 on climate (which you might argue are not too bad if you enjoy playing russian roulette), with the concentration of CO2, which we can measure extremely accurately and for whose increase the mechanism is very well understood: We burn carbon, it ends up in the atmosphere as CO2, increasing the concentration there for a long time. We also understand the impact of CO2 on cognition very well, because we can simply run experiments.

mrfusion 6y ago

I’m definitely on team climate change but this just feels alarmist to me.

recursive 6y ago
I don't think teams and feelings are useful tools for addressing physical problems.
tpmx 6y ago
Yeah, what happened to being solution-oriented? It's odd how on HN you're not supposed to be negative of anything technical even if it's flaming crap, but also at the same time you're also supposed be assuming certain doom when it comes to climate change. How about we try to solve the technical problem at hand?
- adrianN 6y ago
  I don't understand what you're trying to say. The paper just observes that outdoor and indoor CO2 concentrations are related, and that high CO2 impacts cognition. Therefore increasing CO2 in the atmosphere has an impact on indoor cognition. What is the problem with that? Why is it "flaming crap"?
  - tpmx 6y ago
    > Why is it "flaming crap"? You 100% misread my post. I did not claim the article was "flaming crap". Please re-read it, this time reading every word.
    - adrianN 6y ago
      I'm sorry, English is not my first language. I did in fact read every word in your post, but still don't understand it. Can you maybe rephrase it? I am pretty sure that this discussion here is not about climate change, but about the effects of higher CO2 concentrations in the atmosphere, on CO2 concentrations indoors.

salex89 6y ago

So, we're burning fossil fuels, increasing CO2 output, don't have an idea which will reliably improve the situation and are getting stupider by the day, decreasing our chance to ever getting one. Yay...

adrianN 6y ago
We in fact have multiple ideas how to improve the situation. The problem is not a lack of ideas, or deployable technology, the problem is a lack of political will to implement the necessary measures.
cbmuser 6y ago
We do. It’s called nuclear power and it‘s fought by those who claim they are fighting for the environment. > https://www.giss.nasa.gov/research/briefs/kharecha_02/ https://www.giss.nasa.gov/research/briefs/kharecha_02/
- hhjinks 6y ago
  Honest and good faith question here: assuming all electricity on the grid was nuclear, how much CO2 emission would remain? You can't just swap massive cargo ships to nuclear overnight. Would "just" making the power grid green be enough?
  - whatisthiseven 6y ago
    No, power generation is about a quarter: https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emis... Transportation could push that total to 50% if all ICE cars were converted or destroyed and only electric vehicles were used (ignoring ships and trains). "Industry" includes CO2 waste byproducts which are much harder to reduce as many processes may struggle to eliminate that byproduct. Instead capture and sequestration would be needed. This is another 25% The rest are small, but since we need virtually all CO2 emissions to be zero, we are left with nearly another 25% that isn't tied to electric production and is difficult to replace. So, 50% of all CO2 isn't power generation related.

GuB-42 6y ago

Their conclusion is that we should emit less CO2. Certainly a good idea, but their data clearly point to better ventilation. Better ventilation is something we can do right now, that will improve things immediately and 100 years from now. Maybe the best thing would be the mandatory installation of powerful ventilation systems with heat exchangers for new buildings, and incentives to upgrade existing installations. That would help with both problems: getting more fresh air and limiting energy expenditures which can, in turn, reduce CO2 emissions.

fyfy18 6y ago
> mandatory installation of powerful ventilation systems In my country that's already been a thing for the last few years. The HRV system is around €1000, so it isn't a major cost for the benefits you get. From this year all newly installed units need to be 90% efficient. Also "powerful" is probably not needed, the system I have at the lowest speed changes the air in my entire apartment every 3 hours, and is basically the same noise level as a barely audible computer fan.
- zdragnar 6y ago
  The difference in scale between your apartment and most schools is no trivial matter. At my high school, our one building, with tall ceilings, large cafeteria and so forth, housed around 1300 people every day. Some are smaller, some much bigger. Moving all of that air at least once a day would require powerful exchangers indeed. If nothing else, it would probably be cheaper and better for students to have plants everywhere. One of my teachers' classrooms was like a tiny jungle. I can't say that it made a significant difference, but it was pleasant at least.
  - baskire 6y ago
    Plants sadly don’t make a significant impact to indoor co2. I see a future indoor co2 sequestration device being incredibly popular
    - 6y ago

hyperpape 6y ago

Gwern raised some cautions about the studies indicating that these moderate levels of CO2 have cognitive impacts. I haven’t read enough to have an opinion, but any HN readers interested in this should probably follow up on the studies he references: https://news.ycombinator.com/item?id=21569947 https://news.ycombinator.com/item?id=21569947.

dreamcompiler 6y ago

Yes, better ventilation is part of the solution. But the authors point out that in many urban areas a "dome" of increased CO2 hangs over the city. Ventilation won't solve that problem. Only reducing fossil fuel burning will.

kev009 6y ago

Has anyone experimented with supplemental oxygen for cognitive benefit?

frank2 6y ago
Increasing O2 has physiological effects different from the effects of decreasing CO2. It is not just the ratio or difference between the concentrations that matter. For example, a major effect of increasing CO2 is to make the blood more acidic (or to put more stress on the homeostatic mechanisms that maintain a target pH), and my guess is that no amount of increasing O2 will cancel that out.
- matheusmoreira 6y ago
  > a major effect of increasing CO2 is to make the blood more acidic (or to put more stress on the homeostatic mechanisms that maintain a target pH), and my guess is that no amount of increasing O2 will cancel that out True. More details on this mechanism: The body uses buffer systems in order to minimize blood pH changes. For example, the bicarbonate buffer system which is catalazyed by carbonic anhydrase. CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃- + H+ It is converted back to carbon dioxide in the lungs and exhaled. The rate at which this process occurs is mainly influenced by respiratory rate. Oxygen doesn't directly influence it. O₂ enables aerobic cellular respiration, the process which produces carbon dioxide. The hydrogen ions are buffered by proteins such as hemoglobin. They are also excreted by the kidneys. https://en.wikipedia.org/wiki/Buffer_solution https://en.wikipedia.org/wiki/Buffer_solution https://en.wikipedia.org/wiki/Bicarbonate_buffer_system https://en.wikipedia.org/wiki/Bicarbonate_buffer_system https://en.wikipedia.org/wiki/Acid%E2%80%93base_homeostasis https://en.wikipedia.org/wiki/Acid%E2%80%93base_homeostasis https://opentextbc.ca/anatomyandphysiology/chapter/26-4-acid-base-balance/ https://opentextbc.ca/anatomyandphysiology/chapter/26-4-acid...
matheusmoreira 6y ago
I don't think anyone's studied it for every day cognitive benefit but oxygen supplementation is common in medicine. Note that increasing oxygen concentration is not the same as decreasing carbon dioxide concentration. https://en.wikipedia.org/wiki/Oxygen_therapy https://en.wikipedia.org/wiki/Oxygen_therapy https://en.wikipedia.org/wiki/Hypercapnia https://en.wikipedia.org/wiki/Hypercapnia https://en.wikipedia.org/wiki/Arterial_blood_gas_test https://en.wikipedia.org/wiki/Arterial_blood_gas_test Obese people can also experience cognitive symptoms due to hypoventilation. https://en.wikipedia.org/wiki/Obesity_hypoventilation_syndrome https://en.wikipedia.org/wiki/Obesity_hypoventilation_syndro... I suppose this could be considered analogous to breathing in air with high carbon dioxide concentrations.

bjoli 6y ago

Not just indoor. Just google what a 400ppm increase does and look at projections. The IPCC predicts that major cities might reach 1000ppm outdoors.

trhway 6y ago
Looks like in a few decades the AC units will be coming with CO2 scrubbers standard. Just a one more way the global warming is going to tax our economy/society.
- calcifer 6y ago
  Wouldn't home CO2 scrubbers need fairly frequent filter replacement? I can easily imagine units being sold with a subscription, e.g $14.99/month and you get a new filter every month.

derefr 6y ago

Is there any practical way to have less indoor CO2 than outdoor CO2, without needing to buy expensive single-use scrubber chemicals? Maybe presuming you live somewhere with cheap electricity and/or a cheap fresh water supply? Basically I’m asking whether there’s a Maxwell’s Daemon-like device for separating the CO2 from the air, and venting the CO2 back outside, while bringing in the rest of the air. Like a CO2 scrubber, but without any need for CO2 sequestration, since you exist inside an open system instead of in a space station/bunker/submarine.

beefield 6y ago
There are these things called plants that do that kind of stuff, so maybe if you have enough of them inside your house, they eat the CO2 away... :)
- derefr 6y ago
  I don’t think there’s any practical level of plant-having that would result in there being less CO2 in the house than in the atmosphere. IIRC, there’s some point in running an indoor grow-ops where you start needing to worry about spraying CO2-enriched air on the plants; but that’s just to accelerate growth, like a fertilizer. Or, sometimes, it’s because OPSEC requires you to not vent your smelly waste air — and because no human or animal lives in the grow-op house to convert O2 to CO2, the air becomes gradually CO2-poor. But that wouldn’t happen if even one human lived there; humans convert metabolize a lot faster than plants do.
- quaa55 6y ago
  came here for this.
w1 6y ago
I don't think this exists on a small scale yet. On industrial scales, CO2 is commonly removed with reusable scrubber chemicals, referred to as a group as amines. The amine acts as a CO2 solvent, removing the CO2 from the bulk gas. The 'rich' amine is then cycled to a separate location in the process where it is heated up, causing the CO2 to bubble out of solution, regenerating the amine for reuse, etc. I don't see any reason in principal why this can't be miniaturized, but it would be a challenging engineering problem. https://en.wikipedia.org/wiki/Amine_gas_treating https://en.wikipedia.org/wiki/Amine_gas_treating

jug 6y ago

This is already a problem in classrooms etc, and shows itself by tiredness and headaches. As I understand it, this will only push harder towards better ventilation.

offsky 6y ago

A regenerative CO2 scrubber that people could install inline with existing whole house AC systems would be a big success. I would buy it in a heartbeat.