7 ms·

Yes that increases air quality but it would not add oxygen back into the air in place of CO2.

Robotbeat 5y ago
I’ve thought a lot about CO2 scrubbing of indoor air. Oxygen concentrators are cheaper than air scrubbing and much easier to do regeneratively. The simplest and cheapest scrubber is to just use sodalime, but that’s disposable and single-use. A regenerative system that heats up the lime (and vents the CO2 elsewhere) is more complicated and expensive and very energy intensive. Other solutions using amines or other chemicals to remove the oxygen can be more efficient, but many of them don’t work efficiently except at higher CO2 concentrations. We are, of course, talking about miniaturizing a Direct Air CO2 capture system, which usually operates at large scale to get efficiency. Replaceable cartridges that are regenerated at a central location may be a better option. But oxygen concentrators are small and cheap and portable and don’t require much energy to operate.
gpm 5y ago
Oxygen depletion doesn't seem to be the issue though, CO2 toxicity does. At 1400ppm CO2, we've turned what, 1000ppm O2 into CO2 (is it 1-1?), or 1% of the atmosphere. Dropping O2 from (Edit: Fixed numbers) 21% to 20%. Or about a 5% reduction in O2 density. Equivalent to approximately 1500 feet of elevation... That's just not that much. (There's also a long list of papers showing issues with CO2 toxicity at low levels of CO2... I keep intending to write a blog post summarizing them)
- taxicabjesus 5y ago
  > At 1400ppm CO2, we've turned what, 1000ppm O2 into CO2 (is it 1-1?), or 1% of the atmosphere. 1400ppm is 0.14%. Earth's current atmospheric co2 level is around 400ppm, or 0.04%. While the jump from 0.04% to 0.14% might seem significant (3.5x more co2!), it's not. Submariners survive on 3400 to 11300 ppm co2, or 0.34 to 1.13%: > Submarine crew are reported to be the major source of CO2 on board submarines (Crawl 2003). Data collected on nine nuclear-powered ballistic missile submarines indicate an average CO2 concentration of 3,500 ppm with a range of 0-10,600 ppm, and data collected on 10 nuclear-powered attack submarines indicate an average CO2 concentration of 4,100 ppm with a range of 300-11,300 ppm (Hagar 2003). [0] [0] https://www.nap.edu/read/11170/chapter/5 https://www.nap.edu/read/11170/chapter/5 I'd like to emphasize that the average CO2 concentration for submariners is 4,100 ppm or 0.40%, or ten times Earth's current CO2 level. Oxygen is much more toxic than small amounts of CO2. Pure CO2 will kill you quickly, pure o2 will kill you slowly. > (There's also a long list of papers showing issues with CO2 toxicity at low levels of CO2... I keep intending to write a blog post summarizing them) I'm interested.
  - gpm 5y ago
    Oops, today really isn't my day for math apparently :(... 1% did seem high. --- > I'm interested. Well I don't have a blog post ready to go yet, but I can point you to some papers now. - This review cites a bunch of papers about health effects in the 1-10k ppm range: https://www.nature.com/articles/s41893-019-0323-1.epdf?referrer_access_token=eE4mU6nzyLJz_7TLn_xNMNRgN0jAjWel9jnR3ZoTv0Nmh56_6v6IG1wyUXiF6sNTHAt-0vDDZqKRyKQg__8_oxrm08uvJsMrDK8PUmvmArkegYALMahVANSDeRSyA8bTgKfjffuaO26tlP3hD6cHFJFm0RG8oSheeD0KC5mI-WlSIvZFjIL2uyZaN9KCm3_Lbdv7vGDkqNLiWzCKvPLh_8frf88zlrpECCEpeNnT6fFdkuk5mdFgJYeS6LPRWtSJ3t0qVO-l-XeqvTlXVLKdJ67nc_EcZbx81TO5U6j_0n-5SVon62qg8lNRw9-x8xkOCiys08VULZjj_p25Brz_0Q%3D%3D&tracking_referrer=www.theguardian.com https://www.nature.com/articles/s41893-019-0323-1.epdf?refer... - Table 3 in this paper references a bunch of papers around 10kppm: https://www.researchgate.net/profile/Susan-Rice-3/publication/228863103_Human_Health_Risk_Assessment_of_CO2_Survivors_of_Acute_High-Level_Exposure_and_Populations_Sensitive_to_Prolonged_Low-Level_Exposure/links/5526bb3b0cf229e6d635bcbf/Human-Health-Risk-Assessment-of-CO2-Survivors-of-Acute-High-Level-Exposure-and-Populations-Sensitive-to-Prolonged-Low-Level-Exposure.pdf https://www.researchgate.net/profile/Susan-Rice-3/publicatio... - These papers show mental effects in the 1-4k ppm range: https://ehp.niehs.nih.gov/doi/full/10.1289/ehp.1104789 https://ehp.niehs.nih.gov/doi/full/10.1289/ehp.1104789 http://www.aretas.ca/sites/default/files/imce_images/Indoor%20Environment%20in%20Schools%20%E2%80%93%20Pupils%20Health%20%26%20Performance%20in%20Regard%20to%20CO2%20Concentrations.pdf http://www.aretas.ca/sites/default/files/imce_images/Indoor%... - These two are from nasa about the ISS - which brings it's own complications but otherwise also show mental effects in the above range https://web.archive.org/web/20190613133240/https://ston.jsc.nasa.gov/collections/trs/_techrep/TP-2012-217358.pdf https://web.archive.org/web/20190613133240/https://ston.jsc.... https://pubmed.ncbi.nlm.nih.gov/24806559/ https://pubmed.ncbi.nlm.nih.gov/24806559/
    - taxicabjesus 5y ago
      Thanks for the links, I have started perusing them. As someone pointed out in a reply to another comment in this thread, oxygen is especially toxic 33 feet below the surface of the water (because of higher pressure), but can have toxic effects at the surface too. I don't grok respiration yet, but my understanding is that altitude/pressure is essential for putting the relative N2/O2/CO2 partial pressures into context.
- ddeck 5y ago
  >Dropping O2 from 30% to 29% Dry air is ~21% oxygen by volume.
  - gpm 5y ago
    Ah, oops, you're correct of course. The general point still stands though (at 5% instead of 3% and 1500 feet instead of 1000) I'm getting the density numbers from here by the way if you want to check the rest of my math: https://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html https://www.engineeringtoolbox.com/air-altitude-pressure-d_4...
- petre 5y ago
  30% O2 in the atmosphere? Mayve when dinosaurs roamed the Earth. We currently have about 21%.

I’ve thought a lot about CO2 scrubbing of indoor air. Oxygen concentrators are cheaper than air scrubbing and much easier to do regeneratively. The simplest and cheapest scrubber is to just use sodalime, but that’s disposable and single-use. A regenerative system that heats up the lime (and vents the CO2 elsewhere) is more complicated and expensive and very energy intensive. Other solutions using amines or other chemicals to remove the oxygen can be more efficient, but many of them don’t work efficiently except at higher CO2 concentrations. We are, of course, talking about miniaturizing a Direct Air CO2 capture system, which usually operates at large scale to get efficiency. Replaceable cartridges that are regenerated at a central location may be a better option. But oxygen concentrators are small and cheap and portable and don’t require much energy to operate.

gpm 5y ago

Oxygen depletion doesn't seem to be the issue though, CO2 toxicity does. At 1400ppm CO2, we've turned what, 1000ppm O2 into CO2 (is it 1-1?), or 1% of the atmosphere. Dropping O2 from (Edit: Fixed numbers) 21% to 20%. Or about a 5% reduction in O2 density. Equivalent to approximately 1500 feet of elevation... That's just not that much. (There's also a long list of papers showing issues with CO2 toxicity at low levels of CO2... I keep intending to write a blog post summarizing them)

taxicabjesus 5y ago
> At 1400ppm CO2, we've turned what, 1000ppm O2 into CO2 (is it 1-1?), or 1% of the atmosphere. 1400ppm is 0.14%. Earth's current atmospheric co2 level is around 400ppm, or 0.04%. While the jump from 0.04% to 0.14% might seem significant (3.5x more co2!), it's not. Submariners survive on 3400 to 11300 ppm co2, or 0.34 to 1.13%: > Submarine crew are reported to be the major source of CO2 on board submarines (Crawl 2003). Data collected on nine nuclear-powered ballistic missile submarines indicate an average CO2 concentration of 3,500 ppm with a range of 0-10,600 ppm, and data collected on 10 nuclear-powered attack submarines indicate an average CO2 concentration of 4,100 ppm with a range of 300-11,300 ppm (Hagar 2003). [0] [0] https://www.nap.edu/read/11170/chapter/5 https://www.nap.edu/read/11170/chapter/5 I'd like to emphasize that the average CO2 concentration for submariners is 4,100 ppm or 0.40%, or ten times Earth's current CO2 level. Oxygen is much more toxic than small amounts of CO2. Pure CO2 will kill you quickly, pure o2 will kill you slowly. > (There's also a long list of papers showing issues with CO2 toxicity at low levels of CO2... I keep intending to write a blog post summarizing them) I'm interested.
- gpm 5y ago
  Oops, today really isn't my day for math apparently :(... 1% did seem high. --- > I'm interested. Well I don't have a blog post ready to go yet, but I can point you to some papers now. - This review cites a bunch of papers about health effects in the 1-10k ppm range: https://www.nature.com/articles/s41893-019-0323-1.epdf?referrer_access_token=eE4mU6nzyLJz_7TLn_xNMNRgN0jAjWel9jnR3ZoTv0Nmh56_6v6IG1wyUXiF6sNTHAt-0vDDZqKRyKQg__8_oxrm08uvJsMrDK8PUmvmArkegYALMahVANSDeRSyA8bTgKfjffuaO26tlP3hD6cHFJFm0RG8oSheeD0KC5mI-WlSIvZFjIL2uyZaN9KCm3_Lbdv7vGDkqNLiWzCKvPLh_8frf88zlrpECCEpeNnT6fFdkuk5mdFgJYeS6LPRWtSJ3t0qVO-l-XeqvTlXVLKdJ67nc_EcZbx81TO5U6j_0n-5SVon62qg8lNRw9-x8xkOCiys08VULZjj_p25Brz_0Q%3D%3D&tracking_referrer=www.theguardian.com https://www.nature.com/articles/s41893-019-0323-1.epdf?refer... - Table 3 in this paper references a bunch of papers around 10kppm: https://www.researchgate.net/profile/Susan-Rice-3/publication/228863103_Human_Health_Risk_Assessment_of_CO2_Survivors_of_Acute_High-Level_Exposure_and_Populations_Sensitive_to_Prolonged_Low-Level_Exposure/links/5526bb3b0cf229e6d635bcbf/Human-Health-Risk-Assessment-of-CO2-Survivors-of-Acute-High-Level-Exposure-and-Populations-Sensitive-to-Prolonged-Low-Level-Exposure.pdf https://www.researchgate.net/profile/Susan-Rice-3/publicatio... - These papers show mental effects in the 1-4k ppm range: https://ehp.niehs.nih.gov/doi/full/10.1289/ehp.1104789 https://ehp.niehs.nih.gov/doi/full/10.1289/ehp.1104789 http://www.aretas.ca/sites/default/files/imce_images/Indoor%20Environment%20in%20Schools%20%E2%80%93%20Pupils%20Health%20%26%20Performance%20in%20Regard%20to%20CO2%20Concentrations.pdf http://www.aretas.ca/sites/default/files/imce_images/Indoor%... - These two are from nasa about the ISS - which brings it's own complications but otherwise also show mental effects in the above range https://web.archive.org/web/20190613133240/https://ston.jsc.nasa.gov/collections/trs/_techrep/TP-2012-217358.pdf https://web.archive.org/web/20190613133240/https://ston.jsc.... https://pubmed.ncbi.nlm.nih.gov/24806559/ https://pubmed.ncbi.nlm.nih.gov/24806559/
  - taxicabjesus 5y ago
    Thanks for the links, I have started perusing them. As someone pointed out in a reply to another comment in this thread, oxygen is especially toxic 33 feet below the surface of the water (because of higher pressure), but can have toxic effects at the surface too. I don't grok respiration yet, but my understanding is that altitude/pressure is essential for putting the relative N2/O2/CO2 partial pressures into context.
ddeck 5y ago
>Dropping O2 from 30% to 29% Dry air is ~21% oxygen by volume.
- gpm 5y ago
  Ah, oops, you're correct of course. The general point still stands though (at 5% instead of 3% and 1500 feet instead of 1000) I'm getting the density numbers from here by the way if you want to check the rest of my math: https://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html https://www.engineeringtoolbox.com/air-altitude-pressure-d_4...
petre 5y ago
30% O2 in the atmosphere? Mayve when dinosaurs roamed the Earth. We currently have about 21%.