4 ms·

There's one big problem with this entire idea of co2 levels affecting sleep quality or humans in general: Even though there are cognitive effects of CO2, most

There's one big problem with this entire idea of co2 levels affecting sleep quality or humans in general: Even though there are cognitive effects of CO2, most often the CO2 levels in indoor rooms are simply a sign of low oxygen levels. In fact, there should be an inverse relationship between CO2 and oxygen in rooms. So an experiments would need to take this into account and supply pure oxygen to make up for the oxygen that has been used up.

graeme 8y ago
Good observation. That said, co2 and o2 should move pretty much in tandem if the source of high co2 is human breathing + limited ventilation, right? This could potentially account for why no ill effects of high co2 were found in submarines. Presumably o2 supply there is well maintained. Do household air quality standards include o2 levels?
- wnoise 8y ago
  They do move in tandem on a molar basis, but because there is so much more O2 in the air, even very high concentrations of CO2 have barely changed the concentration of O2.
  - graeme 8y ago
    Right, so then in a single night in a poorly ventilated room, a human would not breathe up enough of the O2 to make any difference in their functioning? (Meaning we could rule it out as an explanation for the effects, if the effects do exist)
  - deleted 8y ago
    [deleted]
  - greenleaf2 8y ago
    They probably do not move in direct tandem, because most of the CO2 stays in the body, which means a higher amount of oxygen is taken out of the air, then CO2 being reintroduced to it. Every time you breathe in, you not only breath in O2, but also CO2, thus lowering the amount of CO2 in the room relatively to the amount of oxygen. In other words, 1000 ppm CO2 in the air do not mean 1000 ppm O2 less, but significantly more parts of oxygen less.
    - wnoise 8y ago
      > because most of the CO2 stays in the body Say what? ... not at all. No CO2 is "stored", though it may temporarily hang out in buffers such as the blood. But they have a very limited capacity and the flow out is extremely close to the production on a very very short timescale, and on a longer timescale approaches equality. > which means a higher amount of oxygen is taken out of the air, then CO2 being reintroduced to it. This is true, and I was wrong in my comment, but not for that reason. Only some of the O2 used is paired with CO2 and breathed out. Some joins with hydrogen from foods and becomes water. Most foods are carbon chains, with each carbon atom having two hydrogen atoms, so this ratio can get as high as around 2:1 for low-oxygen foods like fat, but lower for carbs, which tend to have significant quantities of oxygen (which will in balance add to the O2, meaning that more of what is used up when breathed in is breathed out). (Proteins also have nitrogen which complicates things.)
- greenleaf2 8y ago
  Most of the CO2 stays in the body, which ultimately means that significantly more O2 is used up than CO2 is introduced back into the air again. The comment about submarines is highly interesting to me, I will look into the studies! If you have any sources about that to share, I would love to read them.
hannasanarion 8y ago
It should be noted though, that the effects of low oxygen are already very well known and well understood, thanks to decades of research funded by air and space agencies. It should therefore be pretty easy for CO2 researchers to control the outcomes of their experiments against the known physiological effects of hypoxia, to determine what effects are actually caused by CO2. And aside from that, the dosages being discussed here are far, far lower than would be a noticeable dent in the amount of oxygen in the atmosphere. 1000 ppm CO2, the lower bound of observed cognitive effects, is 0.1% CO2, way less than the point where hypoxia is known to cause problems. The atmosphere is 20.9% oxygen at sea level and while I am not an expert in the math of partial pressure, a decrease of atmospheric oxygen to 20.8% doesn't strike me as sufficient to explain the observed effects. That's a 0.4% decrease in the partial pressure of oxygen, or about the equivalent of a 300 foot increase in altitude, or taking an elevator to the 20th floor of a building, nowhere near enough increase in altitude to make you light-headed.
- greenleaf2 8y ago
  The symptoms of slight sub-clinical hypoxia are in line with the observed effects of people in high CO2 office rooms: headaches, concentration problems, tiredness, etc. In a closed small room, the oxygen is mostly used up after a couple of days. One person in a small tightly closed room will lower the oxygen level significantly, by 5-10% (consumption is around 20 cubic feet, and a small room has about 200 cubic feet oxygen in volume in total) CO2 and oxygen work in tandem in the human body, and studies in the medical field have shown that an increase in carbon dioxide increases breathing rate, breathing volume, heart rate and metabolic rate. The result is an increased need for oxygen, which will not be met in a closed room. Thus I speculate that an increase in CO2 with an accompanying increase in oxygen (or at least a stable flow) will mostly negate the observed symptoms. My preliminary working theory would be that the previously observed effects from high CO2 in rooms (office rooms for example) are due to the interaction of both high CO2 and low O2.
- cordonbleu 8y ago
  there is a complication, this is not all about solution chemistry, this is a biological system that uses molecular affinities to transport O2 and CO2. A propertiy of any transport chain is lowest affinity at source of substance, highest affinity at destination. the overall efect is that small variences in atmospheric O2 have a large effect at the lung surface where the lowest O2 affinity occurs. This also is sensative to the promiscuity of haemoglobin, having affinity for BOTH O2 and CO2 kneejerk link below V http://bio1520.biology.gatech.edu/nutrition-transport-and-homeostasis/gas-exchange-in-animals/ http://bio1520.biology.gatech.edu/nutrition-transport-and-ho... https://en.wikipedia.org/wiki/Oxygen%E2%80%93hemoglobin_dissociation_curve https://en.wikipedia.org/wiki/Oxygen%E2%80%93hemoglobin_diss... www2.hawaii.edu/~moeng/Web_Zoo142/Lecture Notes/Zoo142ch23.pdf [PDF]
Symmetry 8y ago
That's intuitively appealing but when you look at the numbers it's almost certainly false. When CO2 goes from 400 ppm to 1000 ppm then oxygen will go from 21000 ppm to 20400 ppm, a 3% drop which isn't going to be enough to change anything.
- greenleaf2 8y ago
  No, the body does not use the same amount of oxygen, as the amount of CO2 it exhales. The amount of oxygen used is way higher. A person consumes 19 cubic feet of oxygen a day. Edit: I looked at the composition of inhaled and exhaled air, and now I realize the reason O2 is being taken out of the air in higher amounts than CO2 is introduced, is that the exhaled amount of carbon dioxide is not the total amount of carbon dioxide that has been created in the body. When the CO2 in the room gets higher, more CO2 is actually taken up again from the room back into the human body, with the exhale rate staying relatively constant. Or in other words, a significant part of the increase in CO2 in the system human <-> room is actually in the human, not in the room. The room measurement thus covers only a part of the CO2 being produced in total, and only the unknown total amount of CO2 produced reflects the totality of O2 being used up. This means a change of 1000 ppm of CO2 in the air will mean a higher amount of oxygen has been used up.
- tasty_freeze 8y ago
  Oxygen is 21% of the atmosphere, so 210000 ppm, not 21000 ppm.

graeme 8y ago

Good observation. That said, co2 and o2 should move pretty much in tandem if the source of high co2 is human breathing + limited ventilation, right? This could potentially account for why no ill effects of high co2 were found in submarines. Presumably o2 supply there is well maintained. Do household air quality standards include o2 levels?

wnoise 8y ago
They do move in tandem on a molar basis, but because there is so much more O2 in the air, even very high concentrations of CO2 have barely changed the concentration of O2.
- graeme 8y ago
  Right, so then in a single night in a poorly ventilated room, a human would not breathe up enough of the O2 to make any difference in their functioning? (Meaning we could rule it out as an explanation for the effects, if the effects do exist)
- deleted 8y ago
  [deleted]
- greenleaf2 8y ago
  They probably do not move in direct tandem, because most of the CO2 stays in the body, which means a higher amount of oxygen is taken out of the air, then CO2 being reintroduced to it. Every time you breathe in, you not only breath in O2, but also CO2, thus lowering the amount of CO2 in the room relatively to the amount of oxygen. In other words, 1000 ppm CO2 in the air do not mean 1000 ppm O2 less, but significantly more parts of oxygen less.
  - wnoise 8y ago
    > because most of the CO2 stays in the body Say what? ... not at all. No CO2 is "stored", though it may temporarily hang out in buffers such as the blood. But they have a very limited capacity and the flow out is extremely close to the production on a very very short timescale, and on a longer timescale approaches equality. > which means a higher amount of oxygen is taken out of the air, then CO2 being reintroduced to it. This is true, and I was wrong in my comment, but not for that reason. Only some of the O2 used is paired with CO2 and breathed out. Some joins with hydrogen from foods and becomes water. Most foods are carbon chains, with each carbon atom having two hydrogen atoms, so this ratio can get as high as around 2:1 for low-oxygen foods like fat, but lower for carbs, which tend to have significant quantities of oxygen (which will in balance add to the O2, meaning that more of what is used up when breathed in is breathed out). (Proteins also have nitrogen which complicates things.)
greenleaf2 8y ago
Most of the CO2 stays in the body, which ultimately means that significantly more O2 is used up than CO2 is introduced back into the air again. The comment about submarines is highly interesting to me, I will look into the studies! If you have any sources about that to share, I would love to read them.

hannasanarion 8y ago

It should be noted though, that the effects of low oxygen are already very well known and well understood, thanks to decades of research funded by air and space agencies. It should therefore be pretty easy for CO2 researchers to control the outcomes of their experiments against the known physiological effects of hypoxia, to determine what effects are actually caused by CO2. And aside from that, the dosages being discussed here are far, far lower than would be a noticeable dent in the amount of oxygen in the atmosphere. 1000 ppm CO2, the lower bound of observed cognitive effects, is 0.1% CO2, way less than the point where hypoxia is known to cause problems. The atmosphere is 20.9% oxygen at sea level and while I am not an expert in the math of partial pressure, a decrease of atmospheric oxygen to 20.8% doesn't strike me as sufficient to explain the observed effects. That's a 0.4% decrease in the partial pressure of oxygen, or about the equivalent of a 300 foot increase in altitude, or taking an elevator to the 20th floor of a building, nowhere near enough increase in altitude to make you light-headed.

greenleaf2 8y ago
The symptoms of slight sub-clinical hypoxia are in line with the observed effects of people in high CO2 office rooms: headaches, concentration problems, tiredness, etc. In a closed small room, the oxygen is mostly used up after a couple of days. One person in a small tightly closed room will lower the oxygen level significantly, by 5-10% (consumption is around 20 cubic feet, and a small room has about 200 cubic feet oxygen in volume in total) CO2 and oxygen work in tandem in the human body, and studies in the medical field have shown that an increase in carbon dioxide increases breathing rate, breathing volume, heart rate and metabolic rate. The result is an increased need for oxygen, which will not be met in a closed room. Thus I speculate that an increase in CO2 with an accompanying increase in oxygen (or at least a stable flow) will mostly negate the observed symptoms. My preliminary working theory would be that the previously observed effects from high CO2 in rooms (office rooms for example) are due to the interaction of both high CO2 and low O2.
cordonbleu 8y ago
there is a complication, this is not all about solution chemistry, this is a biological system that uses molecular affinities to transport O2 and CO2. A propertiy of any transport chain is lowest affinity at source of substance, highest affinity at destination. the overall efect is that small variences in atmospheric O2 have a large effect at the lung surface where the lowest O2 affinity occurs. This also is sensative to the promiscuity of haemoglobin, having affinity for BOTH O2 and CO2 kneejerk link below V http://bio1520.biology.gatech.edu/nutrition-transport-and-homeostasis/gas-exchange-in-animals/ http://bio1520.biology.gatech.edu/nutrition-transport-and-ho... https://en.wikipedia.org/wiki/Oxygen%E2%80%93hemoglobin_dissociation_curve https://en.wikipedia.org/wiki/Oxygen%E2%80%93hemoglobin_diss... www2.hawaii.edu/~moeng/Web_Zoo142/Lecture Notes/Zoo142ch23.pdf [PDF]

Symmetry 8y ago

That's intuitively appealing but when you look at the numbers it's almost certainly false. When CO2 goes from 400 ppm to 1000 ppm then oxygen will go from 21000 ppm to 20400 ppm, a 3% drop which isn't going to be enough to change anything.

greenleaf2 8y ago
No, the body does not use the same amount of oxygen, as the amount of CO2 it exhales. The amount of oxygen used is way higher. A person consumes 19 cubic feet of oxygen a day. Edit: I looked at the composition of inhaled and exhaled air, and now I realize the reason O2 is being taken out of the air in higher amounts than CO2 is introduced, is that the exhaled amount of carbon dioxide is not the total amount of carbon dioxide that has been created in the body. When the CO2 in the room gets higher, more CO2 is actually taken up again from the room back into the human body, with the exhale rate staying relatively constant. Or in other words, a significant part of the increase in CO2 in the system human <-> room is actually in the human, not in the room. The room measurement thus covers only a part of the CO2 being produced in total, and only the unknown total amount of CO2 produced reflects the totality of O2 being used up. This means a change of 1000 ppm of CO2 in the air will mean a higher amount of oxygen has been used up.
tasty_freeze 8y ago
Oxygen is 21% of the atmosphere, so 210000 ppm, not 21000 ppm.