Did a little research
ok, here's a summary from a little research that I did. If anyone spots some errors, please feel free to correct them. For example, I am not a chemist so when I found references to "%" of a gas, I am unsure whether it is expressed in terms of mass, molar equivalent etc. This will screw up some of the conversions that I use below, but not by a whole lot. At any rate, here's what I think I learned:
- The amount of CO2 in out ambient atmosphere is negligible (about 0.03%)
- The volume of C02 produced is approximately equal to the amount of O2 consume (i.e. each molecule of O2 'lost' is converted to a molecule of CO2).
- During normal breathing, we use about 3 kPA of O2 (i.e. at atmospheric pressure, the air going in is about 21% O2 and the air going out is about 18% O2)
- This means that the air in our lungs, just before exhalation, is normally about 3% CO2 (the ambient CO2 is negligible).
Each % of gas in the composition corresponds pretty closely to 1 kPA partial pressure of that gas at sea level. In other words, "%" of gas and kPA partial pressure for that gas are essentially interchangeable at sea level. At any rate, here's a table of physiological effects:
CO2 kPA* Effect (from
http://www.cisatlantic.com/trimix/AQUAcorps/mix/CO2Summary.htm)
Normal (0-4 kPA): May experience mild to moderate dyspnea
High Normal (4-6 kPA): Dyspnea, anxiety (a decent breath-hold will get you to this point -- I sometimes get a flash of paranoia at the end)
High (6-10 kPA): Impaired mental capability (I would be surprised if you could voluntarily hold your breath much beyond this point -- the lowest SAO2 level that I have ever heard of with voluntary apnea was about 40%, which corresponds to 0.6*21% or a CO2 level of about 12% -- i.e. 12 kPA)
Very High (11-15 kPA): Severely mental impairment, discomfort nausea (ok, so some guys can get to the low-end of this range voluntarily, and I think that vigorous anaerobic effort and the accompanying O2 debt can temporarily exceed your ability to ventilate and drive you up in this range)
Super high (16-20 kPA): Loss of consciousness (the likely outcome of zumaz's proposed experiment)
Over the top (> 20 kPA): Uncoordinated twitching and convulsions (another possible outcome of the proposed experiment)