WOW - Great Response to my little question. Before I asked the List I spent about an hour on line trying to answer the question myself but everything I saw was inconclusive.
But I did see some thing that addressed your comments. >>>>>>>>>> If I recall from submarine personnel you will suffocate due to lack of oxygen. The movies always show it nice an clean...its not. But lets face it does it matter. NORM - I did read on the Internet that lack of oxygen creates little or no response in the body. If you don't have enough oxygen you simply fall asleep. This can happen to jet jockeys when "pulling Gs". They simply black out, fall asleep, when the blood drains from their brains. I once knew a respiratory therapist who worked in a hospital. She mentioned one day a patient that came in with a malady that made them insensitive to high CO2 levels. At first they gave the patient O2 but that was a mistake because it removed *all* respiratory distress. When they got a blood gas they saw the CO2 was through the roof. I also recall that a fellow named Beebe made a hollow iron sphere to carry him a mile or two underwater. He had a supply of quicklime to soak up CO2 but I don't recall any O2 supply. The on-line info made it quite clear that (other than the above person) elevated CO2 was very distressful including rapid and deep breathing, panic, convulsions, etc. Carbon Dioxide is not poisonous NORM - the Internet said that Carbon Dioxide will kill you if the levels in your blood get high enough, around 5 to 7 percent I think. Well lack of oxygen seems a slightly more pleasant way to go... NORM - This seems to be true from what I read this morning. They said low O2 puts you to sleep and high CO2 intensifies the urge to breath. IIRC, breathing turns oxygen to carbon dioxide at 1:1 %vol in the air. Normal atmospheric concentration of O2 is around 19%, and CO2 is a trace gas. 5% CO2 is considered to be potentially lethally toxic, whereas the minimum O2 concentration required to survive is generally figured at 17%, so after converting 2% of the air in the compartment from O2 to CO2, you'd be looking at a potentially lethal O2 shortage, but would only be about half way to a potentially lethal CO2 concentration. NORM - The 5% co2 seems right but I would be surprised that O2 dropping from 20% to 17% would have such a big effect, but I really don't know. During the Apollo 13 moonmission (remember the space program?) the astronauts had to fashion a CARBON DIOXIDE scrubber to use the chemicals packs from the command module in the landing module (where they had to stay for the trip back to Earth). Of course they had OXYGEN tanks, but it does demonstrate the toxicity of carbon dioxide. NORM - I have the DVD and have watched it several times. I do recall they did have adequate O2 on board to breath, the main problem was making electricity. They did have to make a CO2 scrubber - Duct Tape's crowning moment! BTW, the worlds most famous quote - "Houston, we have a problem." - was actually "Ah, Houston we've had a problem here." Ahhh, so when shrinking the bits of my winter enclosure that can only be shrunk from the inside, it's when I get somewhere between 2% and 5% CO2 that I stop the heat gun and let the enclosure vent for a minute or two before resuming :) NORM - How did you measure the CO2 levels? Been a sub nuc for 20+ years. While it is a tough way to die (trapped on a nuc sub, no rescue possible) we saw on the Kursk that the 23 sailors died from suffocation, and poison gas. But, the ones that suffocated died because the RATIO of CO2 to O2 was too high. Too much Co2 and one falls asleep. To little O2 and one dies from lack of a oxygen. But the body, with its will to survive, will put itself to sleep in a bid of self protection, and then gradually shut down unneeded parts of the body to keep the brain alive, but ultimately, the combined high co2 / low o2 is just too much and the body shutdowns the brain. If you are ever in a room protected from fire by CO2 fire extinguisher bank, you probably seen signs that say that evacuation is necessary when the alarm sound because the discharge of the CO2 will displace the oxygen, leading to injury / death. But, on a slowly raising ration in a confined atmosphere, I think that the MDs would say that it is chicken / egg. lee NORM - I didn't see anything about the ratio of CO2/O2, but that is an interesting thought. I would think a submariner would have the best info about this. Yet I remember it was a submariner who told us that the battery manufacturers instructed them to "exercise" the battery bank periodically, a policy that is just the opposite of the "conventional wisdom". The search for truth can be confusing. I believe that it has to do with changes to the partial pressure of each gas that causes the problem. As the percentage of CO2 in the air increases the red blood platelets are less able to rid themselves of CO2 gas, and the corresponding decrease of the P.P. of O2 makes it more difficult to pick up the Oxygen. NORM - The Internet was clear in saying red blood cells (not platelets, the clotting factors) carried very little CO2. It is the plasma that absorbs CO2 making carbolic (carbonic?) acid that gets cleared in the lungs. The air is normally at .40% CO2 and the blood normally at .05% CO2. While CO2 is not poisonous, it does not support life. In the case Norm cited the occupants would die of CO2 intoxication. This would be the case even though there were still O2 in the air of the chamber. If you would like to simulate the experience, just put a plastic bag over your head and tie it tight around your neck. (I would recommend a slipped hitch). Pol Pot used this technique to cheaply murderer many of his countryman. Cheaper than bullets and, being the bags are reusable, ecologically sound too. NORM - There is another experiment that I have tried twice when I was a teenager that may shed some light. Seated, I breathed deeply and rapidly until my hands and feet became numb and I became dizzy. With stopwatch in hand I found I did not feel a irristable urge to breath until I had held my breath for five minutes. I read later in Reader's Digest that some adventurous teenaged boys, to impress the girls at the lake, would use this method (hyperventilation) to stay underwater for long periods. Seems some of them ran out of oxygen before the urge to breath returns as CO2 levels rise and drown. I was motionless in a chair or bed - they were swimming. >From what I recall from when I was hitting the books for my dive certification (ended up not going for the high-end cert for a variety of reasons, but I did study up for it), it would be pretty hard to get poisoned by CO2 until the level gets really, really high. That, coupled with the constant necessity for a relatively large volume of oxygen, makes me lean heavily toward hypoxia as the primary danger. In terms of numbers, the normal level of C02 in a room (had to look this stuff up) is about 600ppm, while outdoors it's 300-400ppm (i.e., 0.04% concentration.) The average concentration at which most people become aware of a problem is over 2% (20000ppm), or about 50X the outdoor level, and it takes a 5% concentration to become directly toxic. You'd be oxygen-starved well before that point, I would think. But that's just an educated guess on my part. :) Norm - My thinking is that one O2 molecule changes to one CO2 molecule, so the percentage of CO2 rises at the same rate that O2 declines. I also believe (with little foundation to do so) that 4% of CO is more dangerous than only 16 percent of O2. So with my ignorance at stake, I put a kitchen garbage over my head, gathered it snugly around my neck and sat on the bed listening to the TV. After about five minutes of nothing to report, I smushed most of the air of the bag and continued. Soon I found myself breathing much more deeply than I would normally do. The feeling of not being able to "get my breath" increased gradually and I go slightly dizzy but I never felt "sleepy". When I was breathing as deeply as I could yet feeling it was getting worse I stopped the procedure. Since as time went on I began breathing more deeply and did not feel sleepy my conclusion is that my main stressor was rising CO2 levels. BTW, this whole thing started from watching an episode of "Firefly" last night (recommended) wherein the lifesupport system failed and the script called for the "falling asleep" scenario. Regards, Norm S/V Bandersnatch PS - Since Rosalee was a government industrial safety (OASHA) I consider her an expert... > IDLH for carbon dioxide is 40000 ppm based on acute inhalation toxicity data in humans which would > be about 4% but of course these levels are skewed on the side of safety. > > Death by suffocation in sealed container is normally caused by CO2 poisoning which is at about 7% by > volume. > >Rosalee _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://liveaboardonline.com/mailman/listinfo/liveaboard To subscribe send an email to [email protected] To unsubscribe send an email to [email protected] The archives are at http://www.liveaboardonline.com/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
