Absolutely. When Apollo 13 had their, um “problem,” they had plenty of oxygen on board to make the return trip, in spite of one of their tanks exploding. However, the expected buildup of CO2 in the lunar module (where they planned to hunker down for the return trip) was a major concern. The LM was supposed to keep two people alive for two days, not three people for four days. The command module had enough chemical “scrubber” canisters for removing CO2, but they were designed for the command module and didn’t fit the system in the lunar module. In the end, they had to fabricate an adapter so they could fit the CM’s square canisters to the LM’s round sockets. They didn’t transfer back to the CM until shortly before reentry.
A CO2 concentration of 8% in air appears to be enough to render a person unconscious (possibly dead), even though such a mix would certainly contain enough oxygen to sustain life.
FWIW, the volume in m3 of the command module was 6.2 and the lunar module 6.7. The crew took up a chunk of that so the total was somewhat less. Still less than a fifth of the hypothetical bedroom size given above.
It’s too early for me to do the Math. But we have a volume, number of people, etc. The whole thing lasted 6 days. Without the scrubbers they would have been goners in ??? long? Cf. one person in a volume 5+ times greater for ~1/3 of a day. Doesn’t sound too dangerous to my sleepy mind.
My current residence is very up to date in terms of insulation and windows that seal so tightly and efficiently that virtually no air gets in. Even in the winter, I have windows open, even if it is only a couple of inches. Otherwise, the air gets really stale. If just one of my rooms was sealed that tightly, I could see succumbing to CO2 poisoning, although it might very well take more than just one day.
according to Slate, the typical human exhales about a kilogram of CO2 per day. 1 kilo of CO2 in 6.7 cubic meters at 20C gives a partial pressure of 8.262 kPa.
This is where some uncertainty arises. The resources discussing CO2 toxicity assume a standard-atmospheric-pressure environment, while the CM/LM were reportedly pressurized to about 1/3 of an atmosphere (with pure O2). I will assume for this analysis that the human body, when exchanging CO2 with the atmosphere, responds to the absolute pressure of CO2 rather than simply the CO2 pressure relative to other atmospheric constituents, which would mean that the sub-atmospheric pressure in the CM/LM was irrelevant.
if 8% CO2 in a standard-pressure atmosphere is enough to render a person unconscious, then it looks to me like one person in the LM without any CO2 scrubbing could kill himself in about a day, which would mean that with no scrubbing, three people would be dealing with problematic symptoms after 3-5 hours and would be unconscious after about eight hours. The LM did have some scrubber modules (just not enough for the entire trip), so they were probably able to last longer than 8 hours before having to come up with their famous hack job.
I’m sure I’m screwing up some math there; I’ve always struggled to deal with conversions between partial pressure, percent volume, molar concentration, etc. But I’ll stand by 8 hours as a rough approximation.
So if one person in the LM could hit unconsciousness after 8 hours, then it seems it would take 40 hours for one person in a hermetically sealed bedroom to achieve unconsciousness. But eight hours would still be enough to develop symptoms of mild hypercapnia.
I rarely saw the oxygen levels <20% even when underway submerged for long periods of time. There are oxygen banks and two methods of making oxygen. carbon dioxide/monoxide are also kept very low.
I’m a psychiatrist, and while I’m not a huge slatestarcodex fan, I do check it once in a while, and I have to say his writing does reveal a detailed insider’s knowledge of the medical education system and of the field of psychiatry.
Beyond that, it’s my understanding that his real-life identity is pretty well-known among his readership. I know his full name, and googling it reveals his profile on the website of a hospital system on the West coast, where he says he works. Back when he was saying he was in residency, one got a similar result on a residency program website in a city in the region of the country where he said he was doing residency. He’s held meetups with readers, including at least one at the American Psychiatric Annual meeting, where he posted on the blog that he was presenting a poster on a certain topic on a certain day at a certain time. I checked the APA meeting guide, and there was in fact a poster being presented on that topic at that day and time.
Not sure why you’re so doubtful of him.
I think you may have misunderstood something. (We doctors sometimes forget how un-familiar the lay public is with the system of medical education.) I wonder if you were thinking of this post, or one like it? In it, he’s talking about the general internal medicine and primary care experiences all medical students and first-year residents go through, regardless of their choice of specialty. He also says he did four years of residency. Psychiatry residency is four years long, leaving no time in there for doing something else for 1-2 years then switching into psychiatry.
I’m doubtful because, unlike the other readers you refer to, I don’t know the name under which he practises medicine, which makes it impossible for me to check his medical credentials the way you say you have done yourself. (In case it’s not clear to others reading this discussion, “Scott Alexander” is a pen name.)
O2 tanks on submarines? I never heard that one. They would have been a fire hazard, for one thing.
Having read numerous reports of WW2 submariners being under attack for up to a day or longer, and considering that a submarine is not large but has a large crew, I would suspect that a sealed bedroom is no big deal unless you are a really. really heavy sleeper.
BTW, the submariners did have chemicals to remove CO2 from the air, but this only helped a bit. Nuclear submarines are another issue, they can generate oxygen and scrub out the CO2. And need to, since they can be submerged for weeks.
Stuffiness is mainly a matter of perception. My wife often complains that the car is stuffy if the fan of the A/C is not running. That cool breeze changes your perceptions.
This is a known concern with modern cars. Manufacturers have tried to squeeze better performance from the air conditioning so as to improve fuel economy, and that means a tighter seal when in recirc mode, which in turn means CO2 can build up to levels that can affect not just passenger comfort, but driver cognition.
Careful with that word. “Hypoxic” refers to a condition where the body isn’t getting enough oxygen to sustain normal function; it does not refer to an environment in which the partial pressure of oxygen is a little below its sea-level ambient value. People in Denver are not hypoxic.
That said, a nuclear sub must work to maintain the internal O2 level during its months-long submersion. Since they are actively managing it, why would they deliberately maintain it at a partial pressure below the normal sea-level ambient value?
How much O2 is in the room? We have 76,455 liters of air, 20% of which is O2. So the room contains 15,291 liters of pure O2.
How low can the oxygen concentration get before we’re at risk of hypoxia symptoms? This is harder to answer. When ascending Mount Everest, climbers deliberately take days to get acclimated to high altitudes. In doing so, they can persist at altitudes as high as 26,000 feet, whereas sudden exposure to such conditions (as in a high-altitude simulation chamber can cause a person to pass out in a couple of minutes (fast-forward that video to the 3:00 mark to see what I mean). Let’s say that if a person can drive from Lincoln, NE to Leadville, CO in a day, and expect to not get sick on arrival, then the O2 partial pressure in Leadville is a reasonable lower limit for what we’d consider safe in a bedroom after a night of sleep. Ambient pressure in Leadville is about 70% of sea level, so a sleeper can safely use 30% of the O2 in his bedroom. That’s 4587 liters of O2 available for metabolic use; at 550 liters per day, that’s enough O2 for 8.3 days, whereas the CO2 build-up is already causing problems after just 8 hours.