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Old 09-06-2019, 03:16 PM
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If our bedrooms were air tight, would we be at risk of suffocating overnight?


I know our building methods are no where near being airtight, in fact, I think I read somewhere the air in a room generally turns over multiple times an hour.

But what if didn't? What if absolutely no air leaked through closed windows or doors, or through cracks or the electric ducts and so forth? If, when you retired to your bedroom at night, closing your door sealed the room off completely?

How much oxygen does a human actually use? How does that compare with how much oxygen there is in a normal sized bedroom filled with normal Earth atmosphere? Would we be fine, or wake up gasping for air in the morning, or <gasp> not wake up at all?
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Old 09-06-2019, 03:20 PM
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Nitpick: As I understand it, it's not the lack of Oxygen that would kill you, but the build up of Carbon Dioxide.

(I don't know the answer to the question, but I bet NASA does.)
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Old 09-06-2019, 04:01 PM
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From articles such as this one, Carbon dioxide generation rates for building occupants, in Indoor Air. 2017 Sep; 27(5): 868–879, a general rate of CO2 generation per adult human in 0.005 L/s, at a typical ventilation rate of 7.5 L/s. CO2 has a variety of toxic concentrations, from 100,000 PPM, or 10%, immediately dangerous to life, to 30 minutes at 50,000 PPM resulting in intoxication, to a 8 hour total weighted average of 5,000 PPM. All from this reference, NIOSH's page on CO2. The PPM are listed as weight of CO2 per cubic meter. (listed as mg/m^3) at the reference.

The 8 hour TWA is 9,000 mg/m^3

How big is your bedroom and how long are you sleeping shut in?

Creditdonkey seems to think 309 sq feet is a typical master bedroom. 8 foot ceilings used to be the norm, but 9 feet ceilings in many rooms are in vogue. Call it 2700 cubic feet, or 76,455 L or so. (76.455 m^3) Let's make it 8 hours, or 28,800 seconds. You said we, so let's have two people in the room.

0.005*28,800*2 = 288 L of CO2 exhaled.

CO2's density at STP is ~2.0 kg/m^3. 2 kg * 10^6 mg per kg * 288 L * (1 m^3/1000 L) = 576,000 mg.

Now spread that CO2 over the 76.455 m^3 of the room. I get 7,533 mg/m^3. Less than the 8hr TWA, but getting uncomfortably close. You'd probably notice it.

Obviously this is a gross simplification. I wonder how much the humidity would rise in this environment?

Last edited by Gray Ghost; 09-06-2019 at 04:03 PM.
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Old 09-06-2019, 04:01 PM
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There is some evidence that local build up of carbon dioxide in well sealed bedrooms has negative effects. I don't know of any good scientific studies, but here are three articles from Scott Alexander, who become interested and also asked his internet followers to conduct a non-scientific experiment regarding it. The results are, at least, interesting. I leave it to our doctors and scientists here to comment on the results. Scott is both a medical doctor and psychiatrist.

Thin Air explores apparent links between altitude-related (and possibly O2) obesity levels.

Open Door Policy discusses localized effects of well sealed rooms and CO2 buildup on mental health and well-being.

Nighttime ventilation survey is a followup of the survey results from his followers, who were instructed to try various ventilation methods and report back.

None of this is deep science and math, and I found them all quite readable. Hope it sheds some light, or at least shows other paths to investigate.

Edit: Ninja'd by Gray Ghost with real science. I defer to his math on this, but still find the SSC articles interesting.

Last edited by pullin; 09-06-2019 at 04:03 PM.
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Old 09-06-2019, 04:11 PM
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Originally Posted by pullin View Post
There is some evidence that local build up of carbon dioxide in well sealed bedrooms has negative effects. I don't know of any good scientific studies, but here are three articles from Scott Alexander, who become interested and also asked his internet followers to conduct a non-scientific experiment regarding it. The results are, at least, interesting. I leave it to our doctors and scientists here to comment on the results. Scott is both a medical doctor and psychiatrist.

Thin Air explores apparent links between altitude-related (and possibly O2) obesity levels.

Open Door Policy discusses localized effects of well sealed rooms and CO2 buildup on mental health and well-being.

Nighttime ventilation survey is a followup of the survey results from his followers, who were instructed to try various ventilation methods and report back.

None of this is deep science and math, and I found them all quite readable. Hope it sheds some light, or at least shows other paths to investigate.

Edit: Ninja'd by Gray Ghost with real science. I defer to his math on this, but still find the SSC articles interesting.
I'd be interested if the BMI and altitude stuff also was true at places like Scott Station at the South Pole. I've read that the altitude (9300 feet) has effects like wounds not healing readily, listlessness, and other physiological and psychological effects. Though I doubt that's due to CO2 buildup so much as mild hypoxia.

Edit: Oooh, here's a large pool of people to look at: modern nuclear submariners. Don't they run the atmosphere in a modern nuke at slightly hypoxic levels? I'm sure they keep the CO2 in check, but I'd bet it's still above ambient in the environment on the surface. And the Navy's been doing it for 60 years now, with a broad cross section of male individuals.

Thank you for the compliment on the math, but it's obviously a gross oversimplification of the problem. I'd been curious about that kind of math ever since reading about submerged submarines in WW2 and CO2 buildup in that environment. I don't have the cites handy, but I'm really sure it's the CO2 that kills there, and not depletion of O2. Painful way to go, too.

For real-world numbers, just how sealed is the modern bedroom in a Western home? I mean is there 1 change of air in 8 hours, 1/2 an air change, several air changes? The cited references in the article from Indoor Air I mentioned probably have the answer, but that would involve work.

Last edited by Gray Ghost; 09-06-2019 at 04:14 PM.
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Old 09-06-2019, 04:18 PM
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I was recently surprised when I left a lit deodorizing candle burning in my Jeep and returned a few hours later to find the candle no longer burning. I wouldn't have thought my vehicle was that well sealed.
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Old 09-06-2019, 06:11 PM
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Originally Posted by Procrustus View Post
Nitpick: As I understand it, it's not the lack of Oxygen that would kill you, but the build up of Carbon Dioxide.

(I don't know the answer to the question, but I bet NASA does.)

Huh. This strikes me as strange. I mean, I know we exhale CO2, but I thought it was just a matter of disposing of a waste product we have no use for.

This sounds more like carbon dioxide should be considered a toxic gas, that inhaling it does something bad to you, biologically, not just takes up volume that could be more usefully filled with oxygen.
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Old 09-06-2019, 06:19 PM
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Originally Posted by Gray Ghost View Post
From articles such as this one, Carbon dioxide generation rates for building occupants, in Indoor Air. 2017 Sep; 27(5): 868879, a general rate of CO2 generation per adult human in 0.005 L/s, at a typical ventilation rate of 7.5 L/s. CO2 has a variety of toxic concentrations, from 100,000 PPM, or 10%, immediately dangerous to life, to 30 minutes at 50,000 PPM resulting in intoxication, to a 8 hour total weighted average of 5,000 PPM. All from this reference, NIOSH's page on CO2. The PPM are listed as weight of CO2 per cubic meter. (listed as mg/m^3) at the reference.

The 8 hour TWA is 9,000 mg/m^3

How big is your bedroom and how long are you sleeping shut in?

Creditdonkey seems to think 309 sq feet is a typical master bedroom. 8 foot ceilings used to be the norm, but 9 feet ceilings in many rooms are in vogue. Call it 2700 cubic feet, or 76,455 L or so. (76.455 m^3) Let's make it 8 hours, or 28,800 seconds. You said we, so let's have two people in the room.

0.005*28,800*2 = 288 L of CO2 exhaled.

CO2's density at STP is ~2.0 kg/m^3. 2 kg * 10^6 mg per kg * 288 L * (1 m^3/1000 L) = 576,000 mg.

Now spread that CO2 over the 76.455 m^3 of the room. I get 7,533 mg/m^3. Less than the 8hr TWA, but getting uncomfortably close. You'd probably notice it.

Obviously this is a gross simplification. I wonder how much the humidity would rise in this environment?

You know, I don't speak math, so I'm not sure I follow the details, but it's impressive and sexy when others sling the numbers. (Ooops, was that harassment? Sorry!)


What brought this subject to my mind is how attitudes change over time. My father talked about how his mother insisted that there be an open window in the bedroom each night, regardless of temperature or rain or even a blizzard. He hated it (damned cold) and didn't impose the rule in his household. And now one of his granddaughters is getting some special sealing plastic layer added to most of the windows in her house. She's doing it to cut down on heating bills (older, drafty house) but still .... I imagine her great grandmother would have a fit if she'd known.
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Old 09-06-2019, 08:35 PM
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I'm pleased that this question got more consideration that the one from the guy who asked here about sleeping in a car Because I always thought that the response to that question was a little less convincing than the response shown here.

(Sorry, slow internet means searching is painful)
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Old 09-06-2019, 09:10 PM
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What brought this subject to my mind is how attitudes change over time.
People can get quite superstitious about this sort of thing

https://en.wikipedia.org/wiki/Fan_death
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Old 09-07-2019, 12:03 AM
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My third post ever on these forums was to ask a similar question! Interestingly, the last poster in that thread speculated that the increase in carbon dioxide would probably kill you before the lack of oxygen.

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Originally Posted by pullin View Post
There is some evidence that local build up of carbon dioxide in well sealed bedrooms has negative effects. I don't know of any good scientific studies, but here are three articles from Scott Alexander, who become interested and also asked his internet followers to conduct a non-scientific experiment regarding it. The results are, at least, interesting. I leave it to our doctors and scientists here to comment on the results. Scott is both a medical doctor and psychiatrist.
Nitpick: a psychiatrist is a medical doctor. That would be like saying "Scott is both a medical doctor and a cardiologist."

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Huh. This strikes me as strange. I mean, I know we exhale CO2, but I thought it was just a matter of disposing of a waste product we have no use for.

This sounds more like carbon dioxide should be considered a toxic gas, that inhaling it does something bad to you, biologically, not just takes up volume that could be more usefully filled with oxygen.
If you were placed into totally sealed room with zero oxygen--say, 100% carbon dioxide or 100% nitrogen at standard temperature and pressure--the lack of oxygen would certainly kill you before the buildup of CO2 became appreciable. However, there are conditions, like COPD, that prevent you from getting rid of CO2 fast enough, leading to hypercapnia, or elevated blood CO2 levels. Blood is an aqueous solution, and CO2 in an aqueous solution exists in equilibrium with carbonic acid. So too much CO2 in your blood makes your blood too acidic, a condition called respiratory acidosis, which if untreated can lead to shock, in which your major organs start to shut down, leading to death.
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Old 09-07-2019, 02:06 AM
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Scott is both a medical doctor and psychiatrist.
Is there any evidence for this other than Scott's own claims?
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Old 09-07-2019, 03:23 AM
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All psychiatrists are medical doctors. Scott Alexander's About page does not mention his academic background or license(s), though, just that he is a psychiatrist on the US West Coast.

Last edited by friedo; 09-07-2019 at 03:23 AM.
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Old 09-07-2019, 06:26 AM
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Originally Posted by Gray Ghost View Post
From articles such as this one, Carbon dioxide generation rates for building occupants, in Indoor Air. 2017 Sep; 27(5): 868–879, a general rate of CO2 generation per adult human in 0.005 L/s, at a typical ventilation rate of 7.5 L/s. CO2 has a variety of toxic concentrations, from 100,000 PPM, or 10%, immediately dangerous to life, to 30 minutes at 50,000 PPM resulting in intoxication, to a 8 hour total weighted average of 5,000 PPM. All from this reference, NIOSH's page on CO2. The PPM are listed as weight of CO2 per cubic meter. (listed as mg/m^3) at the reference.

The 8 hour TWA is 9,000 mg/m^3

How big is your bedroom and how long are you sleeping shut in?

Creditdonkey seems to think 309 sq feet is a typical master bedroom. 8 foot ceilings used to be the norm, but 9 feet ceilings in many rooms are in vogue. Call it 2700 cubic feet, or 76,455 L or so. (76.455 m^3) Let's make it 8 hours, or 28,800 seconds. You said we, so let's have two people in the room.

0.005*28,800*2 = 288 L of CO2 exhaled.

CO2's density at STP is ~2.0 kg/m^3. 2 kg * 10^6 mg per kg * 288 L * (1 m^3/1000 L) = 576,000 mg.

Now spread that CO2 over the 76.455 m^3 of the room. I get 7,533 mg/m^3. Less than the 8hr TWA, but getting uncomfortably close. You'd probably notice it.

Obviously this is a gross simplification. I wonder how much the humidity would rise in this environment?
What about the starting level of CO2? You need to add the 288L to the amount of CO2 already in the room when the door shut. I think it might make an appreciable difference.
I think the starting level is 30.6L of CO2?

Last edited by Bear_Nenno; 09-07-2019 at 06:30 AM.
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Old 09-07-2019, 06:45 AM
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All psychiatrists are medical doctors. Scott Alexander's About page does not mention his academic background or license(s), though, just that he is a psychiatrist on the US West Coast.

Sorry, didn't explain it well.

IIRC, in one of his articles he detailed how he first became a general practitioner, discovered he hated it, then returned to school to become a psychiatrist.
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Old 09-07-2019, 07:11 AM
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I was recently surprised when I left a lit deodorizing candle burning in my Jeep and returned a few hours later to find the candle no longer burning. I wouldn't have thought my vehicle was that well sealed.
my husband likes to leave the ventilation system off in our plug in/hybrid car to save electricity (and drive farther before the gas engine fires up). I hate this, and the car feels stuffy to me in about 3-5 minutes. But it must have some passive ventilation as he's survived long trips without turning it on.

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Huh. This strikes me as strange. I mean, I know we exhale CO2, but I thought it was just a matter of disposing of a waste product we have no use for.

This sounds more like carbon dioxide should be considered a toxic gas, that inhaling it does something bad to you, biologically, not just takes up volume that could be more usefully filled with oxygen.
Carbon dioxide and oxygen are both gases that we need in the right concentration. Carbon dioxide is actually the "need to breathe" trigger. With none of it there'd be a risk of forgetting to take your next breath. A little too much and it feels stuffy and uncomfortable. Much too much can kill you, and (having seen hamsters killed that way) it's not a nice way to go.

Oxygen is extremely reactive, and too much can oxidize stuff that was supposed to stay the way it was. Preemies with undeveloped lungs are given supplemental oxygen, and i think there used to be a problem with them going blind from it. I'm general, I think too much oxygen can "age" you.

I have a related question: if CO2 levels continue to rise, at what point does "fresh air" start to feel stuffy to us? When do wealthy people start running CO2 removing devices in their living space? When do employers do that to maintain productivity? Might these happen in our lifetime?
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Old 09-07-2019, 08:08 AM
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Scott Alexander's About page does not mention his academic background or license(s), though, just that he is a psychiatrist on the US West Coast.
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IIRC, in one of his articles he detailed how he first became a general practitioner, discovered he hated it, then returned to school to become a psychiatrist.
So I guess the answer to my question is, "No, there is no evidence corroborating Scott Alexander's claim to be a doctor." In that case, why are we relying on him as a source of medical knowledge for this thread?

Last edited by psychonaut; 09-07-2019 at 08:10 AM.
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Old 09-08-2019, 05:05 PM
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Last weekend I toured a WWII era sub. If I remember what the tour guide said, they ran low on oxygen before electricity. There were compressed O2 tanks throughout the vessel in case they needed to stay down past about 30 hours. Otherwise they surfaced nightly if possible. I don't know the ship volume but that divided among 85 or so people for 30 hours would be a start.
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Old 09-08-2019, 05:47 PM
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What about the starting level of CO2? You need to add the 288L to the amount of CO2 already in the room when the door shut. I think it might make an appreciable difference.
I think the starting level is 30.6L of CO2?
True, I did forget that. No idea what normal ambient CO2 concentration, so we'll use your volume. Which should bump things by about 10 percent, and put the final concentration over the 8hr TWA. Not in violation, since the 8hr TWA for our simple model should be half of that, but again, we'd probably notice it: 'Is it getting stuffy in here?'
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Old 09-08-2019, 05:50 PM
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Last weekend I toured a WWII era sub. If I remember what the tour guide said, they ran low on oxygen before electricity. There were compressed O2 tanks throughout the vessel in case they needed to stay down past about 30 hours. Otherwise they surfaced nightly if possible. I don't know the ship volume but that divided among 85 or so people for 30 hours would be a start.
Depends on how energetic they were getting with the props. I want to say a flank bell submerged will drain the batteries from full in 90 minutes or so. Then again, the speed difference between flank and 1/3 or 2/3 might be the difference between making it away from the destructive radius of the depth charge or not...

I want to say I remember crews opening cans of CO2 absorbant to increase submerged time.
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Old 09-09-2019, 05:40 AM
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Huh. This strikes me as strange. I mean, I know we exhale CO2, but I thought it was just a matter of disposing of a waste product we have no use for.

This sounds more like carbon dioxide should be considered a toxic gas, that inhaling it does something bad to you, biologically, not just takes up volume that could be more usefully filled with oxygen.
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.
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Old 09-09-2019, 07:10 AM
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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.

Last edited by ftg; 09-09-2019 at 07:11 AM.
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Old 09-09-2019, 07:24 AM
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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.
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Old 09-09-2019, 08:09 AM
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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.
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.
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Old 09-09-2019, 04:34 PM
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....Edit: Oooh, here's a large pool of people to look at: modern nuclear submariners. Don't they run the atmosphere in a modern nuke at slightly hypoxic levels? I'm sure they keep the CO2 in check, but I'd bet it's still above ambient in the environment on the surface. And the Navy's been doing it for 60 years now, with a broad cross section of male individuals.
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.
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Old 09-10-2019, 10:20 AM
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So I guess the answer to my question is, "No, there is no evidence corroborating Scott Alexander's claim to be a doctor." In that case, why are we relying on him as a source of medical knowledge for this thread?
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.

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Sorry, didn't explain it well.

IIRC, in one of his articles he detailed how he first became a general practitioner, discovered he hated it, then returned to school to become a psychiatrist.
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.
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Old 09-10-2019, 03:03 PM
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Beyond that, it's my understanding that his real-life identity is pretty well-known among his readership. I know his full name [] Not sure why you're so doubtful of him.
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.)
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Old 09-11-2019, 04:47 AM
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Last weekend I toured a WWII era sub. If I remember what the tour guide said, they ran low on oxygen before electricity. There were compressed O2 tanks throughout the vessel in case they needed to stay down past about 30 hours. Otherwise they surfaced nightly if possible. I don't know the ship volume but that divided among 85 or so people for 30 hours would be a start.
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.
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Old 09-11-2019, 05:36 AM
Machine Elf is offline
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Quote:
Originally Posted by puzzlegal View Post
my husband likes to leave the ventilation system off in our plug in/hybrid car to save electricity (and drive farther before the gas engine fires up). I hate this, and the car feels stuffy to me in about 3-5 minutes. But it must have some passive ventilation as he's survived long trips without turning it on.
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.

Quote:
Originally Posted by Gray Ghost
Edit: Oooh, here's a large pool of people to look at: modern nuclear submariners. Don't they run the atmosphere in a modern nuke at slightly hypoxic levels?
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?
  #30  
Old 09-11-2019, 05:58 AM
Machine Elf is offline
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Originally Posted by Gray Ghost View Post
From articles such as this one, Carbon dioxide generation rates for building occupants, in Indoor Air. 2017 Sep; 27(5): 868879, a general rate of CO2 generation per adult human in 0.005 L/s, at a typical ventilation rate of 7.5 L/s. CO2 has a variety of toxic concentrations, from 100,000 PPM, or 10%, immediately dangerous to life, to 30 minutes at 50,000 PPM resulting in intoxication, to a 8 hour total weighted average of 5,000 PPM. All from this reference, NIOSH's page on CO2. The PPM are listed as weight of CO2 per cubic meter. (listed as mg/m^3) at the reference.

The 8 hour TWA is 9,000 mg/m^3

How big is your bedroom and how long are you sleeping shut in?

Creditdonkey seems to think 309 sq feet is a typical master bedroom. 8 foot ceilings used to be the norm, but 9 feet ceilings in many rooms are in vogue. Call it 2700 cubic feet, or 76,455 L or so. (76.455 m^3) Let's make it 8 hours, or 28,800 seconds. You said we, so let's have two people in the room.

0.005*28,800*2 = 288 L of CO2 exhaled.

CO2's density at STP is ~2.0 kg/m^3. 2 kg * 10^6 mg per kg * 288 L * (1 m^3/1000 L) = 576,000 mg.

Now spread that CO2 over the 76.455 m^3 of the room. I get 7,533 mg/m^3. Less than the 8hr TWA, but getting uncomfortably close. You'd probably notice it.
To more clearly show that CO2 buildup is a bigger problem than an oxygen shortage:

A human consumes about 550 liters of pure O2 per day.

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.
  #31  
Old 09-11-2019, 02:55 PM
kaylasdad99 is offline
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Quote:
Originally Posted by kayaker View Post
I was recently surprised when I left a lit deodorizing candle burning in my Jeep and returned a few hours later to find the candle no longer burning. I wouldn't have thought my vehicle was that well sealed.
Maybe there was a stench in your Jeep that was just so powerful the candle gave up...
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