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How much oxygen for a person to survive in an air-tight enclosure? (2004)
- danielvf 11y agoIf you want to live in an air tight containers, you need to also be concerned about co2 buildup.
- jryan49 11y agoWouldn't the co2 buildup kill you first anyway?
- z92 11y agoCO2 buildup will kill him far before all the O2 has been used up. Even supplying fresh O2 into the room from a cylinder won't save him, unless someone finds a way to remove CO2 from the room.
- sjwright 11y agoIt's useful to remember the makeup of air: 78.1% nitrogen 20.9% oxygen 0.93% argon 0.039% carbon dioxide Carbon dioxide, in very approximate figures, is unpleasant at 0.5%, dangerous at 5%, fatal at 10%.
- Dylan16807 11y agoYou're going to be doing pretty badly with half the oxygen gone even if you had no CO2.
- oh_sigh 11y agoWhat about venting some of the rooms air to space, and then releasing some O2 into it?
- madaxe_again 11y agoCame to say precisely this. Before you run out of o2 the co2 levels will likely render you unconscious, and will potentially also suppress your breathing. I took a lungful (choked on the first breath, coughed, started really choking) of air heavy with co2 in a pub cellar once. Only because I fainted on top of the kegs above the co2 saturated air on the floor (leaky cylinder valve) am I here to tell you about it. Tastes like acidic metal and black velvet rushes in.
- masklinn 11y agoAn other fun danger of insufficiently aerated rooms: in wine countries, until cellars aeration became more widespread a huge danger was CO buildup in cellars from fermentation, to these days people regularly die during initial fermentation, and a warning you get is "if you see somebody unconscious at the bottom of the cellar stairs you do not go down to help, you call the firefighters, trying to help just ensures they have two bodies to retrieve".
- justinclift 11y agoSo, horror movies are realistic for once. If you see your friend lying dead in the cellar... GTFO of there, it really is zombies (or gas buildup of some variety) . :)
- adevine 11y agoThere are, sadly, lots of reports of farmers and their family members dying in manure pits due to a buildup of CO2 and methane. Someone goes in first and passes out, and then anyone else who tries to go in to save him suffers the same fate. In one case 5 members of a dairy farming family all died trying to save their father.
- mrfusion 11y agoWhat if you hold your breath to help?
- 11y ago
- johnernaut 11y agoThis can be alleviated with the use of CO2 scrubbers[0]. Basically you fill fan-powered canisters with minerals ("sodasorb" is a popular product used in the offshore diving industry), which absorbs CO2 from the atmosphere. That's not to say that you need to be able to remove and replace the minerals in the scrubbers every so often. [0] https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber
- junke 11y agoOut of curiosity, do you have an idea of the typical delay before saturating the filter? Do you have some pointer to space suits specification or something like this that I could read to have more information?
- msl 11y agoAccording to Wikipedia, "One gram of anhydrous lithium hydroxide can remove 450cm³ of carbon dioxide gas."[1] Also according to Wikipedia, a person produces some 1kg of the gas a day [2], which translates to roughly 550000cm³. That means around 1.2kg of lithium hydroxide per day per person. The Apollo 13 LM canisters were rated for some 56 hours for two persons, but could only support three for less than 35 hours. That seems to fall somewhere between 5 and 6 kilograms, and apparently includes the scrubbers of the space suits onboard. Each suit was designed to support life for 6 hours (+ 30 minutes of emergency reserves) [3] which means some 350 grams of lithium hydroxide. The longest EVA thus far lasted for just under 9 hours [4], for which you would need a bit more than 450 grams of lithium hydroxide. The Russian Orlan suits are designed to support life for between 5 and 7 hours [5]. An astronaut on an EVA might produce more carbon dioxide than the Wikipedia approximation, so you might want to round those numbers up. Edit: I am also not sure how close to the theoretical maximum that absorption capacity is, so the numbers might really be somewhat optimistic. [1] https://en.wikipedia.org/wiki/Lithium_hydroxide https://en.wikipedia.org/wiki/Lithium_hydroxide [2] https://en.wikipedia.org/wiki/Carbon_dioxide#Human_physiology https://en.wikipedia.org/wiki/Carbon_dioxide#Human_physiolog... [3] https://en.wikipedia.org/wiki/Apollo/Skylab_A7L https://en.wikipedia.org/wiki/Apollo/Skylab_A7L [4] https://en.wikipedia.org/wiki/Extravehicular_activity https://en.wikipedia.org/wiki/Extravehicular_activity [5] https://en.wikipedia.org/wiki/Orlan_space_suit https://en.wikipedia.org/wiki/Orlan_space_suit
- tblomseth 11y agoArguably, that was THE critical issue for crew survival after the Apollo 13 incident leading to the famous 'jury-rigged' CO2 scrubbing device improvised by the engineers on the ground 'Availability of lithium hydroxide (LiOH) for removing carbon dioxide presented a serious problem.'[1] [1] https://en.wikipedia.org/wiki/Apollo_13#Crew_survival_and_return_journey https://en.wikipedia.org/wiki/Apollo_13#Crew_survival_and_re...
- yathern 11y agoOn an unrelated note - I read your term 'jury-rigged' and was thouroughly confused for a good minute. It sounded right in my head, but reading it on paper (screen) it looked wrong. Except looking up 'jury rigged' led to results about... Juries being rigged. Eventually I realized that the term I was looking for is 'Jerry Rigged': http://www.merriam-webster.com/dictionary/jerry%E2%80%93rigged http://www.merriam-webster.com/dictionary/jerry%E2%80%93rigg... Which is 'probably a blend of jerry-built and jury-rigged', so now I don't know what to believe.
- codezero 11y agoThat's odd, the first two results for me when I search for jury rigged is a Google summary box with the definition and the Wikipedia article: https://en.wikipedia.org/wiki/Jury_rigging https://en.wikipedia.org/wiki/Jury_rigging Are you studying law or something, maybe Google is overly personalizing? :)
- dghughes 11y agoI got my parents a NetAtmo device it has an outside thermometer but also one for inside that also has a CO2 detector. It's amazing how often just my two parents plus one cat in a 5mx5m living room will cause it to reach near 1000ppm. At Christmas time with about eight people it easily hit 1000ppm very quickly. Nobody else knew but I was watching the readings and it was interesting to see how that point it seems stuffy so a window was opened for some fresh air. This is a 1970s single floor bungalow with forced air heating but no air exchange.
- lordnacho 11y agoI had a theory this was what caused me to feel really sleepy when attending lectures. Wasn't sure how to prove it, though of course it could make sense with the right figures plugged in.
- mrfusion 11y agoWould anyone be able to update his numbers accounting for co2 buildup? Are you thinking it would be a lot less time than he calculates?
- foobarbecue 11y agoYour result of "0.042 day" is also known as "an hour."
- jsilence 11y agoWould be nice if this calculation were in iPython notebook or Cruncher (https://www.cruncher.io/ https://www.cruncher.io/).
- mirimir 11y agoI'm reminded of A Pail of Air by Fritz Leiber.
- mrfusion 11y agoWhat about the scene from pirates of the Caribbean where they walk underwater in an upside down rowboat. Is that realistic?
- Chilinot 11y agoNot even in the slightest. Yes, i understand this was probably a joke, but still. That scene was pretty dumb.
- coldtea 11y agoActually there's nothing dumb about the scene, except that there would be an upward pressure on the boat (buoyancy). If that was overcome (e.g. with some weights or strings holding it down), it would be perfectly fine to breath in there for a while. So, aside from the buoyancy issue, not only it's not "dumb", but that's exactly how old "diving bells" worked. https://en.wikipedia.org/wiki/Diving_bell https://en.wikipedia.org/wiki/Diving_bell
- agentgt 11y agoReally... you take issue with some exaggeration in buoyancy physics over the undead pirates?
- chc 11y agoIt's pretty normal to be more bothered by casual violations of the way the world works than by fantasy elements. It's similar to the Uncanny Valley. With fantasy elements, our suspension of disbelief allows us to accept them as part of an alternate set of rules for the world. But when a part of the movie that seemed to be the same as the real world suddenly behaves differently, that can be off-putting and feel inconsistent. For example, if a character couldn't carry a small bucket of water but could carry a large man, many people would read that as an inconsistency rather than just accepting it.
- PhasmaFelis 11y agoI hate this argument. Fantasy movies are expected to be internally consistent. That means they follow the fantastical rules they set down, and they otherwise follow normal real-world rules. (Though I agree with coldtea that the PotC scene wasn't that bad.)
- dragonbonheur 11y agoTwenty thousand leagues under the sea had an interesting part about the same problem.
- tzs 11y agoA related question that might be interesting is in a container of a given volume that is perfectly sealed except for one hole to the outside air, and with no fans or other systems to encourage air exchange, how big does the hole need to be to keep oxygen levels high enough and CO2 levels low enough for survival indefinitely? My intuition at first says that it would need to be a big hole because there won't be much airflow since the pressure inside and outside will be the same. But that is looking at it wrong. It's the individual gases that matter. If CO2 is more concentrated inside than out, then there will be a net transfer of CO2 out. Similarly for O2 coming in. It's a diffusion problem, not an airflow problem, and I've got no usable intuition for that. A interesting variant would be to make the hole intermittent. Assuming that my house is perfectly sealed when the doors are closed, do the normal openings for my daily comings and goings provide sufficient time for enough O2 to diffuse in and CO2 to diffuse out to keep my inside air breathable?
- jpeanuts 11y agoThis is a question I've asked myself before too. Here's a back-of-envelope calculation which seems to suggest that diffusion alone will never be enough to keep someone alive inside a box. I'd be really interested to hear if someone can confirm or refute this. Let's assume CO2 transfer is entirely diffusion-limited, i.e. the worst-case of completely still air. The diffusive flux of some gas-component (per unit area per unit time) J is governed by concentration-gradient (dn/dx) multiplied by a magic diffusion coefficient D, which depends on the molecular properties of the gas. For CO2 in air D = 1.6e-5 m^2/s. Let's assume the gradient is linear so dn/dx = (n_{inside} - n_{outside}) / length. Now n_{outside) = 0.04% * 1 kg/m^3 = 4e-4 kg/m^3. We should decide what level of CO2 we can tolerate, 0.5% should be on the safe side, so n_{inside} = 5e-3 kg/m^3. Length is a bit trickier. If (a) we assume completely stagnant air inside and outside, length should be chosen as the size of the box ~1 m say. However if (b) we assume that inside and outside are pretty well-mixed individually, due by breathing, wind etc., then length should be about the depth of the hole, or thickness of the box-material, say 1 cm = 0.01 m. For case (a) CO2 leaves our box at a rate of about 7e-8 kg/s/m^2, for (b) 7e-6 kg/s/m^2. From the original article, a human breaths .84 kg of O2/day, let's estimate a production of 1kg CO2/day (the extra carbon atom can't be all that significant), or 1e-5 kg/s. To compute the area of hole needed to maintain 0.5% CO2, we just divide 1e-5 by J, to get the area. In case (a) we need an enormous area of 135 m^2, in (b) "only" 1.35 m^2. This seems to suggest that "air-holes" must work (if indeed they work at all) with air-flow. This doesn't necessary require an over- or under-pressure in the box - a suction can be generated by wind passing over a box with holes on both sides - this process would be far more efficient at restoring atmosphere than diffusion. But would be less reliable.
- mjw_byrne 11y agoWhoa whoa. This means Sunshine wasn't scientifically accurate?!