In my fantasy world, much of the society takes place in floating cities or airships which rest at 30,000 feet in the air. As you may know, humans can have trouble breathing at such heights, so how would these people cope with the air pressure and the loss of oxygen (does not have to be filters)? It is also necessary for my story that whatever the means is, it cannot be magical.

Note that this civilization has the technology to that of Imperial China. Also note that although they live in the air, they have access to all other resources as well.

Leave any questions below.

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    $\begingroup$ Air filters aren't the problem, air pressure is the problem $\endgroup$ – anon Nov 8 '17 at 19:44
  • $\begingroup$ If everybody must use face masks to breathe, perhaps they communicate using sign languages. $\endgroup$ – user535733 Nov 8 '17 at 19:46
  • $\begingroup$ @anon might make a second question for that, if I add two questions into one then it'll probably get closed. $\endgroup$ – Unhappymarshmellow Nov 8 '17 at 19:47
  • $\begingroup$ @user535733 Would a face mask be enough (I seriously don't know)? $\endgroup$ – Unhappymarshmellow Nov 8 '17 at 19:49
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    $\begingroup$ @annon Sorry, I think it's better now, tell me if I'm wrong. $\endgroup$ – Unhappymarshmellow Nov 8 '17 at 19:56

Filters will never fix this problem. The problem is getting oxygen into your blood.

Humans can live down to about 40% of sea level pressure. (356 millibars) That's called the Death Zone in mountain climbing. (~8000m on earth). With an oxygen mask, you can survive down to the Armstrong limit, at about 6% of sea level (47 millibars).

So, your medieval civilization needs to produce pure oxygen, bottle it and distribute it. That does not sound like medieval technology. Maybe someone with modern understanding of chemistry would be able to do it with medieval tools, but I would still call that modern technology.


Well, if you restrict yourself to rocky worlds, you need a world that is much larger, but also less dense. Air pressure will drop off a lot slower than on a smaller denser world. That might give you problems with a lack of metals, though.

If you don't mind a gas giant world, the sky's the limit.

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    $\begingroup$ Well punned my friend, well punned... $\endgroup$ – Unhappymarshmellow Nov 8 '17 at 20:10
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    $\begingroup$ Also, gas giant fantasy world, not a bad idea rubs hands maniacally $\endgroup$ – Unhappymarshmellow Nov 8 '17 at 20:16

If they can seal the lifting gas they can seal the living space.

Imperial china was well acquainted with bellows for metal work, it is not a stretch that they could be adapted to provide the pressure for the city if sufficient energy could be found.

  • $\begingroup$ I upvoted simply for that duh pointer, $\endgroup$ – anon Nov 8 '17 at 20:26

Genetic Adaptations

Sherpas have evolved to survive at high altitudes coping with both less pressure and less oxygen. In this instance you should try and aim for the same.

There are limits to this (The Armstrong zone for a finite one), though im not entirely sure how to math it. Basically, there is an absolute minimum oxygen concentration necessary for a human to maintain a metabolism and that would be your threshold. At a certain high altitude (way beyond Everest) this becomes impossible. But you could slap out bunches of adaptations to raise your current ceiling to that point starting with improving respiratory efficiency which humans have poor marks in.

Dietary Options

You could editorially create a plant that contains chemicals and enzymes to improve the oxygenation of your people. For instance DEX is a chemical climbers inject themselves with to survive by enhancing their oxygenation capacity. You could create herbal equivalents of this or better. Would fit into this periods technology and attachment to nature.


This is the least applicable because it stretches the periods technology. There are historical examples of pistons in the era which are what you need to make pressure canisters (of air). This is also slightly infeasible for an aireal city using archaic technology. (but don't underestimate the ancient Chinese, afterall they did have public running natural gas lines)

  • $\begingroup$ Unfortunately, the cited altitude is beyond the range even Sherpas can handle.... $\endgroup$ – guildsbounty Nov 8 '17 at 20:16
  • $\begingroup$ @guildsbounty no the cited limit is 30K feet which is also 30k feet below the Armstrong zone so my answer is fine $\endgroup$ – anon Nov 8 '17 at 20:18
  • $\begingroup$ FYI, the sherpas stopped evolving their altitude traits because their settlement is in a fixed position. If they tried to progressively settle higher they would continue their evolution. $\endgroup$ – anon Nov 9 '17 at 13:50
  • $\begingroup$ actually, Scientists say this: "There is a limit to the level of adaptation; mountaineers refer to the altitudes above 8,000 metres (26,000 ft) as the "death zone", where it is generally believed that no human body can acclimatize." They might be wrong, of course...but that's the current stance. $\endgroup$ – guildsbounty Nov 9 '17 at 14:58
  • $\begingroup$ Right, no human body can currently acclimatize to that altitude even the sherpas, BUT people can survive that altitude which means biologically it isn't unconquerable. If over many generations the Sherpas progressively moved their settlement higher, their genepool would be effectively selectively culled thus refining their adaptation. Because we can currently biologically reach that altitude the possibility exists that we could adapt to survive it given enough genetic attempts. $\endgroup$ – anon Nov 9 '17 at 17:13

How did they get their city up that high and floating if their technology level equals to that of Imperial China? And how do they have access to all other resources? Can they just teleport off it? And without using magic?

The only logical explanation to me is that some aliens with high tech built this city originally and left it there. The aliens luckily require all the same essentials for life as humans. All their needs are provided by unseen technology, all the processes and maintenance are automated and their energy sources are infinite and/or renewable.


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