Is it realistic to have a natural oxygen source in a cave? I am writing a story, about people who live underground in a land that is freezing outside. Heat is taken care of by geothermally heated groundwater. How do I make it realistic for these people to breath in the caves?

  • $\begingroup$ If you mean is there a mineral that emits oxygen- I don't think so. Plants will easily give them oxygen and equally absorb carbon dioxide but there is problem- plants give off slightly toxic chemicals- a big problem in enclosed space. You need the air to be cleansed by passing through soil- microbes destroy these toxic chemicals- there are underground ecosystems which are totally cut off from the surface. $\endgroup$ Dec 30, 2013 at 6:25
  • $\begingroup$ There are chemical reactions that could make oxygen if you have enough power to drive them. Or you could use plants with enough lighting to drive photosynthesis. $\endgroup$
    – matt_black
    Dec 30, 2013 at 12:30
  • $\begingroup$ Yes, it is. You can allow outside air to circulate through the cave. $\endgroup$
    – permeakra
    Jan 29, 2014 at 22:11

1 Answer 1


According to this page, the CO2 buildup in the cave might also be a problem.

But, if there was a river that ran on the surface, then oxygen and nitrogen would dissolve into the water. The stream could then pass into the cave and release some of the dissolved oxygen into the oxygen deficient environment in the cave. It would also remove the CO2. Of course, if the surface of the planet is frozen, then the river would have to avoid freezing somehow. But perhaps there is a hot spring on the surface.

My intuition is that the rate of oxygen dissolving out of the water would be very slow and it could be increased by increasing the surface area of the water. In the human lungs, there are many, many tiny branches (Alveoli) that allow the lungs to have a huge surface area so that the slow diffusion of oxygen from the air into our blood can go fast enough for us to survive. Perhaps the cave-people can accomplish something similar if they let their oxygen-rich stream pass over a tall, broad waterfall that would cause the river to break up into tiny droplets, thereby increasing the surface area. This has the added benefit of looking super cool in case your story gets made into a movie :)

Other options: 1) they could generate electricity and use that to make hydrogen and oxygen from water. 2) http://www.mpg.de/621120/pressRelease201003241?filter_order=L

  • $\begingroup$ Thank's, that was a lot of help. I like you're first idea the best. $\endgroup$
    – John Doe
    Dec 31, 2013 at 1:04

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