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I wonder if it is possible to install artificial equipment that would exhaust oxygen into air in otherwise CO2 atmosphere so that locally people could breath in open air without any kind of tent or dome?

I mean, imagine a public park with walking lanes with benches and there are oxygen holes in the pavement that constantly inject oxygen into air so that people can party in the open air without masks.

Is that realistic?

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    $\begingroup$ The thing is, the human respiratory system (and the respiratory system of vertebrates in general) cannot tolerate more than 7% to 10% carbon dioxide in the air, no matter how much oxygen is there. (That because of how hemoglobin works.) Between 1% and 7% CO2 won't kill you, but it will make you dizzy. To be safe and have a pleasant experience, CO2 must be below 0.5%. Now, gases mix freely. Even if you have machines producing oxygen continuously, some of the surrounding CO2 will mix in the atmosphere of the park. $\endgroup$ – AlexP May 9 '20 at 12:58
  • $\begingroup$ @AlexP what about a Nitrogen atmosphere and oxygen being taken from water? $\endgroup$ – Anixx May 9 '20 at 13:09
  • $\begingroup$ We live in an atmosphere which is a mixture of nitrogen and oxygen (with some argon and water vapor), so we already know that it works. $\endgroup$ – AlexP May 9 '20 at 13:14
  • $\begingroup$ @AlexP My question was that the oxygen could flee away more quickly than replenished (I think this depends on whether the air is heavier than oxygen and winds though). $\endgroup$ – Anixx May 9 '20 at 13:16
  • $\begingroup$ Depends on how much oxygen is produced by the machines. Just turn the machines up until they output enough oxygen to enable humans to breathe in the area of interest. (Note that gases mix freely, so the machines must generate oxygen continuously. As soon as they stop, the concentration of oxygen in the park will begin to decrease, because it will mix with surrounding nitrogen.) And yes, wind doesn't help at all. $\endgroup$ – AlexP May 9 '20 at 13:20
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An atmosphere with 7% CO2 is already toxic for humans. 80% CO2 will be therefore lethal.

That apart, diffusing oxygen in a local way it is surely possible, however mind that any local excess would result in an increased fire hazard. Moreover, going from 0 to 20% concentration requires a different flow than what is needed to replace what humans consume with respiration.

It's probably safer to provide each person with an individual bottle, delivering oxygen directly in their nostrils.

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  • $\begingroup$ 7% of CO2 is toxic at normal pressure. What really matters is partial pressure so if the atmosphere has pressure 10% of Earth's, the toxic dose would be 70% of CO2 (if I am correct) $\endgroup$ – Anixx May 9 '20 at 13:18
  • $\begingroup$ @Anixx: Humans need at lest 0.1 atm partial pressure of oxygen, so if the pressure is 0.1 atm then the air must be 100% oxygen for the humans to survive. $\endgroup$ – AlexP May 9 '20 at 13:23
  • $\begingroup$ I meant if the air was 0.1 atm CO2 and half of it replaced, it should be bearable. $\endgroup$ – Anixx May 9 '20 at 13:28
  • $\begingroup$ @Anixx - nope. The O2 part has to be 0.1 atm to meet our needs. Partial pressure. If the entirety of the atmosphere is O2 and it is 0.1 atm, ok, If the entirety of the atmosphere is 0.1 and you replace half ,that is 0.05 atm O2; not enough. $\endgroup$ – Willk May 9 '20 at 18:18
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Temperature differentials.

o2 evaporating

https://www.youtube.com/watch?v=hbAbmI9iA14

Depicted - a liquid oxygen tank vents, and the supercold gas produced hugs the ground. You can see it because it is making the moisture in the air condense. I hope no-one was having a smoke break during this; they would have gone thru their cigarettes fast.

You could do something like what you propose with a temperature differential - an open to the sky park in an alien environment. If you had your park walk sunken down, like a canal, you could flood it with cold oxygen and it would stay down there to some degree, rolling under and pushing up the hotter CO2. O2 is a lighter molecule than CO2 but cold gas is denser that hot gas. You could use that to produce your effect.

Truly you might want to use a cold mix of oxygen and nitrogen in case anyone wanted to smoke in the park.

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  • $\begingroup$ I think this must be the right answer. $CO_2$ is heavier than air, and will sink to the bottom if temperatures are equal. If the temperatures in OPs atmosphere are high, then cooling the gas in the park, and people wearing jackets, might give the desired effect. $\endgroup$ – AtmosphericPrisonEscape May 10 '20 at 21:22
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Dutch scientists already experimented with ultraviolet lasers that can split co2 into oxygen and carbon. But why do that when plant life can do it for you. In an atmosphere made of majority CO2, plants would grow like crazy. enter image description here

Algae and cyanobacteria would also proliferate in this environment.

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    $\begingroup$ Would these plants be producing enough oxygen (and consuming enough CO2) to allow humans to breathe freely? $\endgroup$ – F1Krazy May 12 '20 at 10:13

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