Basically Group A Breaths in water and out Hydrogen, Group B in Hydrogen and out water like us and trees but water and hydrogen instead of oxygen and carbon dioxide. Would the hydrogen in the atmosphere cause Firestorms? plenty of oxygen is around. the humidity is very high would there be Storms raging in the sky like a Thunder Storms? but with burning hydrogen instead of Water vapor Thanks

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    $\begingroup$ How much oxygen is around? $\endgroup$ Sep 24, 2019 at 22:49
  • $\begingroup$ Hi WindWelder, and welcome to Worldbuilding! We could use a little more information to help you get the best answers, because it seems like we already get firestorms on Earth without the extra hydrogen. Are you worried about your atmosphere as a whole igniting? Or whether the fire storms we get on Earth will be larger with the extra hydrogen? I suspect we'll need an atmospheric composition breakdown to give you accurate answers. $\endgroup$
    – Dubukay
    Sep 24, 2019 at 23:08
  • $\begingroup$ I Would like the storms to happen but not Burn the whole atmosphere. I would like humans to be able to walk on the surface without Hazmats if they cant then that's okay. The content of the Atmosphere is up for grabs. $\endgroup$
    – WindWelder
    Sep 24, 2019 at 23:20
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    $\begingroup$ If the atmosphere is oxygen dominated, there will be no free hydrogen. If the atmosphere is hydrogen dominated, there will be no free oxygen. Why? They will react as soon as the minor gas is added, and it will not be able to accumulate. $\endgroup$ Sep 24, 2019 at 23:30
  • $\begingroup$ Greetings and welcome to the madhouse! Your query is in the close queue because it's been flagged as a duplicate. Please check out the linked query to see if that answers your question. If not, please edit your query in order to clarify why it's different and what it is you're looking for that isn't addressed in the other question. In the mean time, please study the tour and the help center so you can get a good idea how this forum works! $\endgroup$
    – elemtilas
    Sep 25, 2019 at 0:18

2 Answers 2


Hydrogen will burn at only 4% concentration, but you will need 18-60% concentration for an explosion. However, you will not reach this limit unless your creatures are in an enclosed space. Hydrogen is much lighter than air and will simply float away before you get to this level.

With storms raging, the excess hydrogen may increase the flammability of objects, but ultimately all of that will wind will only further dilute the already diluted hydrogen gas.


Frame Challenge

As pointed out in the comments, free oxygen or free hydrogen cannot stably exist in an atmosphere dominated by the other gas. Something less reactive, however, has possibilities.

Enter methane.

The Fire Swamps

Due to distance from the solar system's primary star and a thick, water-rich atmosphere, temperatures on Flareworld are remarkably consistent, resulting in a belt of swamps reaching from high to low latitudes all around the planet.

Dominating a particular strata of those swamps is a variety of bacteria which aggressively breaks down dead plant matter, excreting methane at a biologically astonishing rate. These bubbles of methane build pressure beneath the surface of the swamp, occasionally breaking the surface with a distinctive "popping" noise. Mostly the bubbles contribute to the insulating atmosphere of the planet, but the frequent lightning storms often ignite "methane bursts" with predictably spectacular effects.

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(Whether the limited seas on this planet are populated by Shrieking Eels is quite a different story.)

  • $\begingroup$ Conversely, the Hydrogen-Methane option allows for a methanogenic biology for native organisms. It would not produce firestorms however. $\endgroup$ Sep 24, 2019 at 23:48

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