I finally figured out that the nitrogen gas is used for the MELFI (minus eighty freezers). I can't figure out what the argon would be used for, though I can see how helium might be useful for refrigeration also. But what are these actually used for, if anything?

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    $\begingroup$ Nitrogen is used to dilute the oxygen in the atmosphere. It is not a 100% O2 environment on the ISS. They generate oxygen from water, but need additional gasses to get away from 100% Oxygen and the fire risks that entails. $\endgroup$
    – geoffc
    Jul 22 '16 at 19:46
  • $\begingroup$ For the OP: What is the source of your information about these gases being onboard the ISS? $\endgroup$ Jul 22 '16 at 20:25
  • $\begingroup$ Well, for example: books.google.com/… (but you can also find them in the SSP interface documents). $\endgroup$
    – Translunar
    Jul 23 '16 at 21:16
  • $\begingroup$ That document says they are supplied for experiments. $\endgroup$ Jul 24 '16 at 0:42
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    $\begingroup$ @OrganicMarble Do you know of any experiments that actually make use of them? And is there some reason they aren't just included in those payloads, but are instead part of the module's infrastructure? It seems a bit over-designed, but more importantly arbitrary — why these gases but not others? (Also, I thought argon was not allowed on ISS, since it's not scrubbable.) $\endgroup$
    – Translunar
    Jul 25 '16 at 13:55

Helium is used for cryo-storage, and enables freezers that are much colder than those making use of nitrogen.

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    $\begingroup$ Do you have any references for this answer? $\endgroup$ Apr 3 '17 at 17:57
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    $\begingroup$ @JamesJenkins Personal communication with payload providers and CASIS. $\endgroup$
    – Translunar
    Apr 4 '17 at 15:44
  • $\begingroup$ This is very cryptic. I don't understand what this one-sentence answer is saying. Are we talking about liquid helium and liquid nitrogen? And if so, why are liquid helium temperatures needed? $\endgroup$
    – user687
    Jun 3 '17 at 2:54

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