In this answer I said:

In an emergency a pressurized tank of oxygen gas can be an immediate source of oxygen to pressurize the station, and (possibly) other thinks such as tanks for suits. But for a steady, lower rate supply of oxygen, electrolysis of plain old water works quite well, considering there is plenty of electrical power.

Is this how the various space suit air supply systems are provided with oxygen, now that NORS is the preferred method for oxygen transport and storage on the ISS?

Is it mixed with other gases first, or do the suits use pure oxygen at reduced pressure?


1 Answer 1


Yes, O2 for the EMUs must come either from NORS or from the external O2 tanks. There is no other supply of high pressure O2 on the ISS. See here for an overview of the O2 and N2 systems.

The EMUs use pure O2, no other gas is mixed in. Refer to Suited For Spacewalking for the best overview of the EMU I know of. It lists the regulated suit pressure as 29.6 kilopascal (4.3 psi).

  • $\begingroup$ Thanks for the speedy, informative, thorough, and concise answer! I've linked this here - is that information correct or in need of fine tuning? $\endgroup$
    – uhoh
    Commented Dec 7, 2016 at 4:15

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