What's the normal leakage rate for a space suit?

For a modern (as in, the model is still in use today) EVA suit in normal condition, undamaged, etc.

If there is a wide variation in leak rates for different suit versions, national designs, etc. that would all be interesting detail for an answer.

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    $\begingroup$ In this question, there was a link to a suit checklist. The leak test described there: the pressure drop during one minute should be less than 0.3 psi or 2 kPa. To determine the leak rate, we should know the volume contained in the suit. The normal operating pressure for this suit used at the ISS is 4.3 psi or 29.7 kPa. $\endgroup$
    – Uwe
    Commented Nov 10, 2017 at 19:18
  • $\begingroup$ @Uwe so a 0.3 psi / minute drop would mean if at 14 PSI starting the suit would deflate by about 46 minutes. I assume the life support system therefore replenishes at approx the same rate? $\endgroup$ Commented Nov 10, 2017 at 19:25
  • $\begingroup$ The calculation of 46 minutes is wrong anyway. The operating pressure is 4.3 psi, not 14. An astronaut in a suit with 14 psi pressure would need enormous force to close his hands or to move his arms and legs. Of course the life support system keeps the suit pressure constant, even if there is a small leak. But the astronaut consumes oxygen at any time. At rest about 1.3 l per minute and up to 11 l per minute at hard work. The same volume per minute is exhaled as carbon dioxide and absorbed by the scrubber of the life support system to keep the carbon dioxide content in the suit low. $\endgroup$
    – Uwe
    Commented Nov 10, 2017 at 21:58
  • $\begingroup$ The leak test by pressure drop requires an astronaut at rest holding breath during pressure drop measurement. $\endgroup$
    – Uwe
    Commented Nov 11, 2017 at 19:24

2 Answers 2


Updated with current EVM suit documentation:

I was finally able to get the full EMU Systems Workbook (click here to download - 22 MB, this document is awesome and chock full of info too!)

There is all the info you could want on leakage on pages 1-23 and 1-24 (PDF pages 39 and 40) I have circled the relevant number below (in an excerpt from page 1-24EMU Systems workbook with HAND DRAWN red circle


I have just now received an answer to my FOIA request from NASA requesting documents on the current generation space suits. One of the documents of interest was the Extravehicular Mobility Unit Systems Training Workbook (click here to download - 52 MB), it contains a ton of information on the current generation space suits.

If you look on page 131, it states that the automated leak check fails if the suit is losing more than $0.3\ psi/min$, with a nominal suit pressure of $4.3 \pm0.1\ psid$. Unfortunately, the suit volume is not in this document so the mass flow cannot be determined.

The "Apollo Operations Handbook Extravehicular Mobility Unit" (click here to download - 4.4 MB), Revision 5, Table 2-I quotes the Maximum leak rate at 180 cubic centimeters per minute.

The Extravehicular Mobility Unit is the suit used for the Lunar Landings (the linked document contains a wealth of awesome information).

Though the current generation of suits is also called the Extravehicular Mobility Unit and I cannot find out what the relationship between the Apollo era suits and the current generation ones.

Extravehicular Mobility Unit

Extravehicular Mobility Unit

Table 2-I

Table 2-I, (scc stands for Standard Cubic Centimeters)

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    $\begingroup$ The leak rate of less than 0.18 l/min is much lower than the oxygen consumption of an astronaut at rest, about 1.3 l/min. $\endgroup$
    – Uwe
    Commented Nov 13, 2017 at 10:24
  • $\begingroup$ But what is the difference between "leak rate" and "leak rate closed"? $\endgroup$
    – Uwe
    Commented Nov 13, 2017 at 10:26
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    $\begingroup$ Leak rate closed just refers to the leak rate of the pressure relief valve not the whole suit $\endgroup$
    – Mark Omo
    Commented Nov 13, 2017 at 15:49
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    $\begingroup$ I find use this particular stack exchange often and also I got no notifications about your various edits until today. Fabulously researched answer! $\endgroup$ Commented Jun 5, 2018 at 18:02
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    $\begingroup$ @MarkOmo no I didn't take it that way; I always mean to vote up etc. and genuinely felt amiss! $\endgroup$ Commented Jun 5, 2018 at 19:55

The only number I can quote you is the requirement for the Apollo suit.

Which was, "less than 180 standard cubic centimeters/minute at either 0.2 or 3.7 psi"

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This is from the "Early Apollo Spacesuit Development, A-7L Suit Requirements, and Design Details" presentation, which you can find on the Spacesuit Knowledge Capture page, which is an incredible trove of knowledge for those willing to sit through it.


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