[johnernaut]

This can be alleviated with the use of CO2 scrubbers[0]. Basically you fill fan-powered canisters with minerals ("sodasorb" is a popular product used in the offshore diving industry), which absorbs CO2 from the atmosphere. That's not to say that you need to be able to remove and replace the minerals in the scrubbers every so often.

[0] https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber

[junke]

Out of curiosity, do you have an idea of the typical delay before saturating the filter? Do you have some pointer to space suits specification or something like this that I could read to have more information?

[msl]

According to Wikipedia, "One gram of anhydrous lithium hydroxide can remove 450cm³ of carbon dioxide gas."[1] Also according to Wikipedia, a person produces some 1kg of the gas a day [2], which translates to roughly 550000cm³. That means around 1.2kg of lithium hydroxide per day per person.

The Apollo 13 LM canisters were rated for some 56 hours for two persons, but could only support three for less than 35 hours. That seems to fall somewhere between 5 and 6 kilograms, and apparently includes the scrubbers of the space suits onboard. Each suit was designed to support life for 6 hours (+ 30 minutes of emergency reserves) [3] which means some 350 grams of lithium hydroxide.

The longest EVA thus far lasted for just under 9 hours [4], for which you would need a bit more than 450 grams of lithium hydroxide. The Russian Orlan suits are designed to support life for between 5 and 7 hours [5].

An astronaut on an EVA might produce more carbon dioxide than the Wikipedia approximation, so you might want to round those numbers up.

Edit: I am also not sure how close to the theoretical maximum that absorption capacity is, so the numbers might really be somewhat optimistic.

[1] https://en.wikipedia.org/wiki/Lithium_hydroxide

[2] https://en.wikipedia.org/wiki/Carbon_dioxide#Human_physiolog...

[3] https://en.wikipedia.org/wiki/Apollo/Skylab_A7L

[4] https://en.wikipedia.org/wiki/Extravehicular_activity

[5] https://en.wikipedia.org/wiki/Orlan_space_suit