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How O2 & CO2 Work in Starfield: Use Available Oxygen Challenge

Craig Robinson
Nathan Garvin

Stamina has been part of Bethesda Games Studios games for a long time, notable in The Elder Scrolls franchise. Starfield shares similar DNA to other Bethesda games, but in space! So naturally Stamina had to evolve to fit the setting better. Instead of Stamina (or Action Points - the closest Fallout equivalent) you’ll need to manage O2 (oxygen) and CO2 (carbon dioxide) in Starfield, and this page will explain how these gameplay elements work.

(1 of 2) Sprinting, jumping and performing power attacks will all consume O2, noted by the white gauge on the bottom left of the screen.

Sprinting, jumping and performing power attacks will all consume O2, noted by the white gauge on the bottom left of the screen. (left), Once your O2 is fully depleted, further exertion will build up CO2, as indicated by the red gauge on the bottom left of the screen. (right)

How O2 and CO2 Work in Starfield

You O2 meter in Starfield functionally replaces Stamina/Action Points from The Elder Scrolls and Fallout, respectively, and O2 is consumed any time you sprint, jump, perform a power attack with a melee weapon or attempt to move while over-encumbered. Your overall O2 supply is unlimited, but it is possible to temporarily strain your local supply by over-exerting yourself by performing the aforementioned options. Your O2 meter is located on the bottom left of the screen, at the bottom of your minimap, and is represented by a white semi-circle.

Running out of O2 isn’t inherently dangerous, when your O2 is low all you need to do is refrain from exerting yourself and the bar will replenish. If you persist in performing actions that consume O2, however, you’ll start to build up CO2, which is indicated by a red bar that appears in the same place as the O2 bar does. Should your CO2 bar fill completely, further exertion will start causing health damage. You can reduce CO2 buildup the same way you replenish O2 - just avoiding sprinting, jumping or performing power attacks until the red bar is gone. Note that CO2 clears and O2 recovers simultaneously; you don’t have to wait for the CO2 gauge to empty before you start gaining O2.

Ultimately, the O2/CO2 mechanic in Starfield is very similar to the old stamina mechanic in The Elder Scrolls, and it primarily affects melee characters, who may be more inclined to sprint (to close ground with enemies) or perform power attacks. You can increase the amount of O2 you have by purchasing ranks in the "Fitness" iconFitness skill, and you can mitigate O2 expenditure via the Fitness and "Boxing" iconBoxing skills.

How to Use Up All Available Oxygen in Starfield

If you’re someone using the Fitness skill, then you’ll get Starfield’s use up all available oxygen. This challenge is a fairly simple, as it essentially requires you to deplete your “stamina bar” 20 times in one instance of its rank up challenges.

Top do this, you can do a number of things:

  1. Sprint on planets while wearing a helmet
  2. Continue to attack using your fists and deplete you oxygen levels that way.

You essentially want to keep doing this until your Oxygen tank fills its bar fully with the red meter. When this caps out, then your respiration tank will fill with CO2 and then become dangerous and start reducing your HP. When you’re there, you’ll have used up the last big of Oxygen, and you will then start to take damage. Let it reset by standing still and then refill with Oxygen.

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Guide Information
  • Platforms,
    PC, XB X|S
  • Genre
    Action Adventure, Action RPG, Shooter
  • Guide Release
    30 August 2023
  • Last Updated
    18 October 2023
    Version History
  • Guide Author

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Starfield is an action role-playing game from Bethesda Game Studios set in a futuristic interpretation of space exploration and colonization. Earth has long been abandoned, but there are plenty of other planets in different star systems where humans have ventured and settled. You have the freedom to create your own character with a unique background, but the main story will take you through a series of adventures as you uncover more information about mysterious artifacts which create gravitational anomalies. Along the way, you can build and customize your own space ship, establish your own outpost, befriend and romance new companions, and more. As a Bethesda game, you can also expect to see a lot of creative mods which have the potential to change your experience of the base game, or take it in an entirely new direction.

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