You have nothing to fear from CO2 in Starfield: no matter how much you sprint or how much you're carrying, it'll never kill you

 Jumping around in Starfield.
Jumping around in Starfield.

Do you, like me, have an inescapable compulsion to thoroughly survey every barren rock, volcanic wasteland, and frozen desert that Starfield takes you to? Do you, like me, also have a tendency to hoard resources for the game's crafting and research systems? Then you, like me, have probably also experienced the agonising tedium of walking veeery slowly towards a point of interest because you're severely over-encumbered and worried about accidentally killing yourself by running and draining all your O2. But guess what? You don't have to.

Yep, it turns out that—no matter how hard you try or how much loot is weighing you down—you can't die from maxing out your CO2 meter in Starfield. If you drain your O2 gauge and fill your CO2, the worst that will happen is your health getting reduced to 10% of its maximum (and your vision getting a bit swimmy). So unless you're in combat or subject to some kind of other health-draining status effect, you can effectively sprint infinitely whether you're over-burdened or not. Look, here's a video of me verifying it for myself:

The only drawback is you have to keep tapping sprint every couple of seconds, since the game automatically knocks you down to an ordinary run speed whenever you've maxed your CO2. Apart from that, though, there's barely any downside. You can keep sprinting until you reach your destination. And if you can't bear repeatedly tapping sprint, you can just proceed at an ordinary running pace while overweight without worrying about it draining your health: that won't kill you either.

I'm not entirely sure how to feel about this, to be honest. With 29 hours of Starfield under my belt, I'm a little bit aghast at all the time I've wasted walking at an achingly slow pace across the game's many planets because I thought going any faster would do me in. This seems like the kind of thing that should be pointed out either in a loading screen tip or in the game's initial tutorial section, but unless I've missed something (always a possibility, to be fair), this is a tip Bethesda has kept studiously to itself.

Well, no more. We may not have vehicles (yet) to help us get around Starfield's planets, but by god we have our feet. My friends, let us use them without fear.