Not sure which way you mean it, if you mean you never lose any air, you probably don't have the realistic compressed air checked in your options setting.
If you're compressed air icon is lit up and won't go off even after you surface, that is a known bug, one that can't be fixed. You can correct it by simply saving and reloading your game.
However, if it truly reaches a 100% you shouldn't alive. Most agree that this bug happens more when you alt/tab a lot or keep writing over the same save
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