I had to drive a rental car for a bit recently, after getting rear-ended, and I was shocked to discover that it defaulted to recirculation mode every time it was turned on, regardless of whether you'd turned it off the previous time. I felt light-headed in it a few times before I realized I needed to manually turn recirculation off every time. Horrible behavior, and I don't doubt that it's responsible for many accidents.
there is some ambiguity here. submariners are exposed to really high co2 levels and are doing fine. it's possible that regular high co2 is just a proxy for bad air, and that you can acclimate to purely high co2 pretty well.
i have felt bad in high co2 environments before but i have never been in a controlled high co2 environment.
I'm not implying permanent effects. The studies involved show a marginal reduction in cognitive reasoning on standardized tests.
Which is the point: if you're in a room trying to do deep work, that's likely a problem. I suspect submarines are all over the place here: you might be exposed to higher levels routinely but you also have regular access to chemical scrubbers and decent ventilation. I'd be fascinated to know what levels are tracked as normal.
apparently those scrubbers are less efficient the lower the co2 is (also need to move much more air which ruins stealth). iirc submarines are routinely exposed to multiple thousands.