Also, the general safety limit for co2 is around 5000 ppm for up to 8 hours - higher than that, and headaches and other effects will manifest.
I'm quite surprised that "no effect" could be seen at 40k ppm - I wonder if there were some limits to the cognitive tests (like the difference between proving a difficult mathematical theorem vs doing some Calculus).
https://thinkprogress.org/its-taking-less-co2-than-expected-...
Also, the general safety limit for co2 is around 5000 ppm for up to 8 hours - higher than that, and headaches and other effects will manifest.
I'm quite surprised that "no effect" could be seen at 40k ppm - I wonder if there were some limits to the cognitive tests (like the difference between proving a difficult mathematical theorem vs doing some Calculus).