I keep seeing these studies showing that tiny increases in CO2 impair cognition, but I have trouble believing them. The US navy runs their submarines with CO2 l

I keep seeing these studies showing that tiny increases in CO2 impair cognition, but I have trouble believing them. The US navy runs their submarines with CO2 levels that vary from 300-11,300ppm.[1] Their own studies show that CO2 levels of 4% (40,000ppm) do not affect cognition[2]: > Thus, CO2 at 40,000 ppm for 2 weeks did not affect performance on multiple tests of cognitive function in physically fit young airmen, a population probably not unlike submariners. CO2 tended to cause poor sleep, headache, and hand tremor before it caused cognitive issues. Another bit of evidence that makes me doubt these recent studies is that the levels of CO2 in your lungs are much higher than what is in the atmosphere. Exhaled air is around 5% CO2. Each breath doesn't replace 100% of the air in your lungs. If you have a container that is 5% CO2 and you replace 80% of it with air containing 400ppm CO2, you're down to 10,320ppm. Inhale 1,000ppm CO2 and your lungs will be at 10,800ppm CO2. In other words: a 250% increase in atmospheric CO2 levels only causes a 4% increase in lung CO2 levels at the beginning of a breath. If such tiny changes significantly affected cognition, we would see impairment happen in many more circumstances (such as when walking or smoking). If something's impairing cognition in stuffy rooms, I don't think it's CO2. 1. https://www.nap.edu/read/11170/chapter/5#47 https://www.nap.edu/read/11170/chapter/5#47 2. https://www.nap.edu/read/11170/chapter/5#54 https://www.nap.edu/read/11170/chapter/5#54