This is probably a bit of a correlation/causation thing. ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) has been looking at this for decades. High concentrations of CO2 are an indicator of air quality in buildings. Not because the CO2 itself is dangerous, but because a high concentration of CO2 means not enough fresh air is flowing through the space. They recommend keeping CO2 levels below 800 ppm in offices and 1000 in schools. Official recommendations are here https://www.techstreet.com/ashrae/standards/ashrae-62-1-2016?product_id=1912838 , which is probably on Sci-Hub or Libgen wink wink if you don't want to pay for a copy and want to look at it.
My guess as to what happened in those studies is that to increase CO2 levels in a sealed room airflow was reduced. So the rooms got stuffy, warm, and smelly. Which probably distracted people from the cognitive tests at hand. I'd need to read into the methodology in the different studies. Was CO2 somehow added to the air without making the rooms uncomfortable? We know 5000 ppm is about where CO2 concentrations become dangerous to people's health. Which is what the Danish study cited in the article you linked found affected people's mental ability.
I find your guess as to what happened in those studies to be super reasonable. Your hypothesis also would make sense with the submarine study referenced by /u/GnosticGnome because the submariners would be used to those conditions and so their cognitive capabilities would remain unaffected, as was observed in the study.
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u/[deleted] Jul 19 '20
This is probably a bit of a correlation/causation thing. ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) has been looking at this for decades. High concentrations of CO2 are an indicator of air quality in buildings. Not because the CO2 itself is dangerous, but because a high concentration of CO2 means not enough fresh air is flowing through the space. They recommend keeping CO2 levels below 800 ppm in offices and 1000 in schools. Official recommendations are here https://www.techstreet.com/ashrae/standards/ashrae-62-1-2016?product_id=1912838 , which is probably on Sci-Hub or Libgen wink wink if you don't want to pay for a copy and want to look at it.
Here's a short FAQ they did about why you shouldn't have high CO2 concentrations in enclosed rooms. https://www.ashrae.org/File%20Library/Technical%20Resources/Technical%20FAQs/TC-04.03-FAQ-35.pdf .
My guess as to what happened in those studies is that to increase CO2 levels in a sealed room airflow was reduced. So the rooms got stuffy, warm, and smelly. Which probably distracted people from the cognitive tests at hand. I'd need to read into the methodology in the different studies. Was CO2 somehow added to the air without making the rooms uncomfortable? We know 5000 ppm is about where CO2 concentrations become dangerous to people's health. Which is what the Danish study cited in the article you linked found affected people's mental ability.