[nate_meurer]

It's an interesting article overall, but this assertion:

> Carbon dioxide is bad for cognition.

is dubious and unsupported by science. As I point out downthread, we have extensive experience with very high-CO2 environments-- at levels regularly exceeding ten or twenty times current atmospheric levels-- and as yet little good evidence of uncompensated cognitive effects.

Beyond that, modern humans live much of our lives in moderately elevated CO2 with no apparent ill effect. Without deliberate ventilation, any enclosed space like a bedroom or classroom will rapidly achieve elevated CO2 levels, often into the thousand ppm range. Again, we have lots of data, and little of it points to a practical cognitive effect.

The US Navy maintain an informal goal to keep levels on board submarines to below 8000 ppm, loosely informed by what little evidence they have of its effects on crew performance. That's twenty times the current atmospheric levels. In practice, CO2 levels often go over 10,000 ppm, which apparently still doesn't cause them much concern.

[dynm]

There's definitely quite a lot of scientific support, e.g. see this review paper: https://doi.org/10.1016/j.envint.2018.08.059

I'm open to the possibility that this is wrong, but as far as I can tell, the conventional scientific view is that high-CO2 environments are somewhat bad (although not catastrophic, even at 8000 ppm).

[nate_meurer]

This looks like a good review, and it definitely pertains to your effort here. Although the authors play up the positivity of their conclusions a bit (which is useful if they want to continue the research), they are also honest about the limitations of the material they cite. Many positive correlations are cited, but nearly every paragraph is laden with caveats. Here are a few pulled at random:

> However, the relationship between CO2 concentrations and upper respiratory symptoms in this study was no longer statistically significant after adjusting for the number of people in the office

> A 100 ppm increase in CO2 concentration (range, 549–1318 ppm) was positively correlated with non-specific symptoms including headache and dizziness (107 participants from 11 offices) although the correlation was not significant

> Several epidemiological studies indicate a relationship between low-level exposure to CO2 and BRSs. However, BRS is possibly influenced by other comorbid indoor pollutants, including artificial volatile organic compounds (VOCs) brought into buildings or occupant-generated pollutant

> CO2 concentration at 5000 ppm had no effect on acute health symptoms (respiratory, visual and skin-related, headache, and sensory) and performance in cognitive tests (Zhang et al., 2016).

> the relationship between low-level exposure to CO2 and the reported symptoms remain inconsistent between studies

> A relationship between low-level exposure to CO2 and BRSs is therefore very complicated to prove and strength of the evidence is very limited.

My biggest issue with all of this is that we have a ton of data from very high-CO2 environments going back decades, and still very little clear evidence of negative effects. If high CO2 concentration imposes significant cognitive costs for which the human body cannot compensate after some period of time, it seems like that signal should have become clear by now.