> Carbon dioxide can of itself reduce human cognitive capability That seems to be only when the CO2 concentration is raised abruptly. After that the body compe

> Carbon dioxide can of itself reduce human cognitive capability That seems to be only when the CO2 concentration is raised abruptly. After that the body compensates. For example, submarine crews operate perfectly fine in an atmosphere of 2 to 5% CO2 (roughly 100x what is normal), for weeks on end.