I typically see 35-45 mmHg of partial pressure carbon dioxide being cited as the good range
That’s about 5% (since atmospheric pressure is about 760 mmHg) or 50,000 ppm.
Being in a room with that high a concentration of co2 is immediately dangerous
to life and health, which is a good illustration of the fact that this post (your post) is about co2 in exhaled air, which
is distinct from co2 in inhaled air or ambient air, where for example
5,000 ppm of co2 “is the permissible exposure limit for daily workplace exposures” (source).
That’s about 5% (since atmospheric pressure is about 760 mmHg) or 50,000 ppm. Being in a room with that high a concentration of co2 is immediately dangerous to life and health, which is a good illustration of the fact that this post (your post) is about co2 in exhaled air, which is distinct from co2 in inhaled air or ambient air, where for example 5,000 ppm of co2 “is the permissible exposure limit for daily workplace exposures” (source).