Carbon dioxide poisoning
From Memory Alpha, the free Star Trek reference.
Carbon dioxide poisoning or hypercapnia is a condition in which a subject can lose consciousness and eventually (if not treated in time) asphyxiate due to a high level of carbon dioxide in the atmosphere, which prevents the proper distribution of oxygen via the Human circulatory system. This can be prevented by regular doses of triox. (DS9: "The Sound of Her Voice")
