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 tri-ox. In 2373, occupants of the mag-lev carriage Alixia were suffering from the initial stages of carbon dioxide poisoning, except for Tuvok, who was better able to withstand the thin atmosphere. (VOY: "Rise")