CO2 needs to be scrubbed/vented out of the breathable atmosphere. Even if there is abundant of oxygen anyway, too much CO2 will make people feel dizzy and conf

CO2 needs to be scrubbed/vented out of the breathable atmosphere. Even if there is abundant of oxygen anyway, too much CO2 will make people feel dizzy and confused, cause splitting headaches, increased heart rated, reduced senses, and eventually death. CO2 can't take the place of inert nitrogen in a breathable atmosphere, that much CO2 in the air just isn't compatible with human life.