But in your exhalant there is something else: CO2. Carbon dioxide is the waste product of energy transfer, transporting one carbon atom out of Horse Silhouette Moon Halloween shirt body. Now, if you have too much CO2 in your body, that’s not good. Did you know, for example, that breathing is based on your body’s CO2, not O2? That there aren’t many mechanisms in your body that control for O2? Why? Because O2 is not just needed, it’s also a poison. And it’s so abundant, that you don’t have to worry about it in normal room air.