Quote Originally Posted by ChrisL View Post
Please explain further.

Chris L
Like many good things, it is good in a certain range of concentrations.

Take water, for example... you need to take in about 2 quarts per day to flush out toxins and avoid problems. However if you take in more than a certain amount per day and you overload your kidneys... ultimately leading to death if you push it too far. Young healthy kidneys at rest can process between 800ml and 1000ml per hour, go above that and you start having problems. When under stress, your kidneys basically get into water saving mode and decrease the volume of water they process...

Increased CO2 levels in the air stream do tend to create issues for most mammals... the extent of the issues depends on the species and the initial health of the subject. You may want to look up on the subject of hypercapnia.