If CO2 is abundant, the RBC will only take CO2 and will react to the water in the ICF, and due to enzymatic process with the help of carbonic anhydrase that could form the carbonic acid. Carbonic acid will further broken down forming Bicarbonate and Hydrogen ions. Bicarbonate is negative charge and will be released by the RBC and neutralize the increase of the acidity brought by the increase in CO2 in the body. this is an example of negative feedback mechanism.