Carbon dioxide poisoning Carbon dioxide toxicity may be caused by any of the following: Inadequate respiratory effort (hypoventilation) due to high breathing resistance (eg, from regulator malfunction, tight wetsuit) Overexertion Deep diving Air supply contamination by exhaled gases (as occurs with a carbon dioxide scrubber failure in a rebreather air supply) Hypoventilation can increase blood carbon dioxide levels and cause shortness of breath and sedation.