You could technically test your ratio of carbon dioxide you produce to the oxygen you intake to see if you are keto - adapted, but it isn't really practical. (mariamindbodyhealth.com)
But even during exercise our innate respiratory - control system usually does quite well at providing adequate oxygen supply and removing carbon dioxide produced by metabolism. (scientificamerican.com)
It uses carbon dioxide produced in combustion to drive turbines at the plant rather than steam. (greentechmedia.com)