is derived from the Greek a-, "without" + kapnos, "smoke." The word was devised not to mean "smokeless" but rather as a refer ence to diminished CO2 (Carbon Dioxide) in the blood. Insofar as CO2 (Carbon Dioxide) is a major component of the common smoke produced by combustion of carbon-containing fuels, and recognizing the lack of a classical term for CO2 (Carbon Dioxide), the contrivance makes sense. Hypercapnia is an excess of CO2 (Carbon Dioxide) in the blood.