High Quality Content by WIKIPEDIA articles! Carboxyhemoglobin (British English: Carboxyhaemoglobin) (COHb) is a stable complex of carbon monoxide and hemoglobin that forms in red blood cells when carbon monoxide is inhaled or produced in normal metabolism. Large quantities of it hinder delivery of oxygen to the body. Tobacco smoking (through carbon monoxide inhalation) raises the blood levels of COHb by a factor of several times from its normal concentrations. It is bright, cherry red.