Carboxyhemoglobin
Carboxyhemoglobin (carboxyhaemoglobin BrE) (symbol COHb or HbCO, also known as carbonylhemoglobin) is a stable complex of carbon monoxide and hemoglobin (Hb) that forms in red blood cells upon contact with carbon monoxide. Carboxyhemoglobin is often mistaken for the compound formed by the combination of carbon dioxide (carboxyl) and hemoglobin, which is actually carbaminohemoglobin.