Sir John Kendrew (1917-1997) published the structure of haem-proteins, revealing how oxygen is transported in the blood.Carbon monoxide is a poisonous gas which can enter the blood via the lungs and alters oxygen transport. In normal air, Po = 100 mmHg in the lungs. After addition of CO, so Pco = 0.4 mmHg, there are equal molar amounts of CO and O in the blood.