Carbon monoxide (CO) is a pollutant with strong toxicity to the blood and nervous system, Carbon monoxide (CO) in the air enters the human blood through the respiratory system, along with hemoglobin (hb) in the blood. Myoglobin in muscles. The binding of respiratory enzymes containing divalent iron forms reversible binding compounds. The combination of carbon monoxide and hemoglobin not only reduces the ability of blood cells to carry oxygen, but also inhibits and delays the resolution and release of oxyhemoglobin (HbO2), leading to tissue necrosis due to hypoxia. In severe cases, it may endanger human life.

Under low oxygen partial pressure conditions, the ability of hemoglobin to bind oxygen is weak, while under high oxygen partial pressure conditions, the ability of hemoglobin to bind oxygen is greatly enhanced, but cannot exceed CO. This has physiological significance because hemoglobin not only binds oxygen in the alveoli with high oxygen partial pressure, but also releases oxygen in the tissue cells with low oxygen partial pressure. This requires a decrease in its low oxygen affinity, otherwise the tissue will be hypoxic, so its binding ability is not as good as CO.

Under normal circumstances, oxygen entering the bloodstream through the respiratory system will combine with hemoglobin (Hb) to form oxygenated hemoglobin (HbO2), which is transported to various organs and tissues of the body and participates in normal metabolic activities.

If the concentration of carbon monoxide in the air is too high, a lot of carbon monoxide will enter the body's bloodstream. Carbon monoxide entering the bloodstream preferentially combines with hemoglobin (Hb) to form carboxyhemoglobin (HbCO).

The binding force between carbon monoxide and hemoglobin is 2-3 hundred times greater than that between oxygen and hemoglobin. The dissociation rate of HbCO is only 1/36th of that of HbO2. The degree of harm of carbon monoxide to the body mainly depends on the concentration of carbon monoxide in the air and the length of time the body absorbs high concentration carbon monoxide air. The content of HbCO in the blood of carbon monoxide poisoning patients is directly proportional to the concentration of carbon monoxide in the air, and the severity of poisoning is directly related to the content of HbCO in the blood.