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Why is carbon monoxide dangerous even in small concentrations?

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A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — carbon group element Modern version of the periodic table of the elements (printable).

Carbon monoxide is an extremely dangerous poison because it is both odorless and tasteless, providing no sensory warning of its presence.1

Its toxicity stems from its interaction with hemoglobin, the protein in blood responsible for transporting oxygen. Hemoglobin has an affinity for carbon monoxide that is approximately 200 times greater than its affinity for oxygen. Consequently, even at concentrations of less than 1 percent in the air, carbon monoxide binds preferentially to hemoglobin to form a highly stable compound called carboxyhemoglobin.213

This process effectively blocks hemoglobin from binding with oxygen, severely impairing the body's ability to deliver essential oxygen to tissues and organs. As the concentration of carboxyhemoglobin rises, it leads to symptoms ranging from dizziness and impaired judgment to coma and respiratory failure. Because this binding is so stable, it cannot be easily reversed by normal bodily processes, making even small concentrations a significant health hazard that can lead to fatal asphyxiation.132