Why is carbon monoxide considered a hazardous component in a breathing gas mixture?

Carbon monoxide is considered hazardous in a breathing gas mixture primarily because it competes with oxygen for binding sites on hemoglobin in red blood cells. Hemoglobin has a much higher affinity for carbon monoxide than for oxygen, meaning that even small amounts of carbon monoxide can significantly reduce the blood's capacity to carry oxygen. When carbon monoxide binds to hemoglobin, it forms carboxyhemoglobin, which impairs the transport of oxygen throughout the body, leading to potentially life-threatening conditions such as hypoxia.

This characteristic is particularly concerning in diving scenarios, where adequate oxygen supply is critical for sustaining bodily functions under increased pressure conditions. Understanding how carbon monoxide affects hemoglobin is essential for divers who need to ensure the safety and quality of their breathing gas mixtures to prevent any adverse health effects associated with oxygen deprivation.