Britannica Sources used in this answer

Why is carbon monoxide dangerous to breathe?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A labeled diagram of the periodic table entry for carbon, showing its atomic number 6, symbol C, electron configuration, atomic weight range, solid physical state, hexagonal crystal structure, and weakly acidic oxide properties. Color coding and icons indicate it is a nonmetal, solid at room temperature, with hexagonal structure and weak acidity. — carbon Carbon and its properties.

Carbon monoxide is dangerous to breathe because it acts as a potent poison that interferes with the body's ability to transport oxygen.12

The primary mechanism of toxicity involves hemoglobin, the protein in blood responsible for carrying oxygen. Hemoglobin has a significantly higher affinity for carbon monoxide than for oxygen. When inhaled, carbon monoxide binds to hemoglobin to form a stable compound called carboxyhemoglobin.12

Because this bond is so stable, the hemoglobin becomes unavailable to transport oxygen to the body's tissues and organs. This effectively leads to internal suffocation. Because the gas is odorless and tasteless, it provides no warning of its presence, making it particularly hazardous. Severe exposure can result in permanent tissue damage—especially to the heart and nervous system—or death due to respiratory failure and arrhythmia.12