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Why is chlorine gas dangerous to inhale?

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A labeled diagram of the chlorine element from the periodic table shows its atomic number 17, symbol Cl, electron configuration, and atomic weight range. The box is shaded green to indicate chlorine is a halogen, with icons for orthorhombic crystal structure, gas state at room temperature, and strong acidity. A key explains the icons and colors used. — chlorine Properties of chlorine.

Chlorine gas is highly dangerous to inhale due to its toxic effects on the respiratory system. Upon inhalation, the gas causes immediate physical distress, including a choking sensation, constriction of the chest, and tightness in the throat.1

The primary danger lies in the severe damage it inflicts on the lungs. Exposure can lead to edema, a condition where the lungs fill with fluid, which can be fatal. The toxicity of chlorine is extreme; concentrations as low as one part per thousand in the air can cause death within a few minutes. Because of these hazardous properties, chlorine was historically utilized as a chemical weapon during World War I.1