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How does the density of chlorine gas compare with the density of air?

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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 significantly denser than air; specifically, it is two and a half times heavier than air at room temperature and atmospheric pressure.1

Because of this high density, chlorine gas tends to settle in low-lying areas, which is a critical factor in understanding its behavior and the safety risks associated with its toxic and corrosive properties.12