Carbon dioxide (CO2) is a significant component of Earth's atmosphere and plays a crucial role in various natural processes and industrial applications. One of the interesting physical properties of carbon dioxide is its density relative to air.

Carbon dioxide is heavier than air. The molecular weight of CO2 is approximately 44.01 grams per mole, while the average molecular weight of air, which is primarily composed of nitrogen (N2) and oxygen (O2), is about 28.97 grams per mole.

In practical terms, the higher density of carbon dioxide causes it to settle in lower areas when released in an environment. This property is particularly important in various scenarios:

1. Safety in Confined Spaces: In enclosed or poorly ventilated areas, CO2 can accumulate at ground level or in low-lying areas, posing a risk of asphyxiation.
2. Fire Suppression Systems: CO2 is used in fire extinguishers, especially for electrical fires, because it can blanket a fire by displacing the oxygen around it.
3. Greenhouses and Plant Growth: However, the heavier-than-air property means that the distribution of CO2 must be managed carefully to ensure even coverage and avoid pockets of high concentration at the ground level, which could be detrimental to plants and workers.
4. Environmental Considerations: In the natural environment, the heavier-than-air characteristic of CO2 means that it can accumulate in valleys, depressions, and caves.