Smithsonian National Museum of Natural History

The Air We Breathe

Molecules in the air include primarily nitrogen and oxygen as well as water, carbon dioxide, ozone, and many other compounds in trace amounts, some created naturally, others the result of human activity.

In addition to gases, the atmosphere contains extras such as smoke, dust, acid droplets,
and pollen.

The composition of the atmosphere changes constantly and depends on the season, weather, time of day, latitude, longitude, elevation, and geography.