A mixture of gases forming the atmosphere.

The atmosphere is air. Air contains approximately 78% nitrogen N2, 21% oxygen O2, less than 1% inert gas argon Ar by volume, and very trace amounts of carbon dioxide CO2, hydrogen H2, neon, xenon, ozone and other gases can be released. The composition of the air varies slightly, it is slightly enriched with carbon dioxide in cities, and in the forests it contains more oxygen, in the mountains, on the contrary, there is less oxygen, since its molecules are heavier than nitrogen. Also, air can contain water. Humidity depends on the temperature of the environment and the amount of water in it. The weather forecast refers to the relative humidity of the air.