Composition of atmosphere as of mid-2026

Air is the mixture of gases that forms Earth's atmosphere, sustaining respiration, combustion, and countless industrial processes. By mole fraction (i.e., by number of molecules), dry air consists of 78.08% nitrogen, 20.95% oxygen, 0.93% argon, and 0.04% carbon dioxide, together with trace amounts of neon, helium, methane, krypton, hydrogen, and ozone.

Air also contains a variable amount of water vapor, averaging around 1% at sea level but dropping to roughly 0.4% when averaged over the entire atmospheric column, since water vapor concentration decreases sharply with altitude and varies significantly with temperature, humidity, and geography.

Beyond its natural role, air is one of the most important industrial raw materials in the world. Because its major constituents — nitrogen, oxygen, and argon — occur in fixed, predictable proportions, air can be liquefied and separated into its pure components through cryogenic fractional distillation, a process known as air separation.

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