Dry air and percentage by volume
Dry air and percentage by volume
Air is a mixture of gases, not a single substance. In dry air, water vapour has been removed so the composition can be compared clearly. By volume, dry air is about 78%78\%78% nitrogen, 21%21\%21% oxygen, 0.9%0.9\%0.9% argon, and 0.04%0.04\%0.04% carbon dioxide.