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Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide and small amounts of other gases. Air also contains a variable amount of water vapour on average around 1%. In fact, air contains slightly less than 1% argon making it the third most abundant gas in air after nitrogen and oxygen. Argon is the most abundant and most used of the noble gases.