What is the current percentage of oxygen in the atmosphere?

By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0. read more

However, models of past atmospheric oxygen levels often markedly disagree, differing by as much as about 20 percent of Earth's atmosphere, which is oxygen's present-day concentration, the researchers said. 1 It is not even known if atmospheric oxygen levels varied or remained steady over the past 1 million years. read more