Earth's atmosphere (approximate values)

The atmosphere comprises ~80% nitrogen and ~20% oxygen. The atmosphere contains small proportions of various other gases, including CO₂, water vapour and noble gases. The atmosphere thins out with height which makes it harder for humans to breathe sufficient oxygen at high altitude. The atmosphere contains water, mainly in its gas state but in its liquid (or solid) state in clouds and precipitation. The atmosphere also contains a wide range of solid particulates.