Composition of air: Nearly all of Earth's atmosphere

Nearly all of Earth's atmosphere (air) is comprised of a mere five gases: nitrogen, oxygen, water vapor, argon, and carbon dioxide. Several other compounds are also present in our air in trace amounts. Learn about the percentage of nitrogen, oxygen and other gases in the atmosphere, and their properties and effects. Find out the answers to frequently asked questions and test your knowledge on air composition with a quiz. Primarily, dry air at sea level is composed of approximately 78% nitrogen (N2), 21% oxygen (O2), and a small percentage of other gases, including argon (Ar, about 0.93%), carbon dioxide (CO2, about 0.04%), and trace amounts of neon, helium, methane, krypton, hydrogen, and xenon. The composition of air varies from place to place. For example, the air is thinner on mountains as compared to plains. This is the reason why mountaineers always carry oxygen cylinders with them. Also, the percentage of oxygen in the air may be higher in areas where there is more greenery. In the desert areas, the water vapour content will be significantly lower than the regular areas because of the lack of water in desert areas. Properties of Air Air has the following characteristics: Air ...