Pure air is a homogeneous mixture made primarily of nitrogen and oxygen. Its elements are not readily separated or distinguished from one another. The composition of air is not uniform and may be influenced by environmental factors, such as industrial pollution, heavy forestation or volcanic activity.
Some of the elements that compose air include:
- Nitrogen (78 percent)
- Oxygen (roughly 21 percent)
- Argon (nearly 1 percent)
The National Center for Atmospheric Research reports that many other trace elements are present in a typical sample of Earth's atmosphere, including carbon dioxide, helium, methane and neon. These secondary elements tend to occur at very low concentrations in any given sample. Their chemical natures allow them to blend seamlessly together to form what is commonly referred to as air, a mixture breathable to humans and other life.
Pollutants that may change air composition include:
- Carbon dioxide
Because air is a homogeneous mixture, contaminants that integrate effectively with it pose a significant problem and can lead to respiratory disease and other complications for those exposed. Carbon dioxide is a byproduct of many factories, while sulfur is most commonly produced by natural vents or volcanoes.
While air is far from uniform in composition, it does present many constants that can be analyzed to determine a sample's relative purity. Knowledge of air composition allows for a better understanding of how air influences the world's environments and biospheres.