Carbon Dioxide 101


Carbon dioxide (chemical name CO2) is a clear gas composed of one atom of carbon (C) and two atoms of oxygen (O). Carbon dioxide is one of many molecules where carbon is commonly found on the Earth. It does not burn, and in standard temperature and pressure conditions it is stable, inert, and non-toxic. Carbon dioxide occurs naturally in small amounts (about 0.04%) in the Earth's atmosphere.

carbon dioxide molecule
Depiction of a carbon dioxide molecule


Carbon dioxide is a minor part of the air that humans breath. It is also a byproduct of our body’s metabolism and is subsequently exhaled from the lungs.


Despite the minor amount of CO2 in the air, it is essential to plant life and is a key part of the global carbon cycle. Plants take in CO2, break down the CO2 into carbon and oxygen, release the oxygen to the atmosphere, and then retain the carbon to live and grow. When the plant dies or is burned, the carbon recombines with O2 in the air and CO2 is formed again, completing the cycle.

Myth: The presence of CO2 in the atmosphere is bad and only comes from the burning of fossil fuels.
Reality: Carbon dioxide is derived from both natural and anthropogenic sources, is essential to plant life, and is a key part of the Earth’s carbon lifecycle.

In what ways is carbon dioxide one of the many chemical forms of carbon on the Earth?