Carbon dioxide is a gas with a chemical formula of CO2, indicating that it is a carbon atom double-bonded to two oxygen atoms. It is made from burning wood, fuel or anything else that contains carbon.
When it is pure, carbon dioxide is odorless in low concentrations and colorless. It makes up a tiny percentage of the atmosphere of the Earth and a large percentage of the atmosphere of Mars.
Carbon dioxide is heavier than air, and it can be poured from one vessel into another. Because it is incombustible, it is used extensively in fire extinguishers.
Carbon dioxide plays a crucial role in animal respiration. Animals breathe in oxygen and exhale carbon dioxide. Plants absorb carbon dioxide and give off oxygen. In this way, plants and animals sustain each other.
The gas is also produced during decay and can sometimes be found at the bottom of wells, caves and mines. This can pose a suffocation risk to anyone who ventures into these places. Carbon dioxide is not necessarily toxic, but too much of it in the atmosphere can prevent oxygen from getting into the body.
When put under pressure at temperatures of - 5 degrees Fahrenheit, carbon dioxide turns into a liquid. Carbon dioxide can also be frozen as dry ice.