CO2, also known as carbon dioxide or carbonic gas, is a colourless, inert, non-toxic gas.

Its natural sources are numerous: volcanic eruptions, plant, animal and human respiration, forest fires, decomposition of organic material, combustion, etc.

Due to human activity, CO2 concentrations in the atmosphere are increasing every year by an average of 0.5%, which represents a 30% increase over the last two centuries. It is the main greenhouse gas.