Carbon dioxide is a non-corrosive, odorless, colorless gas. During discharge, it presents as a white fog; it does not dirty or otherwise negatively affect the materials with which it comes into contact. The principle of extinguishment is dual: CO2 acts by suffocation or oxygen dilution, reducing the concentration of the oxygen present in the area, and by the cooling caused by the rapid expansion of the gas. Carbon dioxide must not be used for protecting normally-occupied areas, since inhalation can cause asphyxia even at low concentrations. Furthermore, visibility is greatly reduced during discharge due to the formation of CO2 fog. This extinguishing agent can be used in normally-unoccupied areas if suitable safety devices are installed.