What key property of carbon dioxide (CO2) assists in extinguishing fires?

The key property of carbon dioxide (CO2) that assists in extinguishing fires is that it does not support burning. CO2 is an inert gas that displaces oxygen in the environment where a fire is burning. Since fire requires oxygen to sustain combustion, the presence of carbon dioxide effectively reduces the concentration of oxygen around the flames. This suffocation, or lack of oxygen, is what helps extinguish the fire.

By filling the air with carbon dioxide, the fire is deprived of one of the three essential elements of the fire triangle: heat, fuel, and oxygen. Without sufficient oxygen, the chemical reactions that produce fire cannot continue, leading to the fire's extinguishment. This property makes CO2 a valuable firefighting agent, particularly in situations where electrical or flammable liquid fires occur, as it does not leave residue or harmful byproducts after use.