According to the University of South Carolina, carbon dioxide fire extinguishers are only appropriate for Class B and Class C fires. Class B fires are based on flammable liquids, while Class C fires are electrical in nature. Carbon dioxide fire extinguishers are not appropriate for extinguishing any other fires.
Most typical fires that feature combustible solids, such as paper or wood, are best extinguished with water. However, flammable liquids, such as oil, will splatter if water is poured on them. Some oil fires may even explode when sprayed with water. Instead, carbon dioxide fire extinguishers remove the oxygen from the fire, which smothers it without splattering. Electrical fires cannot be extinguished with water because water conducts electricity.