What is a key characteristic of a carbon dioxide extinguisher?

A carbon dioxide extinguisher is distinctive because it does not have a pressure gauge, which is a common feature in many other types of fire extinguishers. This characteristic is due to the fact that carbon dioxide does not need to maintain a specific operating pressure like a compressed gas extinguisher does. Using CO2 ensures that the gas is released effectively, helping to smother the fire by displacing oxygen rather than requiring a gauge to monitor pressure levels.

Other options do not accurately represent the use or properties of carbon dioxide extinguishers. For instance, carbon dioxide extinguishers are not suitable for Class D fires, which involve combustible metals; they are specifically designed for Class B and Class C fires. Additionally, carbon dioxide extinguishers are not particularly effective on Class A fires, which involve ordinary combustibles like wood or paper. While carbon dioxide can be used when water is unavailable, their primary purpose is to extinguish fires involving flammable liquids and electrical equipment rather than serving solely as alternatives when water is not an option.