CO2 extinguishers are fire extinguishers that use carbon dioxide gas to put out fires. They work by displacing oxygen around the fire, which is essential for combustion. This makes them effective for electrical fires and flammable liquids, as they do not leave any residue behind. These extinguishers are typically identified by their black label and are available in various sizes. When using a CO2 extinguisher, it is important to aim at the base of the fire and sweep from side to side. Always ensure you are at a safe distance while operating the extinguisher.