The gas commonly used in fire extinguishers is carbon dioxide (CO2). This gas effectively suppresses flames by displacing oxygen, which is essential for combustion. When CO2 is released from the extinguisher, it cools the surrounding area and interrupts the fire triangle, which consists of heat, fuel, and oxygen. Carbon dioxide extinguishers are particularly effective on flammable liquids and electrical fires. They leave no residue, making them suitable for use in environments like offices and laboratories. However, CO2 extinguishers should not be used on fires involving metals or combustible materials, as they may not effectively suppress those types of fires.