Which extinguishing principle is associated with carbon dioxide extinguishers?

• A. Stored pressure
• B. Cartridge pressure
• C. Piston action
• D. Manual discharge

Answer: (A)

Carbon dioxide extinguishers extinguish fires by displacing and reducing the oxygen around the flame, effectively smothering the fire and interrupting the combustion process. The dense CO2 blankets the flame and lowers the concentration of breathable air, which quickly suppresses many small fires, especially electrical ones where water would be hazardous. The options given describe how the extinguisher is pressurized (stored pressure means the CO2 is already pressurized inside the cylinder; cartridge pressure uses a separate cartridge to pressurize the extinguisher) or relate to other mechanical aspects (piston action, manual discharge). These describe the method of delivering the agent, not the extinguishing mechanism itself. So, the fundamental principle at work for carbon dioxide extinguishers is oxygen displacement (smothering), not the type of pressurization.