Which gas is commonly used to extinguish fires?

• A. Oxygen
• B. Hydrogen
• C. Carbon Dioxide
• D. Nitrogen

Answer: (C)

Fire has to have heat, fuel, and enough oxygen to keep burning, so one effective way to stop a fire is to reduce the oxygen available or shield the flame from air. Carbon dioxide does this well: it is heavier than air, blankets the fire, and displaces the oxygen the flames need, so combustion slows or stops. It’s also non-flammable and doesn’t leave residue, which is why it’s commonly used in extinguishers, especially for electrical fires. Of course, using CO2 in occupied spaces can be dangerous because it can cause asphyxiation, so safety precautions are important. Oxygen would feed a fire, hydrogen is a fuel and would make it worse, and nitrogen is used in some specialized inerting systems but isn’t the standard, versatile extinguishing gas for everyday fires.