Carbon dioxide extinguishes the fire by which mechanism?

Carbon dioxide extinguishes the fire by which mechanism?

• A. Reducing the overall oxygen content in the room below a sustainable level, usually below 15%
• B. Absorbing heat from the flame
• C. Cooling the fuel
• D. Forming a chemical barrier

Answer: (A)

Carbon dioxide extinguishes fire by starving the flame of oxygen. CO2 is denser than air, so when it is released into a room it blankets the fire and displaces some of the surrounding air, lowering the local oxygen concentration. Flames struggle and often cannot sustain combustion when the oxygen level drops below about 15% of the air. Because the primary effect is reducing the amount of oxygen available for the chemical reactions of combustion, the cooling or heat-absorbing effects of CO2 aren’t the main reason the fire goes out, and CO2 doesn’t create a chemical barrier to the fuel. This method works best in enclosed spaces, but it also reduces breathable air, so safety for people is a critical concern.

Carbon dioxide extinguishes fire by starving the flame of oxygen. CO2 is denser than air, so when it is released into a room it blankets the fire and displaces some of the surrounding air, lowering the local oxygen concentration. Flames struggle and often cannot sustain combustion when the oxygen level drops below about 15% of the air. Because the primary effect is reducing the amount of oxygen available for the chemical reactions of combustion, the cooling or heat-absorbing effects of CO2 aren’t the main reason the fire goes out, and CO2 doesn’t create a chemical barrier to the fuel. This method works best in enclosed spaces, but it also reduces breathable air, so safety for people is a critical concern.