For Class B fires, which extinguishing agent is commonly used as the primary?

For Class B fires, which extinguishing agent is commonly used as the primary?

• A. FOAM
• B. WATER
• C. DRY CHEMICAL
• D. CO2

Answer: (A)

Fires involving flammable liquids (Class B) are fought best with an agent that blankets the liquid surface, cools it, and blocks vapor from escaping. Foam does exactly that: it forms a stable foam layer that floats on the liquid, cooling the fuel and separating it from the air so vapors can’t sustain the flame. This surface blanket is especially important for hydrocarbon spills, like gasoline or oil, where you need rapid vapor suppression over a wide area. Water isn’t ideal here because it can spread the flammable liquid and extend the burn rather than smother it. Other options, like dry chemical, can extinguish but aren’t as effective for large liquid spills since they don’t provide the same sustained vapor suppression and cooling as foam. CO2 can displace oxygen in enclosed spaces but doesn’t create the surface barrier needed for a Class B liquid fire and isn’t practical for open spills. So, foam is the best primary extinguisher for Class B fires because it blankets and cools the liquid, effectively cutting off the fire’s fuel supply.

Fires involving flammable liquids (Class B) are fought best with an agent that blankets the liquid surface, cools it, and blocks vapor from escaping. Foam does exactly that: it forms a stable foam layer that floats on the liquid, cooling the fuel and separating it from the air so vapors can’t sustain the flame. This surface blanket is especially important for hydrocarbon spills, like gasoline or oil, where you need rapid vapor suppression over a wide area.

Water isn’t ideal here because it can spread the flammable liquid and extend the burn rather than smother it. Other options, like dry chemical, can extinguish but aren’t as effective for large liquid spills since they don’t provide the same sustained vapor suppression and cooling as foam. CO2 can displace oxygen in enclosed spaces but doesn’t create the surface barrier needed for a Class B liquid fire and isn’t practical for open spills.

So, foam is the best primary extinguisher for Class B fires because it blankets and cools the liquid, effectively cutting off the fire’s fuel supply.