What extinguishing method is used when a foam blanket is placed over a burning liquid?

• A. Cutting off the oxygen
• B. Cooling the fuel below its kindling temperature
• C. Chemically converting the fuel to a non-fuel
• D. Reflecting evolved heat back into the fire

Answer: (A)

The correct answer involves the method by which a foam blanket is deployed over a burning liquid. This technique primarily functions by cutting off the oxygen supply to the flames. When foam is applied, it forms a blanket over the surface of the burning liquid. The foam's structure helps to smother the fire by creating a barrier that limits the availability of oxygen needed for combustion.

This is particularly effective for flammable liquids, as it not only suppresses the flames but also prevents the vaporization of flammable gases that can lead to re-ignition or spread of the fire. The properties of the foam help to trap the vapors underneath, effectively inhibiting the fire's ability to sustain itself.

Other methods of extinguishing fires, such as cooling the fuel or chemically converting it, do not specifically apply in the context of foam application over liquids. Reflecting heat back into the fire is also not relevant when discussing the primary function of the foam in creating an oxygen-deprived environment. Therefore, utilizing foam to cut off the oxygen aligns best with the goal of extinguishing a fire involving burning liquids.