What should not be used to extinguish a class B fire?

What should not be used to extinguish a class B fire?

• A. Water
• B. Foam
• C. Dry chemical powder
• D. CO2

Answer: (A)

For a fire involving flammable liquids, the aim is to separate the fuel from the heat and air or to blanket and cool the liquid so it cannot continue to burn. Water is not effective here because most flammable liquids don’t mix with it and will spread when water is applied. The liquid can float on or beneath the water, spreading across a larger area, creating more vapor and a larger, more dangerous fire. Water also doesn’t address the chemical reactions occurring in the flame, so the fire can re-ignite once the water boils away. In contrast, foam blankets the liquid and cools it, dry chemical powder interferes with the flame chemistry, and CO2 displaces the surrounding oxygen. That’s why water should not be used on Class B fires.

For a fire involving flammable liquids, the aim is to separate the fuel from the heat and air or to blanket and cool the liquid so it cannot continue to burn. Water is not effective here because most flammable liquids don’t mix with it and will spread when water is applied. The liquid can float on or beneath the water, spreading across a larger area, creating more vapor and a larger, more dangerous fire. Water also doesn’t address the chemical reactions occurring in the flame, so the fire can re-ignite once the water boils away. In contrast, foam blankets the liquid and cools it, dry chemical powder interferes with the flame chemistry, and CO2 displaces the surrounding oxygen. That’s why water should not be used on Class B fires.