Fires involving flammable liquids, greases, and gases are which class?

• A. Class A
• B. Class B
• C. Class C
• D. Class D

Answer: (B)

Fires fueled by liquids and gases are categorized by the fuel involved, so those caused by flammable liquids, greases, and gases are Class B fires. This matters because the suppression approach focuses on cooling and isolating the fuel rather than the solid material. Extinguishing options typically include foam, dry chemical powders, or CO2, which help separate the fuel from the air or cool the liquid surface. Water is generally avoided for Class B because it can spread the liquid or push vapors, potentially making the fire worse. Note that in commercial kitchens cooking-oil fires are often addressed with Class K extinguishers, but in this broader classification, greases are grouped under Class B. The key idea is that the class is defined by the fuel type, guiding the appropriate extinguishing method.