Before you purchase a fire extinguisher, it's important to understand the different types of fires. Chemical fire extinguishers are filled with different fire suppressants, and choosing a type of extinguisher with the wrong contents could actually make a fire worse (like throwing water on a grease fire). Household fires fall under three classifications, depending on the type of fuel burning. The most common fire extinguisher classifications are A, B, C, and K. Class A: Solid combustible materials that are not metals, like wood, paper, cloth, plastics, and rubber Class B: Flammable liquids, like gasoline, oil, grease, and paints Class C: Electrical equipment, like appliances and outlets Class K: Cooking oils and greases, animal fats, and vegetable fats ABC fire extinguishers will handle most household fires, but just to be on the safe side, it's smart to also have a K-rated fire extinguisher on hand for your kitchen.