There are five classes of fire extinguishers. Each class (A, B, C, D, and K) is used to extinguish different types of fires. Class A extinguishers are used on paper and wood fires; Class B extinguishers put out grease, oil, gasoline, and other flammable liquid fires; Class C extinguishers are for electric fires; Class D extinguishers are used on flammable metals; and Class K extinguishers put out fires in commercial cooking equipment. Multipurpose extinguishers are labeled as such and can be used on more than one type of fire.