How Are Fire Extinguishers Classified?

There are five classes of fire extinguishers.

In the United States, fire extinguishers are classified according to the type of fire they are designed to extinguish. There are five classes of portable fire extinguishers, and they are labeled with a corresponding letter. Some fire extinguishers can be used on more than one type of fire, which means these extinguishers have two or more classes on their labels.

Class A: Ordinary Combustibles

Class A fires involve ordinary combustibles such as wood, paper, cloth, plastic or rubber. These fire extinguishers contain pressurized water. They are labeled with an "A" within a green triangle.

Class B: Flammable Liquids

In Class B fires, flammable liquids such as oils, grease, solvents, gasoline and some paints, would be burning. These extinguishers contain pressurized carbon dioxide. Class B fire extinguishers are labeled with a red square containing a "B."

Class C: Electrical Equipment

Class C fires are fires that involve electrical equipment such as computers, wiring or fuse boxes. They contain either carbon dioxide or dry chemicals. The labels of Class C fire extinguishers have the letter "C" within a blue circle.

Class D: Metals

Class D fire extinguishers are specialty extinguishers that are used for fires involving shavings or flakes of combustible metals, which include titanium and sodium. These extinguishers contain a dry powder consisting of sodium chloride, but most are specialized to extinguish a specific metal. The "D" will be in a yellow decagon.

Class K: Combustible Cooking Fluids

Class K fires involve burning cooking oils or fats. These specialty extinguishers are used in some restaurant kitchens because Class B extinguishers don't always work on fires in commercial cookers. Class K extinguishers may contain either dry or wet chemicals. They are labeled with a "K" in a black hexagon.

References

• New York City Fire Department: Classes of Extinguishers
• Select Safety Sales: Fire Extinguishers---Classes, Types and Use

Resources

• University of Oklahoma Police Department: How to Use a Fire Extinguisher