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How Many Types of Fire Extinguishers Are There?

There are five primary types of fire extinguishers, each designed for specific classes of fire: Class A, Class B, Class C, Class D, and Class K. Some sources list additional specialized extinguishing agents, but the five main classes cover the vast majority of residential and commercial needs. Choosing the correct extinguisher for the fire type is critical for safety and effectiveness.

The Five Main Classes of Fire Extinguishers

Fire extinguishers are categorized by the classes of fires they can extinguish. The U.S. Fire Administration identifies five primary types, each corresponding to a fire class:

Many extinguishers are multi-purpose and can handle multiple classes, such as A-B-C extinguishers commonly found in homes.

Class A: Ordinary Combustibles

Class A extinguishers are for fires involving ordinary combustible materials like wood, paper, cloth, rubber, and many plastics. These are the most common type of fire in homes and offices. The numerical rating on a Class A extinguisher indicates the amount of water it holds and the relative fire-extinguishing capacity. For example, a 2-A extinguisher has twice the extinguishing capability of a 1-A extinguisher. Water and foam extinguishers are typical for Class A fires, but dry chemical multi-purpose extinguishers are also effective.

Class B: Flammable Liquids and Gases

Class B extinguishers are designed for fires involving flammable liquids such as gasoline, oil, grease, and oil-based paints. They are also suitable for flammable gases like propane and butane. The numerical rating on a Class B extinguisher indicates the approximate square footage of a flammable liquid fire that a non-expert can extinguish. For instance, a 10-B extinguisher can cover about 10 square feet of burning liquid. Common extinguishing agents include carbon dioxide, dry chemical, and foam. Never use water on a Class B fire, as it can spread the flammable liquid.

Class C: Energized Electrical Equipment

Class C extinguishers are for fires involving energized electrical equipment, such as appliances, wiring, circuit breakers, and outlets. The extinguishing agent must be non-conductive to prevent electrical shock. Class C extinguishers do not have a numerical rating; the letter "C" indicates that the agent is non-conductive. Carbon dioxide and dry chemical extinguishers are commonly rated for Class C fires. Once the electrical equipment is de-energized, the fire may be treated as Class A or B, depending on the materials involved.

Class D: Combustible Metals

Class D extinguishers are for fires involving combustible metals such as magnesium, titanium, potassium, and sodium. These metals burn at extremely high temperatures and can react violently with water or other common extinguishing agents. Class D extinguishers use dry powder agents specifically formulated for the particular metal. They do not have a numerical rating or a picture designator. These extinguishers are typically found in industrial settings, laboratories, and facilities that handle combustible metals.

Class K: Cooking Oils and Fats

Class K extinguishers are designed for fires involving cooking oils and fats, such as those in deep fryers. They are required in commercial kitchens according to NFPA 10. Class K extinguishers use wet chemical agents that cool the fire and create a soap-like foam to prevent re-ignition. They are not interchangeable with Class B extinguishers for cooking oil fires because of the high temperatures involved. Home kitchens typically do not require a Class K extinguisher, but a multi-purpose A-B-C extinguisher is recommended.

Multi-Class and Specialized Extinguishers

Many extinguishers are rated for multiple fire classes. The most common is the A-B-C dry chemical extinguisher, which is suitable for ordinary combustibles, flammable liquids, and electrical fires. B-C extinguishers are also available for flammable liquids and electrical fires. Some sources list additional extinguishing agents beyond the five classes, such as water mist, foam, and clean agent extinguishers. For example, the City of Lompoc notes eight different extinguishing agents, including ABC Dry Chemical, BC Dry Chemical, Dry Powder, Water, Foam, Wet Chemical, and Clean Agent. However, these agents are used within the five fire classes.

Choosing the Right Fire Extinguisher

Selecting the correct extinguisher depends on the potential fire hazards in your environment. For most homes, a multi-purpose A-B-C extinguisher is recommended. The NFPA advises that you should only use a fire extinguisher if the fire is small, contained, and you have a clear escape route. Always call 911 first and ensure everyone is safe. For commercial settings, a fire risk assessment should determine the appropriate types and placement of extinguishers. Regular inspection and maintenance are essential to ensure extinguishers are functional when needed.

How to Use a Fire Extinguisher

The ABC Fire service notes that with the correct extinguisher, most fires can be brought under control within two minutes. Remember the PASS technique:

If the fire does not go out quickly, evacuate immediately and close doors behind you to contain the fire.