The 5 Classes of Fire Explained (A to K)

Chris HuntAbout the Author: Hi! I'm Chris Hunt, and I wrote this article. With years of experience as a former firefighter and knowledge of combustible materials, I have personally researched and compiled the information presented here. Please note that the content provided is solely my opinion and should not be construed as professional advice. Additionally, I do not guarantee the quality or performance of any of the products featured. Please be sure to review the website's Disclaimer, Terms and Conditions before using the site. As an Amazon Associate I earn from qualifying purchases (without additional cost or expense to you).

Fires are classified into different types or ‘classes of fire,’ so we know how best to control them.

The most common time you’ll come across the different types of fire is when you look at fire extinguishers.

Not all fire extinguishers are the same. In addition, different fire extinguishers fight different types of fires.

For example, you wouldn’t want to put out an oil fire with a water-based extinguisher because oil floats on water. Similarly, a water extinguisher wouldn’t be great for an electrical fire because water is a conduit for electricity.

Safety Note: Follow the guidance of your local fire authority about the safety equipment best for you. If there is an active fire, evacuate from the vicinity of the fire and call your fire emergency hotline immediately.

Related Article: The 5 Best Fire Extinguishers for the Home, Kitchen, and Garage

The 5 Classes of Fire (USA)

Note that five fire classifications follow the USA standard system for classifying fires. However, the European and Australian categories slightly differ (jump to the international comparison chart).

The five classes of fire are:

  • Class A Fire: Ordinary Combustible
  • Class B Fire: Flammable Liquids and Gases
  • Class C Fire: Electrical Equipment
  • Class D Fire: Combustible Metals
  • Class K Fire: Cooking Oils and Fats

Class A Fires: Ordinary Combustibles

Ordinary combustibles are the sorts of materials that you will often find around the house. They are typical fuels for house fires.

Examples of ordinary combustibles include:

  • Wood: logs for fireplaces, furniture, and wood-building structures.
  • Paper: such as the paper you might find in the trash and books on your bookshelf.
  • Plastic: such as Tupperware containers, toys, and bags.
  • Cloth: such as clothing and curtains.
  • Rubber: such as the rubber found in shoes.

If you need to extinguish an ordinary combustible fire, it is possible to use most fire suppression techniques, including:

  • Water: Such as water from a garden hose or tap.
  • Dry Chemicals: ABC fire extinguishers usually contain dry chemicals.
  • Other Methods: Fire blankets can deprive a small fire of oxygen.

Because ordinary combustibles are so common in house fires, authorities recommend getting a fire extinguisher with at least an AB rating (Most common fire extinguishers are class ABC).

Extinguisher and Fire Hose

Class B Fires: Flammable Liquids and Gases

In the United States, all flammable liquids and gases are Class B. In Europe and Australia, flammable liquids are Class B, and flammable gasses are Class C. Flammable liquids and gases are commonly found in garages and workshops. In addition, you might find other Class B flammables around your house, such as in your paint kit, alcohol cabinet, and household heating if you use natural gas.

Flammable liquids include:

  • Gasoline: The gas (petrol) you put in your car fits this category. Diesel is part of this category.
  • Most oils: including the oil you put in your car and your chainsaw, car-bike chains.
  • Most paints: Oil-based paints are considered flammable liquids.
  • Alcohol: The spirits on your cocktail shelf are considered flammable liquids.

Flammable gases include:

  • Hydrogen: Commonly used in party balloons (to help them float above air) and as a fuel for some bus transport systems.
  • Butane: There’s a good chance you’ll find this in your cigarette lighter. It may be in your refrigerator as part of the cooling process.
  • Methane: If you use natural gas to heat your home, it’s full of methane. It works in cooking and hot water systems.
  • Ethylene: The agriculture industry often uses it.

The best materials for extinguishing a Class B fire are:

  • Halon was in fire extinguishers until the 1990s when scientists found it was terrible for the Ozone layer.
  • Dry Chemical Fire Extinguisher: Your regular ABC household fire extinguisher is a dry chemical extinguisher capable of fighting Class B fires.
  • Foam: This can be effective for extinguishing liquid gas fires.

Water is not usually recommended for Class B fires as water can scatter the liquid fuel. Further, some liquids float on water, meaning the water is not the best substance for separating the energy from an oxygen source.

Standard household ABC fire extinguishers can suppress flammable liquids and gases (check your extinguisher – most fire districts mandate an ABC extinguisher for your home).

Flying sparks

Class C Fires: Electrical Equipment

In the United States, electrical equipment is considered Class C flammable material. Electrical appliances are considered Class K materials in Europe and Class E materials in Australia (see comparison chart below).

Electrical fires are one of the most common household fire types. In the United States alone, firefighters attend up to 44,880 electrical-related household fires annually.

Electrical equipment that commonly causes fire includes:

  • Clothes Dryers: Clothes dryers can cause fires when not adequately maintained. Lint build-up acts like kindling for sparks, and poorly installed or maintained lint traps can cause problems.
  • Wiring and Cords: Poorly installed wiring can cause sparks. Overloaded power banks can lead to short circuits and power surges.
  • Space Heaters: It is common for people to leave space heaters near loose clothes like bedding, curtains, and clothing left to dry.

The best materials for extinguishing electrical fires include:

  • Dry Chemical Extinguisher: The ideal way to fight a small electrical fire is to use a dry chemical fire extinguisher, such as an ABC-rated household extinguisher.

It is important to note that fire and water are not very good at extinguishing electrical fires because they are electrical conduits. However, it is notable that electricity does not burn – it is the spark and heat required to burn surrounding fuels. Therefore, the fire may resemble another fire class depending on the remaining materials once you remove the electrical source.

Class D Fires: Combustible Metals

Class D fires involve combustible metals as the fuel for the fire. The US, Europe, and Australia consider combustible metals as ”Class D.”

Combustible metals usually have a very high flash point because you must expose vast amounts of heat to the metal before it burns. However, sodium is a metal that can burn upon contact with air or water. In addition, metal shavings are a hazard because the high accessibility of oxygen to the metal surfaces can make combustion more likely.

Combustible metals include:

  • Sodium is a highly reactive metal that can cause combustion when exposed to air or water.
  • Lithium: Such as in laptops and intelligent phone batteries.

The best materials for extinguishing combustible metal fires include:

  • Dry powder: Dry powder is not confused with dry chemical extinguishers. Dry powder extinguishers can extinguish Class D fires.

Combustible metals are less common in households and more common in industrial fires. Therefore, it is usual that fire control districts will not mandate Class D extinguishers to be present at your home (check for your local circumstances).

A regular ABC fire extinguisher is not usually the best for fighting Class D fires. It may, in some instances, exacerbate the fire’s intensity. For example, a scorching combustible metal fire may break water into hydrogen gas and oxygen, acting as reactants for spurring the fire.

Class D dry powder extinguishers absorb heat and separate the metal from oxygen sources.

Cooking with fire stove

Class K Fires: Cooking Fires Involving Oils and Fats

Class K fires are fires that involve cooking oils and fats. In Europe and Australia, these are class F fires.

Common materials in class K fires include:

  • Vegetable Oil: Oils such as vegetable oil, canola oil, butter, etc., for cooking are in this category.
  • Cooking Grease: Grease can accumulate behind and undercooking appliances. Safety inspections of the industrial kitchen will often be checked to ensure no grease build-up, as it poses a severe fire risk.

Typical substances used to suppress fires include:

  • Water Mist: Water is not the best for Class K fires, but misty water can be a good suppressant.
  • Foam: Most Class K fire extinguishers use a substance that turns oils into foams.
  • Fire Suppression Blanket: Fire blankets are regularly used in kitchens if the fire is small enough to be covered entirely by the mantle. The blanket will suffocate the fire by denying it access to oxygen.

Many industrial kitchens, restaurants, etc., must have a Class K fire extinguisher proximal to the kitchen. Check your local requirements.

International Classes (Europe & Australia)

Materials Examples USA Europe Australia
Ordinary Combustibles. Wood, trash, paper, plastic. Class A Class A Class A
Flammable and Combustible Liquids. Gasoline, most oils, oily paints, ethanol. Class B Class B Class B
Flammable and Combustible Gases. Hydrogen, butane, methane, ethylene. Class B Class C Class C
Electrical Fires. Extension cords, space heaters, toasters, and hair dryers. Class C Class K Class E
Flammable Metals. Lithium, potassium, magnesium, titanium, and zirconium. Class D Class D Class D
Cooking Oils and Fats. Vegetable oil, unsaturated fats, lard, butter. Class K Class F Class F

What about a Class E Fire?

Sorry, someone pulled a joke on you. There is no Class E Fire classification in the United States. Canada, Europe, or Australia.

Conclusion

There are five standard classes of fire. Fires are split into these classifications to identify the best ways to suppress them. In addition, various forms of fire extinguishers are used to stop multiple types of fires. Ensure you use a fire extinguisher mandated by your local fire district for your specific establishment, and keep it in an approved fire extinguisher cabinet.