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A Guide to the 5 Main Types of Fire

Created on 11.21

Imagine a fire has just broken out in your facility. Your first instinct is to grab the nearest fire extinguisher. But did you know that using the wrong type of extinguisher can be ineffective at best, and at worst, catastrophically dangerous? Using water on a grease fire, for example, can cause a violent explosion of flames. This is why a fundamental understanding of the different types of fire is not just for firefighters—it's essential knowledge for everyone.

Knowing what is burning—the fuel source—is the key to safely and effectively controlling a blaze. For engineers, facility managers, and safety officers, this knowledge is the bedrock of a robust fire safety plan. This guide will break down the fire classification system, explain each category in detail, and provide the practical insights you need to make life-saving decisions.

Why Fire Classification Matters

At its core, fire classification is a system of categorizing fires based on their fuel source. The simple reason this matters is that different fuels require different extinguishing agents. Think of it like a medical diagnosis: you can't prescribe the right treatment without first identifying the illness. In the same way, you can't choose the right fire extinguisher without knowing the class of fire you are facing.

Applying the wrong agent can be disastrous. Water on an electrical fire can lead to electrocution. Water on a flammable liquid fire can spread the burning fuel across a wider area. Therefore, a proper fire safety strategy begins with identifying the potential types of fire in your environment.

A Tale of Two Systems: US vs. International Standards

While the science of fire is universal, the way we classify it can vary slightly by region. Most of the world, including Europe and Australia, uses a system that includes Class F. In the United States, the system is slightly different, most notably classifying commercial kitchen fires as Class K.

Here’s a quick comparison:

United States Classification	Fuel Source	European/International Equivalent
Class A	Ordinary Combustibles	Class A
Class B	Flammable Liquids & Gases	Class B
Class C	Energized Electrical	Class C (sometimes unclassified)
Class D	Combustible Metals	Class D
Class K	Cooking Oils & Fats	Class F

For the purpose of this guide, we will focus on the American system (Classes A, B, C, D, and K), a classification standard detailed in fire safety resources from top authorities like the U.S. Fire Administration (USFA).

An infographic detailing the five main types of fire classifications used in the United States.

A Detailed Breakdown of the 5 Main Types of Fire

Understanding each fire class is the most critical step. Let's dive into the specifics of what defines them and how they should be handled.

Class A: Ordinary Combustibles

This is the most common type of fire. Class A fires involve solid, organic materials that leave behind ash.

Fuels: Wood, paper, cloth, rubber, plastics, and trash.
Where to Find Them: Office buildings, schools, homes—virtually any environment.
How to Extinguish: Water-based extinguishers are highly effective as they cool the fuel. ABC dry chemical extinguishers also work by interrupting the fire's chemical reaction.

Class B: Flammable Liquids and Gases

Class B fires are incredibly dangerous because their fuel can spread quickly and reignite easily.

Fuels: Gasoline, diesel fuel, oil, propane, natural gas, paint, and solvents.
Where to Find Them: Garages, workshops, manufacturing plants, and fuel storage areas.
How to Extinguish: The goal is to smother the fire, cutting off its oxygen supply. Carbon dioxide (CO2) and ABC dry chemical extinguishers are effective. Crucially, never use water, as it can cause the burning liquid to splash and spread.

Class C: Energized Electrical Equipment

The defining characteristic of a Class C fire is that it involves live electrical equipment. The primary hazard here is not just the fire, but the risk of electric shock.

Fuels: Overloaded wiring, short circuits, appliances, computers, and power tools.
Where to Find Them: Data centers, server rooms, office spaces, and anywhere with electrical machinery.
How to Extinguish: You need a non-conductive agent. CO2 and ABC dry chemical extinguishers are the standard choices. Once the power source to the equipment is shut off, the fire essentially becomes a Class A or B fire.

Class D: Combustible Metals

This is a highly specialized and dangerous class of fire typically found only in industrial or laboratory settings. These fires burn at extremely high temperatures and react violently with water.

Fuels: Magnesium, titanium, potassium, and sodium.
Where to Find Them: Aerospace facilities, chemical labs, and high-tech manufacturing.
How to Extinguish: Requires a special Class D dry powder agent (not to be confused with dry chemical). These agents work by smothering the metal and absorbing heat. Never use water or any other common extinguisher.

Class K: Commercial Kitchens

While they involve flammable liquids (cooking oils), these fires are in their own category due to their unique properties and high temperatures.

Fuels: Cooking oils, grease, and animal fats.
Where to Find Them: Restaurants, cafeterias, and commercial food processing facilities.
How to Extinguish: Class K fires require a wet chemical extinguisher. The agent is sprayed as a fine mist that cools the fire and reacts with the oil in a process called saponification, creating a thick, soapy foam that smothers the fire and prevents re-ignition. Explore Our Kitchen Fire Suppression Systems

How to Identify the Type of Fire

In a real emergency, you won't have time for a detailed analysis. Your identification needs to be quick and based on context. Ask yourself:

What is burning? Can you clearly see if it's a trash can, a puddle of liquid, or a piece of equipment?
Where is the fire located? A fire in a kitchen is likely Class K. A fire in a server room is likely Class C.
Are there symbols nearby? Most commercial environments have signs indicating the types of fire risks present.

The most important rule: If you are ever in doubt about the class of fire or your ability to fight it safely, do not hesitate. Your priority is to evacuate and call for professional help.

The label of an ABC fire extinguisher showing it is rated for different classes of fire.

Beyond the Basics: International Classifications

As mentioned, other parts of the world use slightly different systems. For example, the Fire Industry Association (FIA) in the UK outlines a system where Class F is the direct equivalent of the US Class K. While the letters may differ, the underlying science and the principle of matching the extinguisher to the fuel remain exactly the same.

Conclusion: Knowledge Is Your Best Defense

Understanding the main types of fire is the first and most critical step toward real preparedness. It informs every decision, from the type of extinguishers you purchase to the training you provide your team. By recognizing that a fire's fuel source dictates the method of attack, you move beyond guesswork and into the realm of effective, life-saving action. This knowledge empowers you to create a truly resilient safety environment.

Are you confident your facility is equipped with the right fire safety solutions for all potential risks? The experts at our fire safety company can provide a comprehensive risk assessment to ensure you are fully protected. Contact us today to learn more.