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A grease fire flares up on the stovetop. Across town, a fuse box sparks and starts to smoke. Same day, two very different fires, and neither calls for the same kind of fire extinguisher. That’s the catch: not all fires behave the same, and reaching for the wrong extinguisher can do more harm than good.

The classes of fire chart isn’t something to glance at during safety training; it’s a practical tool that helps you act quickly, safely, and effectively when it matters most.

Key Takeaways

• Not all fires are the same—each class is defined by what’s burning and requires a specific response.
• Using the wrong fire extinguisher can be dangerous and non-compliant, especially in commercial or public buildings.
• Swartz Fire & Safety helps ensure your property is prepared with the right extinguishers, inspections, and expert guidance.

Quick Overview: What Are Fire Classes, Really?

Fires don’t start the same way and they definitely don’t need the same response. What’s burning is what defines the type of fire, and that’s exactly what fire classes are based on.

Some fires involve ordinary combustible materials like paper or wood. Others start with flammable liquids, electrical equipment, or even cooking oils. These differences matter more than most people realize because the wrong move or the wrong fire extinguisher can actually make the situation worse.

The fire chart

The fire classes chart groups fires into categories—Class A, B, C, D, and K—based on the type of fuel that’s burning. It also helps match each class to the right fire extinguisher, whether it's a wet chemical extinguisher for a kitchen fire or a clean agent fire extinguisher for electronic equipment.

Understanding the chart means you’re better equipped to handle everything from class B fires involving flammable or combustible liquids to class C fires tied to electrical hazards and even rare but dangerous class D fires involving combustible metals.

In short, knowing your fire classes means staying safe in a real fire emergency.

The Fire Classes

Not all fires are the same, and neither are the extinguishers used to stop them. Below is a breakdown of the five main fire classes recognized in the U.S., each defined by what’s burning and how best to put it out.

Class A fires

These are the most common fires—burning materials you find in just about any home or office.

Examples: Wood, paper, fabric, trash

Where it happens: Living rooms, offices, schools

Best extinguishers: Water, foam, or multi-use ABC fire extinguishers

Class B fires

These fires involve substances that ignite quickly and burn hot—flammable liquids and sometimes gases.

Examples: Gasoline, oil-based paint, alcohol, propane

Where it happens: Garages, workshops, fuel storage, industrial settings

Best extinguishers: Foam, carbon dioxide (CO₂), dry chemical extinguishers

Important: Never use water—it spreads the flames.

Class C fires

Caused by energized electrical equipment, these fires carry the added risk of electric shock.

Examples: Wiring, circuit breakers, power tools, outlets

Where it happens: Kitchens, server rooms, offices

Best extinguishers: CO₂ or dry chemical fire extinguishers and never water

Class D fires

Rare but serious, metal fires need special attention and specialized agents.

Examples: Magnesium, titanium, sodium

Where it happens: Labs, factories, industrial settings

Best extinguishers: Class D powder extinguishers—never water or foam

Class K fires

These fires involve cooking oils, animal fats, or grease at high heat—especially in commercial kitchens.

Examples: Deep fryers, stovetops, ovens

Where it happens: Restaurants, food trucks, cafeterias, homes

Best extinguishers: Wet chemical extinguishers designed to cool and prevent re-ignition

One Chart, Big Difference

The Classes of Fire Chart isn’t some behind-the-scenes tool meant only for first responders. It’s a quick-reference lifesaver for anyone responsible for a building—whether that’s a small business owner, a facility manager, or a homeowner who wants to be ready for the unexpected.

This simple chart ties each type of fire to the right fire extinguisher, so you’re not guessing when it matters most. Whether you're dealing with class A fires involving paper and wood, class B fires fueled by flammable liquids, or class C fires started by electrical equipment, the chart makes it easy to connect the risk to the right response.

Color-coded icons, extinguisher labels, and symbols help you identify the proper tool fast, like reaching for a class B fire extinguisher when facing a flammable liquid fire or choosing a class K fire extinguisher in a grease-filled kitchen. It’s about avoiding fire risks, minimizing damage, and stopping the situation from escalating.

Why It Matters for Your Property

Fires don’t wait for convenience, and neither do inspections, insurance audits, or safety codes. Having the right type of fire extinguisher on hand is just smart. 

Many commercial and public buildings are required to be equipped for specific types of fire, from fires involving electrical equipment to those caused by cooking appliances, natural gas, or even chemical reactions.

When an inspector walks in—or worse, when a fire breaks out—what matters is that your portable fire extinguishers match the risks in your space. That means having class C fire extinguishers near electronics and panels or ensuring your kitchen is ready for hot grease, animal oils, and toxic fumes with the proper wet chemical units. 

The goal is to avoid escalation, injury, and noncompliance.

And let’s not forget peace of mind. The right equipment, inspected and placed in the right locations, removes the guesswork in a moment of urgency. It’s about being prepared.

How Swartz Fire & Safety Can Help

Fire safety doesn’t end with buying an extinguisher. That’s where Swartz Fire & Safety comes in. We offer full-service support for commercial and public buildings across Central Pennsylvania so you stay equipped and compliant, no matter what type of fire you're facing.

Our team inspects, services, and supplies extinguishers for everything from class A fires to fires involving flammable liquids, electrical fires, and even burning metal in industrial settings. We also install and maintain fire suppression systems tailored to high-risk areas, like kitchens, server rooms, or any space with sensitive electrical equipment.

Need support on-site? Our mobile service fleet covers a wide area, bringing extinguisher recharging, inspections, and emergency support directly to your location so you’re not left scrambling when a fire hazard becomes real.

From preventing electrical shock to making sure you're equipped to extinguish fires involving flammable gases or conducting electricity, we’re here to help you feel confident in your fire protection plan, not just as a vendor but as a safety partner.

Know the Chart. Match the Risk. Get It Right.

Not sure if your extinguishers match your fire risks? Let’s walk through your property together—class by class. Contact us today!

Conclusion

Fire safety starts with knowledge, but it’s the follow-through that protects lives and property. With the classes of fire chart in hand—and the right support from Swartz Fire & Safety—you’re not just ready. You’re prepared.

Frequently Asked Questions

What are the 5 classes of fires?

In the U.S., fires are grouped into five main classes based on the type of fuel involved:

1. Class A: Ordinary combustibles like paper, wood, and fabric
2. Class B: Flammable liquids and gases such as gasoline or oil
3. Class C: Fires involving energized electrical equipment
4. Class D: Combustible metals like magnesium or titanium
5. Class K: Cooking oils and fats—mostly found in commercial kitchens

Each class requires a specific type of fire extinguisher for safe and effective response.

What is class A, class B, class C, and class D fire?

These labels refer to different types of fires:

1. Class A fires involve things like wood, trash, or cloth.
2. Class B fires come from flammable liquids or gases.
3. Class C fires start in electrical wiring, panels, or devices.
4. Class D fires are rare and involve burning metals, mostly in industrial environments.

Knowing the class helps you choose the right extinguisher and avoid making the fire worse.

What is the ISO standard for classes of fire?

The ISO standard (ISO 3941) also classifies fires, but it includes Class F instead of Class K. Class F in the ISO system covers cooking oil and fat fires—the same as Class K in the U.S. system. So, while the naming varies slightly, the fire types are essentially the same.

What are the classes of fire onboard?

Onboard ships or marine vessels, the same basic fire classes apply—but with more emphasis on certain types:

1. Class A: Solids like bedding, wood, or textiles
2. Class B: Fuel oils, lubricants, and other liquids
3. Class C: Electrical systems
4. Class D: Metals, if present in specialized equipment
5. Class K (or F): Cooking appliances in galleys

Because fire at sea is especially dangerous, proper extinguishers and training are critical onboard.