Req 2 — Fire Extinguishers

Not all fires are the same, and not all extinguishers work on all fires. Using the wrong extinguisher can make a fire worse—sometimes dangerously worse. This requirement teaches you to match the right tool to the right fire.

Classes of Fires

Fires are classified by what’s burning. Each class has different behavior and requires a different approach.

Class A: Ordinary Combustibles

Wood, paper, cloth, rubber, most plastics—these are materials in almost every building. Class A fires burn solid materials and produce ash. They’re the most common type of house fire. Water works well on Class A fires because it cools the fuel below the ignition temperature.

Class B: Flammable Liquids & Gases

Gasoline, kerosene, paint, propane, natural gas. These burn hot and fast, and water should never be used on a Class B fire. Why? Water is denser than gasoline—if you spray water on burning gasoline, the water sinks below the fuel, turns to steam, and explodes upward, spreading burning fuel everywhere. Class B fires need foam, CO₂, or dry powder extinguishers that smother or cool without water.

Class C: Electrical Equipment

Fires involving live electrical equipment (appliances plugged in, electrical panels, live wires). The danger is that water conducts electricity—if you spray water on live electrical equipment, the water becomes a path for electricity, and you can be electrocuted. Class C fires need non-conductive agents like CO₂ or dry powder. Once the electricity is turned off, a Class C fire becomes a Class A or B fire, depending on what was burning.

Class D: Flammable Metals

Magnesium, titanium, potassium—reactive metals burn at extreme temperatures and ignite easily. These fires are rare but extremely dangerous because water actually accelerates the burn. Class D fires need special dry powder extinguishers designed for metal fires.

Class K: Commercial Cooking Oils

In commercial kitchens, fires often involve hot cooking oil (olive oil, vegetable oil, or animal fat). When water hits hot oil, it flashes to steam, and burning oil spatters everywhere. Class K fires need wet chemical agents that cool the oil and form a foam blanket.

Fire Extinguisher Types & Labels

Every fire extinguisher is labeled with the classes it can handle. A multipurpose ABC extinguisher works on ordinary combustibles, flammable liquids, and electrical equipment. A CO₂ extinguisher is best for Class B and C fires. A wet chemical extinguisher is designed for Class K fires in commercial kitchens.

The label shows which classes the extinguisher handles, and the rating number (like 3A:40B:C) indicates the size of fire it can tackle.

Water & Foam Extinguishers (Class A, some B)

• Use water or water-based foam
• Effective on burning wood, paper, cloth
• Never use on electrical fires or flammable liquid fires
• Heavy and large; common in homes and offices

Dry Powder Extinguishers (ABC, BC, or D)

• Use pressurized powder that coats fuel and breaks the chain reaction
• ABC multipurpose type works on most common fires
• BC type works on flammable liquids and electrical fires (no Class A)
• D type is specialized for metal fires
• Can reduce visibility due to powder cloud; use in short bursts

CO₂ Extinguishers (Class B, C)

• Use compressed carbon dioxide gas
• Displaces oxygen and cools the fire
• Safe for electrical equipment (non-conductive)
• Makes a loud hissing sound and can frost your hands
• Effective but requires getting close to the fire

Wet Chemical Extinguishers (Class K, some A)

• Spray a liquid that cools oil and forms a protective foam blanket
• Designed for commercial kitchen fires with hot oil
• Never use water instead—it will cause the oil to splatter

How to Use a Fire Extinguisher: PASS

The standard method for using any fire extinguisher is remembered as PASS:

P — Pull the pin at the top of the extinguisher. This breaks the seal and readies the device.

A — Aim low at the base of the flames, not at the top. The flames you see are the result of combustion—the real burning is happening at the fuel source. Aiming at the base attacks the fuel.

S — Squeeze the lever (the handle) with steady pressure. The extinguisher will discharge its contents.

S — Sweep side to side across the fire until the flames are out. Don’t just hold the trigger—use sweeping motions to cover all the burning area.

After the fire is out, watch it for a minute. If flames restart (a common problem because some fuel wasn’t cooled enough), repeat the process.

Fire Blankets

A fire blanket is a woven sheet made from fire-resistant material (usually fiberglass or wool). It’s designed to smother small fires, especially Class A and B fires, by removing oxygen.

How to use a fire blanket:

1. Locate the blanket. Keep it accessible in the kitchen or near a fireplace.
2. Pull the corners to unfold it fully.
3. Hold it at arm’s length to protect your hands.
4. Drape it over the fire completely, covering all flames. If it’s a pan fire, carefully place it over the pan.
5. Leave it in place for several minutes to cool the fuel and ensure the fire doesn’t restart.
6. Do not remove it too quickly. If you pull it away and flames reignite, you’ve just made the problem worse.

Fire blankets are best for small fires in pots or pans. For larger fires, a fire extinguisher or evacuation is safer.

Practice Matters

The best time to learn how to use a fire extinguisher is before a fire happens. Some fire departments offer training sessions or allow public observation of extinguisher training. If your merit badge counselor can arrange a supervised demonstration or training, take advantage of it. Holding a real extinguisher and hearing the sound it makes when discharged will prepare you far better than reading about it alone.

Now that you understand how to fight fires with tools, let’s shift to protecting people from fire. What happens when fire injures someone, and what do you do?