Fires burn, but they don’t burn the same. Using the wrong fire extinguisher type can lead to injuries, death, and property loss.

Class B fire extinguishers are designed to put out dangerous fires caused by flammable liquids and gases. But how exactly do they work? What do they contain? How do you use them safely?

In this guide, we’ll go over Class B fire extinguishers, what they’re used for, what they’re made of, and how to use them. We’ll also cover more affordable and lightweight alternatives that are just as effective.

What Is a Class B Fire Extinguisher?

As the term suggests, a Class B fire extinguisher puts out Class B fires. These fires are tricky to put out because they sometimes include something invisible: gas. They’re caused by flammable liquids and gases such as:

• Paint
• Paint Thinner
• Alcohol
• Gasoline
• Ethanol
• Propane
• Butane
• Methane

Most fire extinguishers, particularly foam, carbon dioxide, powder, and water mist, can put out Class B fires. Class B foam fire extinguishers are the best when putting out flammable liquid fires because the agent floats on top and secures the liquid surface. This helps prevent reignition, which can be life-threatening. 

Take note that you can’t extinguish Class B fires with water. Flammable liquids and gases are volatile, and water will only make the fire spread or react violently. For this reason, you should only use Class B fire extinguishers to put out flammable liquid and gas fires. 

What Is a Class B Fire Extinguisher Used For?

Knowing what a Class B fire extinguisher is used for could mean the difference between life and death. Here are the most common flammable liquids and gases you can use Class B fire extinguishers on: 

Gasoline

Gasoline is everywhere—in your car, lawnmower, power tools, or machines. It’s highly flammable and can easily ignite from a spark or no-flame heat source. In particular, it has a flashpoint of -49°F or -45 °C. Gasoline fumes can also ignite up to 12 feet from a pooled source. Because of this, smoking is prohibited near gas pumps.  

For instance, if you accidentally spill gasoline while filling up your lawnmower, it can catch fire if the engine is hot. You need a Class B fire extinguisher in this case because it can smother the flames and prevent the fire from devouring your lawn. 

Alcohol

Alcohol is commonly used for cleaning or as a beverage. Rubbing alcohol and liquor easily ignites when spilled, and there’s an open flame nearby. For instance, accidentally knocking over a bottle of whiskey near a stove with open flames can start a Class B fire. Using a Class B fire extinguisher is your best option here since it can quickly put out the fire and prevent it from spreading to the rest of your kitchen. 

Cleaning Products

Many cleaning products contain flammable solvents. They’re often stored under the kitchen sink or in a cleaning closet. For instance, some window cleaners or degreasers can catch fire if they’re used near a heat source, like a space heater. A Class B extinguisher can effectively put out these fires and prevent them from causing more damage.

Aerosol Sprays

Aerosol sprays, including hair sprays and air fresheners, can cause Class B fires. While they don’t seem dangerous, they can be life-threatening when exposed to heat because they might ignite or explode on your face. 

For example, a Class B fire will start if you’re using spray paint in a garage and a power tool produces sparks nearby. In this situation, you need a Class B fire extinguisher to ensure everyone’s safety. 

Kerosene

Kerosene is commonly used for heating and cooking, especially in rural areas. Like gasoline, kerosene is highly flammable. Heat, sparks, and flames easily ignite it. Its vapors may also mix with air and ignite. For example, if a kerosene lamp tips over and leaks, it can ignite quickly. Having a Class B fire extinguisher prevents the fire from spreading and causing injuries.

Paint Thinners

Paint thinners are commonly found in workshops and garages. While they look harmless, they’re highly flammable and potentially explosive. They’re also made of volatile organic compounds like acetone, toluene, and xylene, which can react violently to heat. For instance, using paint thinner for a DIY project can start a fire if you accidentally drop a lighter on it. 

What Is a Class B Fire Extinguisher Made Of? 

Class B fire extinguishers are available in many forms, from foam to powder. These extinguishing agents remove at least one element of the fire triangle. Here’s what Class B fire extinguishers are made of:

Foam

Foam fire extinguishers are either aqueous film-forming or film-forming fluoroprotein. They’re made to extinguish Class A and B fires by discharging foam. The foam creates a barrier between the flames, fuel, and oxygen. The main advantage of using foam on flammable liquid fires is its ability to float and coat the liquid’s surface. This prevents the Class B fire from reigniting. 

Carbon Dioxide

Some Class B fire extinguishers are made of carbon dioxide. This type of fire extinguisher uses air to put out Class B fires. In particular, the carbon dioxide is discharged in gas or snow cloud form. The carbon dioxide then displaces the oxygen that keeps the fire burning. Carbon dioxide extinguishers are also useful for situations where delicate and expensive equipment and tools are involved. Since these extinguishers use air, they don’t leave residues. However, carbon dioxide extinguishers have limited reach, ranging from three to eight feet. 

Powder

You can use powder fire extinguishers on Class B fires as well. They’re usually made of fine powder that contains sodium bicarbonate (baking soda), potassium bicarbonate (nearly identical to baking soda), monoammonium phosphate, or a mix of the said substances. 

This Class B fire extinguisher works by coating the fuel. This creates a barrier between the fuel and oxygen in the air. As a result, the fire eventually dies. The powder also covers the fuel from radiated heat to prevent the fire from reigniting. 

These chemicals extinguish a fire by spreading and melting over the flames. The powder coats the fuel, which separates it from the oxygen in the air. As a result, the fire dies down.

Water Mist

Contrary to popular belief, you can use water mist fire extinguishers on Class B fires. They use deionized water, which is non-conductive and non-toxic. Class B water mist extinguishers release tiny water particles, forming a mist curtain. The water particles then cool the air and fill it to reduce the oxygen feeding the fire. As a result, the Class B fire dies. Since the particles are so tiny, they don’t leave residues. 

How to Identify Class B Fire Extinguishers

Class B fire extinguishers have a specific symbol: a red square with the letter B inside it. The red square indicates that the extinguisher can put out fires caused by flammable gases and liquids, such as alcohol, gasoline, kerosene, propane, and butane. If you see a square with a B in it, it’s the right extinguisher for a Class B fire.

You can also use multi-purpose extinguishers to handle Class A, B, and C fires. These fire extinguishers usually show the letters A, B, and C in different shapes. An A inside a triangle means you can use the extinguisher against fires caused by solid combustibles like wood, paper, rubber, and most plastics. Meanwhile, a C inside a circle means you can use the extinguisher to put out electrical fires. 

In most cases, Class B fire extinguishers come with ratings. The numerical ratings indicate how much area the extinguisher can cover in square feet. 

How to Use a Class B Fire Extinguisher

Knowing how to use a Class B fire extinguisher is crucial to everyone’s safety, especially if flammable liquids and gases are around. Class B fires can spread quickly and be life-threatening, so knowing how to put them out makes a huge difference. You never know when a fire might occur, and having the right knowledge helps you act fast. 

The PASS fire extinguisher technique is a basic acronym for using Class B fire extinguishers. It stands for Pull, Aim, Squeeze, and Sweep. Safety experts made this acronym so people can easily remember the four basic steps to use a fire extinguisher.

Pull: Pull the fire extinguisher’s safety pin to unlock the Class B fire extinguisher.

Aim: Aim the hose or nozzle at the base of the fire. 

Squeeze: Squeeze the lever or handle to release the extinguishing agent. 

Sweep: Sweep the Class B fire extinguisher from side to side until the fire dies.

Please note that PASS is just one part of the equation. You should also determine whether it’s safe to extinguish the fire. Don’t try to put out the fire if it’s too large, even if you know how to use a Class B fire extinguisher. Instead, evacuate your house and call for help immediately. 

How to Maintain Class B Fire Extinguishers

Keeping your Class B fire extinguisher in top shape ensures it works against flammable liquid and gas fires. 

Start with regular checks. Inspect your fire extinguisher every month to see any signs of damage. Is the safety pin intact? How about the pressure? Does it need to be refilled? Answering these questions lets you determine if your Class B fire extinguisher needs to be replaced or refilled.

You can also contact a professional to inspect your Class B fire extinguisher at least once every year. They can check it thoroughly and make sure everything’s up to standard. Watch out for fire safety regulations as well. Doing this ensures that you comply with laws and regulations. 

Consider hydrostatic testing, too. In general, Class B fire extinguishers need to be tested every five years. However, stick to specific manufacturer guidelines if they say otherwise. 

When to Replace Class B Fire Extinguishers

Imagine having a Class B fire extinguisher that doesn’t work when you need it the most. Scary, right? Prevent this from happening by knowing when to replace your fire extinguisher. Look out for the signs below: 

1. Your Class B fire extinguisher is expired.

Replace your Class B fire extinguisher if it’s expired. Fire extinguishers have expiration dates that you should honor even if you haven’t used them. The expiration date depends on many factors, including the extinguishing agent and container used. Remember, it’s not safe to use an expired fire extinguisher because it might not work and put everyone at risk. 

2. Your Class B fire extinguisher is damaged.

Replace your fire extinguisher if you see dents, broken safety pins, loose nozzles, rust, cracked hoses, and the like. Physical damages can compromise its effectiveness against Class B fires. Remember, it’s always better to be safe than sorry. You might have to spend money, but getting injured or losing your property is more expensive. 

3. Your Class B fire extinguisher has low pressure.

Check your Class B fire extinguisher’s pressure gauge. If the pressure’s low, replace your fire extinguisher as soon as possible. Low pressure means the extinguishing agent won’t come out with enough force to put out a Class B fire. Worst, it might not come out at all, leaving you defenseless. 

4. Regulations or the environment changed.

Authorities update fire regulations and standards to keep everyone safe. Plus, your house’s layout and the fire hazards around you might change, so you need more Class B fire extinguishers. For instance, you might need more Class B fire extinguishers if you have flammable liquids and gases in your kitchen, garage, or workshop. 

How Much Are Class B Fire Extinguishers? 

Class B fire extinguisher prices vary based on many factors, including the size and extinguishing agent. In general, Class B fire extinguishers range from $70 to $300.

Small, portable Class B fire extinguishers weighing two to five pounds cost $60 to $100 each. These fire extinguishers are made for single use. Bigger Class B fire extinguishers weighing 10 pounds or more can cost $90 to $300 each. Multi-purpose fire extinguishers are usually more expensive because they can put out different types of fire. 

Class B Fire Extinguisher Alternatives

While Class B fire extinguishers help a lot, they can be expensive, heavy, and hard to store. They might also contain toxic chemicals and leave a mess that’s hard to clean up. 

A fire spray is an easy-to-use, lightweight, and affordable alternative to Class B fire extinguishers. Prepared Hero’s fire spray is also biodegradable and non-toxic. Unlike a fire extinguisher, you can safely use it around your family and pets. 

Here’s a table summarizing the differences between Prepared Hero’s fire spray and a regular fire Class B extinguisher:

Another alternative is a fire blanket, which depletes the fire’s oxygen supply. By doing this, it puts out small Class B fires in seconds. It also doesn’t leave a mess because it simply covers the fire.

Unlike fire extinguishers, Prepared Hero’s fire blanket doesn’t expire. You can reuse it as many times as you want as long as it’s not damaged. Plus, you can use it to save someone on fire. 

Here’s a table summarizing the differences between Prepared Hero’s fire blanket and a regular fire extinguisher: