How To Choose and Use Fire Extinguishers

A fire extinguisher can prevent a minor incident from becoming a devastating house fire. Every homeowner should know how to choose the right type, where to place it, and how to use it effectively.

This guide to selecting a fire extinguisher will cover everything you need to know about fire extinguishers, from understanding the different classes to proper maintenance and usage techniques.

Understanding Fire Extinguisher Classes

Fire extinguishers are classified based on the types of fires they can put out. Let’s break down the five main classes of fire extinguishers and what they’re designed to handle.

Most fire extinguishers you find at a hardware store will be rated for multiple classes. The most common is an A:B:C fire extinguisher that can handle the three most common types of fires you’ll want to guard against in your home.

Pro Tip

Captain Hugh Duffy, drill master at the Boston Fire Training Academy, explains that not all A:B:C extinguishers are created equal: “There’s also a numerical rating on the effectiveness of the extinguisher.” As he demonstrated to Ask This Old House host Kevin O’Connor, an extinguisher rated 8-A is “two and a half times as effective” as one rated 3-A—so pay attention to those numbers on the label, not just the letter classifications.

Class A: Ordinary Combustibles

Class A extinguishers are designed to extinguish fires involving ordinary combustible materials such as wood, paper, cloth, and many plastics. These are the most common types of house fires. Class A extinguishers typically use water or foam to cool and quench the fire.

Pro Tip

Not all Class A extinguishers are created equal. As Captain Hugh Duffy of the Boston Fire Training Academy explained to This Old House host Kevin O’Connor, there’s a numerical rating on each extinguisher that indicates its effectiveness. For example, an extinguisher rated 8-A is about two and a half times as effective as one rated 3-A. That number matters when you’re sizing an extinguisher for a larger room or an area with more combustible materials.

Class B: Flammable Liquids

These extinguishers are effective against fires involving flammable liquids such as gasoline, oil, grease, and some paints. Class B extinguishers often use dry chemicals or carbon dioxide to smother the fire and prevent reignition.

Pro Tip

When This Old House host Kevin O’Connor visited the Boston Fire Training Academy, Captain Hugh Duffy, the academy’s drill master, demonstrated Class B fires using a mixture of diesel fuel and gasoline. Kevin identified the fire classification on the spot: “Well, it’s liquid, so it’s gonna boil. So that’s a B, right?” Captain Duffy confirmed, then walked Kevin through selecting the right extinguisher—noting that both a dedicated B-rated unit and a multi-purpose A, B, C extinguisher would be effective against the flammable-liquid blaze.

Class C: Electrical Fires

Class C extinguishers are specifically for fires involving energized electrical equipment. They use non-conductive agents like carbon dioxide or dry chemicals to extinguish the fire without risking electrical shock to the user.

Pro Tip

Heath Eastman, This Old House master electrician, advises: “There are lots of small, easy things homeowners can do to eliminate electrical fire hazards. Inspect cords often for damage or strain. Keep them off the floor. And match lightbulbs to the recommended wattage to decrease the chance of fixtures overheating.”

Class D: Flammable Metals

While less common in household settings, Class D extinguishers are designed for fires involving combustible metals such as magnesium, titanium, and sodium. These specialized extinguishers use dry powder agents to smother and cool the fire.

Class K: Kitchen Fires

Class K extinguishers are specifically for kitchen fires involving cooking oils and fats. They use a fine mist of potassium compounds to create a soapy foam that cools and smothers the fire, preventing re-ignition.

Understanding Fire Extinguisher Labels

Fire extinguisher labels provide important information about the extinguisher’s capabilities and effectiveness, but can be confusing at first glance. Let’s break down what these terms mean and how to interpret them.

After the letters we just described, you’ll see numbers on fire extinguisher labels. These numbers indicate the extinguisher’s relative effectiveness against each type of fire. For example, a 4-A:80-B:C rating means the following:

4-A: Effective against Class A fires, with 4 referring to a measure of water equivalency (a 1 equals 1 ¼ gallons of water)
80-B: The number here deals with the size of the fire it can handle. In this case, the extinguisher can put out 80 square feet of Class B fire
C: Suitable for use on electrical fires (no number is associated with C ratings)

The higher the number, the more effective the extinguisher is for that class of fire.

Underwriters Laboratory (LB) Certification

Look for the Underwriters Laboratory (UL) certification on the extinguisher. This indicates that the extinguisher has been tested and meets safety standards. The UL label also provides information about the extinguisher’s size, type, and proper use.

Pro Tip

Beyond the UL certification, pay close attention to the numerical rating on the label. As demonstrated during a visit to the Boston Fire Training Academy on Ask This Old House, a fire extinguisher rated 8-A is two and a half times as effective as one rated 3-A. The higher the number, the more firefighting capacity the unit provides—a critical distinction when you’re comparing models at the store.

Selecting the Right Size Fire Extinguisher

Choosing the right-sized fire extinguisher is crucial for effective fire suppression. The size of the extinguisher affects its weight, discharge time, and overall effectiveness. Here’s a guide to help you select the correct size for different areas of your home.

2-Pound Extinguishers

These small, portable extinguishers are ideal for cars, boats, or small areas in your home. They’re lightweight and easy to handle but have limited discharge times and coverage areas.

Keep in mind that a 2-pound extinguisher may only be rated for B and C fires (flammable liquids and electrical), not A fires (ordinary combustibles like paper and wood). As Captain Hugh Duffy confirmed during a training session with Kevin O’Connor, a B,C-rated unit is “not good for, say, a paper fire.” To cover all your bases, look for a multipurpose A,B,C extinguisher — even in the smaller size — so you’re “rated for all three types” of fires. And check your gauge at least monthly: fire experts recommend replacing any extinguisher whose pointer shows “empty.”

Pro Tip

A Word of Caution for Auto Use: Jeff Weidner, a professional firefighter and general contractor, wrote to This Old House Magazine warning that newer-model cars contain far more plastics and carbon-fiber-based materials that produce deadly by-products when on fire. His advice: “If your automobile catches fire, no matter how small it starts, think twice before deploying an auto fire extinguisher. It would be better to take your cell phone as you exit the vehicle and call the fire department.” This Old House fire-safety expert Mark Conroy agreed, noting that “these are tricky fires, even for firefighters who are trained and equipped to handle them.”

5-Pound Extinguishers

A1 5-pound extinguisher offers a good balance between portability and effectiveness for most household needs. It’s suitable for the following areas:

Kitchens
Laundry rooms
Living areas
Small workshops

10-Pound Extinguishers

These are intended for larger areas or where a fire might grow before being noticed, including:

Garages
Workshops
Basements
Commercial kitchens

Prices taken at time of publishing.

Key Features

Weighs 2.5 pounds
Works on Class A, B, and C fires
Includes a six-year warranty
Approved by the U.S. Coast Guard
Comes with a mounting bracket and strap
Has a dry chemical extinguishing agent
Has a UL safety rating

Best Locations for Fire Extinguishers in Your Home

The National Fire Protection Association recommends placing fire extinguishers along normal travel paths for easy access. Here are some specific guidelines for key areas.

Kitchens

The kitchen is one of the most common places for fires to start. Place a fire extinguisher near an exit and away from potential fire sources. A 5-pound ABC-rated extinguisher is typically suitable for kitchen use. For added protection against grease fires, consider a Class K extinguisher.

Garages and Workshops

Garages and workshops often contain flammable liquids and power tools, increasing fire risk. We suggest a 10-pound ABC-rated extinguisher for these areas. Mount it near the exit, ensuring it’s easily visible and accessible.

Bedrooms

Having a fire extinguisher near bedrooms can protect you during nighttime emergencies. Place a 5-pound ABC-rated extinguisher in the hallway outside bedrooms, ensuring it’s easily accessible to all family members.

How To Use a Fire Extinguisher: The PASS Technique

Knowing how to use a fire extinguisher correctly can make all the difference in an emergency. The PASS technique is a simple, effective method for operating most fire extinguishers.

Remember, you should only use fire extinguishers on small, contained fires. If the fire is large or spreading, evacuate immediately and call 911.

Step 1: Pull the Pin

The first step is to pull the pin at the top of the extinguisher. This breaks the tamper seal and allows you to discharge the extinguisher.

Step 2: Aim at the Base of the Fire

Aim the nozzle or hose at the base of the fire — not at the flames. This is crucial, as you want to extinguish the source of the fire, not just the visible flames.

Step 3: Squeeze the Lever

Squeeze the lever slowly and evenly. This releases the extinguishing agent. Some extinguishers may have a button instead of a lever.

Step 4: Sweep from Side To Side

Using a sweeping motion, move the nozzle from side to side at the base of the fire. Continue until the fire appears to be out. Watch the area carefully for re-ignition and repeat the process if necessary.

Common Mistakes When Using Fire Extinguishers

Even with proper training, people can make mistakes when using fire extinguishers in high-stress situations.

One of the most common mistakes is aiming the extinguisher at the flames rather than the base of the fire. People also often get too close to the fire in the heat of the moment. This can be dangerous and reduce the effectiveness of the extinguisher. Stay at least 6–8 feet away from the fire when using an extinguisher.

Always position yourself with an exit at your back when fighting a fire. This ensures you have a clear escape route if the fire grows or the extinguisher runs out. Never let the fire come between you and your exit.

Maintaining Your Fire Extinguisher

Regular checks and proper care can significantly extend the life of your extinguishers and maintain their effectiveness.

Regular Inspections

Perform monthly visual inspections of your fire extinguishers. Take the following steps:

Check that the pressure gauge is in the green zone
Ensure the pin and tamper seal are intact
Look for signs of damage, corrosion, or leakage
Verify that the nozzle is unobstructed

You should also have a professional inspect your fire extinguishers annually to make sure they meet safety standards.

Recharging vs. Replacing

A fire extinguisher must be recharged or replaced after use, even if only partially discharged. For rechargeable models with metal valves, professional recharging is often more cost-effective than replacement. Disposable extinguishers with plastic valves should be replaced after use.

If the pressure gauge shows low pressure or the extinguisher is over 12 years old, it’s time for replacement or professional servicing.

Our Conclusion

Fire extinguishers are invaluable tools for home safety, but they’re only effective when used correctly. By understanding the different classes, choosing the right size and type for your needs, and knowing proper placement and usage techniques, you can enhance your home’s fire safety.

While fire extinguishers can handle small fires, they don’t substitute for a comprehensive fire safety plan. Always prioritize personal safety, have working smoke detectors, and regularly practice your family’s fire escape plan.

For additional fire safety measures, consider installing a fire sprinkler system in your home. This can provide an extra layer of protection and potentially save lives in the event of a larger fire. With the right knowledge and preparation, you can create a safer environment for you and your loved ones.