Fire Extinguishers – Do You Know How (and When) to Use Them?

We’ve discussed the dust explosion pentagon, which explains the five components needed for a combustible dust explosion, before. Today we’re going to discuss a diagram that is simpler, but no less important for people to understand: the fire triangle.

The fire triangle is made up of the three components necessary for a fire to start: a fuel source, heat and oxygen. When these things are present in the workplace and a fire starts, do you and your employees know what to do? Many people might answer that they would get the fire extinguisher and put it out, which could be a viable solution. But do all of your employees know how to operate a fire extinguisher, and do they understand the circumstances under which they should and should not use one?

Table of Contents

Types of Fire & Fire Extinguishers

While all fire produces flames, not all fire is the same. This means not all fires can be extinguished with the same fire extinguisher. A fire’s type (or “class”) is determined by the kind of fuel that allows it to burn. According to the Federal Emergency Management Agency (FEMA), five fire classes exist:

A – Fueled by typical combustible sources like wood, paper, cloth and many plastics.
B – Fueled by flammable or combustible liquids like oil, gas or kerosene.
C – Fueled by electrical equipment that’s energized such as wiring or machinery.
D – Fueled by combustible metals such as aluminum or titanium.
K – Fueled by vegetable oils or fats. Generally restricted to large cooking appliances.

Each class of fire needs to be treated with an appropriate extinguishing agent. Have you ever heard someone say you shouldn’t throw water on a grease fire? There’s a good reason for that. Water doesn’t mix well with flammable liquids and it can actually spread the fire, making the situation worse. Problems also arise when water comes into contact with an electrical fire because water is a conductor; the person trying to put out the fire could be electrocuted.

Some types of fire extinguishers do contain water and are perfectly appropriate for use on standard fires fueled by wood or paper. Other types of extinguishers are designed specifically for use with other types of fire, though, and contain different extinguishing agents.

The best way to know a fire extinguisher is appropriate for a fire is to check the label. Devices intended for use with class A fires will have an A on the label. An extinguisher for class B fires will have a B on the label (and so on and so forth). It’s also helpful to understand what’s in each type of fire extinguisher. A few main types of extinguisher contents exist, according to OSHA:

Water – These extinguishers contain air-pressurized water and can only combat class A fires. They stop fire by cooling the surface of the fuel. Their containers are silver.
CO2 – These extinguishers contain carbon dioxide and can put out fires fueled by flammable liquids (class B). They can also put out electrical fires (class C). They function by displacing oxygen. Their containers are red.
Multi-purpose Dry Chemical – These extinguishers contain dry chemicals that can be used to put out class A, B or C fires. They cover the fuel in a fire retardant powder that interrupts the chemical reaction taking place. Their containers are red. As A, B or C fires are the kinds experienced in most workplaces, a fire extinguisher labeled ABC would likely be a good purchase for most businesses.

Note: If your workplace deals with metals or your business operates a restaurant or commercial kitchen, class D or K fire extinguishers may also be necessary additions to your facility and your emergency plans.

Fire Safety — This demonstration shows where to stand when putting out a fire. Photo: Barry Bahler/FEMA

All the technical classifications may get a little complicated and go beyond what employees need to know, so safety managers and business owners should just make sure to select fire extinguishers that are appropriate for the hazards of their workplaces and inform workers of which letters (A/B/C/D/K) are meant for which type of fire.

Using a Fire Extinguisher

The most important thing during a fire is the safety of people, so while a fire extinguisher can effectively put out many small fires, it may not always be the appropriate response during a fire.

When a fire starts, people in the area should consider the following questions before using a fire extinguisher:

Has the fire department been contacted?
Are there two ways to safely exit the area?
Is the right type of fire extinguisher available?
Is the extinguisher large enough for the fire? (Fire extinguishers come in different sizes and are labeled as such.)
Is the fire small/contained?
Are there any other dangers in the area like hazardous materials?

If the answer to any of these questions is affirmative, it’s not advisable to fight the fire. Instead, everyone should evacuate and contact the fire department. Additionally, anyone who doubts his or her ability to put the fire out should not attempt to fight the fire.

The PASS Method

Parts of a Fire Extinguisher — Photo: OSHA

Those who might be called on to operate fire extinguishers should receive training in how to do so. This training should cover the PASS method, which stands for “pull, aim, squeeze and sweep.” First, users should pull the fire extinguisher’s pin, which will break the tamper seal. Next, users should aim the nozzle at the base of the fire (where the fuel is) rather than at the flames. Third, they should squeeze the handle to spray the fire, and finally, they should move the fire extinguisher from side to side in a sweeping motion until the flames are put out.

FEMA states that the fire should be extinguished within 5 seconds. If that isn’t the case, the fire is likely too big to be put out with an extinguisher, and it’s time to evacuate.

Additional Best Practices for Fire Extinguisher Use

Fire moves quickly, and people need to avoid being in the wrong place at the wrong time. Consequently, in addition to following the recommendations above, potential fire extinguisher operators should also do the following:

Have an exit nearby. Never put the fire between you and an exit.
Stand back from the fire at least a few feet. Extinguishers typically have a range of eight to 12 feet.
Don’t touch the nozzle of a CO2 extinguisher as it can be very cold and damage the skin.
Don’t use CO2 extinguishers in confined spaces without respiratory protection.
Once the fire is out, watch the area to make sure it doesn’t reignite.
Service fire extinguishers according to manufacturer instructions.

When used properly for small fires, fire extinguishers should be very effective at putting out fires. Just make sure everyone understands the basics of fire extinguisher use and can quickly assess whether a fire is manageable. If the fire is too big, leave it to the professionals.

Can workers easily find fire extinguishers at your facility? Be sure to mark them with appropriate signs and labels.