Fire Extinguishers 101: Choosing The Right One

Before I get started, let me give you a little bit of my background. My family and I have been in the fire equipment business for a long time. My uncle started in 1970, and I started in 1980. Over the years, fire fighting equipment has gone through many changes and advances, yet fire still claims the lives and property of the unprepared, costing money and  downtime.

It is amazing to me, how many people I have met , who don’t know how to use a fire extinguisher. It is also shocking to know that there are a great many people who don’t know where the fire extinguisher in their workplace is located. Hopefully this article will help.

Before you fight a fire, it helps to understand it, and to have a plan of attack and/or escape in case you are faced with the unfortunate event of a fire. Many of you may already know that fire is a chemical reaction, and there are the basic elements of heat, fuel, oxygen, and/or an ignition source. If any of the basic elements are removed, the fire will die. The basic elements of a fire are often referred to as: The fire triangle.

Now, let’s take a look at the different classes of fires.

While fire extinguishers range in size from as small as a can of spray paint to over 350 pounds, there are many different choices, depending on the needs of the prospective user.Looking at the classes of fires, you can determine which type of fire extinguisher to use, according to the hazard.  For simplicity, class A fires involve any material that produces an ash. Class A fires can generally be put out by water.

2.5-Gallon Pressurized Water Fire Extinguisher

Class A fires can also be put out by other fire extinguishers, such as: Afff (Aqueous film forming foam), ABC dry chemical (monoammonium phosphate), Halon (bromodiflouromethane), Halotron, and soda and acid (Generally no longer used).

Deionized Water Mist Fire Extinguisher

2.5-Gallon AFFF (Foam) Extinguisher

9-Pound Halon 1211

5-Pound ABC dry chemical extinguisher.

1920’s Soda and Acid by Elkhart Brass Company

Soda and acid extinguishers are no longer in use, and in many states, they are illegal.

As you can see from the pictures above, there is more than one type of extinguisher for a particular application. Generally speaking, fire extinguishers can be grouped into the following categories:

1. Dry Chemical (or powder). One of the most common, less expensive solutions for many types of fires, especially when clean up is not a major concern, as dry chemical is very corrosive to some metals, and usually makes quite a mess. Also, visibility is an issue when discharging dry chemical indoors.
2. Wet chemical (or wet agents, including AFFF foam). Usually for a specific type of fire such as vegetable oils or certain types of petroleum based fuels, where cooling and reingnition containment are required.
3. Gas (CO2). A more economial approach to small fires where clean up or damage to equipment is of concern. (Small engine fires, electrical motor fires). Visibility and oxygen displacement should be considered before deciding to use any pressurized gas indoors.
4. Clean agents (Halon,Halotron,FM200, and Inergen). These types of extinguishers are usually for delicate and expensive electronic equipment, and they reduce the amount of clean up after a fire. There are some dangers associated with clean agent extinguishers, in that the extinguishing agent breaks down into toxic gases when in contact with a fire. Quite often, these type of extinguishers are automatic, and intended for use in unoccupied areas.

A class “B” fire involves flammable liquids, and depending on the temperature of the flame, determines the best extinguisher for the hazard. For example: An ABC fire extinguisher can be used on a grease fire, but it probably won’t be as effective as a class “K” liquid extinguishing agent – which has the ability to cool down the grease, and in NO CASE should an ABC (monoammonium phosphate) fire extinguisher ever be used in the presence of chlorine or pool cleaning chemicals, because ABC dry chemical contains a high concentration of ammonia, which would produce a very toxic reaction if it should mix with certain chemicals.

Also. depending on whether the grease fire is animal fat or vegetable oil will make a big difference. Vegetable oil burns with a higher temperature, and the old fashioned baking soda trick won’t work very well. Baking soda is the main ingredient in a BC dry chemical fire extinguisher, and it works by smothering the fire, and providing a barrier over the fire (animal fat or lard fires). This action is called: Sapponification.BC dry chemical typically does not work as well on vegetable oil fires because of the high temperature. CO2 is rated for flammable liquids, although it should be used according to the type of liquid. CO2 would be a poor choice for a hot grease fire, and is more suited for a small gasoline fire. AFFF (Foam) is an excellent choice for a wide range of liquid fires, as it has the ability to take the oxygen away, and blanket the fire with a barrier to prevent reignition. AFFF also has cooling ability. Halon and halotron are suited for class B fires, however it is a very expensive way to go, and they are usually used for delicate electronic equipment. Below are some pictures of class “B” rated fire extinguishers.

20-Pound BC Dry Chemical (Sodium bicarbonate) Extinguisher

20-Pound Purple K (Potassium Bicarbonate)

5-Pound CO2

A class”C” fire is an energized electrical fire, and usually will involve elements of a class “A” and “B” fire. Most of the extinguishers listed for use on class “B” fires will work on class “C” fires. IN NO CASE should water ever be used if electricty is a fire suspect.

Next we have class”D”. Flammable metals. Usually these types of fires involve oxygen producing metals- or light metals such as: Magnesium,sodium, and titanium. The extinguisher for this type of fire is unique, in the fact that the extinguishing agent combines with the burning metal, and cancels out the oxygen. Usually the agent is salt, or it has varying degrees of fine particles of sodium. Generally a burning metal fire would be followed by foam after it is extinguished, to prevent reignition. Below is a class “D” fire extinguisher.

Class “D” Extinguisher

There are many more types of fire extinguishers, but I feel that the ones in this list are the most common. As for using a fire extinguisher, most of the ones in this list involve: Pulling the pin, aiming the hose (or nozzle) at the base of the fire, squeezing the handle, and using a side to side sweeping motion to distribute the extinguishing agent. In any case a fire extinguisher is intended to be used as a first line of defense, and when a fire is in its incipient stage. Never attempt to use a fire extinguisher if you are unsure of your safety.