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Now In: Fire Extinguishers - Classes, Types and Use


Fire Extinguishers - Classes, Types and Use

If you need to purchase a fire extinguisher, you may have questions about the different types that are available.  Select Safety Sales has compiled this FAQ Sheet to help you make the correct choice when making your purchase.
When should a person attempt to put a fire out with a fire extinguisher?
You should ONLY attempt to put out a fire in the early stages when it is small and contained and ONLY when there is a means of escape behind you that is clear of fire.  If the fire has spread beyond the early stages, it is time to evacuate the building.  Be sure that the fire extinguisher is large enough to put out the fire because many portable fire extinguishers will discharge completely within a matter of seconds.  It is important to know the capabilities of the extinguishers that you have in your facility before a fire starts.   
What type of fire extinguisher should I purchase?
There are different types of fire extinguishers just as there are different types of fires. This FAQ sheet will provide information regarding the different types available to fight various fires.  Some fire extinguishers can only be used on certain types of fires.  It could actually be dangerous to use the wrong extinguisher.
How can I be sure that the fire extinguisher I choose is approved for the type of fire that I need to extinguish?
All fire extinguishers must be (UL) Underwriters Laboratory approved. Underwriter’s laboratory is a nationally recognized testing laboratory that verifies compliance with applicable standards (29.CFR 1910.157(c)(2).  Fire extinguishers that pass the tests are given an alpha numeric classification based on the type and size of the fire it will extinguish; ie. 3A:40B:C
What do the letters  mean in the alpha numeric classification?
The letter represents the type of fire that can be extinguished with a particular type of fire extinguisher. The types of fires are given the following classifications:
  • (A) ordinary combustibles
  • (B) flammable liquids
  • (C) electrical equipment
  • (D) metals
  • (K) combustible cooking fluids such as oils and fats.
What do the numbers in the alpha numeric classification mean (ie. 1A:10B:C)?
Fire extinguishers have a number rating.  For Type A fires, a 1 would have the equivalent of 1¼ gallons of water, a 2 would be equivalent to 2½ gallons, 3 would be 3¾ gallons of water, and so forth.  For Type B and Type C fires, the number represents the square footage the extinguishing agent would cover. For example, a number 2 would cover two square feet and a 5 would extinguish an area five square feet and so forth. 
Why do some fire extinguishers have more than one letter and number?
Fire extinguishers can also be made to extinguish more than one type of fire.  If the extinguisher's label reads 2A:5B, then the extinguisher would work on Type A fires with a 2½ gallon equivalence and for Type B fires with a 5 square feet equivalency.  
Where can I find these classifications?
These classifications are right on the side of the fire extinguisher. You will also see labels for each type of fire that the fire extinguisher can be used for.
Who makes the determination of how many fire extinguishers are needed in commercial buildings and the workplace?
Building codes (for buildings) and OSHA Standards (for the workplace) include the requirements of when and where fire extinguishers are required in building structures.  The National Fire Protection Association (NFPA) writes the standard for fire extinguisher selection, use and maintenance.
Do fire extinguishers require any type of maintenance once they are purchased?
Fire extinguishers should be inspected every month to insure that the units are in good working order.  This is essential to ensure that they will operate effectively if needed. The pressure gauge should be checked to make sure that the unit is fully charged.  Make sure that the needle on the gauge is in the green zone. Also, check that the pin and tamper seal (located at the top of the unit) are intact. Inspect each unit to make sure that they look to be in good physical condition.
Does a fire extinguisher require any special storage space?
Fire extinguishers should be mounted on brackets or in wall cabinets.  The carrying handle should be placed three and one half feet to five feet above the floor.  Larger units should be mounted at a lower height and the carrying handle should be approximately three feet from the floor
How do I use a fire extinguisher to put out a fire?
There is a simple pneumonic to remember when using a fire extinguisher.
P ull the pin at the top of the extinguisher and this will release the lock.
A im the nozzle at the back of the fire
S queeze the handle of the fire extinguisher
S weep the fire extinguisher from side to side (back and forth)


Fire Extinguishers For Class A Fires

Kidde A Type
What type of materials would be burning for a fire to be classified as a Class A fire?
What type of fire extinguisher is labeled for Class A fires?
The Air Pressurized Water (APW) Fire Extinguisher is labeled a Class A fire extinguisher. Water is one of the most commonly used extinguishing agents for fires involving ordinary combustibles.
What does an APW fire extinguisher look like?
The APW fire extinguisher can be recognized by its large silver container. The fire extinguisher stands about three feet in height and weighs about 25 lbs. when full.
What are the components in an APW fire extinguisher?
Two thirds of the container is filled with water and the remainder is pressurized air.
How is a fire extinguished with an APW fire extinguisher?
Fire is extinguished by cooling the surface of the fuel to remove the HEAT element of the fire.
Are there any recommendations for the placement of these fire extinguishers in a workplace or public area?
The National Fire Protection Agency (NFPA) does recommend that offices, classrooms and assembly halls that mainly contain Type A combustible materials have one 2:A fire extinguisher for every three thousand square feet..  For workers protection in the workplace OSHA requires that all employees have access to an extinguisher within seventy five feet of travel distance.
What type of fires should never be extinguished with an Air Pressurized Water (APW) fire extinguisher?
Flammable liquid fires and electrical fires should never be extinguished with an air pressured water fire extinguisher.  A flammable liquid fire could be spread with this type of extinguisher and an electrocution could occur if water is used to extinguish an electrical fire. Also, never use this type of fire extinguisher on a deep fat fryer fire in a commercial kitchen. An explosive type reaction could result.


Fire Extinguishers For Class B Fires

   Kidde B Type
What type of materials would be burning for a fire to be classified as a Class B fire?
Some Paints                             
Grease                                  FLAMMABLE LIQUIDS
Flammable liquids
What type of fire extinguisher is labeled for Class B fires?
CO2 carbon dioxide fire extinguishers and dry chemical fire extinguishers are both labeled for Class B fires.
What does a CO2 fire extinguisher look like?
This type of fire extinguisher has a hard horn and NO pressure gauge. They are red and range in size from five to one hundred pounds or larger.
What are the components of a CO2 fire extinguisher?
The fire extinguisher is filled with Carbon Dioxide (CO2), a non flammable gas under extreme pressure.
How is the fire extinguished with a CO2 fire extinguisher?
A CO2 fire extinguisher puts out fires by displacing oxygen. It takes away the oxygen from the fire. It has such high pressure that pieces of dry ice will shoot from the horn which has a cooling effect on the fire.
What type of fires should never be extinguished with CO2 fire extinguisher?
CO2 fire extinguishers should never be used with fires involving ordinary combustibles (paper, cloth, wood, rubber and plastic) because the fire could continue to smolder and then reignite after the dissipation of the CO2.
What are the components of a BC Dry Chemical Fire Extinguisher?
BC fire extinguishers are filled with sodium bicarbonate or potassium bicarbonate.
Are there any recommendations for the placement of class B fire extinguishers in the workplace?
OSHA requires that all employees have access to a Fire Extinguisher for type B fires within fifty feet travel distance
Would the degree of risk of a flammable liquid have any effect on the size of the fire extinguisher needed?
According to the Standard for Portable Fire Extinguishers NFTA 10 (2007) Table, Fire Extinguisher Size and Placement for Class B Hazards the following information should be used:
     Flammable Liquids used for copy machines, art departments, etc. that are stored safety in closed containers.
This would be considered a low hazard because small amounts of flammable liquids are being used. The recommendation is to use a 5 B Extinguisher with 30” Spacing for this level of risk.
     • Flammable Liquids used in garages, workshops or support service areas.
This would be considered a moderate hazard because flammable liquids are more prevalent than in a low hazard area. The recommendation is to use a 10 B Fire Extinguisher with 30’ Spacing or a 20 B Extinguisher with 50’ Spacing.
     • Flammable Liquids used for storage, production, woodwork finishing, vehicle repair, aircraft and boat servicing or where painting, dipping and coating are done with flammable liquids.
This would be considered a high hazard because flammable liquids are present and used in large quantities. The recommendation is to use a 40 B Fire Extinguisher with 30’ spacing/ 80 B Fire Extinguisher with 50’ Spacing


Fire Extinguishers For Class C Fires

Kidde C Type
What type of materials would be burning for a fire to be classified as a Class C fire?
Fuse boxes
Energized electrical equipment           ELECTRICAL EQUIPMENT 
Other electrical sources
* For fires involving electrical equipment, Carbon Dioxide (CO2) fire extinguishers and Dry Chemical fire extinguishers are used.  See FAQ under Type B fires.  CO2 fire extinguishers and dry chemical fire extinguishers are both used for electrical equipment fires.
Would there be any reason to use a CO2 fire extinguisher over a dry chemical extinguisher for an electrical fire?
BC and ABC fire extinguishers both leave a residue after the fire has been put out.  If the fire has started on delicate electrical equipment such as a computer or TV, it might be wise to consider a CO2 fire extinguisher because it does not leave a residue. A dry chemical fire extinguisher will leave a residue that can damage the equipment.


Fire Extinguishers For Class A, B & C Fires

Are there any multipurpose fire extinguishers that are labeled A, B and C altogether?
Yes, there is the ABC Fire Extinguisher. These fire extinguishers will be labeled that they are rated for B and C fires and may be marked multipurpose for use on A, B and C fires.
What does an ABC fire extinguisher look like?
ABC fire extinguishers are red in color and range in size from five pounds to twenty pounds.
What are the components of an ABC fire extinguisher?
ABC fire extinguishers use dry chemical fire retardant powder made up of monoammonium phosphate. It is a yellow powder that will leave a sticky residue once the fire has been extinguished.
How is the fire extinguished with an ABC fire extinguisher?
An ABC fire extinguisher is a dry chemical extinguisher that puts out fires by coating the fuel with a thin layer of a fire retardant powder.  It will separate the fuel from the oxygen.  The powder will also interrupt the chemical reaction of the fire.
Does an ABC fire extinguisher require any special maintenance?
The powder in dry chemical fire extinguishers can “pack” inside the unit over time so lightly rock this type of extinguisher every few months to ensure that this does not happen..
Are ABC fire extinguishers the most popular unit sold being that they can put out almost any kind of fire?
Yes, 5 and 10 pound ABC fire extinguishers represent over 80% of fire extinguishers sold.  They meet most codes for standard requirements.  It is important to note that code requirements are only minimum guidelines.

Other Special Type of Fires and Fire Extinguishers:

Fire Extinguishers For Class D Fires

What type of materials would be burning for a fire to be classified as a Class D fire?
Powders, flakes or shavings of combustible METALS (such as magnesium, titanium, potassium and sodium).
What are the components of a Class D fire extinguisher?
Fire extinguishers labeled for a type D fire can contain a sodium chloride based dry powder extinguishing agent, but most of the fire extinguishers labeled Class D have components that are geared to a specific metal.
Why isn’t there a picture on the side of this type of extinguisher?
There is no picture for class D fire extinguishers.
Are there any recommendations for the placement of these fire extinguishers?
OSHA recommends that these fire extinguishers are not more than 75 feet from the hazard.

Fire Extinguishers For Class K Fires

What type of materials would be burning for a fire to be classified as a Class K fire?
Fats                              COMBUSTIBLE COOKING FLUIDS
When would you need to use a fire extinguisher labeled for a Class K fire?
This type of fire extinguisher is now required to be installed in all applicable restaurant kitchens because of the higher heating rates of vegetable oils used in commercial cooking.  If a fire starts in a deep fryer, it is not always possible to extinguish it with a Class B fire extinguisher or traditional range hood installed in the kitchen. 
How would you know when to use this special type of fire extinguisher?
These fire extinguishers are only to be used AFTER the activation of a built-in hood suppression system.  If there is no built in hood suppression system, then there is no requirement to use a Class K fire extinguisher.
What are the components in a Class K fire extinguisher?
There are different agents that are used in fire extinguishers labeled Class K.  Some of these agents are dry and some are wet.  Potassium bicarbonate is used in some dry chemical fire extinguishers and some wet fire extinguishers spray a fine chemical mist.
Are there any special precautions that need to be taken with this type of fire extinguisher?
The extinguishing agents in a fire extinguisher labeled for type K fires are sometimes electrically conductive and should only be used AFTER the power has been turned off in the electrical appliance.
Are there any recommendations for the placement of these fire extinguishers?
These fire extinguishers must be placed at a maximum travel distance of thirty feet.
Is there anywhere that I can find more information on the use of a Class K fire extinguisher?
For more information on the use of a Class K fires extinguishers see Seattle Fire Department Bulletin #2000-2 -. Requirement Seattle Fire Department (2005,January) 135 KB PDF, 2 pages.  We have searched the internet for you and found that this bulletin has some good information pertaining to Class K fire extinguishers.

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Disclaimer: We have provided this article as general information on the use of this article.  We make no claims as to the accuracy or completeness of the information as it may apply to an infinite amount of conditions and situations.  It is the responsibility of the person or persons reading and using this information to refer to the instructions and information provided by the manufacturer in the product package before testing or using this product.  Users of this information agree to hold Select Safety Sales LLC harmless from liability of any kind relating to the use of this information.
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