Throw Back to Basics: Fire Extinguishers

By Brian Zaitz

Almost every fire apparatus in the United States carries some type of portable extinguisher, whether it’s the water can on the truck or a full complement on the engine. All firefighters should know the operation and use of their portable extinguisher.

Portable extinguishers work by one of four methods to extinguish a fire:

  1. Smother the fire by excluding oxygen.
  2. Cooling to reduce the temperature of the burning materials below ignition.
  3. Breaking the chain reaction.
  4. Saponification to create a foam solution to exclude oxygen.

These four methods are directly related to the extinguishing agent in the extinguisher. Traditionally, there are three types of extinguishers found in play in today’s fire service: the water can, the dry chemical, and the carbon dioxide. Each extinguisher is useful for a specific situation and material. Remember being taught the classes of fire in recruit school? You must know them and, ultimately, be familiar with their fire behavior and their required extinguishing agent.

(1)

 

The most common extinguisher is the water can or pressurized water extinguisher (photo 1). These extinguishers are used for class A fires. Because of their ease and portability, they are a great tool for overhaul and miscellaneous fires. The extinguisher works by adding water to the can, then using air or nitrogen as a pressurizing agent. When they are needed, simply pull the pin and use the rubber hose fitted with a solid bore tip to facilitated extinguishment. The pressurized water can uses cooling as its method of extinguishment. The water can is a great asset and should be on every apparatus.

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The dry chemical extinguisher is often found on many engine companies. It is the most common extinguisher found outside of the fire service because of its ability to suppress class A, B, and C fires. Note that a dry powder extinguisher is not the same and is used as an extinguishing agent for class D or metal fires. The dry chemical extinguisher commonly uses sodium bicarbonate mixed with an inert material to reduce moisture absorption during storage. These extinguishers work by breaking the chain reaction as well as separating the fuel from the oxygen supply. These are great extinguishers for the pan on the stove or small grease fires; they provide quick extinguishment and the relatively minimal secondary damage commonly seen with water.

(2)

 

The carbon dioxide extinguisher (photo 2) is the third and often times less seen extinguisher. This extinguisher is easily identified by its large bell or nozzle. It is considered a clean extinguisher because carbon dioxide gas leaves little residue. Although this is good and because no product remains, the risk of reignition is higher with carbon dioxide than any other extinguishing agent. Carbon dioxide extinguishers work by displacing available oxygen to the fire. The liquefied carbon dioxide is released from the extinguisher and forms a carbon dioxide gas cloud over the fire. Note that when using this extinguisher, never hold the bell or nozzle; the carbon dioxide produces frost and subzero temperatures during release. Interestingly enough, this extinguisher has little to no effect on cooling of the burning materials. These extinguishers are rated for class B and C fires, but they are predominantly used for electrical or computer room fires.

Portable extinguishers are great tools; they provide quick and effective fire control when properly applied. Take the time on your next tour to review your cache of portable extinguishers and review their functionality and operation.

Download this training bulletin as a PDF HERE (3.4 MB).

 

Brian Zaitz is a 14-year student of the fire service, currently assigned as the captain/training officer with the Metro West (MO) Fire Protection District. Brian is an instructor with Engine House Training, LLC as well as instructor at the St. Louis County Fire Academy.  Brian holds several degrees, including an associates in paramedic technology, a bachelors in fire science management, and a masters in human resource development. Brian is currently and accredited chief training officer and student of the National Fire Academy’s Executive Fire Officer Program.

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