Understanding Fires in Orlando, Florida

There are several types of fire extinguishers available to choose from. Manufacturer’s typically will design them to suppress specific classes of fire or special fire hazards. Fire extinguishers are designed by fire extinguisher manufacturer’s for specific use and specific fire hazards.

Fire extinguishers that have been rated and carry UL and ANSI ratings and certifications help to ensure the fire extinguisher will meet the highest degree of safety and performance in Orlando, Florida.

BASIC ELEMENTS OF FIRE

Four elements must be present in order for fire to exist. These elements are HEAT,
FUEL, OXYGEN and CHAIN REACTION. While not everything is known about the
combustion process, it is generally accepted that fire is a chemical reaction. This
reaction is dependent upon a material rapidly oxidizing, or uniting with oxygen so rapidly
that it produces heat and flame. Until the advent of newer fire extinguishing agents, fire
was thought of as a triangle with the three sides represented by heat, fuel, and oxygen.
If any one of the three sides were to be taken away, the fire would cease to exist.
Studies of modern fire extinguishing agents have revealed a fourth element – a self
propagating chain reaction in the combustion process. As a result, the basic elements
of fire are represented by the fire tetrahedron – HEAT, FUEL, OXYGEN and CHAIN
REACTION. The theory of fire extinguishment is based on removing any one or more
of the four elements in the fire tetrahedron to suppress the fire.

REMOVING THE HEAT

In order to remove the heat, something must be applied to the fire to absorb the heat or
act as a heat exchanger. Water is not the only agent used to accomplish this, but it is
the most common. A more detailed discussion of how to apply water on a fire and
some theories regarding its use as an extinguishing agent will be covered in a later
section.

REMOVING THE FUEL

Under many circumstances, it is not practical to attempt to remove the fuel from the fire.
When dealing with flammable liquid fires, valves can be shut off and storage vessels
pumped to safe areas to help eliminate the supply of fuel to the fire. Flammable gas
fires are completely extinguished by shutting off the fuel supply.

REMOVE THE OXYGEN

Oxygen as it exists in our atmosphere (21%) is sufficient to support combustion in most
fire situations. Removal of the air or oxygen can be accomplished by separating it from
the fuel source or by displacing it with an inert gas. Examples of separation would be
foam on a flammable liquid fire, a wet blanket on a trash fire, or a tight fitting lid on a
skillet fire. Agents such as CO2, nitrogen, and steam are often used to displace the
oxygen.

INTERRUPT THE CHAIN REACTION

Modern extinguishing agents, such as dry chemical and halons, have proven to be
effective on various fires even though these agents do not remove heat, fuel, or oxygen.
Dry chemical and halogenated agents are thought to suspend or bond with “free
radicals” that are created in the combustion process and thus prevent them from

continuing the chain reaction. A more detailed study of this phenomenon is available
from the NFPA Fire Protection Handbook and various manufacturers of special fire
extinguishing agents.

CLASSIFICATION OF FIRES

CLASS “A” FIRES

A class “A” fire can involve any material that has a burning ember or leaves an ash.
Common examples of class “A” fires would be wood, paper, or pulp. The preferred
method for extinguishing class “A” fires is to remove the heat. Water is the most
common agent, but others such as dry chemical, halon, halogenated agents and foam
can be used effectively.

CLASS “B” FIRES

A class “B” fire involves flammable liquid or gas. Familiar examples would be gasoline,
oil, propane, and natural gas. A variety of fire extinguishing agents are used on
flammable liquid fires employing all theories of fire extinguishment. Which agent is best

to use is dependent upon the circumstances involved. Flammable liquids do not ignite
in their liquid state; rather it is the vapors being generated by these liquids that ignite.
The mixture of oxygen and flammable vapors in proper proportion needs only an ignition
source to start the combustion process.

CLASS “C” FIRES

Class “C” fires involve live electrical equipment and require the use of an extinguishing
agent and/or extinguisher that will not conduct electricity back to the fire fighter(s).
Electricity is an energy source and an ignition source, but by itself will not burn. Instead,
the live electrical equipment may serve as a source of ignition for a class “A “fire such
as insulation or packing, or a class “B” fire.

CLASS “D” FIRES

Class “D” fires involve exotic metals such as titanium, zirconium, magnesium, and
sodium. These fires require special agents such as dry powders and special application
techniques. The extinguishing agents and techniques used on “A”, “B”, or “C” fires will
not work on class “D” fires, nor will the agents and techniques used for class “D” fires
work on any other classification of fire. Many common agents like water will actually
react to burning metals and increase the intensity of the fire in a violent manner.

CLASS “K” FIRES

Class “K” fires involve cooking media. These can be any animal or vegetable based fats or oils. These fires require special agents such as wet chemical extinguishers and
systems that are alkaline in nature and have superior cooling capabilities. The entire
mass of the cooking medium in a deep fat fryer must be secured and cooled below its
auto ignition point in order to achieve complete extinguishment. Prior to the 1998 edition
of NFPA 10 these fires were considered to be Class “B” fires. After extensive testing it
was decided that they are unique in nature and are totally different than Class “B” fires.