Fire Safety

Fire

Fire is a chemical reaction between a flammable or

combustible material and oxygen. This process converts
the flammable or combustible materials and oxygen into
energy. Other by-products of fire include light, smoke
and other gases. Many of these gases such as carbon
monoxide, carbon dioxide, hydrogen bromide, hydrogen
cyanide, hydrogen sulfide, sulfur dioxide, nitrogen
dioxide, etc. are toxic to humans.
The fire triangle and the pyramid of
fire illustrate the elements necessary
for fire to start and the methods of
extinguishment. Each side represents
an essential ingredient for fire.

The three elements are Fuel, Oxygen

and Heat. When a fire starts, a fourth
element, which is the chemical
reaction itself, is necessary for flame
propagation. The four-sided figure is
called the Fire Tetrahedron.
Fuel
• Fuel: Any material that
will burn is classified as
fuel. Identify examples of
fuel you can find in your
workplace. Do you know
the difference between a
flammable or
combustible substance?
Flammable
Substance
• Flammable substance – is a
substance having a flashpoint below
100 °F (37.8 °C) and vapor
pressure not exceeding 20 psia at
100 °F. Examples of flammable
substances with their flashpoint are
shown below:
 Flashpoint
Flammable substances °F °C
• Gasoline -45 -42.8
• Ether -49 -45
• Acetone 0 -17.8
• Alcohol 55 12.8
Flash Point
• Flashpoint - the lowest
temperature at which fuel
begins to give off flammable
vapors and form an
ignitable mixture in air.
 Which is more dangerous: a
substance with low flashpoint or a
substance with a high flashpoint?
Answer: The lower
the flashpoint, the
more dangerous a
substance is.
Oxygen
• From our definition of
FIRE, we need oxygen
which combines with fuel
while burning. Normally,
the air has 21% oxygen
and 78% while nitrogen.
Heat

Heat – completes the chemistry of fire

• Even if found together, fuel and oxygen
will not burn. An example is a piece of
paper. This fuel is exposed to oxygen in
the air but will not burn. Why? Because
we need to introduce the third element
which is Heat.
• It is when we heat up the piece of paper
sufficiently that it will start to burn.
 The fire triangle
demonstrates the
How to principles of
extinguishing fire. If we
extinguish remove any of the
a fire? three legs of the
triangle, we will be able
to extinguish the fire.
 • Taking away fuel from a fire is difficult and
often times dangerous. However, there are
examples that can be employed in controlling
A. fire such as:
LPG tank flame at the nozzle of the valve
is best extinguished by shutting off the
Removing valve. When there is no fuel supply the
flame will die out.
Flammable liquid storage tanks can be
fuel arranged so that contents can be pumped
to an empty tank in case of fire.
Fire lanes cut in forests prevents
conflagration
Grasses and undergrowth are burned
ahead of an advancing bush fire so that
when the main fire reaches these burnt
areas, there is no more fuel to feed the
fire.
 • Oxygen cannot be eliminated
completely so what one can do is:
B. 1. Separate it from the fire through
smothering the burning area with a
Removing non-combustible material – this is
called “suffocating the fire.”
oxygen Examples:
If there are oil spills, you can
cover it with wet blanket or you
can throw sand or soil on it.
Covering with foam
Smothering it with inert gas
 • 2. Reduce the concentration of
oxygen below the concentration
B. necessary to support combustion.
This is accomplished by
Removing discharging carbon dioxide or
oxygen other inert gases into the fire.
 • If we reduce the heat below the kindling
point or flashpoint, we stop the release
of combustible vapors and gases and
C. extinguish the fire. To achieve this, it is
necessary to remove the heat at a
Removing greater rate than the total heat that is
being evolved from the fire. The most
heat common agent used is water or
incorporated in foam.
• Example:
• After cooking barbeque we
normally put off the charcoal
using water applied directly to the
flame.
 • In order for fire to propagate
continuously, there must be uninhibited
D. and continuous chain reaction. Speed
up the process and an explosion
Interrupting results.
• Interrupt the chain reaction by inhibiting
the chain the oxidation process and the
reaction production of flammable vapors that
react with oxygen, then we extinguish
the fire.
• Example:
• Use of dry chemicals extinguishes
fire with this principle.
Classification of
Fires

• There are four classes of fires, categorized

according to the kind of material that is
burning. For the first three classes of fires,
there are two sets of color-coded icons
commonly used. One or both kinds of
icons appear on most fire extinguishers to
indicate the kinds of fire against which the
unit is intended to be used.
Knowing the classification of
fires is important for the speedy
extinguishment and safety of the
fire fighters. Using the wrong
extinguishing medium may
cause the fire to spread and
endanger the fire fighters.
 We prevent fire by preventing the
combination of the three elements at
Principles the right proportion. Ordinarily, oxygen
is the most difficult of the three factors
of fire to control, since it is in the air and is a
prevention necessity of life. But fuel and heat can
be controlled. Therefore the simplest
and control measures will have to do with
control fuel and heat. Actually, control in this
sense merely means keeping them
separated.
It will be good to examine the hazards from which most fires originate. These are
sometimes described as causes of fire.
 Except for explosions, most fires start
out as small ones. At the initial stage,
extinguishing a fire seldom presents
Provide for much of a problem. Once the fire
early begins to gain headway, it may
detection of develop into conflagration of
disastrous proportions. Fire can be
fire more easily controlled if detected
early. It is critical that fire be
extinguished in the first five minutes.
 Once a fire is discovered, it is of
prime importance to confine it to
the smallest area possible - that is,
Prevent the to prevent its spread. This can be
accomplished by details of
spread of construction and by safe practices,
but neither is sufficient alone. An
fire understanding of the means by
which heat is transmitted will be of
value in taking the necessary steps
to prevent the spread of fire.
 In providing for prompt
extinguishment, the two
Provide for categories of fire
prompt extinguishers should be
extinguishment kept in mind – permanent or
“built-in” extinguishers and
portable fire extinguishers.
In the absence of modern fire extinguishers,
the following can be used to stop fire in its
initial stage.
For A fire - water is the best.
For B fire - a metal cover, wet sack,
towel, cloth, or blanket will do. Sand and
soil are very useful
For C fire - the main switch is the first
consideration. Pull it down to cut off the
current. What is useful on A & B can also
be useful here.
 The information given here
describes how a fire
extinguisher should be used to
fight a fire. However, do not
believe, because you have
read this, that you know how
Fire Extinguisher to use a fire extinguisher! If
Operation you really want to learn how to
use a fire extinguisher properly
(and you should), you should
seek out a hands-on training
class in which you will have the
opportunity to put out some real
fires using portable
extinguishers.
PASS
When should
you fight a fire?
Attempt to
use a fire
extinguisher
if and only
if...