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1. Fundamentals
of Fire

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What is Fire ??
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Fundamentals of Fire
Fire is a Oxidation Combustion Reaction
Self sustaining
rapid
Oxidation of fuel
which produces
light, heat &
combustion
by-products
Fuel (Vapour) + Oxygen + Ignition Source
Heat + Light + Combustion by-products
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Ignition Source
Fire

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What is there in the Fire which keeps it burning?
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The chemical chain reaction or the high molecular activity is
needed to keep the fire burning.
Molecular activity in the burning of paper:
For something to burn, it must first reach ignition
temperature. Consider an unintentional fire in a trash can.
The embers ignite paper in the can and a fire begins. Once
the fire starts, significant heat is generated. This heat causes
unburned paper next to the flame to increase its molecular
activity. The unburned paper vaporizes and turns to a gas.
This flammable gas provides more fuel to the fire and it
continues to burn.
Fundamentals of Fire

4. Fundamentals of Fire
Fire Propagation
Recent studies indicate that the spread or
propagation of a fire is also dependent on a fourth
factor: the chemical chain reactions that can occur as
a result of heat produced by the fire.

5. Fundamentals of Fire
Chain Reaction
The fourth factor which acts as a
catalyst in rapid oxidation
process is OH(-) radical which is
also termed as Chain Carrier
which results in Chain reaction of
combustion process.
Fire is the availability of H(+) and
OH(-) ions in the flame zone.
H H H
CH4 CH3 CH2 CH
HCs

6. 6
Fundamentals of Fire
Understanding a Chain reaction
•Chain reaction or high molecular activity is needed to keep the fire burning.
• The collision of molecules in the oxidation / reduction process causes heat to
build up, which sustains the combustion process.
• The continuous collision of molecules create thermal energy which sustain the
combustion.
• This sustained combustion is what is referred to as a Chain Reaction.

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Fundamentals of Fire
Classification of Fire
C
D
Solid Cellulose materials Flammable Gases
Hydrocarbon Liquids Combustible metals
• wood
• cloth
• paper
• rubber
• many plastics
•Ethylene
• Propylene
• Hydrogen
• Other Flammable gases
• Gasoline
• oil
• grease
• tar
• oil-based paint
• Diesel
• magnesium
• sodium
• potassium
• titanium
• zirconium
• other
flammable
metals

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Fundamentals of Fire
Extinguishing Media
 Water
 Steam
 Foam
 Clean agent, Inert Gases , CO2 & Nitrogen Gases
 Dry Chemical Powder

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Fundamentals of Fire
Water as an extinguishing agent
Cooling action of water is due to High heat of vaporization 2260 KJ/Kg
 Specific heat of water is high as compared to other substances, 4.2
KJ/Kg/0C
 It absorbs 1 BTU for every increase of 1degree Farhenite.
 Expansion ratio of liquid water to steam is 1: 1700
Molecular stability is around 1650 0C.
 Solvent ability.
 Water absorbs the most heat when it is converted into steam & it will be
easily converted into steam from droplets (spray) than from a solid stream.

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Fundamentals of Fire
Carbon Di-Oxide as an Extinguishing agent.
High expansion as 1: 450
 Inert Gas.
 Clean agent and leaves no residue.
 Critical temperature is 31.1 0C.
 Bad conductor of electricity.
 Heavier than Air.
 Easy Penetration.
 Cannot be further Oxidized.

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Fundamentals of Fire
Carbon Di-Oxide……
No decomposition product formation.
 No separate propellant required.
 Discharge pressure doesn’t fall until all gas is discharged.
 Solid CO2 (Dry Ice) sublimes that is it goes directly from solid to
gas at atm. Pressure & this occurs at -78 0C.
 CO2 gas at 25 0C is compressed to a pressure above 67 Atm.,
it liquefies. (Can be kept in liquid form in Cylinder)
 Rapid expansion causing rapid cooling due to Joule’s Thomson
Effect.

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Fundamentals of Fire
Dry Chemical Powder
Types of dry chemical
Some basic dry chemicals powders are:
Sodium bicarbonate
Potassium bicarbonate
Potassium chloride
Urea + potassium bicarbonate = Monnex Powder
Mono-ammonium phosphate(MAP)
Standard dry chemical consists principally (over 90%) of parent
bicarbonate with additives to improve fluidity, non-caking and water
repellent characteristics.

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Fundamentals of Fire
How DCP extinguishes Fire
Chemical action, by breaking the chain reaction.
 DCP reacts with the combustion radicals
(Active chain H+ & OH- radicals)
 3-D extinguishing agent: Cooling, smothering & chain
Inhibition,

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Fundamentals of Fire
Inhibition of Chain Reaction
Example : Breaking of Chain Carrier
When Dry Chemical Powder Decomposes-
2KHCO3 --------> K2CO3 + H2O + CO2
K2CO3 ----------->K2O + CO2
K2O + H2O -----> 2KOH
KOH + H* -------> K* + H2O
KOH + OH* -----> KO* + H2O
KO * + H* --------> KOH
K* + OH* --------> KOH
OH * & H * (Active radicals of Fire)

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Fundamentals of Fire
What is Foam ?
Foam is essentially expanded water and, apart from its
density, has the general characteristics of water.
Standard foam is made by introducing the foam compound
into the water & agitating or mixing with special type of
equipments / branches & inducing air through venturi or
eductor to yield finished foam of concentration 1% or 3% or
6%, based on the induction of formulation of foam
concentrate.

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Fundamentals of Fire
Foam….
Foam smoothers the fire and prevents air from mixing with flammable
vapours.
 Foam suppresses flammable vapours & prevents their release.
 Foam separates the flames from the fuel surface.
 Foam cools the fuel & adjacent metal surface which in turn prevents foam
burn Off and cools flammable liquid below their flash point.
 Fire control and extinguishment is not the only use of Aqueous Film
foam. Another important application is the suppression of
vaporization from toxic liquid spills
AFFF has low viscosity and spreads easily over a liquid
surface.
Fuel

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Fundamentals of Fire
Clean Agents
Inergen (N2-50 % + Ar-42% + CO2-8%)
Argonite (N2- 50% + Ar-50 %)
Nitrogen
FM-200
Clean agents extinguishes the fire by reducing the concentration
level of oxygen in the enclosed area

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Fundamentals of Fire
Important definitions
Flash Point
The flash point of a product is the lowest temperature at which
sufficient amount of vapours are given off to create a mixture with the
air which is flammable on contact with an open flame or spark. The
lower the flash point of a liquid, the higher the risk of fire.
Auto-Ignition Temperature
Lowest temperature at which combustion of the product begins in the
absence of any flame or spark. Auto ignition temperature of a material
is reached due to conduction, convection or radiation of heat. The
closer the auto-ignition temperature to the ambient temperature, the
greater the risk of fire.
Spontaneous Combustion
Combustion occurred due to heat produced within a material due to
chemical oxidation reaction & raising its temperature to its ignition
temperature.
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Fundamentals of Fire
Important definitions…
Flammability / Explosive Limit
Minimum and maximum concentration of a product in the air forming a
mixture which is flammable or explosive in the presence of an ignition
source. It is expressed as a percentage of the volume in the air.
Pyrophoric material
Any material igniting spontaneously or burning spontaneously in air.
Vapour Pressure
Expressed in millimeters of mercury (mm of Hg), at NTP. The higher a
product's vapor pressure, the more it tends to evaporate.
Vapour Density
Expresses the number of times that the vapours of a product are heavier or
lighter than air at its Boiling Point.

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Fundamentals of Fire
Important definitions…
Petroleum Classification
 Class A : Liquids having Flash Point below 230 C
 Class B : 230 C>Flash Point<650 C
 Class C : 650 C > Flash Point < 930 C
 Unclassified /Excluded: Flash Point > 930 C
 Flammable Liquids: Liquids having flash point below 37.80 C
are termed as Flammable Liquids.
Combustible Liquids: Above 37.80C flash point are termed as
Combustible Liquids.

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Fundamentals of Fire
Important Definitions
Convection
Conduction
Radiation
Heat Transfer

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Fundamentals of Fire
Important Definitions…
• Fuel removal – Starvation
• Excluding Oxygen – Smothering
• Reducing Temperature - Cooling
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Ignition Source
No
Fire

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Fundamentals of Fire
What you should do in case of Fire..
Try to extinguish the fire with available resources, without endangering
yourself.
Shout FIRE- FIRE to warn or to aware nearby persons
Inform Fire Service for necessary help
Inform your Superiors / Supervisors
Ask unnecessary personnel to evacuate from affected area & assemble them
at safe locations
Always try to handle emergency from upwind direction
Guide Fire Tender to reach the emergency site
Help Fire Personnel in activities of fire fighting and rescuing of casualties

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Thank you
…. For your attention