This document provides information on fire chemistry and combustion. It defines fire as a chemical reaction that releases energy in the form of heat and light. Modern fire theory involves four elements - an oxidizing agent, reducing agent, heat, and an uninhibited chain reaction. It also describes methods of fire extinguishment like starvation, cooling, and blanketing. Fires are classified into different classes based on the type of fuel. The document outlines various fire suppression techniques and important fire safety concepts.

2. WELCOME TO THE LESSON
PLAN
CHEMISTRY OF
COMBUSTION
PREPARED BY: SANDEEP DIXIT
CLP India

3. • FIRE is an associated series of
chemical reactions, which
releases the energy stored in
fuel, such as heat and light
(flame).

4. OLD CONCEPT OF FIRE
AIR
H
EA
T
FUEL
FIRE TRIANGLE THEORY

5. MODERN CONCEPT OF FIRE
TETRAHEDRON THEORY
FORMULATED BY WALTER . M . HAESSLAR
1. OXIDIZING AGENT
2. REDUCING AGENT
3. TEMPERATURE
4. UN-INHIBITED
CHAIN REACTION

6. Fuel vapour
Solid fuel
Liquid fuel
Cracking zone
H
CH3
CH
H
CH3
H
O
O
O
C
H
C
CHO
OH
C
O
C
O N
O N
O N
O N
O N
O N
Combustion zone
Products of
combustion I.e
C,CO,CO2,O,N,
HO
ANATOMY OF FIRE

7. METHODS OF EXTINCTION OF FIRE
1. STARVATION
2. COOLING
3. SMOOTHERING OR BLANKETING
4. CUTTING OFF THE CHAIN REACTION

8. PRINCIPLES OF FIRE EXTINCTION
FUEL AIR
HEAT
FUEL AIR
HEAT
COOLING
STARVATION
HEAT
AIRFUEL
SMOOTHERIN
G

9. CLASSIFICATION OF FIRE
• CLASS “A” :
FIRE IN SOLID CARBONAEOUS
SUBSTANCES LIKE WOOD, PAPER,
JUTE, COAL, CLOTH ETC.

10. CLASSIFICATION OF FIRE
• CLASS “B” :
LIQUID FIRE- FIRE IN
FLAMMABLE LIQUID LIKE PETROL,
KEROSENE OIL, ALCOHOL, BENZENE
ETC.

11. • CLASS “C” :
GAS FIRE- FIRE IN GASES LIKE
L.P.G., HYDROGEN, ACETELENE ETC.
CLASSIFICATION OF FIRE

12. • CLASS“D” :
METAL FIRE- FIRE IN
METALS Like Sodium, Magnesium,
Aluminum etc.
CLASSIFICATION OF FIRE

13. • Fire of any class (i.e. Class A, B, C Or D) ,
when associated with Electrical power
supply, shall be taken extra care.
CLASSIFICATION OF FIRE

14. Flash Point
• The minimum Temp. at
which any substance gives off
sufficient combustible vapours to
produce a momentary flash on the
application of any external source
of flame.

15. Fire Point
• The minimum Temp. at
which any substance gives off
sufficient combustible vapours to
continue the flame on the
application of any external source
of flame.

16. Ignition Temperature
• The minimum temp. at which
any combustible material starts
burning itself without any
application of external source of
flame.

17. FLAMMABILITY LIMITS
• Limits within which the
vapours of fuel can produce a
flame after mixing with air.

18. Flammability limits
FUEL LFL UFL
• H2 4.0 75.0
• CO 12.5 74.2
• CH4 5.0 15.0
• C3H8 2.2 9.5
• C4H10 1.5 9.0

19. Fire Suppression Procedures
PRIMARY
• Removal of Fuel
• Reduction of Heat
• Reduction of Air
SECONDARY
• Shock Wave
• Critical Vibration
• Ion Separation
(strong electric field)

20. PRIMARY FIRE SUPRESSION
COOLING (limitation of temperature)
SMOTHERING (limitation of oxygen)
STARVATION (limitation of fuel)

21. COOLING
• The cooling principle is the one most commonly
employed for fire extinction
• The extinguishing medium operates by
absorbing heat from the fire.
• Its temperature is raised.
• It is converted to the vapour state.
• For Fire fighting, Water is the best coolant

22. WHY WATER?
• Easily available.
• Comparatively cost is less than other
extinguishing media.
• High latent heat of vapourisation i.e. 536 cal/
gm
• After evapourisation it expands enormously
(1:1700 times).
• Thus removing the oxygen from the scene of
Fire.

23. Starvation
• By removing combustible material
from the neighborhood of the fire.
• By removing the fire from the
neighborhood of combustible
material .

24. Smothering
• If the oxygen content of the
atmosphere in the immediate
neighborhood of burning material can
be sufficiently reduced, combustion
will cease.
• Agents- Foam, CO2,DCP, Sand etc

25. SECONDARY FIRE SUPRESSION
• Shock Wave
• Critical Vibration
• Ion Separation (strong electric field)

26. SHOCK WAVE
• Shock Waves are normally generated by explosion,
Resulting in
– Rise in temp. & Pressure in a coffined space.
– Time lag between Ignition and destructive pressure.
– Suppression system can react between this time
lapse.
• Explosion may be single or Multiple

27. CRITICAL VIBRATIONS
• It is done to disrupt the mixing of fuel
vapour and oxygen in a proper ratio.
This disruption will create a time lag
and that is the time for activating
primary fire suppression system.
• Precision is essential.

28. ION SEPARATION
 Fire is a chemical process between
Reducing and Oxidising agents. Chemically,
positive and negative charged ions participate
in the exothermic reaction i.e,. Fire. Creation of
strong electric field in the vicinity of Fire, will
force the ions to move towards the electrodes,
thus not allowing them to mix up and react with
each other.
 Hence fire will not sustain.

29. • Bad house-keeping
• Electrical
• Careless smoking
• Poor maintenance of machinery
e.g: Mechanical heat, Spillage of hot
oils/ lubricants.

30. Contd…..
• Unsafe handling of Hazardous chemicals
and gases
• Lack of periodical maintenance of
pipelines carrying steam, gas, fuels
• Poor awareness about fire safety systems
• Poor manpower training in Fire fighting

31. • Scorch marks on furniture or fittings.
• Discoloured or charred electrical plugs,
sockets.
• Cigarette burns.
DO NOT LOSE SIGHT

32. • Hazards
–Arcing
–Overheating
–Shock
• Causes
–Improper installation
–Lack of maintenance
–Improper use
–Carelessness or over-sight

33. • Prevention
– Use of proper size conductor appropriate to
the load
– Suitable insulation of environment
– Correct rated fuse/MCB
– Provision of ventilation/air circulation
– Prevention /Dissipation of static charges

34. • Good house keeping
• Separation of process from storage.
• Preventive maintenance of machinery and
periodical lubrication.
• Regular fire safety checks and fire drills.
• Standard work practices.
• Maintenance of fire safety systems.
• Training of personnel.

35. Diffusion Flame
• Flame in which reactants are
mixed by diffusion, hence called
Diffusion flame.

36. Pre- Mixed Flame
• Occurs when a Fuel is well mixed
with an oxidising agent before the
ignition source is applied

37. BE ALERT AND AVERT FIRE
LOSSES
THANK YOU