Fire is a rapid oxidation reaction that releases heat and light. It requires fuel, oxygen, and heat in a self-sustaining chain reaction known as the fire tetrahedron. There are different stages of a fire from ignition to growth to decay. Fires can be classified based on the type of fuel, such as class A for ordinary combustibles, class B for flammable liquids, and class C for energized electrical equipment. Each class requires specific extinguishing agents to safely put out the fire.

2. • FIRE is a phenomenon which when harnessed, the power and energy
from fire can serve us well ,however when it is uncontrolled a fire can
quickly consume & destroy whatever lies in its path.
• CHEMISTRY OF FIRE
OXIDATION is a chemical reaction between the molecules of a substance
& the oxygen molecule in the surrounding atmosphere.
Eg: rusting of iron, the tarnishing of silver or the rotting of wood.
• FIRE is actually a chemical reaction involving the oxidation of the fuel
molecule.
• What is called burning or combustion is actually the continous rapid
oxidation of millions of fuel molecules.
• The Oxidation reaction is an exothermic process
• In case of rusting heat released is minimal since oxidation process
occurs at a slow rate.
• In fire , the oxidation rate of the fuel molecule is much faster
( because of rapid reaction, energy is released at a much greater rate)
Explosion – oxidation at an extremely fast rate.

3. • THE FIRE TRIANGLE
The three components required for combustion to occur
• Fuel – to vapourize and burn
Fuel – solid –wood etc
liquid – paints
gas - LPG
• Oxygen – to combine with fuel vapour
• Heat – to raise the temperature of the fuel vapour to its
ignition temperature

4. • If any of the three
components are missing,
then a fire cannot start.
• If any of the three
components are removed,
then fire will go out.

5. THE FIRE TETRAHEDRON
Illustrates how flamming combustion is supported & sustained through
the chain reaction of the oxidation process.
Chain reaction face keeps the other three faces from falling apart.
A fire can be extinguished if any one side of the fire
tetrahedron can be destroyed

6. • Stages of fire
• Ignition: Fuel, oxygen and heat join together in a sustained chemical
reaction. At this stage, a fire extinguisher can control the fire.
• Growth: With the initial flame as a heat source, additional fuel
ignites. Convection and radiation ignite more surfaces. The size of
the fire increases and the plume reaches the ceiling. Hot gases
collecting at the ceiling transfer heat, allowing all fuels in a room to
come closer to their ignition temperature at the same time.
• Fully developed: Fire has spread over much if not all the available
fuel; temperatures reach their peak, resulting in heat damage.
Oxygen is consumed rapidly.
• Decay (Burnout): The fire consumes available fuel, temperatures
decrease, fire gets less intense.

7. • Fire classifications based on fuel type:
• Class A: Ordinary combustible materials, such as wood, cloth, paper, rubber and
many plastics. They burn with an ember and leave an ash. Extinguish by cooling
the fuel to a temperature that is below the ignition temp. Water and other
extinguishing agents are effective.
• Class B: Flammable liquids (burn at room temperature) and combustible liquids
(require heat to ignite). Petroleum greases, tars, oils, oil-based paints, solvents,
lacquers, alcohols, and flammable gases. High fire hazard; water may not
extinguish. Extinguish by creating a barrier between the fuel and the oxygen,
such as layer of foam.
• Class C: Fuels that would be A or B except that they involve energized electrical
equipment. Special techniques and agents required to extinguish, most
commonly carbon dioxide or dry chemical agents. Use of water is very
dangerous because water conducts electricity.
• Class D: Combustible metals, such as magnesium, titanium, zirconium, sodium,
lithium and potassium. Most cars contain numerous such metals. Because of
extremely high flame temperatures, water can break down into hydrogen and
oxygen, enhancing burning or exploding. Extinguish with special powders based
on sodium chloride or other salts; also clean dry sand.
• Class K: Fires in cooking appliances that involve combustible cooking media
(vegetable or animal oils and fats).