2. What is Fire?
A process in which substances combine
chemically with oxygen from the air
and typically give out bright light, heat,
and smoke; combustion or burning.
3. Elements of fire
Fuel
– Combustible substance in the form of
vapour, Liquid or Solid.
Heat
– A Source of Ignition sufficient to initiate
and propagate the Chemical Reaction of
Combustion.
Oxygen
– Oxygen content in atmospheric Air in
sufficient proportion to form a
combustible Vapour-Air mixture.
4. Explosion results from
• Chemical changes such as in the detonation
of explosive or the combustion of a
flammable gas-air mixture
• Physical or Mechanical changes such as
bursting of pressure vessels
• Atomic changes
5.
6. Chain reaction
For a Fire to be self sustaining, the oxidation
process should be self sustaining.
The Ignition which triggers the oxidation
reaction between one tiny bundle of
Oxygen and one tiny bundle of fuel must
produce enough energy to trigger oxidation
between two more tiny bundles of oxygen
and fuel.
In this manner, the combustion continues
like a CHAIN REACTION
7. IF ANY ONE OF THREE IS REMOVED ,THE FIRE IS IMPOSSIBLE
HEAT
CHAIN
REACTION
OXYGEN FUEL
AT ALL TIMES,
PREVENT THE
COMPLETION OF
THE CHAIN
REACTION FOR
AVOIDING THE
FIRE
8. Tetrahedron of FIRE
The fire tetrahedron is a four-sided
geometric representation of the four factors
necessary for fire: fuel (any substance that
can undergo combustion), heat (heat energy
sufficient to release vapor from the fuel and
cause ignition), oxidizing agent (air
containing oxygen), and uninhibited
chemical chain reaction.
8
10. How fire transmitted
Conduction of Heat: Transfer of heat through a solid
material from a region of high temp
Convection of Heat: Transfer of heat in or by liquid or a gas
by the movement of medium.
Radiation of Heat: Transfer of heat through a gas or vacuum
other than by heating of intervening space.
12. Few Terminology
• Flash point; It is the lowest temperature at
which the substance gives off sufficient vapour
to be ignited at the surface. The concentration of
vapour above this temp forms an ignitable
mixture with air.
• Flammability limits: These limits give the range
between the lowest and highest concentration of
vapour in air that will burn or explode when an
ignition source (such as a spark or open flame) is
present.
• Fire Point:The temp at which a liquid fuel will
produce sufficient vapours to support continuous
combustion once ignite.
