Products of Fire
Combustion is a chemical reaction between fuel
and oxygen at a suitable temperature as result of
which heat, flame and light is produced. In addition
to these factors there are so many products appeared
as a result of fire. Four of them are very important.
Products of Fire
 Smoke
 Toxic gases

Heat

Flame
Smoke
Smoke is a result of incomplete combustion if the
three elements of combustion e.g. fuel, oxygen and
heat are in proper proportion, a complete
combustion take place but if a reaction take place at
a lesser temperature compared to the fuel or oxygen
and incomplete combustion take place and the
result is, the release of un burnt carbon particles
turmed as smoke.
Toxic Gases
Combustible materials are usually based on
complicated organic as well as in organic
substances, so toxic gases are produced during
combustion process.
Toxic Gases
A. Carbon dioxide
B. Carbon monoxide
C. Sulfur monoxide
D. Hydrogen cyanide
E. Ammonia etc.
Heat
Heat is also generated in the chemical reaction
and has its own affects like:
A. Further propagation of fire.
B. Burns caused to the fire fighter.
Flame
Flame, a result of combustion, produces special
risks like:
A. Fire due to direct contact with flame
B.
Emits light
C.
Release of sufficient heat.
Spread of Fire
The fire which is a composition of large number of
products and the major product is the release of heat
(thermal waves) in all direction. Heat is a form of
energy and energy travels from one body to the
other bodies in three possible ways which are:
Spread of Fire
 Conduction
 Convection
 Radiation
Conduction
Conduction is the phenomenon of spread of heat
from one body to another, through the collision of
molecules, conduction occur in solid. In conduction
heat energy passes on from one molecule to the next.
Metals are good conductors whereas liquids, non
metallic solids and gases are considered as bad
conductors and some of them are insulators e.g. a
steel girder passing though an otherwise fire proof
ceiling may be a cause of fire spread because of heat
conducted through it.
Convection
The second mode of heat transfer is due to
convection which occurs in liquids and gases,
when a liquid or a gas is heated it expands and
therefore become less dense, the lighter fluid rises
being displaced by colder and denser fluid. This in
turn becomes heated and a circulation is setup, heat
energy is carried through out the fluid by actual
movement of molecules until a state of uniform
temperature is reached.
Radiation
Heat may also be transmitted through straight lines
which are neither conduction nor convection, just as
the heat from sun reaches the earth. This method of
heat transmission as radiation and does not involve
any contact between a bodies. All forms of radiated
energy travel in straight lines at a speed of 3 × 108
meters/sec. The intensity falls inversely as the
square of distance, from the source of radiation.
Elements of Combustion
Fuel
According to the law of triangle of fire,
fuel is the substance which have great affinity with
oxygen and react with it at comparatively low
temperature.
Different Types of Fuel
 Carbon
 Carbon monoxide
 Readily oxidizable non-metals such as sulphur
and phosphorous
Different Types of Fuel
 Compounds rich in carbon and hydrogen (hydro
carbons and Gasoline)
 Cellulosic substances (Wood and textile etc.)

Metals (Aluminum, magnesium, titanium) and
alkali metals (Sodium and potassium)
Oxidizing Agents
An oxidizing agent is a chemical substance that
provide the oxygen necessary for completion of
oxidizing process.
Different Types of Oxidizing Agents
 Oxygen and ozone (air).
 Hydrogen peroxide.
 Halogens (chlorine, fluorine, bromine and
iodine).
Different Types of Oxidizing Agents
 Concentrated nitric acid and sulfuric acid.
 Oxides of heavy metals (manganese dioxide and
lead dioxide.
 Nitrates and chlorates.
Temperature
Temperature is defined as the degree of hotness or
coldness of a body. When heat is applied to a body
its temperature and intermolecular collision
is increased and internal energy is also increased.
The rise in temperature also supports the
evaporation process and thus the number of
molecules evaporated is extensively increased.
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