Page 348 - IGC BOOK

Principles of Heat Transmission and Fire Spread

Heat Transmission and Fire Spread

The fire and the smoke during the combustion process can spread through four ways which are
convection, conduction, radiation and direct burning.

Convection

Hot air becomes less dense and rises to the atmosphere, this hot
air continuous to rise temperature; in turn causes the materials in
the atmosphere at higher level eventually ignite the flammable
materials.

Hot air then becomes colder, falls down to supply fresh source of
oxygen to combustion.

Outdoors, these convection currents will contain burning embers
that are carried in the currents until the air cools and the embers Fire Spread - Convection
are dropped to the ground. This is a common way for forest fires
to travel and jump over obstacles (such as roads).

Conduction

Transfer of heat through matter through thermal motion of
atoms and molecules. Heat transfer takes place from higher
temperature to lower temperature especially in solids or between
solid objects in thermal contact. Fluids and gases are less
conductive than solids. A further example of conduction is how
hot the end of a metal spoon gets if you leave it in a pan of
boiling water.
Metals are considered as good conductors of heat, when there is
fire in the building the heat is transferred through conduction
method to the metal structure in the building resulting in Fire Spread - Conduction
spread of fire.

ENSIGN | Unit IG2 – Element 10 –Fire 3