Fire-Behavior-Lecture.ppt

Fire Description of Protection

1. Fire Behavior

2. Fire Behavior
•Introduction
•Physical Science
–Definition
–Basic Components
–Fire Tetrahedron
–Fire Extinguishment Theory
–Classification of Fires
•Other References

3. Introduction
•Fire has been both a help and hindrance to
mankind
–heated homes, cooked our food, helped us to
become technologically advanced
•Firefighters should have a basic
understanding of the science of fire and the
factors that affect its ignition, growth, and
spread to perform safely and effectively in
any firefighting function

4. Physical Science
•Definition
–Fireis a rapid oxidation of combustible materials
accompanied by the released of heat and light at
various intensities.
–Pyrolysisis the chemical change brought about by heat.
•Basic Components:
–Oxidizing Agent (Oxygen)
•those materials that yield oxygen or other oxidizing gases
during the course of a chemical reaction
•bromates, bromine, chlorates, chlorine, fluorine, iodine, nitrates,
nitric acid, nitrites, perchlorates, permanganates, peroxides

5. Physical Science (Cont…)
–Heat
•a form of energy; energy in transit
•sources
–chemical –chemical reactions generate heat
–electrical –current flow generates heat; ex. overloading, static,
lightning
–mechanical –friction and compression
–nuclear –fission or fusion of atoms
•ways on how heat supports the combustion reaction
–causes the pyrolysis or vaporization of solid and liquid fuels and
the production of ignitable vapors or gases
–provides the energy necessary for ignition
–causes the continuous production and ignition of fuel vapors or
gases so that the combustion reaction can continue

6. Physical Science (Cont…)
–Fuel
•the material or substance being oxidized or burned in the
combustion process
•also known as the reducing agent
•forms
–Solid –coal, wood, plastic, paper, cloth, wax, grease, leather, cork,
etc
–Liquid –gasoline, kerosene, turpentine, alcohol, paint, varnish, oil,
etc
–Gas –natural gas, propane, butane, hydrogen, acetylene, carbon
monoxide, etc
–Chemical Chain Reaction
•a series of reactions that occur in sequence with the results of
each individual reaction being added to the rest

7. Physical Science (Cont…)
The Fire Tetrahedron

8. Physical Science (Cont…)
•Fire Extinguishment Theory
–Temperature Reduction
–Fuel Removal
–Exclusion of Oxygen
–Chemical Flame Inhibition

9. Physical Science (Cont…)
•Classification of Fire
–Class A –Ordinary combustible materials
•wood, paper, cloth, paper, rubber, and many plastics
•can be extinguished by temperature reduction
–Class B –Flammable/combustible liquids
•gasoline, kerosene, alcohol, paint, varnish, etc
•oxygen exclusion is the most effective extinguishing method
•removal of fuel and temperature reduction can also be applied,
as well as interruption of the chain reaction by dry chemical
agents

10. Physical Science (Cont…)
•Classification of Fire (Cont…)
–Class C –Energized electrical fires
•household appliances, computers, transformers, and
overhead transmission lines
•can sometimes be controlled by a non-conducting
extinguishing agent such as halon, dry chemical, or
CO
2
•safest procedure is to de-energize high voltage
circuits and fight the fire appropriately depending
upon the fuel involved

11. Physical Science (Cont…)
•Classification of Fire (Cont…)
–Class D –Combustible metal fires
•aluminum, magnesium, titanium, zirconium, sodium.,
potassium, etc
•hazardous in powdered form
•water and other common extinguishing agents are
ineffective due to extremely high temperature
•special extinguishing agents are available for control
of fire in each of the metals

12. Physical Science (Cont…)
•Mechanism of Heat
Transfer
–Conduction
•the point-to-point
transmission of heat
energy
•result of direct contact
with a heat source

13. Physical Science (Cont…)
•Mechanism of Heat
Transfer (Cont…)
–Convection
•the transfer of heat
energy by the
movement of heated
liquids or gases
•there is movement or
circulation of a fluid

14. Physical Science (Cont…)
–Radiation
•the transmission of
energy as an
electromagnetic
wave without an
intervening medium

15. Physical Science (Cont…)
•Phases of Fire
–Incipient
•the oxygen content in the air has not been significantly reduced
•fire maybe producing a flame temperature well above 1000
O
F
(537
O
C), but the room temperature may be only slightly
increased
–Free-Burning
•oxygen-rich air is drawn into the flame as convection carries the
heat to the uppermost regions of the confined area
•temperature in the upper regions can exceed 1300
O
F (700
O
C)
•it continues to consume the free oxygen until it reaches the
point where there is insufficient oxygen to react with the fuel

16. Physical Science (Cont…)
•Phases of Fire (Cont…)
–Smoldering
•flame may cease to exist if the area of confinement is
sufficiently airtight
•burning is reduced to glowing embers
•fire will continue to smolder, and the room will
completely fill with dense smoke and gases of
combustion at a temperature of well over 1000
O
F
(537
O
C)
•creates the possibility of a backdraft (an explosive
ignition resulting from the combination of air with hot
gases)