basicfirescience&fireseverity-fsm-2010 12 15

8/7/2019 BasicFireScience&FireSeverity-FSM-2010 12 15

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Building Capacity Enhancing Capabilities Globally

CLASSIFICATION OF FIRECLASSIFICATION OF FIRE

Fire is classified into four main categories:Fire is classified into four main categories:

Class AClass A -- fires involving ordinary combustible materials.fires involving ordinary combustible materials.

Class BClass B -- fires involving flammable/combustiblefires involving flammable/combustible

liquids and gasesliquids and gases

Class CClass C -- fires involving energized electrical equipmentfires involving energized electrical equipment

Class DClass D -- fires involving combustible metalsfires involving combustible metals


BASIC STAGES OF FIREBASIC STAGES OF FIREDEVELOPMENTDEVELOPMENT

INITIAL STAGEINITIAL STAGE -- fire develops from its point of fire originfire develops from its point of fire origin


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BASIC STAGES OF FIREBASIC STAGES OF FIRE

DEVELOPMENTDEVELOPMENT

INITIAL STAGEINITIAL STAGE -- propagation of combustionpropagation of combustion



FLASHOVERFLASHOVER -- transition stage between initial and fulltransition stage between initial and full

development stagedevelopment stage


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BASIC STAGES OF FIREBASIC STAGES OF FIRE

DEVELOPMENTDEVELOPMENT

FLASHOVERFLASHOVER -- transition stage between initial and fulltransition stage between initial and full

development stagedevelopment stage



FULLY DEVELOPEDFULLY DEVELOPED -- fire burning at its maximum intensityfire burning at its maximum intensity

DECAYDECAY -- fire slowing down due to depletion of fuel or oxygenfire slowing down due to depletion of fuel or oxygen


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COMBUSTIONCOMBUSTION

CombustionCombustion is a reaction between a substanceis a reaction between a substance

and oxygen in which heat is given out.and oxygen in which heat is given out.

Where a reaction between substance and oxygenWhere a reaction between substance and oxygen

requires heat to maintain its reaction and therequires heat to maintain its reaction and the

reaction stops when the applied heat is removedreaction stops when the applied heat is removed

isis NOTNOT a process of combustiona process of combustion


COMBUSTIONCOMBUSTION

AllAll combustible materialscombustible materials burn as vapourburn as vapour

phase reactionsphase reactions

Solid combustibles will vaporise or decomposeSolid combustibles will vaporise or decompose

(pyrolysis)(pyrolysis) and then burn.and then burn.

Liquids also vaporises before combustionLiquids also vaporises before combustion

can take place.can take place.


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PRODUCTS OF COMBUSTIONPRODUCTS OF COMBUSTION

The products of a combustion process are:The products of a combustion process are:

THERMALTHERMAL -- FlameFlameHeatHeat

NONNON--THERMALTHERMAL -- SmokeSmoke

GasesGases


FIRE SEVERITYFIRE SEVERITYFire SeverityFire Severity is the condition of a fire in whichis the condition of a fire in which

is related to the maximum temperatureis related to the maximum temperature

reached and to the duration of burning.reached and to the duration of burning.

The factors which control the fire behaviourThe factors which control the fire behaviour

and thus the fire severity are interand thus the fire severity are inter--related.related.

These are:These are:

Nature of the fuelNature of the fuel

Amount of the fuelAmount of the fuel

Arrangement of the fuelArrangement of the fuel

Size and shape of roomSize and shape of room

Thermal insulation of walls and claddingThermal insulation of walls and cladding


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Rate ofBurningof Fuel

FIRE SEVERITYFIRE SEVERITYDeterminants from fire

Conditions to

Load and Occupancy

Minimize FireSeverity____________

NatureOf Fuel

Low burning

Rate andIgnition

AmountFuel

of Fuel

As low asPossible

MaximumTemp. Arrangmt

Reached Of Fuel

In Large BlocksMinimum AreaExposed to Air

Air

Supply

Size andShape of

Room

Maximum Minimum Size

Shallow asPossible

Time at

High Temp

WindowArea and

Maximum

AreaShape

Loss ofHeat

ThermalInsulation As low as possibleOf Walls &

cladding

Duration

of Fuel

Burn

FireSeverity

Determinants from Design


Possible Impacts on

CERT-FireFighting Team??

Fire Wardens??General workers??


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EFFECTS OF PRODUCTEFFECTS OF PRODUCT

OF COMBUSTIONOF COMBUSTION-- NON THERMALNON THERMAL

Corrosive or become corrosiveCorrosive or become corrosive

in solution with waterin solution with water

Attributed to more fire deathsAttributed to more fire deathsfrom smoke inhalation andfrom smoke inhalation and

suffocationsuffocation

Cause PanicCause Panic


SMOKESMOKESmokeSmoke is the general term for the solid andis the general term for the solid and

gaseous product of the combustion in the risinggaseous product of the combustion in the rising

plume of heated airplume of heated air

SMOKESMOKEBurntBurnt UnburntUnburntFuelFuel

Gases produced byGases produced by

degradation of the fueldegradation of the fuel


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SMOKESMOKE

SmokeSmoke is the general term for the solid andis the general term for the solid and

gaseous product of the combustion in the risinggaseous product of the combustion in the rising

plume of heated airplume of heated air

SMOKESMOKEBurntBurnt UnburntUnburnt

FuelFuel

Gases produced byGases produced by

degradation of the fueldegradation of the fuel


QUANTITY OF SMOKEQUANTITY OF SMOKE

Smoke LayerSmoke Layer

Temperature can reachTemperature can reach

bet 400 to 500 Cbet 400 to 500 C


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QUALITY OF SMOKEQUALITY OF SMOKE


VISIBILITY IN SMOKEVISIBILITY IN SMOKE

Visibility in SmokeVisibility in Smoke

is dependant on:is dependant on:

SmokeSmoke

-- colourcolour

-- size of particlessize of particles-- densitydensity

-- physiologicalphysiological

effecteffect


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EnvironmentEnvironment

-- size & coloursize & colour

of objectof object

-- illumination ofillumination of

objectobject





ObserverObserver

-- Physical & mentalPhysical & mental

statestate-- conditionsconditions --

controlled orcontrolled or

panic statepanic state


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Optical DensityOptical Density

Dense and undiluted smokeDense and undiluted smoke

OD = 10 cmOD = 10 cm


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EFFECTS OF HEAT ONEFFECTS OF HEAT ON

MATERIAL PROPERTIESMATERIAL PROPERTIES

The behaviour of any part of the buildingThe behaviour of any part of the building

under the effect of heat depends on:under the effect of heat depends on: thermalthermal

mechanical propertiesmechanical properties

of the materials used in the structuralof the materials used in the structural

elements.elements.


EFFECTS OF HEAT ONEFFECTS OF HEAT ONMATERIAL PROPERTIESMATERIAL PROPERTIES

ConcreteConcrete

SpallingSpalling -- caused by:caused by:

Excessive compressionExcessive compression

of the materialof the material

Formation of highFormation of highpressure steam in thepressure steam in the

materialmaterial

Slitting of the aggregateSlitting of the aggregate


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Brick and BlockworkBrick and Blockwork

Failure of brickwallFailure of brickwall isis

usually due to excessiveusually due to excessive

distortion caused bydistortion caused by

greater expansion of thegreater expansion of the

surface nearest the heatsurface nearest the heat

sourcesource



SteelSteel

Quickly weaken whenQuickly weaken when

exposed to fireexposed to fire


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WoodWood

When burn it chars toWhen burn it chars to

insulate and protect theinsulate and protect the

unburnt wood below.unburnt wood below.



PlasticPlastic

ThermoplasticThermoplastic -- oneone

that soften and melt onthat soften and melt on

the application of heat.the application of heat.

Thermosetting plasticThermosetting plastic --

one which have beenone which have been

soldified by thesoldified by the

application of heat andapplication of heat and

will not soften whenwill not soften when

heat is re applied.heat is re applied.


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SUMMARYSUMMARY

basicfirescience&fireseverity-fsm-2010 12 15

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