Chapter 7 Compartment Fire

Chapter 7 Compartment Fire

Lesson 1Development of Compartment Fire

Key Words & PhrasesKey Words & Phrases

Compartment fire Compartment fire 室内火灾室内火灾Flashover Flashover 轰燃轰燃 Pre-flashover Pre-flashover 轰燃前轰燃前 post-flashover post-flashover 轰燃后轰燃后Flammable (Flame) Flammable (Flame) 可燃的可燃的Combustible (combustion) Combustible (combustion) 可燃的可燃的Smoulder Smoulder 阴燃、无焰燃烧阴燃、无焰燃烧Smouldering fire Smouldering fire 无焰燃烧无焰燃烧Flaming fire Flaming fire 有焰燃烧有焰燃烧

Ventilate (ventilation) Ventilate (ventilation) 通风通风Ventilation Factor Ventilation Factor 通风因子通风因子Opening Factor Opening Factor 开口因子开口因子


1.Definition of compartment fire1.Definition of compartment fire

Fires happen in a room, a bus, a car, a Fires happen in a room, a bus, a car, a ship or train compartment, etc. are all ship or train compartment, etc. are all compartment fires.compartment fires.

A compartment fire ( 室内火灾 ) means a fire that takes place in a compartment.

A compartment is an enclosure with walls, roof and openings (such as windows and doors).

WTC 911

The big Garley building fire

,1996, Hongkong

Airport terminal fire,

1996, Duesseldorf, Germany

MTR train compartment arson fire（纵火） , January 2004 (up)

Ship fire: The fire broke out an hour after the ship left the port of Miami (Right)

Bus fires: Bus fires: Burnt to the top Burnt to the top

within 10 minwithin 10 min

Burnt Burnt completely completely

within 10 minwithin 10 min

2. Why compartment fires present 2. Why compartment fires present added danger?added danger?

Compartment fires are quite different from Compartment fires are quite different from those fires burning in the open air because of those fires burning in the open air because of the the walls and ceilingwalls and ceiling. .

When a fire occurs in free space, heat anWhen a fire occurs in free space, heat and smoke generated would be lost to the ambid smoke generated would be lost to the ambient ent ( 环境 ) rapidly. But for a compartment fire, rapidly. But for a compartment fire, most of the heat and smoke generated would most of the heat and smoke generated would be confined in the upper part of the compartmbe confined in the upper part of the compartment. ent.

Outdoors, fire grows steadily.

Indoors, trapped heat and smoke cause temperature to suddenly go up.

3. Ignition (3. Ignition ( 点燃点燃 ) of a Compartment Fir) of a Compartment Firee

For ignition of a fire to occur, a fuel must be heated above its auto-ignition teauto-ignition temperaturemperature ( 自燃点 ) in the presence of sufficient oxidizeroxidizer （氧化剂）（氧化剂） for a fire to occur. An ignition source is anything which can heat even a small portion of a fuel to its auto-ignition temperature.

Smouldering FiresSmouldering Fires

After ignition two kinds of fires may follow:After ignition two kinds of fires may follow:

A fire in solid fuel which is heat-limited (energy-limited) or ventilation limited will smoulder.

3. Development of a Compartment Fire3. Development of a Compartment Fire3. Ignition (3. Ignition ( 点燃点燃 ) of a Compartment Fir) of a Compartment Firee

Flaming FiresFlaming Fires

3.1 Smouldering Fires3.1 Smouldering Fires

A Heat-limited Smouldering Fire

A Ventilation-limited Smouldering Fire

Fate of a Smouldering Fire

The smouldering fire may eventually gain enough heat (through reflected radiation or enhanced ventilation) to burst into flames;Alternatively, the fire may self-extinguish due to radiant heat loss or lack of fuel or oxygen.

After Ignition After Ignition Two Kinds of Fires May Follow:Two Kinds of Fires May Follow:

3.2 Flaming Fires

A flaming fire may develop immediately after ignition, particularly in cases of arson ( 纵火 ), or may develop from a smouldering fire after a delay which may be hours.

A Flaming FireA Flaming Fire

Fate of a Flaming Fire:Fate of a Flaming Fire:

The fire burn itself out without involving The fire burn itself out without involving other items of combustible material;other items of combustible material;If there is enough fuel but inadequate If there is enough fuel but inadequate ventilation, the fire may self-extinguish or ventilation, the fire may self-extinguish or continue to burn at a very slow rate dictated continue to burn at a very slow rate dictated by the availability of oxygen; by the availability of oxygen; If there is sufficient fuel and ventilation, the If there is sufficient fuel and ventilation, the fire may progress to full room involvement fire may progress to full room involvement in which all exposed combustible surfaces in which all exposed combustible surfaces are burning. are burning.

Temperature

Time

4. Development of a compartment fire4. Development of a compartment fire

Flashover 轰燃

Growth stage

(pre-flashover)初期增长阶段

Fully developed stage

(post-flashover)

充分发展阶段

Decay 衰减阶段

4.1 Growth stage (Pre-flashover)4.1 Growth stage (Pre-flashover)

(1) Average temperature is low.(1) Average temperature is low.

(2) Fire localization is small.(2) Fire localization is small.

In the growth or pre-flashover stage, In the growth or pre-flashover stage, the average compartment temperature is the average compartment temperature is relatively low and the fire is localized in the relatively low and the fire is localized in the vicinity of its origin.vicinity of its origin.

4.2 Fully developed stage (post-flashover)4.2 Fully developed stage (post-flashover)

(1) Average temperature is high.(1) Average temperature is high.

(2) The whole compartment is in fire.(2) The whole compartment is in fire.

In the fully developed or post-flashover fiIn the fully developed or post-flashover fire, all combustible items are on fire. Flames re, all combustible items are on fire. Flames appear to fill the whole compartment and emappear to fill the whole compartment and emerge from the windows and other ventilation erge from the windows and other ventilation (( 通风通风 )) openings. This may continue until th openings. This may continue until the available fuel is consumed. e available fuel is consumed.

4.2 Fully developed stage (post-flashover)4.2 Fully developed stage (post-flashover)

4.3 Decay Stage4.3 Decay Stage

Average T ≤ 80%TAverage T ≤ 80%Tmaxmax

The decay period is often identified as The decay period is often identified as the stage of fire after the average the stage of fire after the average temperature has fallen to 80% of its peak temperature has fallen to 80% of its peak value.value.

At this stage, fire becomes smaller At this stage, fire becomes smaller and temperature drops lower due to the and temperature drops lower due to the consumption of fuel. consumption of fuel.

4.4 Flashover4.4 Flashover

Growth stage Growth stage Fully developed stage Fully developed stage Transition

Flashover

The transitionThe transition( 转变 ) is very short. So flashover is very short. So flashover is considered as an event not a stage.is considered as an event not a stage.

Temperature will increase quickly. Temperature can reach as high as 1000 .℃

During flashover, flames will spread rapidly from the area of localized burning to all combustible surfaces within the room.

Once flashover has occurred in one compartOnce flashover has occurred in one compartment, it’s hardly for the occupants of the rest ment, it’s hardly for the occupants of the rest of the building to evacuate (of the building to evacuate ( 疏散疏散 ).).The duration from onset of burning to flashovThe duration from onset of burning to flashover is directly relevant to life safety within the er is directly relevant to life safety within the buiding.buiding.

5. The Necessary Condition for 5. The Necessary Condition for Safe EvacuationSafe Evacuation

Where tp is the time elapsed from ignition to the perception ( 感觉 ) that a fire exists; ta is the time between perception to the start of the escape action; trs is the time taken to move to a place of relative safety; tu is the time (from ignition) for the fire to produce untenable ( 难以忍受的 ) conditions at the location.

tp + ta+ trs ≤ tu

6. Factors Affecting Fire Growth6. Factors Affecting Fire Growth

The nature, amount and distribution of the The nature, amount and distribution of the combustible contents;combustible contents;The size and shape the compartment;The size and shape the compartment;The width and height of the ventilation The width and height of the ventilation openings.openings.

Influences of VentilationInfluences of Ventilation

Ventilation factor AH1/2(m5/2)

Bur

ning

rate

(kg/

min

)

Ventilation FactorVentilation Factorm

2/15.5 AHm

2/109.0 AHm

kg/min

kg/sor

Here AH1/2 is called ventilation factor. opening. the

ofheight theH and area opening A the fuel, theof rate burning mass theis where m

Theoretical Deduction of the Ventilation FactorTheoretical Deduction of the Ventilation Factor

gyPP 101 gyPP 002

22 :equation Bernoulli

22

2

221

1

1 vPvP

2

22

2

00

1

10 vgyPgyP

21

2/1

1

102

)(2

gyv

2/1

0 )(2

F

FF

gyv

2/1

0

00

)(2

gyv F

0

000

:Inflowhdair dyvBCm

Fh

FFdF dyvBCm0

:Outflow

2/1

0

00

2/30 )2()(

32

F

dair ghBCm

2/1

0

02/3 )2()(32

F

FFdF ghBCm

2/15.5 AHm

2/109.0 AHm

kg/min

kg/sor

Ventilation FactorVentilation Factor

Control Forms of a Compartment FireControl Forms of a Compartment Fire

Fuel-controlled Fuel-controlled （燃料控制）（燃料控制） firefire

Ventilation-controlled Ventilation-controlled （通风控制）（通风控制） firefire

Fuel

Air (oxygen) Supply

/Af Kg/m2s2/12/1 AHg

m/A

f kg/

m2s

235.0/2/12/1 fAAHg

290.0/2/12/1 fAAHg

Influence of Ventilation on the Influence of Ventilation on the Control forms of fireControl forms of fire

Fuel-controlled fireFuel-controlled fire

Ventilation-Ventilation-controlled firecontrolled fire

Opening FactorOpening Factor

Opening FactorOpening Factor

factor. opening called is 2/1/AHAT

m 8 -1/22/1 /AHAT

m 10 -1/22/1 /AHAT

Fuel-controlled fireFuel-controlled fire

Ventilation-Ventilation-controlled firecontrolled fire

SummarySummary

4. Factors Affecting Fire Growth (ventilation)4. Factors Affecting Fire Growth (ventilation)

1. Introduction of compartment fire.1. Introduction of compartment fire.

2. Explanation of why compartment fires 2. Explanation of why compartment fires are more dangerous than outdoor fires.are more dangerous than outdoor fires.

3. Ignition & development of a compartment 3. Ignition & development of a compartment fire.fire.

Growth Fully-developed DecayFlashover

QuestionsQuestions

What are the two control forms of the What are the two control forms of the compartment fire? What is the difference compartment fire? What is the difference between them?between them?Why indoor fires are more dangerous than Why indoor fires are more dangerous than outdoor fires?outdoor fires?Calculate the ventilation factor and opening Calculate the ventilation factor and opening factor of this classroom. factor of this classroom.

33wood kg/m 104.0

Thanks!Thanks!Please feel free to raise Please feel free to raise

any question!any question!

Chapter 7 Chapter 7 Compartment FireCompartment Fire

Lesson 2 FlashoverLesson 2 Flashover


Flashover Flashover 轰燃轰燃 Fire plume Fire plume 火羽火羽Heat flux Heat flux 热通量热通量Pyrolyze (pyrolysis) Pyrolyze (pyrolysis) 高温裂解高温裂解 RRadiation feedback heatadiation feedback heat 辐射热反馈辐射热反馈Structural failure Structural failure 结构破坏结构破坏Collapse Collapse 坍塌、倒塌坍塌、倒塌Hose-line Hose-line 消防水带消防水带

Temperature

Time

Development of a compartment fireDevelopment of a compartment fire

Flashover 轰燃

Growth period

(pre-flashover)初期增长阶段

Fully developed period

(post-flashover)

充分发展阶段

Decayperiod 衰减阶段

The term 'flashover' was first introduced by The term 'flashover' was first introduced by UK scientist P.H. Thomas in the 1960s and UK scientist P.H. Thomas in the 1960s and was used to describe the theory of a fire's was used to describe the theory of a fire's growth up to the point where it became growth up to the point where it became fully developed.fully developed.

1. Definition of Flashover1. Definition of Flashover

The transition from a localized fire to the geneThe transition from a localized fire to the general conflagration ral conflagration ( 大火灾 ) within the compart within the compartment when all fuel surfaces are burning;ment when all fuel surfaces are burning;The transition from a fuel The transition from a fuel ( 燃料 ) controlled fir controlled fire to a ventilation e to a ventilation ( 通风 ) controlled fire; controlled fire;The sudden propagation The sudden propagation ( 传播 ) of flame throu of flame through unburnt gases and vapors collected under thgh unburnt gases and vapors collected under the ceiling.e ceiling.

Most commonly used Definitions of flashover are as follows:

Definition of FlashoverDefinition of Flashover

The International Standards Organisation (ISThe International Standards Organisation (ISO) use a similar wording: O) use a similar wording:

"The rapid transition to a state of total surface "The rapid transition to a state of total surface involvement in a fire of combustible materials involvement in a fire of combustible materials within an enclosure".within an enclosure".

Other Popular DefinitionsOther Popular Definitions

The definition of flashover is given in a British The definition of flashover is given in a British Standard as a: Standard as a: "Sudden transition to a state of total surface "Sudden transition to a state of total surface involvement in a fire of combustible materials involvement in a fire of combustible materials within a compartment". (BS 4422, 1987)within a compartment". (BS 4422, 1987)

Initial development of a Fire Plume ( 火羽 ) in a Compartment.

2. Formation of flashover2. Formation of flashover

A hot layer of smoke forms under the ceiA hot layer of smoke forms under the ceiling of the room. And it will produce radiling of the room. And it will produce radi

ation feedback heat ation feedback heat （辐射热反馈） ..

When all the combustible surfaces reacWhen all the combustible surfaces reach a certain high T, they will pyrolyze anh a certain high T, they will pyrolyze an

d release flammable gases.d release flammable gases.

4TEradiation

When the temperature reaches a certain vWhen the temperature reaches a certain value, other combustible objects will pyrolyalue, other combustible objects will pyrolyzeze(( 高温裂解高温裂解 )) and release pyrolysis gases. and release pyrolysis gases.

There is a certain auto-ignition temperature (AIT)

( 自燃点 ) for a certain mixture of flammable gases.

When T reaches the auto-ignition temperature of the flammable gases inside the room, suddenly, all the flammable gases and all the combustible surfaces will be on fire.

The T will suddenly go up and it can exceed 1000 The T will suddenly go up and it can exceed 1000 .℃.℃

The flames will fill the whole compartment and get The flames will fill the whole compartment and get out of the openings.out of the openings.

Flashover Fire Cases

Video 1: Flashover experiment

Fire in Bradford City Soccer Stadium, England, 1985.

P1: first visible flames

P2: 90 seconds

P3: 150 seconds

3. Consequences of Flashover3. Consequences of Flashover

Great damage

Large number of deaths and injuriesLarge number of deaths and injuries

Trapped building occupants Trapped building occupants (( 被困居被困居民民 ))FirefightersFirefighters

Building structure

Properties

3.1 Death and injury caused by 3.1 Death and injury caused by flashoverflashover

Flashover happens very suddenly. During flashover, fire grows so rapidly that people do not see the need for evacuation( 疏散 ) until evacuation is impossible. Flashover usually leads to tripled( 三倍的 ) death in fire.

FirefightersFirefighters : : If wearing full protective clothes, any firefighters caught in a compartment which reaches flashover still have seconds to evacuate.

Most firefighting tragedies happen because most of time firefighters are too focusing on searching and rescuing others without noting that flashover is going to happen.

Year Place Death

1981 Dublin 48

1982 Los Angeles 24

1991 Petersburg 8

1996 Dusseldorf 17

1997 UK 32002 Paris 5

Death caused by flashover in some fire cases

In the USA, NFPIn the USA, NFPA A ( 美国消防协会 ) st statistics recorded batistics recorded between 1985 and etween 1985 and 1994 demonstrate1994 demonstrated a total of d a total of 4747 US US firefighters lost thfirefighters lost their lives to 'flashoveir lives to 'flashover'.er'.

Firefighters confronted a flashover.

Firefighter caught inside a flashover.

Wooden beams( 木梁 ) will char( 烧焦 );

Steel ( 钢筋 ) will be permanently weakened. Then it will expand and damage surrounding structural components ( 构件 );

Concrete ( 水泥 ) and masonry ( 砖瓦 ) will spall ( 破碎 ) and may crack into pieces.

3.2 Great damage caused by flashover

Great damageBuilding structureBuilding structure

PropertiesProperties

Structural Failure

Structural Structural FailureFailure

After those structural failures, the roof of a building will generally collapse( 倒塌 ) first, due to the concentration of high temperature gases and flames at the top of the structure.The walls may follow.

Firefighters must be aware that the Firefighters must be aware that the building could collapse at any point after a building could collapse at any point after a compartment reaches flashover.compartment reaches flashover.

Catastrophic Collapse of a BuildingCatastrophic Collapse of a Building

Video 2: Non-Flashover experiment

Does flashover occur in all the Does flashover occur in all the compartment fires?compartment fires?

The Development of Fire With and The Development of Fire With and Without FlashoverWithout Flashover

4. Fuel and Ventilation 4. Fuel and Ventilation Conditions Necessary for Conditions Necessary for

FlashoverFlashover

Fuel and Ventilation Conditions Fuel and Ventilation Conditions Necessary for FlashoverNecessary for Flashover

1. Mass burning rate:1. Mass burning rate:

g/s 3.330.50 2/1limit AHm

2. Ventilation factor:2. Ventilation factor:

observed.not wasflashover ,m 8.0When 5/22/1 AH

observed.not wasflashover g/s, 80When m

4. Criteria of flashover ( 轰燃判据 )

Based on the observations and measurements of compartment fires, different criteria of flashover were proposed:

Radiation heat flux at floor level ( 地面热辐射通量 ) reaches 20kW/m2;

Gas Temperature at ceiling level ( 顶棚气体温度 ) reaches 600 ;℃

Influencing Factors of FlashoverInfluencing Factors of Flashover

The amount of combustible materials.The amount of combustible materials.

The building materials of the walls and ceiling.The building materials of the walls and ceiling.

The height and width of the opening.The height and width of the opening.

The kinds of combustible materials.The kinds of combustible materials.

6. Three ways to delay 6. Three ways to delay flashover:flashover:

Venting:Venting: By venting windows of a burning room By venting windows of a burning room you release the build up of heat in the room. This you release the build up of heat in the room. This slows down flashover in addition to improving slows down flashover in addition to improving visibility in a smoke-filled room. visibility in a smoke-filled room. Not venting:Not venting: by not venting and instead closing the by not venting and instead closing the door to the burning room, you can also delay door to the burning room, you can also delay flashover. By not venting, you starve the fire of flashover. By not venting, you starve the fire of oxygen, which slows down the combustion rate and oxygen, which slows down the combustion rate and the build up of heat in the room. the build up of heat in the room. This may be done This may be done when there is a delay in stretching a hose-line and when there is a delay in stretching a hose-line and all persons are out of the burning room. all persons are out of the burning room. Portable extinguisher:Portable extinguisher: The use of a portable The use of a portable extinguisher can cool the heat down in a burning extinguisher can cool the heat down in a burning room temporarily and delay flashover.room temporarily and delay flashover.

The sudden lowering of the existing smoke The sudden lowering of the existing smoke layer (smoke interface). layer (smoke interface). Sudden increases of heat forcing you to Sudden increases of heat forcing you to crouch low;crouch low;

7. Warning signs of 7. Warning signs of flashoverflashover

Flames are running overhead on the ceiling;Flames are running overhead on the ceiling; Perception of rollover:Perception of rollover: Rollover is defined, as Rollover is defined, as sporadic sporadic (( 零星的零星的 )) fl flashes of flame mixed with smoke at ceiling leashes of flame mixed with smoke at ceiling level. vel.

8. Point of no return 8. Point of no return The point of no return is a distance inside a The point of no return is a distance inside a burning room beyond which a searching burning room beyond which a searching firefighter will not escape and will not reach the firefighter will not escape and will not reach the door or window entered. door or window entered. How far inside a burning room can a firefighter How far inside a burning room can a firefighter be and still escape back out the door alive and be and still escape back out the door alive and not suffer serious bums after a flashover occurs? not suffer serious bums after a flashover occurs? How far into the burning room that appears How far into the burning room that appears about to flashover should a firefighter go? about to flashover should a firefighter go? Five feet is the point of no return after the Five feet is the point of no return after the room explodes into a flashover.room explodes into a flashover.

8. Point of no return 8. Point of no return 1. Fire temperatures of 280‘-320’ F cause intense pain a1. Fire temperatures of 280‘-320’ F cause intense pain and damage to exposed skin. (nd damage to exposed skin. (138-160138-160 ℃℃ ))2. The average temperature in a room that flashes over i2. The average temperature in a room that flashes over is 1000' to 1500' F. (537-816 s 1000' to 1500' F. (537-816 ℃℃ ))3. The average person moves 2.5-feet per second when 3. The average person moves 2.5-feet per second when walkingwalking4. How long can a firefighter take 1000'-1500' F on the 4. How long can a firefighter take 1000'-1500' F on the neck, ears, wrists and any other exposed portion of the neck, ears, wrists and any other exposed portion of the body? Just two seconds.body? Just two seconds.

Five feet is the point of Five feet is the point of no returnno return

9. Defensive Search 9. Defensive Search Procedures:Procedures:

A firefighter should check behind the door A firefighter should check behind the door for the victim, then enter the hallway or room for the victim, then enter the hallway or room not not more than five feetmore than five feet, sweep the floor, look for , sweep the floor, look for unconscious persons, call out and listen for a unconscious persons, call out and listen for a response. If no response is forthcoming, close the response. If no response is forthcoming, close the door and wait for the hose-line. As the attack door and wait for the hose-line. As the attack hose-line advances, conduct a search and rescue hose-line advances, conduct a search and rescue behind the line, searching room and space behind the line, searching room and space outward from the hose-line.outward from the hose-line.

At a Doorway:At a Doorway:

At a Window:At a Window: If smoke and signs of rollover are seen in the smIf smoke and signs of rollover are seen in the smoke, the firefighteroke, the firefighter should notshould not enter the burning wienter the burning window. ndow. InsteadInstead the firefighter should crouch down bthe firefighter should crouch down below the heat and sweep the area below the windowelow the heat and sweep the area below the windowsill (sill ( 窗台窗台 ) with a tool. ) with a tool.

In some instances a person may collapse at the In some instances a person may collapse at the window and fall right below the sill. If a victim is fowindow and fall right below the sill. If a victim is found, a firefighter on the ladder might be able to und, a firefighter on the ladder might be able to crocrouch belowuch below the heated smoke and flashes of flames the heated smoke and flashes of flames mixed with smoke coming out the window and pull mixed with smoke coming out the window and pull the victim to safety on the ladder.the victim to safety on the ladder.

SUMMARYSUMMARY

1) Definition of flashover; 1) Definition of flashover; 2) Formation of flashover;2) Formation of flashover;3) Sequences of flashover;3) Sequences of flashover;4) Conditions Necessary for Flashover;4) Conditions Necessary for Flashover;5) Criteria of flashover;5) Criteria of flashover;6) Equipment to study those influencing factors;6) Equipment to study those influencing factors;7) Three ways to delay flashover;7) Three ways to delay flashover;8) Warning signs of flashover;8) Warning signs of flashover;9) Point of no return;9) Point of no return;10) Defensive Search Procedures.10) Defensive Search Procedures.

QUESTIONSQUESTIONS

1. How does a flashover happen?1. How does a flashover happen?

2. What are the consequences of flashover?2. What are the consequences of flashover?

3. What are the warning signs of flashover?3. What are the warning signs of flashover?

QUESTIONSQUESTIONS

4. According to fire protection engineers flashover 4. According to fire protection engineers flashover is caused by which one of the following? is caused by which one of the following? A. Radiation heat B. Radiation feedback heat A. Radiation heat B. Radiation feedback heat C. Conduction heat D. None of the above C. Conduction heat D. None of the above

5. Which one of the following is not a method used by 5. Which one of the following is not a method used by firefighters to delay flashover? firefighters to delay flashover? A. Venting to release heat A. Venting to release heat B. Not venting to starve the fire of oxygen and thus B. Not venting to starve the fire of oxygen and thus slow down heat generationslow down heat generation C. Use a portable extinguisher on the fire to cool it down C. Use a portable extinguisher on the fire to cool it down D. Remove combustible from the fire area D. Remove combustible from the fire area



Under the leadership of Prof. Chen, this lab was set Under the leadership of Prof. Chen, this lab was set up in 2001 with support from our academy and fire up in 2001 with support from our academy and fire engineering department. engineering department. And this equipment represents the first class level And this equipment represents the first class level inside our country.inside our country.

5. Compartment Fire Research Lab5. Compartment Fire Research Lab


1. A box with opening

3. An electronic Balance ( 电子天平 )

4. A printer ( 打印机 )

2. A tray ( 托盘 )

5. Signal detector

( 信号检测仪 )

①~ Thermal couples⑦ ( 热电偶 )

2

1

34

5

1. This box can be disassembled. That means we 1. This box can be disassembled. That means we can change the material of its walls and ceiling. can change the material of its walls and ceiling.

The building materials of the walls and ceilingThe building materials of the walls and ceiling

2. Both the width and height of the door can be 2. Both the width and height of the door can be adjusted.adjusted.

The height and width of the openingThe height and width of the opening

3. Different materials of different mass 3. Different materials of different mass ( 质量 ) can be put on the tray and used can be put on the tray and used as combustible material.as combustible material.

The kinds of combustible materialsThe kinds of combustible materials The amount of combustible materialsThe amount of combustible materials

4. Besides the above influencing factors, usi4. Besides the above influencing factors, using this equipment, we can also study the mang this equipment, we can also study the mass burning ratess burning rate （质量燃烧速率） during during process of each compartment fire.process of each compartment fire.

To Know More about Our Study To Participate in Our work

Chapter 7 Compartment Fire

Lesson 3 Backdraft


Backdraft/backdraught Backdraft/backdraught 回燃回燃 Explode (explosion) Explode (explosion) 爆炸爆炸Pyrolyzate (pyrolyze; pyrolysis) Pyrolyzate (pyrolyze; pyrolysis) 热解产物热解产物Flammability Limits Flammability Limits 爆炸极限爆炸极限 DDeflagrationeflagration 爆燃爆燃Vent Vent 通风、排出通风、排出Quench Quench 熄灭、结束熄灭、结束Flank Flank 侧翼攻击侧翼攻击

1. Definition of Backdraft1. Definition of Backdraft

The NFPA definition: The NFPA definition: “ “The explosive or rapid burning of heated gaseThe explosive or rapid burning of heated gase

s that occurs when oxygen is introduced into a s that occurs when oxygen is introduced into a building that has not been properly ventilated abuilding that has not been properly ventilated and has a depleted nd has a depleted ((减少的减少的 )) supply of oxygen d supply of oxygen due to fire." ue to fire."

The IFE (Institution of Fire Engineers) definition:The IFE (Institution of Fire Engineers) definition: “ “An explosion, of greater or lesser degree, caused An explosion, of greater or lesser degree, caused by the inrush (by the inrush ( 涌入涌入 ) of fresh air from any source or ) of fresh air from any source or cause, into a burning building, where combustion hacause, into a burning building, where combustion has been taking place in a shortage of air." s been taking place in a shortage of air."

Smoke Is CombustibleSmoke Is Combustible

Air IntroductionAir Introduction

Limited ventilation can lead to a fire in a compartment producing fire gases containing significant proportions of partial combustion products and un-burnt pyrolysis products, which are all combustible. If these accumulate then the admission of air when an opening is made to the compartment can lead to a sudden deflagration. This deflagration moving through the compartment and out of the opening is a backdraft.

A Basic ScenarioA Basic Scenario

BACKDRAFTBACKDRAFT

BACKDRAFTBACKDRAFT

2. Formation of Backdraft2. Formation of Backdraft

1) A fire burning in a room with poor ventilation1) A fire burning in a room with poor ventilation2) Accumulation of flammable gases 2) Accumulation of flammable gases 3) Air introduction at the breaking of openings3) Air introduction at the breaking of openings4) Formation of mixture within flammability limits4) Formation of mixture within flammability limits5) Ignition of the mixture5) Ignition of the mixture6) Explosion or deflagration and pressure rise 6) Explosion or deflagration and pressure rise

3. Conditions Nece3. Conditions Necesssary for Backdrsary for Backdraftaft

1) The accumulation of smoke consisting of un-bur1) The accumulation of smoke consisting of un-burnt pyrolyzates and incomplete combustion productnt pyrolyzates and incomplete combustion products in a poorly ventilated compartment.s in a poorly ventilated compartment.2) Air introduction when windows or doors are ope2) Air introduction when windows or doors are opened or broken.ned or broken.3) The newly formed mixture of air and flammable 3) The newly formed mixture of air and flammable smoke issmoke is within its within its flammabilityflammability limits (limits ( 爆炸极限爆炸极限 ).).4) An ignition source of sufficient energy such as a 4) An ignition source of sufficient energy such as a flame, spark or flame, spark or glowing ember (glowing ember ( 余火余火 ). ). It is also p It is also possible for super-heated gases to ignite (auto-ignitiossible for super-heated gases to ignite (auto-ignition), without a source of ignition being introduced. on), without a source of ignition being introduced.

Pressure rise due to backdraft will force the burning gases in the compartment out through the openings with a high velocity, possibly igniting some of the unburnt pyrolyzate ( 热解产物 ) that had already left the compartment. This can create a significant fire-ball outside the compartment.

4. Consequences of Backdraf4. Consequences of Backdraftt

Backdraft Is a Kind of ExplosionBackdraft Is a Kind of Explosion

Explosions kill and injure firefighters in several ways. The blast ( 爆炸 ) can blow a firefighter across a street; flying glass and shrapnel ( 碎片 ) can decapitate ( 斩首 ) a firefighter; flame accompanying the explosion can cause serious burns and an explosion can collapse walls, partitions and iron shutters ( 卷帘铁门 ), crushing firefighters beneath them.

4. Consequences of Backdraf4. Consequences of Backdraftt

Great damage

Deaths and injuries (Deaths and injuries (FirefightersFirefighters))

Building structure

Properties

Destructive Effects Caused by Backdraft ExDestructive Effects Caused by Backdraft Explosion Pressuresplosion Pressures

Effect of Explosion Destructive Peak Pressure (psi)

Glass shattering (破碎 ) 0-5Firefighter knock down 1Wood partition collapse 1-2Cinder block (煤渣空心砖 ) wall collapse

2-3

Brick wall collapse 7-8Firefighter lung(肺 ) damag

e15

Threshold for fatalities 3550% fatalities 5099% fatalities 65

Before opening a door or window to the cBefore opening a door or window to the compartment, the firefighter should be aware oompartment, the firefighter should be aware of: f: 1) A fire in a compartment with few openings 1) A fire in a compartment with few openings that has been burning for some time. that has been burning for some time. 2) Oily deposits (2) Oily deposits ( 沉淀物沉淀物 ) in windows. ) in windows. 3) Pulsating (3) Pulsating ( 跳动的跳动的 ) smoke from openings. ) smoke from openings. 4) Hot doors and door handles (windows);4) Hot doors and door handles (windows);

5. Warning Signs of Backdraft5. Warning Signs of Backdraft

1) Blue flames (‘ghosting’ or ‘dancing’ flame1) Blue flames (‘ghosting’ or ‘dancing’ flames) in the hot gas layer. s) in the hot gas layer. 2) Smoke drawn back through opening:2) Smoke drawn back through opening:3) Whistling and roaring sounds3) Whistling and roaring sounds

It may be an indication that a backdraft is in prIt may be an indication that a backdraft is in progress at which stage there is probably little acogress at which stage there is probably little action that can be taken by a firefighter to prevention that can be taken by a firefighter to prevent it.t it.

5. Warning Signs of Backdraft5. Warning Signs of Backdraft

When inside, or looking into a compartment When inside, or looking into a compartment a potential backdraft may be indicated by:a potential backdraft may be indicated by:

Smoke Drawn Back through OpeningSmoke Drawn Back through Opening

Lessons LearnedLessons Learned1. These warning signs are important to know.2. Firefighters must know that explosions happen fast, sometimes too fast for firefighters to take cover and protect themselves. The only real protection from the blast of a backdraft or a flashover is full protective gear: helmets(头盔 ), hoods(防护帽 ), gloves(手套 ), boots(长靴 ), bunker pants(防护裤 ), coat and face mask(面具 ). Protective fire gear may be hot, cumbersome (笨重的 ) and slow you down, but if you are caught in an explosion, it will determine whether you survive the blast and how serious your burns will be.

The Peru ( 秘鲁 ) firefighters force entry just prior to the backdraft

Amazing Peru BackdraftThe Aftermath ( 后期 )!!!

An exterior defensive operation is mounted follo

wing the backdraft.

6. Preventing Death and Injury

There are three tactics that can reduce the chances of getting caught in a backdraft:

VentingVenting ( ( 通风通风 ))

QuenchingQuenching ( ( 熄灭熄灭 ))

FlankingFlanking ( ( 侧翼攻击侧翼攻击 ))

6.1 Venting 6.1 Venting (( 通通风风 ))Venting a roof skylight ( 天窗 ) over a burning room is one of the most effective methods of protecting firefighters from the blast of a backdraft.

1) When roof conditions permit, the quick removal of a glass skylight by firefighters can vent a smoke filled room and break up an explosive mixture.

2) Even if the smoke explosion occurs, the blast will be diverted upward out of the roof vent opening away from the firefighters advancing the hose-line.

Quenching: Quenching: Before a superheated confined room Before a superheated confined room is entered, charged hose-line should be positioneis entered, charged hose-line should be positioned near the entrance. Firefighters in full protective d near the entrance. Firefighters in full protective equipment should immediately discharge (equipment should immediately discharge ( 射水射水 ) ) a hose stream into a fire area when it is opened ua hose stream into a fire area when it is opened up. p.

11 ）） This water can This water can coolcool a potentially explosive atm a potentially explosive atmosphere. osphere.

22 ）） Before the air and searching firefighters enter a Before the air and searching firefighters enter a potentially explosive fire area, the stream of a popotentially explosive fire area, the stream of a powerful water discharge might werful water discharge might break up the explbreak up the explosive atmosphere.osive atmosphere.

6.2 Quenching6.2 Quenching (( 熄熄灭灭 ))

Flanking: When there can be no venting and the quenching of a quick dash of a hose stream is not possible, the officer in command can order two hose-lines into position, one on each side of a door or window of a burning room.After the hose lines are charged with water and firefighters are in full protective equipment, the door or window is broken. Both flanking hose lines, safely out of the path of any potential explosive blast coming out of the opening, can be directed into the burning room.

6.3 Flanking (( 侧翼攻击侧翼攻击 ))

The backdraft that blew apart an Illinois church on February 9th, 2004 has been named the largest backdraft ever documented in the U.S.

The firefighters determined it was too hot and smokey to enter the church basement, so they opened the ground level windows. The door to the basement felt cold but suddenly blew out when the backdraft occurred.

A Backdraft CaseA Backdraft Case

Riddle had been in his command vehicle when the baRiddle had been in his command vehicle when the backdraft occurred. "I heard the noise and I looked up... ckdraft occurred. "I heard the noise and I looked up... this piece of roof was just being removed - it went up this piece of roof was just being removed - it went up about 10 feet and then came back down," he said. about 10 feet and then came back down," he said. There was no warning except that immediately before There was no warning except that immediately before he blast, “The guys on the scene said they heard a he blast, “The guys on the scene said they heard a sucsucking (king (吸气吸气 )) sound," Riddle said. sound," Riddle said. The backdraft blew the roof off the Church and knockThe backdraft blew the roof off the Church and knocked flat the eight firefighters on scene and two firefighted flat the eight firefighters on scene and two firefighters were injured. A firefighter who had felt the door sers were injured. A firefighter who had felt the door suffered burns to his hand because he had taken his glouffered burns to his hand because he had taken his glove off. Another firefighter was blown out of the cab ove off. Another firefighter was blown out of the cab of the engine, and another was blown across an alley. f the engine, and another was blown across an alley.

7. Backdraft and flashover, wha7. Backdraft and flashover, what is the difference?t is the difference?

Flashover and backdraft are distinctly different evenFlashover and backdraft are distinctly different events which occur in different ways. ts which occur in different ways. A flashover can occur in a compartment when a small lA flashover can occur in a compartment when a small localized fire rapidly develops into a fire involving all tocalized fire rapidly develops into a fire involving all the combustible surfaces.he combustible surfaces. In contrast a backdraft occurs after air is admitted to a In contrast a backdraft occurs after air is admitted to a poorly ventilated compartment and mixes with un-burnpoorly ventilated compartment and mixes with un-burnt pyrolysis products from the oxygen starved fire. Any t pyrolysis products from the oxygen starved fire. Any ignition source, such as a glowing ember, can ignite the ignition source, such as a glowing ember, can ignite the resulting flammable mixture. Expansion due to heat creresulting flammable mixture. Expansion due to heat created by combustion can then expel burning gases out thated by combustion can then expel burning gases out through the opening.rough the opening.

DifferencesDifferences

There are four main differences:1. First of all, backdraft does not happen often at fires as flashover does.

You may experience only one or two during your entire career. Flashover - sudden full room involvement in flame - happens often. You will probably see one at your next fire.

2. A second difference is that a backdraft is an explosion; a flashover is not.

There will be shock waves (冲击波 ) during a backdraft that will break the confining structure around the explosion. Windows may break blasts of smoke and flame may blow out a doorway or a part of the structure may collapse. Flashover is rapid fire development, but it stops short of an explosion's speed of chemical reaction.


3. The triggering or cause of them.


Flashover: a heat induced development of the fireFlashover: a heat induced development of the fire

Backdraft: a ventilation induced ignition of the gases Backdraft: a ventilation induced ignition of the gases Air introduction sets off the backdraft explosion. As firefighters enter a confined smoke filled area and bring fresh air with them, sometimes a backdraft or smoke explosion happens;

The trigger of a flashover is heat. The theory of flashover is that heat, which is re-radiated back into a burning room, raises the gases and furnishings in the room to the auto-ignition temperature and triggers a flashover.

4. The stage of fire growth in which they occur. Backdraft explosions occur when there is smok

e in a confined space that is during the first and third stage of a fire. During the growth and decay stages, smoldering can take place and generate explosive CO gas;

Flashover, on the other hand, only occurs in the growth stage of a fire and signals the end of the growth stage.


Flashover or Backdraft?Flashover or Backdraft?

Firefighters in Australia get to grips with an 'entry & attack-module' trainer.

Au centre d'instruction, les instructeurs pompiers reconstituent le phénomène meutrier du Backdraft (Retour de flammes) pour sensibiliser les jeunes recrues. En France le "Backdraft" a tué cinq sapeurs pompiers de Paris en septembre 2002 alors qu'ils intervennaient sur un feu de chambre de bonne

Tactical Firefighting TrainingTactical Firefighting Training

Staffordshire County firefighters (UK) training with a backdraft demonstrator ( 示范装置 )

1. Definition of backdraft1. Definition of backdraft2. Formation of backdraft2. Formation of backdraft3. Conditions Necessary for Backdraft3. Conditions Necessary for Backdraft4. Consequences of Backdraft4. Consequences of Backdraft5. Warning Signs of Backdraft5. Warning Signs of Backdraft6. Preventing Death and Injury6. Preventing Death and Injury7. The differences between Backdraft and f7. The differences between Backdraft and flashover.lashover.

SUMMARY SUMMARY

QUESTIONS

3. What are the differences between a backdraft and 3. What are the differences between a backdraft and flashover?flashover?

2. 2. What are the three firefighting tactics that can redWhat are the three firefighting tactics that can reduce destructive effects of a backdraft explosion?uce destructive effects of a backdraft explosion?

1. What are the warning signs of a backdraft?1. What are the warning signs of a backdraft?

Under the leadership of Prof. Chen, this lab was set Under the leadership of Prof. Chen, this lab was set up in 2001 with support from our academy and fire up in 2001 with support from our academy and fire engineering department. engineering department. And this equipment represents the first class level And this equipment represents the first class level inside our country.inside our country.

Compartment Fire Research LabCompartment Fire Research Lab


1. A box with opening

3. An electronic Balance ( 电子天平 )

4. A printer ( 打印机 )

2. A tray ( 托盘 )

5. Signal detector

( 信号检测仪 )

①~ Thermal couples⑦ ( 热电偶 )

2

1

34

5

1. This box can be disassembled. That means we 1. This box can be disassembled. That means we can change the material of its walls and ceiling. can change the material of its walls and ceiling.

The building materials of the walls and ceilingThe building materials of the walls and ceiling

2. Both the width and height of the door can be 2. Both the width and height of the door can be adjusted.adjusted.

The height and width of the openingThe height and width of the opening

3. Different materials of different mass 3. Different materials of different mass ( 质量 ) can be put on the tray and used can be put on the tray and used as combustible material.as combustible material.

The kinds of combustible materialsThe kinds of combustible materials The amount of combustible materialsThe amount of combustible materials

4. Besides the above influencing factors, usi4. Besides the above influencing factors, using this equipment, we can also study the mang this equipment, we can also study the mass burning ratess burning rate （质量燃烧速率） during during process of each compartment fire.process of each compartment fire.

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Chapter 7 Compartment Fire