Chapter 7 compartment fire
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Chapter 7 Compartment Fire. Lesson 1 Development of Compartment Fire. Key Words & Phrases. Compartment fire 室内火灾 Flashover 轰燃 Pre-flashover 轰燃前 post-flashover 轰燃后

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Chapter 7 Compartment Fire

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Chapter 7 compartment fire

Chapter 7 Compartment Fire

Lesson 1

Development of Compartment Fire


Key words phrases

Key Words & Phrases

Compartment fire 室内火灾

Flashover 轰燃

Pre-flashover 轰燃前

post-flashover 轰燃后

Flammable (Flame) 可燃的

Combustible (combustion) 可燃的

Smoulder 阴燃、无焰燃烧

Smouldering fire 无焰燃烧

Flaming fire 有焰燃烧


Key words phrases1

Key Words & Phrases

Ventilate (ventilation) 通风

Ventilation Factor 通风因子

Opening Factor 开口因子


1 definition of compartment fire

1.Definition of compartment fire

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


Chapter 7 compartment fire

WTC 911


Chapter 7 compartment fire

The big Garley building fire

,1996, Hongkong

Airport terminal fire,

1996, Duesseldorf, Germany


Chapter 7 compartment fire

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)


Chapter 7 compartment fire

Bus fires:

Burnt to the top within 10 min

Burnt completely

within 10 min


2 why compartment fires present added danger

2. Why compartment fires present added danger?

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

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


Chapter 7 compartment fire

Outdoors, fire grows steadily.

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


3 ignition of a compartment fire

3. Ignition (点燃) of a Compartment Fire

For ignition of a fire to occur, a fuel must be heated above its auto-ignition temperature (自燃点) in the presence of sufficient oxidizer(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.


3 development of a compartment fire

3. Ignition (点燃) of a Compartment Fire

3. Development of a Compartment Fire

After ignition two kinds of fires may follow:

Smouldering Fires

Flaming Fires

3.1 Smouldering Fires

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


A heat limited smouldering fire

A Heat-limited Smouldering Fire


A ventilation limited smouldering fire

A Ventilation-limited Smouldering Fire


Fate of a 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 two kinds of fires may follow

After Ignition 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 fire

A Flaming Fire


Fate of a flaming fire

Fate of a Flaming Fire:

  • The fire burn itself out without involving other items of combustible material;

  • If there is enough fuel but inadequate ventilation, the fire may self-extinguish or continue to burn at a very slow rate dictated by the availability of oxygen;

  • If there is sufficient fuel and ventilation, the fire may progress to full room involvement in which all exposed combustible surfaces are burning.


4 development of a compartment fire

Temperature

Time

4. Development of a compartment fire

Flashover轰燃

Decay

衰减阶段

Fully developed stage

(post-flashover)

充分发展阶段

Growth stage

(pre-flashover)初期增长阶段


4 1 growth stage pre flashover

4.1 Growth stage (Pre-flashover)

  • (1) Average temperature is low.

  • (2) Fire localization is small.

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


4 2 fully developed stage post flashover

4.2 Fully developed stage (post-flashover)

  • (1) Average temperature is high.

  • (2) The whole compartment is in fire.

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


4 2 fully developed stage post flashover1

4.2 Fully developed stage (post-flashover)


4 3 decay stage

4.3 Decay Stage

  • Average T ≤ 80%Tmax

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

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


4 4 flashover

4.4 Flashover

Transition

Growth stage

Fully developed stage

Flashover

The transition(转变) is very short. So flashover 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.


Chapter 7 compartment fire

  • Once flashover has occurred in one compartment, it’s hardly for the occupants of the rest of the building to evacuate (疏散).

  • The duration from onset of burning to flashover is directly relevant to life safety within the buiding.


5 the necessary condition for safe evacuation

5. The Necessary Condition for Safe Evacuation

tp + ta+ trs≤ tu

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.


6 factors affecting fire growth

6. Factors Affecting Fire Growth

  • The nature, amount and distribution of the combustible contents;

  • The size and shape the compartment;

  • The width and height of the ventilation openings.


Influences of ventilation

Burning rate (kg/min)

Ventilation factor AH1/2(m5/2)

Influences of Ventilation


Ventilation factor

kg/min

or

kg/s

Ventilation Factor

Here AH1/2is calledventilation factor.


Theoretical deduction of the ventilation factor

Theoretical Deduction of the Ventilation Factor


Ventilation factor1

kg/min

or

kg/s

Ventilation Factor


Control forms of a compartment fire

Fuel

Control Forms of a Compartment Fire

Fuel-controlled (燃料控制) fire

Ventilation-controlled (通风控制) fire

Air (oxygen) Supply


Chapter 7 compartment fire

m/Af kg/m2s

/AfKg/m2s


Chapter 7 compartment fire

Influence of Ventilation on the Control forms of fire

Ventilation-controlled fire

Fuel-controlled fire


Opening factor

Opening Factor


Opening factor1

Opening Factor

Fuel-controlled fire

Ventilation-controlled fire


Summary

Fully-developed

Decay

Summary

1. Introduction of compartment fire.

  • 4. Factors Affecting Fire Growth (ventilation)

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

3. Ignition & development of a compartment fire.

Flashover

Growth


Questions

Questions

  • What are the two control forms of the compartment fire? What is the difference between them?

  • Why indoor fires are more dangerous than outdoor fires?

  • Calculate the ventilation factor and opening factor of this classroom.


Thanks

Thanks!

Please feel free to raise any question!


Chapter 7 compartment fire1

Chapter 7 Compartment Fire

Lesson 2 Flashover


Key words phrases2

Key Words & Phrases

Flashover 轰燃

Fire plume 火羽

Heat flux 热通量

Pyrolyze (pyrolysis) 高温裂解

Radiation feedback heat辐射热反馈

Structural failure 结构破坏

Collapse 坍塌、倒塌

Hose-line 消防水带


Development of a compartment fire

Temperature

Time

Development of a compartment fire

Flashover轰燃

Decay

period衰减阶段

Fully developed period

(post-flashover)

充分发展阶段

Growth period

(pre-flashover)初期增长阶段


1 definition of flashover

1. Definition of Flashover

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


Most commonly used definitions of flashover are as follows

Most commonly used Definitions of flashover are as follows:

  • The transition from a localized fire to the general conflagration (大火灾) within the compartment when all fuel surfaces are burning;

  • The transition from a fuel (燃料) controlled fire to a ventilation (通风) controlled fire;

  • The sudden propagation (传播) of flame through unburnt gases and vapors collected under the ceiling.


Definition of flashover

Other Popular Definitions

Definition of Flashover

  • The definition of flashover is given in a British Standard as a:

    "Sudden transition to a state of total surface involvement in a fire of combustible materials within a compartment".   (BS 4422, 1987)

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

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


Initial development of a fire plume in a compartment

2. Formation of flashover

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


Chapter 7 compartment fire

A hot layer of smoke forms under the ceiling of the room. And it will produce radiation feedback heat (辐射热反馈).


Chapter 7 compartment fire

When all the combustible surfaces reach a certain high T, they will pyrolyze and release flammable gases.

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


Chapter 7 compartment fire

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


Chapter 7 compartment fire

Flashover Fire Cases


Chapter 7 compartment fire

Video 1: Flashover experiment


Chapter 7 compartment fire

Fire in Bradford City Soccer Stadium, England, 1985.

P1: first visible flames

P2: 90 seconds

P3: 150 seconds


3 consequences of flashover

Firefighters

Properties

Building structure

3. Consequences of Flashover

Large number of deaths and injuries

Trapped building occupants (被困居民)

Great damage


3 1 death and injury caused by flashover

3.1 Death and injury caused by flashover

  • Flashover happens very suddenly.

  • During flashover, fire grows sorapidly 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.

    Firefighters : 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.


Chapter 7 compartment fire

Death caused by flashover in some fire cases

In the USA, NFPA (美国消防协会) statistics recorded between 1985 and 1994 demonstrated a total of 47 US firefighters lost their lives to 'flashover'.


Chapter 7 compartment fire

Firefighters confronted a flashover.

Firefighter caught inside a

flashover.


Chapter 7 compartment fire

Properties

3.2 Great damage caused by 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.

Great damage

Building structure

Structural Failure


Structural failure

Structural Failure

  • After those structural failures, the roofof 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 building could collapse at any point after a compartment reaches flashover.


Catastrophic collapse of a building

Catastrophic Collapse of a Building


Does flashover occur in all the compartment fires

Does flashover occur in all the compartment fires?

Video 2: Non-Flashover experiment


The development of fire with and without flashover

The Development of Fire With and Without Flashover


4 fuel and ventilation conditions necessary for flashover

4. Fuel and Ventilation Conditions Necessary for Flashover


Fuel and ventilation conditions necessary for flashover

Fuel and Ventilation Conditions Necessary for Flashover

1. Mass burning rate:

2. Ventilation factor:


4 criteria of flashover

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 flashover

Influencing Factors of Flashover

  • The amount of combustible materials.

  • The building materials of the walls and ceiling.

  • The height and width of the opening.

  • The kinds of combustible materials.


6 three ways to delay flashover

6. Three ways to delay flashover:

  • Venting: By venting windows of a burning room you release the build up of heat in the room. This slows down flashover in addition to improving visibility in a smoke-filled room.

  • Not venting:by not venting and instead closing the door to the burning room, you can also delay flashover. By not venting, you starve the fire of oxygen, which slows down the combustion rate and the build up of heat in the room. This may be done when there is a delay in stretching a hose-line and all persons are out of the burning room.

  • Portable extinguisher: The use of a portable extinguisher can cool the heat down in a burning room temporarily and delay flashover.


Chapter 7 compartment fire

7. Warning signs of flashover

  • Flames are running overhead on the ceiling;

  • The sudden lowering of the existing smoke layer (smoke interface).

  • Sudden increases of heat forcing you to crouch low;

  • Perception of rollover:

    Rollover is defined, as sporadic (零星的) flashes of flame mixed with smoke at ceiling level.


8 point of no return

8. Point of no return

  • The point of no return is a distance inside a burning room beyond which a searching firefighter will not escape and will not reach the door or window entered.

  • How far inside a burning room can a firefighter be and still escape back out the door alive and not suffer serious bums after a flashover occurs? How far into the burning room that appears about to flashover should a firefighter go?

  • Five feet is the point of no return after the room explodes into a flashover.


8 point of no return1

8. Point of no return

1. Fire temperatures of 280‘-320’ F cause intense pain and damage to exposed skin. (138-160℃)

2. The average temperature in a room that flashes over is 1000' to 1500' F. (537-816 ℃)

3. The average person moves 2.5-feet per second when walking

4. How long can a firefighter take 1000'-1500' F on the neck, ears, wrists and any other exposed portion of the body? Just two seconds.

Five feet is the point of no return


9 defensive search procedures

9. Defensive Search Procedures:

At a Doorway:

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


At a window

At a Window:

If smoke and signs of rollover are seen in the smoke, the firefightershould notenter the burning window. Insteadthe firefighter should crouch down below the heat and sweep the area below the windowsill (窗台) with a tool.

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


Summary1

SUMMARY

1) Definition of flashover;

2) Formation of flashover;

3) Sequences of flashover;

4) Conditions Necessary for Flashover;

5) Criteria of flashover;

6) Equipment to study those influencing factors;

7) Three ways to delay flashover;

8) Warning signs of flashover;

9) Point of no return;

10) Defensive Search Procedures.


Questions1

QUESTIONS

1. How does a flashover happen?

2. What are the consequences of flashover?

3. What are the warning signs of flashover?


Questions2

QUESTIONS

4. According to fire protection engineers flashover is caused by which one of the following?

A. Radiation heat B. Radiation feedback heat

C. Conduction heat D. None of the above

5. Which one of the following is not a method used by firefighters to delay flashover?

A. Venting to release heat

B. Not venting to starve the fire of oxygen and thus

slow down heat generation

C. Use a portable extinguisher on the fire to cool it down

D. Remove combustible from the fire area


Thanks1

Thanks!

Please feel free to raise any question!


5 compartment fire research lab

5. Compartment Fire Research Lab

  • Under the leadership of Prof. Chen, this lab was set up in 2001 with support from our academy and fire engineering department.

  • And this equipment represents the first class level inside our country.


5 compartment fire research lab1

1

2

4

3

5

5. Compartment Fire Research Lab

1.A box with opening

2.A tray(托盘)

3. An electronic

Balance (电子天平)

4. A printer(打印机)

5.Signal detector

(信号检测仪)

①~⑦Thermal couples

(热电偶)


Chapter 7 compartment fire

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

    The building materials of the walls and ceiling

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

    The height and width of the opening


Chapter 7 compartment fire

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

    The kinds of combustible materials

    The amount of combustible materials

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


Chapter 7 compartment fire

Welcome to Our lab!

To Know More about Our Study

To Participate in Our work


Chapter 7 compartment fire2

Chapter 7 Compartment Fire

Lesson 3 Backdraft


Key words phrases3

Key Words & Phrases

Backdraft/backdraught 回燃

Explode (explosion) 爆炸

Pyrolyzate (pyrolyze; pyrolysis) 热解产物

Flammability Limits 爆炸极限

Deflagration爆燃

Vent 通风、排出

Quench 熄灭、结束

Flank 侧翼攻击


1 definition of backdraft

1. Definition of Backdraft

  • The NFPA definition:

    “The explosive or rapid burning of heated gases that occurs when oxygen is introduced into a building that has not been properly ventilated and has a depleted (减少的) supply of oxygen due to fire."

  • The IFE (Institution of Fire Engineers) definition:

    “An explosion, of greater or lesser degree, caused by the inrush (涌入) of fresh air from any source or cause, into a burning building, where combustion has been taking place in a shortage of air."


Smoke is combustible

Smoke Is Combustible


Air introduction

Air Introduction


A basic scenario

A Basic Scenario

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.


Backdraft

BACKDRAFT


Backdraft1

BACKDRAFT


2 formation of backdraft

2. Formation of Backdraft

  • 1) A fire burning in a room with poor ventilation

  • 2) Accumulation of flammable gases

  • 3) Air introduction at the breaking of openings

  • 4) Formation of mixture within flammability limits

  • 5) Ignition of the mixture

  • 6) Explosion or deflagration and pressure rise


3 conditions nece s sary for backdraft

3. Conditions Necessary for Backdraft

  • 1) The accumulation of smoke consisting of un-burnt pyrolyzates and incomplete combustion products in a poorly ventilated compartment.

  • 2) Air introduction when windows or doors are opened or broken.

  • 3) The newly formed mixture of air and flammable smoke is within its flammabilitylimits (爆炸极限).

  • 4) An ignition source of sufficient energy such as a flame, spark or glowing ember (余火). It is also possible for super-heated gases to ignite (auto-ignition), without a source of ignition being introduced.


4 consequences of backdraft

4. Consequences of Backdraft

  • 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.


Backdraft is a kind of explosion

Backdraft 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 backdraft1

Properties

Building structure

4. Consequences of Backdraft

Deaths and injuries (Firefighters)

Great damage


Destructive effects caused by backdraft explosion pressures

Destructive Effects Caused by Backdraft Explosion Pressures


Chapter 7 compartment fire

5. Warning Signs of Backdraft

Before opening a door or window to the compartment, the firefighter should be aware of:

  • 1) A fire in a compartment with few openings that has been burning for some time.

  • 2) Oily deposits (沉淀物) in windows.

  • 3) Pulsating (跳动的) smoke from openings.

  • 4) Hot doors and door handles (windows);


5 warning signs of backdraft

5. Warning Signs of Backdraft

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

  • 1) Blue flames (‘ghosting’ or ‘dancing’ flames) in the hot gas layer.

  • 2) Smoke drawn back through opening:

  • 3) Whistling and roaring sounds

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


Smoke drawn back through opening

Smoke Drawn Back through Opening


Lessons learned

Lessons Learned

1. 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.


Chapter 7 compartment fire

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

Amazing Peru Backdraft

The Aftermath (后期)!!!An exterior defensive operation is mounted following the backdraft.


6 preventing death and injury

6. Preventing Death and Injury

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

Venting (通风)

Quenching (熄灭)

Flanking (侧翼攻击)


6 1 venting

6.1 Venting (通风)

  • 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.


Chapter 7 compartment fire

6.2 Quenching(熄灭)

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

    1)This water can cool a potentially explosive atmosphere.

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


Chapter 7 compartment fire

6.3 Flanking(侧翼攻击)

  • 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.


A backdraft case

A Backdraft Case

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.


Chapter 7 compartment fire

  • Riddle had been in his command vehicle when the backdraft occurred. "I heard the noise and I looked up... this piece of roof was just being removed - it went up about 10 feet and then came back down," he said.

  • There was no warning except that immediately before he blast, “The guys on the scene said they heard a sucking (吸气) sound," Riddle said.

  • The backdraft blew the roof off the Church and knocked flat the eight firefighters on scene and two firefighters were injured. A firefighter who had felt the door suffered burns to his hand because he had taken his glove off. Another firefighter was blown out of the cab of the engine, and another was blown across an alley.


7 backdraft and flashover what is the difference

7. Backdraft and flashover, what is the difference?

Flashover and backdraft are distinctly different events which occur in different ways.

  • A flashover can occur in a compartment when a small localized fire rapidly develops into a fire involving all the combustible surfaces.

  • In contrast a backdraft occurs after air is admitted to a poorly ventilated compartment and mixes with un-burnt pyrolysis products from the oxygen starved fire. Any ignition source, such as a glowing ember, can ignite the resulting flammable mixture. Expansion due to heat created by combustion can then expel burning gases out through the opening.


Differences

Differences

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.


Chapter 7 compartment fire

Differences

  • 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.


Differences1

Differences

  • 3. The triggering or cause of them.

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;

Flashover: a heat induced development of the fire

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.


Differences2

Differences

  • 4. The stage of fire growth in which they occur.

    Backdraft explosions occur when there is smoke 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?


Chapter 7 compartment fire

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

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


Tactical firefighting training

Tactical Firefighting Training

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


Summary2

SUMMARY

  • 1. Definition of backdraft

  • 2. Formation of backdraft

  • 3. Conditions Necessary for Backdraft

  • 4. Consequences of Backdraft

  • 5. Warning Signs of Backdraft

  • 6. Preventing Death and Injury

  • 7. The differences between Backdraft and flashover.


Questions3

QUESTIONS

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

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

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


Compartment fire research lab

Compartment Fire Research Lab

  • Under the leadership of Prof. Chen, this lab was set up in 2001 with support from our academy and fire engineering department.

  • And this equipment represents the first class level inside our country.


5 compartment fire research lab2

1

2

4

3

5

5. Compartment Fire Research Lab

1.A box with opening

2.A tray(托盘)

3. An electronic

Balance (电子天平)

4. A printer(打印机)

5.Signal detector

(信号检测仪)

①~⑦Thermal couples

(热电偶)


Chapter 7 compartment fire

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

    The building materials of the walls and ceiling

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

    The height and width of the opening


Chapter 7 compartment fire

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

    The kinds of combustible materials

    The amount of combustible materials

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


Chapter 7 compartment fire

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Thanks2

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