chapter 7 compartment fire
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Chapter 7 Compartment Fire. Lesson 3 Backdraft. Don’t do the crime if you can’t do the time. (要想人不知,除非己莫为). content. 1. Definition of backdraft 2. Formation of backdraft 3. Necessary Conditions for Backdraft 4. Consequences of Backdraft 5. Warning Signs of Backdraft - PowerPoint PPT PresentationTRANSCRIPT
Combustion fundamentals of fire
Don’t do the crime if you can’t do the time.
(要想人不知,除非己莫为)
Lesson 3 BackdraftLesson 3 Backdraft
Chapter 7Compartment Fire
Combustion fundamentals of fire
1. Definition of backdraft2. Formation of backdraft3. Necessary Conditions for Backdraft4. Consequences of Backdraft5. Warning Signs of Backdraft6. Preventing Death and Injury7. Differences between Backdraft and
flashover.
contentcontent
Combustion fundamentals of fire
Snippet from the film of LADDER 49
Combustion fundamentals of fire
1. Definition of Backdraft
Definition from NFPA:
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 supply of oxygen due to fire.
Other definition from IFE (Institution of Fire Engineers) : An explosion of greater or lesser degree, caused by the inrush of fresh air from any source or cause, into a burning building, where combustion has been taking place in a shortage of air.
insufficieninsufficiencycy
Combustion fundamentals of fire
Limited ventilationLimited ventilation can lead to a fire in a can lead to a fire in a compartment producing compartment producing fire gasesfire gases containing significant proportions of containing significant proportions of partial combustion productspartial combustion products and and un-un-burnt pyrolysis productsburnt pyrolysis products, which are all , which are all combustiblecombustible..
If these accumulate then If these accumulate then the admission the admission of airof air when an opening is made to the when an opening is made to the compartment can compartment can lead to a sudden lead to a sudden deflagrationdeflagration. .
This deflagration moving through the This deflagration moving through the compartment and out of the opening is compartment and out of the opening is BACKDRAFTBACKDRAFT..
A Basic Scenario 想象
Combustion fundamentals of fire
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 , pressure
rise
Combustion fundamentals of fire
3.Necessary Conditions for Backdraft(1) The accumulation of smoke consisting of un-burnt pyrolyzates ANDAND 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 flammability limits.(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.
Combustion fundamentals of fire
1. Definition of backdraft2. Formation of backdraft3. Necessary Conditions for Backdraft4. Consequences of Backdraft5. Warning Signs of Backdraft6. Preventing Death and Injury7. Differences between Backdraft and
flashover.
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Combustion fundamentals of fire
4. Consequences of Backdraft
Pressure
Death and injure
Great damage
firefightersespecially
Properties
Building structure
Combustion fundamentals of fire
Pressure rise because backdraft will force the burning gases in the compartment out through the openings with a high velocity, possibly igniting some of the unburned pyrolyzates that had be left in the compartment. This can create a significant fire-ball outside the compartment.
4. Consequences of Backdraft
4.1 Pressure
Combustion fundamentals of fire
Combustion fundamentals of fire
4. Consequences of Backdraft
4.2 Death and injure
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.
Combustion fundamentals of fire
4. Consequences of Backdraft
4.3 Great damage
Flame accompanying the explosion can cause cause serious burns, collapsecollapse walls, partitionpartition and ironiron shutters ( 卷帘铁门 ) and crushcrush firefighters beneath them.
Combustion fundamentals of fire
4. Consequences of Backdraft
Pressure
Death and injure
Great damage
firefightersespecially
Properties
Building structure
Combustion fundamentals of fire
5. Warning Signs of Backdraft
Outside the roomOutside the room
Inside the roomInside the room
Combustion fundamentals of fire
Before opening a door or window to the compartment, the firefighter should be aware of:
(1) A fire in a compartment with few openings has been burning for a long time.
(2) Oily deposits on windows. (3) ( 跳动的 ) Pulsating smoke from
openings. (4) Hot doors and door handles
(windows).
5. Warning Signs of Backdraft
4.1 Outside the room
awareaware
seesee
feelfeel
Combustion fundamentals of fire
5. Warning Signs of Backdraft
4.2 Inside the room
(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( 进行 ), there is probably little action that can be taken by a firefighter to prevent it.
Combustion fundamentals of fire
Smoke Drawn Back through the Door
Combustion fundamentals of fire
Full protective gear:
helmets( 头盔 )
hoods( 防护帽 )
gloves( 手套 )
boots( 长靴 )bunker pants
( 防护裤 )
coat
Backdraft is very dangerous, Firefighters should know that explosions happen fast, sometimes too fast for firefighters to take cover and protect themselves.
fire water branch
Combustion fundamentals of fire
but if you were caught in an explosion, it may protect you survive from the blast and not be hurt hardly.
Full protective gear:
Backdraft is very dangerous, Firefighters should know that explosions happen fast, sometimes too fast for firefighters to take cover and protect themselves.
Protective fire gear may be hot, cumbersome ( 笨重的 ) and slow you down,
Combustion fundamentals of 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.
Combustion fundamentals of fire
1. Definition of backdraft2. Formation of backdraft3. Necessary Conditions for Backdraft4. Consequences of Backdraft5. Warning Signs of Backdraft6. Preventing Death and Injury7. Differences between Backdraft and
flashover.
contentcontent
Combustion fundamentals of fire
6. Preventing Death and Injury
There are three tactics( 战术 ) that can reduce the chances of getting caught in a backdraft:
6.1 Venting (6.1 Venting ( 通风通风 ))
6.2 Quenching (6.2 Quenching ( 熄灭熄灭 ))
6.3 Flanking (6.3 Flanking ( 侧翼攻击侧翼攻击 ))
Combustion fundamentals of fire
6. Preventing Death and Injury6.1 Venting
Venting a roof skylight ( 天窗 ) over a burning room is one of the most effective method to protect firefighters from the blast of the backdraft.(1) When roof conditions permit, the quick removal of the skylight can vent smoke-filled room and break up the explosive mixture. (2) Even if the smoke explosion occurs, the blast will be diverted( 转移 ) upward and out of the room from the opening, and be away from the firefighters advancing the hose-line.
Combustion fundamentals of fire
6. Preventing Death and Injury6.2 Quenching
Before entering a superheated confined room, charged hose-line (fire water branch) 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)The water can cool a potential and explosive atmosphere. (2)The powerful water stream might break up the explosive atmosphere.
Combustion fundamentals of fire
Firefighters in Australia get to grips with an 'entry & attack-module' trainer.
Combustion fundamentals of fire
6. Preventing Death and Injury6.3 Flanking
When venting and quenching are impossible, the officer in command can order two hose-lines into position, one on each side of a door or window of the 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.
Combustion fundamentals of fire
Tactical Firefighting Training
Staffordshire County firefighters (UK) training with a backdraft demonstrator ( 示范装置 )
Training in other aspects
Combustion fundamentals of fire
7. Differences between Backdraft and flashover7. Differences between Backdraft and flashover
There are FOURFOUR main differences:
There will be shock waves ( 冲击波 ) during backdraft fire, which will break the confining structure and windows around the explosion; blasts of smoke and flame may blow out a doorway; part of the structure may collapse. Flashover is rapid fire development, but without the speed of explosion of the chemical reaction.
7.1 Backdraft is an explosion, flashover is a transition.
Combustion fundamentals of fire
7. Differences between Backdraft and flashover7. Differences between Backdraft and flashover
There are FOURFOUR main differences:
You may experience only one or two backdraft during your entire career. But flashover happens often (flame suddenly full the whole room). You will probably face flashover again next time.
7.2 backdraft does not happen as often
as flashover does.
Combustion fundamentals of fire
7. Differences between Backdraft and flashover7. Differences between Backdraft and flashover
There are FOURFOUR main differences:
Basic scientific definitions of flashover and backdraft suggest that flashover is primarily "heat induced" whilst backdraft is "ventilation induced".
7.3 The triggering or cause of them are different.
Combustion fundamentals of fire
7. Differences between Backdraft and flashover7. Differences between Backdraft and flashover
There are FOURFOUR main differences:
backdraft is "ventilation induced".
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.
7.3 The triggering or cause of them are different.
Combustion fundamentals of fire
7. Differences between Backdraft and flashover7. Differences between Backdraft and flashover
There are FOURFOUR main differences:
flashover is primarily “ heat induced“.
The trigger of a flashover is heat. The theory of flashover is heat, which raises the temperature of the gases and furnishings in the room to the auto-ignition temperature and triggers a flashover.
7.3 The triggering or cause of them are different.
Combustion fundamentals of fire
7. Differences between Backdraft and flashover7. Differences between Backdraft and flashover
There are FOURFOUR main differences:
Page301 The last paragraph
7.3 The triggering or cause of them are different.
Combustion fundamentals of fire
7. Differences between Backdraft and flashover7. Differences between Backdraft and flashover
There are FOURFOUR main differences:
Backdraft explosions occur during the first and the third stages of fire, when the combustible smoke is in a confined space. During the growth and decay stages, smoldering can take place and generate explosive gas such as CO (carbon monoxide).
7.4 Flashover and backdraft occours at
different stage.
Combustion fundamentals of fire
7. Differences between Backdraft and flashover7. Differences between Backdraft and flashover
There are FOURFOUR main differences:
On the other hand, flashover is the transition of and , so it only occurs between the two stages, it signals the end of the growth stage.
7.4 Flashover and backdraft occours at
different stage.
Combustion fundamentals of fire
Flashover or Backdraft?Extension Reading
Extreme Fire Behavior
Modelling
Modelling of FLASHOVER and BACKDRAFT Using Fire Field Models
Combustion fundamentals of fire
Combustion fundamentals of fire
Combustion fundamentals of fire
Combustion fundamentals of fire
Combustion fundamentals of fire
The backdraft that blew apart an Illinois church (伊利诺斯州教堂) on February 9th, 2004 has been named the largest backdraft ever documented in the U.S.
A Backdraft Case
Combustion fundamentals of fire
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.
Combustion fundamentals of fire
Riddle was in his command vehicle (消防指挥车) when the backdraft occurred. “I heard the noise and I looked up... the piece of the roof was being removed - it went up about 10 feet and then came back down.” he said. There was no warning except that immediately before the blast, “The guys on the scene said they heard a sucking sound.” Riddle said.
Combustion fundamentals of fire
The backdraft blew the roof off the Church and knocked flat 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.
Study the case Study the case in detailin detail
Combustion fundamentals of fire
1. Definition of backdraft2. Formation of backdraft3. Necessary Conditions for Backdraft4. Consequences of Backdraft5. Warning Signs of Backdraft6. Preventing Death and Injury7. Differences between Backdraft and
flashover.
SummarySummary
Combustion fundamentals of fire
1. What are the warning signs of a backdraft?
2. What are the three firefighting tactics that can reduce destructive effects of a backdraft explosion?
3. What are the differences between a backdraft and flashover?
Homework
Combustion fundamentals of fire