【安全】第7章室內(nèi)火災(zāi)簡(jiǎn)介ppt課件

1、Chapter 7 Compartment FireLesson 1Development of Compartment FireKey Words & Phrases Compartment fire 室內(nèi)火災(zāi)Flashover 轟燃 Pre-flashover 轟燃前 post-flashover 轟燃后Flammable (Flame) 可燃的Combustible (combustion) 可燃的Smoulder 陰燃、無焰熄滅Smouldering fire 無焰熄滅Flaming fire 有焰熄滅Ventilate (ventilation) 通風(fēng)Ventilation Fact

2、or 通風(fēng)因子Opening Factor 開口因子Key Words & Phrases 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 (室內(nèi)火災(zāi)) means a fire that takes place in a compartment. A compartment is an enclosure with walls, roof a

3、nd openings (such as windows and doors).WTC 911The big Garley building fire,1996, HongkongAirport terminal fire, 1996, Duesseldorf, GermanyMTR train compartment arson fire縱火, January 2004 (up)Ship fire: The fire broke out an hour after the ship left the port of Miami (Right)Bus fires: Burnt to the t

4、op within 10 minBurnt completely within 10 min2. 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 (環(huán)境) r

5、apidly. But for a compartment fire, most of the heat and smoke generated would be confined in the upper part of the compartment. Outdoors, fire grows steadily.Indoors, trapped heat and smoke cause temperature to suddenly go up.3. Ignition (點(diǎn)燃) of a Compartment Fire For ignition of a fire to occur, a

6、 fuel must be heated above its auto-ignition temperature (自燃點(diǎn)) in the presence of sufficient oxidizer氧化劑 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 Fires After ignition two kinds of fires may follow:

7、A fire in solid fuel which is heat-limited (energy-limited) or ventilation limited will smoulder.3. Development of a Compartment Fire3. Ignition (點(diǎn)燃) of a Compartment FireFlaming Fires3.1 Smouldering FiresA Heat-limited Smouldering FireA Ventilation-limited Smouldering FireFate of a Smouldering Fire

8、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:3.2 Flaming Fires A flaming fire

9、 may develop immediately after ignition, particularly in cases of arson (縱火), or may develop from a smouldering fire after a delay which may be hours.A Flaming FireFate of a Flaming Fire:The fire burn itself out without involving other items of combustible material;If there is enough fuel but inadeq

10、uate 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. TemperatureTime4. Developm

11、ent of a compartment fireFlashover 轟燃Growth stage (pre-flashover)初期增長(zhǎng)階段Fully developed stage (post-flashover)充分開展階段Decay 衰減階段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 rel

12、atively low and the fire is localized in the vicinity of its origin.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 compa

13、rtment and emerge from the windows and other ventilation (通風(fēng)) openings. This may continue until the available fuel is consumed. 4.2 Fully developed stage (post-flashover) 4.3 Decay Stage Average T 80%Tmax The decay period is often identified as the stage of fire after the average temperature has fal

14、len to 80% of its peak value. At this stage, fire becomes smaller and temperature drops lower due to the consumption of fuel. 4.4 FlashoverGrowth stage Fully developed stage TransitionFlashoverThe transition(轉(zhuǎn)變) is very short. So flashover is considered as an event not a stage.Temperature will incre

15、ase 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 compartment, its hardly for the occupants of the rest of the building to evacuate (疏散).The

16、 duration from onset of burning to flashover is directly relevant to life safety within the buiding.5. The Necessary Condition for Safe Evacuation Where tp is the time elapsed from ignition to the perception (覺得) that a fire exists; ta is the time between perception to the start of the escape action

17、; 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 (難以忍受的) conditions at the location. tp + ta+ trs tu6. Factors Affecting Fire GrowthThe nature, amount and distribution of the combustible contents;The size and shape the co

18、mpartment;The width and height of the ventilation openings.Influences of VentilationVentilation factor AH1/2(m5/2)Burning rate (kg/min)Ventilation Factorkg/minkg/sorHere AH1/2 is called ventilation factor.Theoretical Deduction of the Ventilation Factorkg/minkg/sorVentilation FactorControl Forms of a

19、 Compartment FireFuel-controlled 燃料控制 fireVentilation-controlled 通風(fēng)控制 fireFuelAir (oxygen) Supply/Af Kg/m2sm/Af kg/m2sInfluence of Ventilation on the Control forms of fire Fuel-controlled fireVentilation-controlled fireOpening FactorOpening FactorFuel-controlled fireVentilation-controlled fireSummar

20、y4. Factors Affecting Fire Growth (ventilation)1. Introduction of compartment fire.2. Explanation of why compartment fires are more dangerous than outdoor fires.3. Ignition & development of a compartment fire.GrowthFully-developedDecayFlashoverQuestionsWhat are the two control forms of the compartme

21、nt 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!Please feel free to raise any question!Chapter 7 Compartment FireLesson 2 FlashoverKey Words & Phrases Flashover 轟燃 Fire p

22、lume 火羽Heat flux 熱通量Pyrolyze (pyrolysis) 高溫裂解 Radiation feedback heat 輻射熱反響Structural failure 構(gòu)造破壞Collapse 坍塌、倒塌Hose-line 消防水帶 TemperatureTimeDevelopment of a compartment fireFlashover 轟燃Growth period (pre-flashover)初期增長(zhǎng)階段Fully developed period (post-flashover)充分開展階段Decayperiod 衰減階段The term flashove

23、r was first introduced by UK scientist P.H. Thomas in the 1960s and was used to describe the theory of a fires growth up to the point where it became fully developed.1. Definition of FlashoverThe transition from a localized fire to the general conflagration (大火災(zāi)) within the compartment when all fuel

24、 surfaces are burning;The transition from a fuel (燃料) controlled fire to a ventilation (通風(fēng)) controlled fire;The sudden propagation (傳播) of flame through unburnt gases and vapors collected under the ceiling. Most commonly used Definitions of flashover are as follows:Definition of FlashoverThe Interna

25、tional 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. Other Popular DefinitionsThe definition of flashover is given in a British Standard as a: Sudden transition to a state of to

26、tal surface involvement in a fire of combustible materials within a compartment. (BS 4422, 1987)Initial development of a Fire Plume (火羽) in a Compartment.2. Formation of flashoverA hot layer of smoke forms under the ceiling of the room. And it will produce radiation feedback heat 輻射熱反響.When all the

27、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(高溫裂解) and release pyrolysis gases.There is a certain auto-ignition temperature (AIT) (自燃點(diǎn)) for a certain mixture of flamma

28、ble 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

29、. Flashover Fire Cases Video 1: Flashover experiment Fire in Bradford City Soccer Stadium, England, 1985.P1: first visible flamesP2: 90 secondsP3: 150 seconds3. Consequences of Flashover Great damage Large number of deaths and injuriesTrapped building occupants (被困居民)FirefightersBuilding structurePr

30、operties3.1 Death and injury caused by flashoverFlashover 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. Firefighters : If wearing full protective

31、 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. YearPlaceDeath1981Dublin

32、481982Los Angeles241991Petersburg81996Dusseldorf171997UK32002Paris5Death caused by flashover in some fire casesIn the USA, NFPA (美國(guó)消防協(xié)會(huì)) statistics recorded between 1985 and 1994 demonstrated a total of 47 US firefighters lost their lives to flashover.Firefighters confronted a flashover. Firefighter

33、 caught inside a flashover.Wooden beams(木梁) will char(燒焦);Steel (鋼筋) will be permanently weakened. Then it will expand and damage surrounding structural components (構(gòu)件);Concrete (水泥) and masonry (磚瓦) will spall (破碎) and may crack into pieces. 3.2 Great damage caused by flashoverGreat damageBuilding

34、structurePropertiesStructural FailureStructural FailureAfter 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 buildi

35、ng could collapse at any point after a compartment reaches flashover.Catastrophic Collapse of a BuildingVideo 2: Non-Flashover experiment Does flashover occur in all the compartment fires? The Development of Fire With and Without Flashover4. Fuel and Ventilation Conditions Necessary for FlashoverFue

36、l and Ventilation Conditions Necessary for Flashover1. Mass burning rate:2. Ventilation factor:4. Criteria of flashover (轟燃判據(jù)) Based on the observations and measurements of compartment fires, different criteria of flashover were proposed: Radiation heat flux at floor level (地面熱輻射通量) reaches 20kW/m2;

37、 Gas Temperature at ceiling level (頂棚氣體溫度) reaches 600;Influencing Factors of FlashoverThe 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:Venting: By venting windo

38、ws 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

39、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 temporar

40、ily and delay flashover. The sudden lowering of the existing smoke layer (smoke interface). Sudden increases of heat forcing you to crouch low; 7. Warning signs of flashover Flames are running overhead on the ceiling; Perception of rollover: Rollover is defined, as sporadic (零星的) flashes of flame mi

41、xed with smoke at ceiling level. 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

42、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 return 1. Fire temperatures of 280-320 F cause intense pain

43、and damage to exposed skin. (-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 walking4. How long can a firefighter take 1000-1500 F on the neck, ears, wrists and any other exposed portion of the body? Just

44、two seconds.Five feet is the point of no return9. Defensive Search Procedures: 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 forth

45、coming, 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 Doorway: At a Window: If smoke and signs of rollover are seen in the smoke, the firefighter should not enter the

46、 burning window. Instead the firefighter should crouch down below the heat and sweep the area below the windowsill (窗臺(tái)) 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 th

47、e heated smoke and flashes of flames mixed with smoke coming out the window and pull the victim to safety on the ladder.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 i

48、nfluencing factors;7) Three ways to delay flashover;8) Warning signs of flashover;9) Point of no return;10) Defensive Search Procedures.QUESTIONS1. How does a flashover happen?2. What are the consequences of flashover?3. What are the warning signs of flashover?QUESTIONS4. According to fire protectio

49、n 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 o

50、xygen 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 Relative Code and standard for flashoverNFPA 555 - Guide on Methods for Evaluating Potential for Room Flashover Current Edition: 2004 Thanks!Please feel free t

51、o raise any question!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 Lab5. Compartment Fire Research Lab1. A box with ope

52、ning3. An electronic Balance (電子天平)4. A printer (打印機(jī))2. A tray (托盤)5. Signal detector (信號(hào)檢測(cè)儀) Thermal couples (熱電偶)21345Use of Each DeviceTray (托盤): combustible materials will be put on the tray.Electronic balance (電子天平): Detect the mass change (質(zhì)量變化) during the fire process.Printer：Print out the de

53、tected mass change.Signal detector (信號(hào)檢測(cè)儀): Detect the temperature and radiation heat flux (輻射熱通量) both inside and outside the compartment.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 ceiling2. Both the width

54、 and height of the door can be adjusted. The height and width of the opening3. Different materials of different mass (質(zhì)量) can be put on the tray and used as combustible material. The kinds of combustible materials The amount of combustible materials4. Besides the above influencing factors, using thi

55、s equipment, we can also study the mass burning rate質(zhì)量熄滅速率during process of each compartment fire. To Know More about Our Study To Participate in Our work Welcome to Our lab!Chapter 7 Compartment FireLesson 3 Backdraft Key Words & Phrases Backdraft/backdraught 回燃 Explode (explosion) 爆炸Pyrolyzate (py

56、rolyze; pyrolysis) 熱解產(chǎn)物Flammability Limits 爆炸極限 Deflagration 爆燃Vent 通風(fēng)、排出Quench 熄滅、終了Flank 側(cè)翼攻擊1. Definition of BackdraftThe 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

57、 (減少的) 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 Combust

58、ibleAir 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

59、 compartment can lead to a sudden deflagration. This deflagration moving through the compartment and out of the opening is a backdraft.A Basic ScenarioBACKDRAFTBACKDRAFT2. Formation of Backdraft1) A fire burning in a room with poor ventilation2) Accumulation of flammable gases 3) Air introduction at

60、 the breaking of openings4) Formation of mixture within flammability limits5) Ignition of the mixture6) Explosion or deflagration and pressure rise 3. Conditions Necessary for Backdraft1) The accumulation of smoke consisting of un-burnt pyrolyzates and incomplete combustion products in a poorly vent