2_什么是火灾风险评估ppt课件

1、Chapter2 What is Fire Risk AssessmentChapter2 火灾风险评价的根本概念本章引入火灾风险评价的根本概念火灾风险评价fire risk assessment指对火灾人们所不希望发生的这类事故的后果，带给人员和财富的风险的评价。2.1 综述Basic concepts of fire risk assessment will be introduced in this chapter.The term fire risk assessment refers to assessing risks to both people and property as

2、a consequence of unwanted fires. 2.1 overviewIn a simple risk assessment the probability of a certain unwanted fire scenario is considered and the consequence of that scenario are explored. In a comprehensive risk assessment all probable unwanted fire scenarios and their consequences are considered.

3、在简单的火灾风险评价过程中，仅对某些或某类火灾场景发生的能够性和结果进展分析和评价；在全面或综合的火灾风险评价过程中，对一切的能够火灾场景发生的能够性或结果进展分析和评价。一个火灾场景(fire scenario )由一系列的火灾中的事件组成，这些火灾事件是推测能够在火灾过程中发生的事件，将某些防、灭火技术或管理措施的胜利或失效/失败的过程连缀起来，就可以构成一个火灾场景。因此一个火灾场景发生的能够性(probability)决议于这一系列事件中每一个防、灭火技术或管理措施的胜利或失效/失败的能够性。A fire scenario involves the projection of a se

4、t of fire events, all of which are linked together by whether the fire protection measures succeed or fail. The probability of a fire scenario is dependent on the individual probabilities of success or failure of fire protection measures.对人员的风险(risk)既决议于可以对人员产生损害(harm)的火灾场景发生的能够性，又决议于火灾场景或者说火灾场景产生的后

5、果(consequence )对人员呵斥损害的程度或程度(level of harm )。通常运用火势增长、烟气传播、人员疏散、建筑构造呼应和消防人员灭火效能等模型来对火灾场景的结果进展计算和模拟。这部分内容不是本课程的授课内容，将在课程中讲述；而在了解火灾各个过程和阶段根本特征的根底上，建立相应火灾场景，分析火灾场景发生的能够性，是本课程的主要内容。The risk to the occupants depends not only on the probability of the fire scenario that can lead to harm to the occupants,

6、but also the level of harm to the occupants as a result of the consequence of that scenario. The consequence of a fire scenario can be assessed by using time-dependent modeling of fire and smoke spread, occupant evacuation and fire department response.2.2 What is Fire Risk Assessment?前面讲过，火灾风险评价是指对火

7、灾人们所不希望发生的这类事故的后果，带给人员和财富的风险(risk)的评价。 它所运用到的根本原理与其他领域风险评价的原理是一致的。2.2 火灾风险评价(Fire Risk Assessment)的根本概念Fire risk assessment is the assessment of the risks to the people and property as a result of unwanted fires. It employs the same basic principles of risk assessment that are used in many other fie

8、lds. A simple risk assessment considers the probability of the occurrence of a certain unwanted fire scenario and the consequence of that scenario.A comprehensive risk assessment considers all probable unwanted fire scenarios and their consequences. The definition of fire scenario will be discussed

9、in the next section. It involves the linking of anticipated fire events by the success or failure of certain fire protection measures.例如，评价建筑中的某一个火灾场景的后果对人生命呵斥的风险，这个估计的生命风险可由(2.1)式来表达：式中P是这个特定的火灾场景发生的能够性(频次或概率，rate或probability );C 是这个特定火灾场景呵斥后果估计导致的死亡人数。 (2.1)Consider, as an example, the assessment

10、of the expected risk to life to the occupants in a building as a result of one single fire scenario. The expected risk to life can be expressed by the following equation:where P is the probability of a certain fire scenario and C is the expected number of deaths as a consequence of that fire scenari

11、o.(2.1)If the probability of a certain fire scenario occurring in a building is once every 20 years, then P = 0.05 fires per year. If the consequence of that fire scenario is two deaths, then C = 2 deaths per fire. From Equation 2.1, the expected risk to life as a result of that fire scenario is equ

12、al to 0.1 deaths per year, or 1 death every 10 years.比如建筑中某一火灾场景发生的能够是年一次，那么：P = 0.05 fires per year假设这个火灾场景的后果是死亡人，那么C = 2 deaths per fire从式(2.1)可知，这个火灾场景的估计生命风险为the expected risk to life 0.1 deaths per year或都 1 death every 10 years.每年0.1人死亡或每10年死亡人。当然在建筑中发生火灾的方式不止一种，那么对人员的风险通常要基于一切能够的火灾场景来进展评价。那么一

13、个全面的comprehensive fire risk assessment 风险可由(2.2)式来表达：式中的代表了对一切能够的火灾场景进展求和。Pi 是某一个火灾场景 i 发生的能够性;Ci火灾场景 i 的后果呵斥的估计死亡人数 。(2.2)Because fires can occur in a building in more ways than one, the risk to the occupants is usually assessed based on all probable fire scenarios.A comprehensive fire risk assessm

14、ent can be expressed by the following equation:(2.2)要留意的是，火灾风险评价不仅包括对人员生命风险的评价，还能够包括对财富损失、对运营或消费的影响等呵斥损失的评价。此时方程(2.1)和方程(2.2)中的后果也相应地改换为财富损失的后果。It should be noted that fire risk assessments involve more than the assessment of the risk to life. It involves also the assessment of the loss of property,

15、 loss of business and so on, as a result of fires. Equations similar to Equation 2.1 and 2.2 can also be expressed for the other losses.2.2.1 Fire ScenariosA fire scenario is a sequential set of fire events that are linked together by the success or failure of certain fire protection measures. A fir

16、e event is an occurrence that is related to fire initiation, or fire growth, or smoke spread, or occupant evacuation, or fire department response.2.2.1 火灾场景-Fire Scenarios一个火灾场景由一系列火灾中延续发生的事件组成，经过把某些特定的防、灭火技术或管理措施胜利或失败/失效的结果连缀起来而得到。火灾中的一个事件A fire event 是火灾中发生的，与起火、火灾增长、烟气传播、建筑物构造呼应、人员疏散或消防人员呼应相关的事件，

17、假设不是在火灾中发生的，或与火灾的上述过程无关的事件，那么不视为火灾中的一个事件。比如，火灾中发生的声、光报警是一个火灾事件；火灾中发生的断电或停水也是火灾不同的两个事件；而没有发生火灾时的停水，就不是一个火灾事件了。For example, a fire event can be: a fire develops into a post-flashover fire, or the occupants can not evacuate quickly enough and are trapped in the building, or the fire department responds

18、 in time and rescues the trapped occupants. A fire protection measure is a measure that can be a fire protection system, such as sprinklers and alarms; or a fire protection action, such as occupant evacuation training and drills.防、灭火技术或管理措施包括消防安装，比如自动喷水灭火系统、火灾探测、报警系统、防排烟系统等；还包括人员应急呼应的演练，如处置火情，报警、扑灭初

19、期火灾的训练和疏散演练等。A simple example of a fire scenario is the following set of events that are linked together by the failure of fire protection measures: Another simple example is the following set of events that are linked together by the success of fire protection measures: a fire does not develop into

20、 a post-flashover fire, the alarm system activates, and the occupants receive the warning signals and evacuate the building.火灾场景的简单例子：(1)火灾发生了轰燃报警系统没有启动人员没有接纳到报警信号人员被因于火场中。(2)没有发生轰燃报警系统启动胜利人员及时接纳到报警信号人员胜利疏散。In real-world fires, fire scenarios are much more complex and the possible number of fire sce

21、narios can be many. The number of fire scenarios depends on the number of permutations that can be constructed based on all the fire protection measures that are in place and all the fire events that are anticipated. The proper construction of fire scenarios and the proper analysis of the consequenc

22、e of the fire scenarios, however, are the key to a credible fire risk assessment.就真实的火灾而言，火灾情况要复杂得多，因此能够的火灾场景数量也会有很多。火灾场景的数量决议于火场中防灭火技术和管理措施的数量和估计的火灾事件的数量。合理构建火灾场景并分析其发生的能够性，对所建立的火灾场景后果的尽量符合实践的分析、计算或模拟，是决议火灾风险评价结果可信度的关键。前者是本课程所要到达的主要目的；而后者将重点在课程中讨论。The general principle of how fire scenarios can be

23、constructed will be discussed in the next section. But before we discuss how they can be constructed, take the simple case where there is no fire protection measure at all. Take, for example, the case where a fire occurs at the only exit door in a room with a number of people inside the room.在后续的部分中

24、，我们将论述构建火灾场景的根本方法。在此之前，我们要讨论一个极端的情况：没有任何防、灭火技术和管理措施的情况。比如，我们以一个发生在房间独一平安出口处的火灾为例，发生火灾的房间中有一定数量的人员。With no fire protection in the room to control the fire, the fire develops into a post-flashover fire and subsequently kills all the people in the room. The risk of this simple fire scenario is the prob

25、ability of a fire occurring at the only exit door of a room, multiplied by the number of people killed by this fire. Obviously, fire risk assessment is not as simple as this.在房间中没有任何控制火势增长的措施的情况下-轰燃迅速发生-火灾进入全盛期-房间内一切人员死于火灾。这个比较简单而极端的火灾场景，火灾的风险等于火灾发生于此房间独一平安出口处的能够性与死于火灾中人员数量的乘积。当然，普通火灾风险的评价，情况都要比这个例子

26、复杂得多。通常建筑内有控制火灾增长或迅速传播的措施，为人员和财富提供了维护，延缓了火灾的传播，如灭火系统或烟气阻隔措施；通常还有火灾早期探测和报警的措施，协助人们在火势扩展前及时疏散到平安的区域； 通常消防人员也能够较早地接纳到火警，可以及时赶赴火场并展开灭火和人员施救。There are normally fire protection measures in place to protect the occupants and property. For example, there are normally fire protection measures in place to con

27、trol the development of a fire and also to prevent the fire from spreading to other parts of a building.There are also normally fire protection measures in place to provide early warnings to the people and to help the people to get to a safe place before the fire spreads. There are also expectations

28、 that the fire department is notified and that they will come to extinguish the fire and rescue the people.Hence, fire risk assessment involves the use of fire scenarios that are based on the success and failure of these fire protection measures in order to assess the expected risks to the occupants

29、 and the property.因此，火灾风险评价中的火灾场景必需包含和思索到这些防灭火技术和管理措施，思索它们胜利启动、发扬其效能的程度，或失败/失效的能够性，这样才干对人员和财富所面临的预期风险进展估计或计算。A set of fire scenarios can be constructed based on the well-known event-tree concept, where events are linked together like the branches of a tree (Custer and Meacham, 1997).运用广为所知的事件树方法 eve

30、nt-tree concept ，可以构建一系列的火灾场景；在这种方法中，火灾中的事件被连缀起来，构成树状。 (Custer and Meacham, 1997).Figure 2.1 A simple event tree where an initiating event can lead to different events depending on the success and failure of fire protection measures at the branch points.Figure 2.1 一个简单的事件树Figure 2.1 shows a simple e

31、vent tree where an initiating event can lead to different events depending on the success or failure of the fire protection measures at the branch points. For example, Event A terminates in Event C if the fire protection measure for that event succeeds, whereas Event A continues with Event B to othe

32、rs if the fire protection measure fails.由图2.1可件，在分支点上，事件的胜利或失败，即某一防、灭火技术或管理措施的胜利与否，将使得初始事件产生不同的结果。比如，事件运用灭火器灭火胜利，那么接下来到事件C熄灭熄灭，火灾终结终了； 而假设事件运用灭火器灭火失败，那么接下来继续到事件B运用消火栓灭火。如此，将建立起一系列的火灾场景。A particular set of events that are linked together forms one fire scenario. For example, the set of Event A and Ev

33、ent C forms one scenario. A set of all possible combinations of the linked events forms a complete set of all possible fire scenarios.For example, the combinations of AC, ABD and ABE form a complete set of three fire scenarios.一系列的火灾事件连缀起来，那么可以构成一个火灾场景。例如，事件A-C构成一个火灾场景。而事件AC, ABD 和 ABE 构成了此事件树全部的火灾场

34、景，共有三个。场景： A-C场景2： ABD场景3： ABEFigure 2.1 also shows the probability of success or failure of these two fire protection measures at the two branch points. The probabilities of failure at the two branch points are assumed, for this example, to be the same, at 10% or 0.1. 在图2.1的分支上，还给出这两个防、灭火技术措施胜利和失败的

35、概率，在此例中，假定这两个措施胜利的概率均为90%，失败的概率为10%。基于此，场景AC 发生的能够性为0.9. 场景ABE 发生的能够性为0.09, 由AB (0.1) 的能够性与BE (0.9)的能够性相乘得到. 类似地，场景ABD发生的能够性0.01. 三个场景发生的结合概率为(combined probability) 为1。注：由于三个不同的火灾场景之间是互斥的。Mutually exclusive eventsBased on this, Scenario AC has a probability of 0.9. Scenario ABE has a probability of

36、0.09, obtained by multiplying the probability of AB (0.1) and that of BE (0.9). Similarly, Scenario ABD has a probability of 0.01. The combined probability of all three fire scenarios is one.The important thing to note here is that the probabilities of success or failure of fire protection measures

37、affect the probabilities of all fire scenarios. The lower the probabilities of failure of fire protection measures, the lower the probabilities of all those fire scenarios that will lead to an undesirable outcome.这里有一点比较重要，需引起我们的留意。显然，某一防灭火技术或管理措施胜利或失败的能够性能够影响到一切或全部火灾场景发生的能够性。某一防灭火技术或管理措施失败的能够性越低，那么

38、那些导致不希望发生后果的火灾场景发生的能够性就越低。For example, if Event D is not the desired end point, then lower probabilities of failure of fire protection measures will lead to a lower probability of the undesirable fire Scenario ABD. If the probabilities of failure of the two fire protection measures are reduced to 0.

39、01, the probability of the undesirable Scenario ABD is reduced to 0.0001.2.2.2 将防、灭火技术或管理措施视为“火灾妨碍措施在建筑火灾风险评价的过程中，可基于以下五个重要事件来构建事件树：.起火fire ignition, 2.火势增长fire growth, 3.烟气传播smoke spread, 4.人员疏散失败failure of occupants to evacuate, 5-消防人员呼应失败failure of fire department to respond (Yung and Benichou, 2

40、003).将它们视为重要事件是由于每个事件都与火灾开展的主要阶段或危害有关。2.2.2 Fire Protection Measures as Fire BarriersFor fire risk assessments in buildings, the event tree can be constructed based on the following five major fire events. They are considered major events because each is related to a major phase of fire development

41、and hazard: fire ignition, fire growth, smoke spread, failure of occupants to evacuate, and failure of fire department to respond (Yung and Benichou, 2003).1. 起火是初始事件，比如烟蒂引燃卧室床上物品或引燃起居室的沙发。防、灭火技术或管理措施包括防火教育、控制火源、运用阻燃资料等，这些都将降低起火的能够性和相应的风险。1. Fire ignition is the initiating event, such as cigarette i

42、gnition of a couch in a living room or a mattress in a bedroom. Fire protection measures include fire prevention education, or the use of fire-retarded material in furniture, which would help to reduce the probability of occurrence of this event and the consequential risks.2. 火势增长是第二个重要事件，这个过程包括多种火势

43、增长类型，比如阴燃火灾(smouldering fires)或轰燃后的全盛期火灾(post-flashover fires)。防、灭火技术或管理措施包括喷水系统、防火分隔和带有自闭器的门，这些措施可以控制或限制火势并降低其相应的风险。风险降低的程度决议于这些火势增长控制措施的可靠性和有效性(reliability and effectiveness)。2. Fire growth is the second event, which includes various types of fire growths, from fires developing into smouldering fi

44、res to fires developing into post-flashover fires. Fire protection measures include sprinklers, compartmentation and door self-closers, which would help to contain these fires and reduce their consequential risks.The reduction in risk depends on the reliability and effectiveness of these fire contro

45、l systems.3. Smoke spread to critical egress routes and other locations in a building is the third event. Fire protection measures include door self-closers, smoke control, and stairwell pressurization, which would help to contain the smoke and reduce its consequential risks.The reduction in risk de

46、pends on the reliability and effectiveness of these smoke control systems.3. 烟气传播到疏散必经的途径上或传播到建筑内某些位置上，是第三个重要的事件。防、灭火技术或管理措施包括带有自闭器的门、防排烟系统和疏散楼梯间/前室的加压送风系统等，这些措施有助于将火灾产生的烟气限制在一定空间内或排出到建筑外，从而降低其相应的风险。风险降低的程度决议于这些控烟措施或系统的可靠性和有效性(reliability and effectiveness)。4.人员疏散失败是第四个重要事件，它通常是火或烟气传播到疏散途径上的结果。防、灭火技

47、术或管理措施包括感烟、感温等火灾报警器、语音通讯设备、被维护的疏散通道、避难区或避难层、应急呼应教育和疏散演练，这些措施可以向人员提供火灾的早期报警，平安的疏散通道，快速的应急呼应和迅速的疏散，疏散到暂时平安的避难区域或疏散到着火建筑外。风险降低的程度决议于早期报警系统和疏散通道维护系统的可靠性和有效性，常规的人员应急呼应教育和疏散演练的实施贯彻情况。4. Failure of occupants to evacuate as a result of the spread of fire and smoke to egress routes is the fourth event. Fire

48、protection measures include smoke alarms, voice communication, protected egress routes, refuge areas, and evacuation training and drills, which would help to provide early warnings to occupants, safe egress routes, quick occupant response and evacuation to either exit the building or to seek tempora

49、ry protection in refuge areas.The reduction in risk depends on the reliability and effectiveness of these early warning and evacuation systems and the implementation of regular occupant training and evacuation drills.5.消防人员呼应失败为第五个重要事件，即消防人员没能及时呼应，赶至火场挽救被困人员和实施灭火。防、灭火技术或管理措施包括向消防部门的火灾早期报警安装和足够的可调配灭火

50、资源。可调配的灭火资源普通不完全是火灾平安工程工程的设计内容，但却是火灾风险评价过程中需求思索的要素。风险降低的程度决议于向消防部门早期火灾报警安装的可靠性和可调配灭火资源的充分程度。5. Failure of fire department to respond in time to rescue any trapped occupants and control the fire is the fifth event. Protection measures include early fire department notification and adequate fire depar

51、tment resources. The reduction in risk depends on the reliability of early notification and adequacy of fire department resources.Except for the occupants in the room of fire origin, all of the above five major hazardous events must occur before a fire can cause harm to the occupants. Each of the fi

52、ve hazardous events, however, can only happen if the fire protection measure for that event fails to prevent that event from happening. The fire protection measure for each event, therefore, can be viewed as a major barrier to that event.除了起火房间内的人员，一切以上五个重要的危害性事件必需全部发生才干对人员产生损害，使其受伤或导致人员死亡。只需在针对某一重要

53、危害性事件的防、灭火技术或管理措施失效或失败的条件下，这一危害性事件才可以发生。因此将针对某一危害性事件的防、灭火技术或管理措施视为“针对这一重要火灾事件的重要妨碍措施(a major barrier to that event)。如图2.2，在发生火灾和使人员遭到损伤之间，可以有五种“重要妨碍措施。妨碍人员疏散失败的措施即为方便人员疏散胜利的措施。妨碍消防人员呼应失败的措施即为方便消防人员胜利呼应的措施。Potentially, there can be five major barriers between a fire and the people, as depicted in Fig

54、ure 2.2. The barrier to prevent failure of occupant to evacuate is to facilitate occupant evacuation. The barrier to prevent failure of fire department to respond is to facilitate fire department response.应留意的是，每一个“重要的妨碍措施是由一系列单独的妨碍措施组成的，一个“重要的妨碍措施 失败的缘由能够是这些单独的“妨碍措施部分或全部失效的结果，要详细进展分析。比如，火灾增长的“重要的妨碍

55、措施 能够包括自喷系统、耐火分隔和带有自闭器的门等。显然，在某一建筑中往往并不同时全部具备以上五种“重要的妨碍措施。详细能够具有哪些“火灾妨碍措施决议于建筑规范的要求和建筑防火设计和管理情况。但应该说， 一个建筑具有的“火灾妨碍措施 越多，具有的“火灾妨碍措施越有效，其火灾平安情况就会越好。Obviously, not all of these fire barriers are necessarily put in place in any building. How many are put in place depends on how many are required by the

56、building regulations and how well the fire protection design is. But the more they are put in place, the better is the protection. Also, the more effective the barrier is, the better is the protection.图2.2 火源和人员致命伤亡之间的五种“重要火灾妨碍措施 Figure 2.2 Five major fire barriers between a fire source and fatality

57、 (from Yung and Benichou, 2003).如前面章节的论述，人员面临的风险决议于一切防、灭火技术或管理措施，即“火灾妨碍措施失败或失效的概率或能够性。比如，假设根本没有任何“火灾妨碍措施，就意味着没有任何防、灭火技术或管理措施，那么导致人员损伤或死亡的火场场景发生的能够性为100%或概率为。因其所构成的火灾场景为：火灾发生火势增长烟气传播人员平安疏散失败消防人员施救和灭火失败。假设五种“重要的火灾妨碍措施同时具备，每一种“重要的火灾妨碍措施 都有一半的能够(失效概率为0.5)失效，一切这五种“重要的火灾妨碍措施都失效的概率为：0.5 0.5 0.5 0.5 0.5 =0.

58、03125.这种情况下，五种“重要的火灾妨碍措施全部失效的火灾场景发生，导致人员伤亡的能够性为0.03125。The risk to the occupants depends, as discussed in the previous section, on the probability of failure of all fire protection measures, or barriers. For example, if there are no barriers at all, there is no protection. The probability of the fir

59、e scenario that can lead to harm to the occupants is 100 %, or 1.If there are five barriers and each barrier has a probability of failure of 0.5, the probability of failure of all five barriers is 0.5 0.5 0.5 0.5 0.5 or 0.03125.The probability of the fire scenario that can lead to harm to the occupa

60、nts is 0.03125. 人员面临的风险并不仅仅决议于火灾场景发生的能够性或概率的大小，还决议于火灾场景所产生后果对人员呵斥的真实的损伤或危害程度(见方程2.2) 。火灾场景的后果断定于建筑内火势增长的速度、烟气传播的速度以及人员疏散的速度，这些将在下一节中进展简单的讨论。The risk to the occupants depends not only on the probability of the fire scenario, but also the actual harm to the occupants as a result of the consequence of