【正文】 d the occupants receive the warning signals and evacuate the building. ? 火災(zāi)場(chǎng)景的簡(jiǎn)單例子： ? (1)火災(zāi)發(fā)生了轟燃－報(bào)警系統(tǒng)沒有啟動(dòng)－人員沒有接收到報(bào)警信號(hào)－人員被因于火場(chǎng)中。比如，我們以一個(gè)發(fā)生在房間唯一安全出口處的火災(zāi)為例，發(fā)生火災(zāi)的房間中有一定數(shù)量的人員。 ? 比如，事件Ａ（應(yīng)用滅火器滅火）成功，則接下來到事件 C（燃燒熄滅，火災(zāi)終結(jié)）結(jié)束； ? 而如果事件Ａ（應(yīng)用滅火器滅火）失敗，則接下來繼續(xù)到事件 B（應(yīng)用消火栓滅火）。 ? Mutually exclusive events ? Based on this, Scenario A–C has a probability of . Scenario A–B–E has a probability of , obtained by multiplying the probability of A–B () and that of B–E (). ? Similarly, Scenario A–B–D has a probability of . ? The bined 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 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 oute. ? 這里有一點(diǎn)比較重要，需引起我們的注意。 ? 風(fēng)險(xiǎn)降低的程度決定于這些火勢(shì)增長(zhǎng)控制措施的可靠性和有效性 (reliability and effectiveness)。 防、滅火技術(shù)或管理措施包括向消防部門的火災(zāi)早期報(bào)警裝置和足夠的可調(diào)配滅火資源。阻礙消防人員響應(yīng)失敗的措施即為方便消防人員成功響應(yīng)的措施。因其所形成的火災(zāi)場(chǎng)景為： ? 火災(zāi)發(fā)生－火勢(shì)增長(zhǎng)－煙氣傳播－人員安全疏散失?。廊藛T施救和滅火失敗。則兩種措施均失敗的概率為 ，這時(shí)導(dǎo)致人員傷亡發(fā)生的火災(zāi)場(chǎng)景出現(xiàn)的概率亦為 ，這個(gè)可能性要小于前面具備五種“重要的火災(zāi)阻礙措施”的情況，因?yàn)榍懊胬又忻糠N“重要的火災(zāi)阻礙措施”失敗的概率為 。圖 ，在火災(zāi)風(fēng)險(xiǎn)評(píng)估過程中，人員的疏散與火勢(shì)的控制同樣重要，在疏散路徑上，如果在危險(xiǎn)臨界條件出現(xiàn)之前，人員能夠疏散到安全的地方，可以說對(duì)人員而言，不存在風(fēng)險(xiǎn)。 ? 再者，多數(shù)住宅沒有噴水系統(tǒng)或能防火隔離的起居室，包括有隔離功能的門，通常也不具備，以將火災(zāi)限制在起居室中。如果人員能夠在轟燃發(fā)生前逃生，則“阻礙措施４”具備。 ? 通常還會(huì)有火災(zāi)報(bào)警系統(tǒng) (“火災(zāi)阻礙措施 4” )以向公寓中的人員提供火災(zāi)初期的報(bào)警，還具備疏散樓梯間 (“火災(zāi)阻礙措施 4” ) ，幫助人員安全疏散。 ? 簡(jiǎn)言之，住宅建筑只有“阻礙措施 4” 和“阻礙措施 5”，并且在火勢(shì)增長(zhǎng)迅速的情況下，它們只有及早動(dòng)作或及時(shí)響應(yīng)才有效。 ? Secondly, most houses don’t have sprinklers or enclosed living rooms, including closed doors, to contain the fire in the living room. Therefore, Barrier 2 is not there and fire will grow with certainty. ? Thirdly, most houses don’t have smoke control system to prevent the smoke from spreading to the whole house, including any egress paths such as stairs. Therefore, Barrier 3 is not there and smoke will spread with certainty. ? Fourthly, houses usually have smoke alarms to give early warnings. However, they are only effective if they work and work early so occupants can have enough time to escape. But fires involving upholstered furniture can be very fast, developing into flashover fires in just minutes. ? That is why the time factor is important in fire risk assessment. If the occupants can escape before the fire develops into a flashover fire, then Barrier 4 is there. ? 第四方面，住宅建筑通常有感煙報(bào)警器，能夠較早報(bào)警。 ? 在后續(xù)章節(jié)中，將討論按時(shí)間變化的火災(zāi)場(chǎng)景計(jì)算模型的基本原理。 ? For example, two fire protection measures with an individual probability of failure of would provide a bined probability of failure of , which is less than that of one fire protection measure alone. ? 火災(zāi)后果模化中的時(shí)間因素 ? 如前面所述，“火災(zāi)阻礙措施”以兩種途徑幫助降低火災(zāi)風(fēng)險(xiǎn)： ? (1) 控制火災(zāi)發(fā)生區(qū)域火勢(shì)的增長(zhǎng)，控制火勢(shì)向其他區(qū)域的傳播； ? (2)方便人員的疏散和消防人員的響應(yīng)。 ? 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 that scenario (see Equation ). The consequence of that fire scenario depends on how fast the fire and smoke spread in the building and how quickly the occupants evacuate the building, which will be discussed briefly in the next section. ? 評(píng)估火災(zāi)場(chǎng)景的可能性、后果和風(fēng)險(xiǎn)的大小是本課程后續(xù)章節(jié)的重點(diǎn)。具體可能具有哪些“火災(zāi)阻礙措施”決定于建筑規(guī)范的要求和建筑防火設(shè)計(jì)和管理情況。只有在針對(duì)某一重要危害性事件的防、滅火技術(shù)或管理措施失效或失敗的條件下，這一危害性事件才能夠發(fā)生。 ? ，它通常是火或煙氣傳播到疏散路徑上的結(jié)果。 Fire Protection Measures as Fire Barriers ? For 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 and hazard: fire ignition, fire growth, smoke spread, failure of occupants to evacuate, and failure of fire department to respond (Yung and Benichou, 2023). ? 1. 起火是初始事件，比如煙蒂引燃臥室床上物品或引燃起居室的沙發(fā)。 ? 而事件 A–C, A–B–D 和 A–B–E 形成了此事件樹全部的火災(zāi)場(chǎng)景，共有三個(gè)。 ? 通常建筑內(nèi)有控制火災(zāi)增長(zhǎng)或迅速傳播的措施，為人員和財(cái)產(chǎn)提供了保護(hù)，延緩了火災(zāi)的傳播，如滅火系統(tǒng)或煙氣阻隔措施； ? 通常還有火災(zāi)早期探測(cè)和報(bào)警的措施，幫助人們?cè)诨饎?shì)擴(kuò)大前及時(shí)疏散到安全的區(qū)域； ? 通常消防人員也可能較早地接收到火警，能夠及時(shí)趕赴火場(chǎng)并展開滅火和人員施救。 ? 合理構(gòu)建火災(zāi)場(chǎng)景并分析其發(fā)生的可能性，對(duì)所建立的火災(zāi)場(chǎng)景后果的盡量符合實(shí)際的分析、計(jì)算或模擬，是決定火災(zāi)風(fēng)險(xiǎn)評(píng)估結(jié)果可信度的關(guān)鍵。 ? 火災(zāi)中的一個(gè)事件－ A fire event 是火災(zāi)中發(fā)生的，與起火、火災(zāi)增長(zhǎng)、煙氣傳播、建筑物結(jié)構(gòu)響應(yīng)、人員疏散或消防人員響應(yīng)相關(guān)的事件，如果不是在火災(zāi)中發(fā)生的，或與火災(zāi)的上述過程無關(guān)的事件，則不視為火災(zāi)中的一個(gè)事件。 () ? Consider, as an example, the assessment 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 scenario. () ? If the probability of a certain fire scenario occurring in a building is once every 20 years, then P = fires per year. ? If the consequence of that fire scenario is two deaths, then C = 2 deaths per fire. ? From Equation , the expected risk to life as a result of that fire scenario is equal to deaths per year, or 1 death every 10 years. ? 比如建筑中某一火災(zāi)場(chǎng)景發(fā)生的可能是２０年一次，則： P = fires per year ? 如果這個(gè)火災(zāi)場(chǎng)景的后果是死亡２人，則 C = 2 deaths per fire ? 從式 ()可知，這個(gè)火災(zāi)場(chǎng)景的預(yù)計(jì)生命風(fēng)險(xiǎn)為 the expected risk to life ＝ deaths per year 或都 1 death every 10 years. 每年 10年死亡１人。 ? 因此一個(gè)火災(zāi)場(chǎng)景發(fā)生的可能性 (probability)決定于這一系列事件中每一個(gè)防、滅火技術(shù)或管理措施的成功或失效 /失敗的可能性。 ? A fire scenario involves the projection of a set 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. ? 對(duì)人員的風(fēng)險(xiǎn) (risk)既決定于能夠?qū)θ藛T產(chǎn)生損害(harm)的火災(zāi)場(chǎng)景發(fā)生的可能性，又決定于火災(zāi)場(chǎng)景或者說火災(zāi)場(chǎng)景產(chǎn)生的后果 (consequence )對(duì)人員造成損害的程度或水平 (level of harm )。 ? 當(dāng)然在建筑中發(fā)生火災(zāi)的方式不止一種，那么對(duì)人員的風(fēng)險(xiǎn)通常要基于所有可能的火災(zāi)場(chǎng)景來進(jìn)行評(píng)估。 比如，火災(zāi)中發(fā)生的聲、光報(bào)警是一個(gè)火災(zāi)事件；火災(zāi)中發(fā)生的斷電或停水也是火災(zāi)不同的兩個(gè)事件；而沒有發(fā)生火災(zāi)時(shí)的停水，就不是一個(gè)火災(zāi)