5_定量火災(zāi)風(fēng)險(xiǎn)評(píng)估(已修改)
2025-03-17 05:22 本頁(yè)面
【正文】 ? Overview ? In this chapter, quantitative fire risk assessment is introduced. ? The term quantitative fire risk assessment refers to an assessment involving numerical quantifications not only of the probability a fire hazard, or fire scenario occurring, but also the consequences of that fire hazard or fire scenario. ? By multiplying the numerical values of probability and consequence each fire scenario is given a numerical fire risk value. ? By accumulating the sum of the risk values from all probable fire scenarios we can obtain an overall fire risk value. ? The overall fire risk value can be used for parisons with those of alternative or codepliant fire safety designs. ? In general there are two ways to perform systematic quantitative fire risk assessments as follows: ? 1. by using a checklist to go through a list of potential fire hazards and the quantitative assessment of their fire risks。 ? 2. by using an event tree to go through a set of potential fire scenarios and the quantitative assessment of their fire risks. ? In both these methods, the values for the probability and consequence parameters are obtained from statistical data, if they are available, or from subjective judgment, if such data are not available. ? (僅在我們本課程的講解中，采用了統(tǒng)計(jì)或主觀估計(jì)的方式，火災(zāi)的結(jié)果還可以通過確定性的分析計(jì)算獲得 ) ? Checklist Method ? As was discussed in Chapter 4, the checklist method employs the creation of a checklist of potential fire hazards and the consideration of fire protection measures, either in place or to be added, to arrive at an assessment of the fire risks. ? The creation of a checklist of potential fire hazards allows a systematic check of potential fire hazards that are in place. ? The listing of fire protection measures alongside with the potential fire hazards allows a quick check of any safety deficiencies and any need to provide additional fire protection measures to minimize the risk. ? The checklist method, therefore, is an enumeration of potential fire hazards, fire protection measures, either in place or to be added, and the assessment of the residual fire risks. ? It is used to identify any deficiencies and any corrective measures needed to minimize the fire risks. ? It does not include, however, the consideration of the logical development of fire events, which will be discussed in Section using an event tree. ? An example of a checklist method employing quantitative fire risk assessment is shown in Table . This is the same example that was used in Chapter 4, except that quantitative assessment is employed here rather than qualitative assessment. ? This example looks at a potential fire hazard in the living room of a house and the consideration of a number of additional fire protection measures to minimize the risk. ? Obviously, there could be many potential fire hazards in a house. ? A plete fire risk assessment would involve the identification of all potential fire hazards and the consideration of various fire protection measures to minimize the risk. ? A typical house usually has some fire protection measures, such as smoke alarms. Additional fire protection measures would lower the risk further. Similar to the example in Chapter 4, this example considers six different binations of three additional fire protection measures. ? The three additional fire protection measures are: ? (1) no smoking material (such as cigarettes) in the living room, ? (2) sprinklers ? (3) regular evacuation drills. ? Each of the three fire protection measures has an impact on either the probability of fire occurrence or the consequence of a fire occurrence. ? For example, the measure of ‘no smoking material in the living room’ would have an impact on lowering the probability of fire occurrence。 ? whereas the measures of ‘sprinklers’ and ‘regular evacuation drills’ would have an impact on lowering the consequence of a fire occurrence by suppressing or controlling the fire or by allowing the occupants to evacuate more quickly. ? It should be emphasized that this is just an example to show how quantitative fire risk assessment can be carried out using a checklist method. There are no standard checklist methods in fire risk assessment. ? In Table , the inherent fire risk values (without the help of any fire protection measures) were obtained previously in Chapter 3. Table in Chapter 3 shows that the probability of fire occurrence in Canadian houses was 10?3 fires/house/year in 1996 and the percentage of these house fires that occurred in the main living area was %. ? Using these figures, the probability of fire occurrence in the main living area in Canadian houses in 1996 was, therefore, 10?3 % or 10?4 fires/house/year. ? Table in Chapter 3 also shows that the consequence of fires originating in the main living area in 1996 was 10?3 deaths/fire, and the resultant risk to life from these fires was 10?6 deaths/house/year. ? These previously obtained inherent risk values are used in the present example and are shown in Table . ? The inherent risk values in Table were based on fire statistics which included some fire protection measures, such as smoke alarms, that were required by regulations. If additional fire protection measures are put in place, the inherent fire risks would be further reduced. ? In Table , the impact of each of the six fire protection
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