5_定量火災(zāi)風(fēng)險(xiǎn)評(píng)估-文庫(kù)吧
2025-02-27 05:22 本頁(yè)面
【正文】 binations is assessed using a residual multiplication factor of the inherent values of the probability or the consequence. ? This allows the fire protection engineers and the regulators to assess the impact of these fire protection measures based on their assessments of the reduction of the inherent values. ? One way to assess the impact of fire protection measures is through the use of statistical information, if they are available. ? Unfortunately, such information is not always available. ? The information may be in the databases of collection agencies, but not necessarily in their published reports which usually show general information and not the specific information that is required for fire risk assessment. ? If no such information is available, subjective judgment may be required. ? Otherwise, the use of fundamental and rational approach to quantification is required, including the use of mathematical modeling of fire development and occupant evacuation, which will be discussed in later chapters. ? For example, there is some statistical information on the benefits of restricting smoking material and of installing sprinklers, but not much information on the benefits of implementing regular evacuation drills. ? NFPA statistics show that approximately 7% of fires in homes are caused by smoking materials (NFPA Fire Statistics, 2023) and approximately 14%of these fires occur in the main living area (Hall, 2023). ? Therefore, 7 14% or approximately % of fires in homes are fires that both originate in the main living area and are caused by smoking material. ? If these fire statistics can also apply to Canadian homes, then restricting smoking material in the main living area would reduce the number of fire occurrence in the main living area from % (see Table in Chapter 3) to % of house fires. ? The reduction of fire occurrence from to % is 12 %. The corresponding residual multiplication factor of the inherent probability value by restricting smoking material is therefore , which is shown in Table . ? NFPA statistics also show that, based on 1989–1998 data, the reduction in deaths in one and two family dwellings with sprinklers is 51% when pared with similar dwellings without sprinklers (Kimberly and Hall, 2023). ? The corresponding residual multiplication factor of the inherent consequence value by installing sprinklers is therefore , which is shown in Table . ? With regard to the benefits of implementing regular evacuation drills, there is no information on the reduction of death rates that is easily available. ? For this example, we have to make an assumption. ? We know that if regular evacuation drills are carried out, there will be faster evacuations and therefore lower death rates. For this example, let us assume a reduction of the death rate by 60 %. ? The residual multiplication factor of the inherent consequence value by implementing regular evacuation drills is therefore , which is shown in Table . ? In actual fire risk assessments, this value needs to be judged and agreed upon between the fire protection engineers and regulators. ? Table also shows that the impacts on the consequence of installing sprinklers and of implementing regular evacuation drills are multiplied together. That is, the benefits of sprinklers and of regular evacuation drills have a bined residual consequence factor of or . ? The multiplication of the residual factors is based on the argument that each fire protection measure reduces the residual death rate by a certain percentage in succession. ? The death rate is first reduced by the sprinklers suppressing the severity of the fires, and then further reduced by faster evacuation of the occupants. ? The reduction of the risk values of the six binations of additional fire protection measures is shown in Table . ? The residual risk multiplication factors range from to . ? The quantification of the risk values allows numerical parisons of the various fire protection options. ? This is not the case in qualitative fire risk assessment (Table in Chapter 4). ? It should be emphasized again that the values in Table are selected as an example to show how such a checklist method can be carried out. These values were selected from available statistical information without much indepth search. ? As more statistical information bees available, more extensive search and detailed analysis are needed to find the correct values. ? In actual fire risk assessments, these values need to be carefully selected and agreed upon by stakeholders. ? In actual fire risk assessments, these values need to be carefully selected and agreed upon by stakeholders. ? Subjective judgment of the probabilities and consequences provides a quick assessment of the potential fire risks. ? More fundamental and rational approaches to quantification, including the use of mathematical modeling of fire development and occupant evacuation, will be discussed in later chapters. ? EventTree Method ? An event tree is another way to identify potential fire hazards, assess their probabilities and consequences, and arrive at risk values. Different from the checklist method, an event tree shows more than a list of potential fire hazards and fire protection measures for the assessment of the probabilities, consequences and eventually the risk values. ? The e
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