當區劃空間的火災燃燒猛列程度達到大規模火災時，會對建築物結構完整防火性能構成威脅。結構防火完整性能係指阻隔元件能夠在一區劃空間發生最大的火災猛列度下繼續履行阻隔元件所具備的功能，不因火勢的侵害，造成裂縫、破洞或穿孔，而使火勢與高溫煙氣蔓延至阻隔元件的非受火面。為了針對區劃空間在發生閃燃火災情境下，結構完整性能失敗之情形作進一步的瞭解，文中建立預測閃燃火災發生的模式，估計閃燃發生的機率□值；以可靠度設計為基礎，建構機率型模式，來預測閃燃火災發生條件下，區劃空間結構完整性失敗之條件機率□，並利用一階二次矩估計機率值□，文中也列舉一實際應用所建構的預測模式；最後以閃燃發生的機率，與閃燃火災發生條件下區劃空間結構完整性失敗之條件機率，兩者的乘積即□×□來估計閃燃火災發生時，區劃空間結構完整防火性能失敗的機率（□）。

When fire severity of a building compartment reaches fully-developed phase, it probably threatens the structural fire resistance. Structural integrity is defined as the ability of performing its fire separating function from preventing the occurrence of element crack, penetration and fire spread to unexposed parts during maximum ire severity. In order to understand the probability of failure of structural integrity under flashover fire situation, the model for predicting the probability of flashover fire (□) is established. Based on reliability-based design a probabilistic model for estimating the failure probability in compartment structural integrity given flashover occurrence (□) is also established. First Order Second Moment is employed to analyze the system performance of structural integrity. An example is illustrated to validate the model. Finally, the failure probability of structural integrity (□) in a compartment is estimated by the product of Pt and □.