[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-109-1-fire-science-035":3},{"subject":4,"subjectSlug":5,"subjectKicker":6,"subjectShort":7,"question":8,"related":27,"sameNumber":52,"hasEssay":26},"火災學概要","fire-science","火災學 · Fire Science","火災學",{"id":9,"webId":10,"year":11,"session":12,"subject":4,"number":13,"stem":14,"options":15,"answer":20,"answerNote":21,"images":22,"imagesPending":23,"lawTimestamp":11,"explanation":24,"explanationDeep":25,"freq":12,"indexable":26},"fire-109-1-火災學概要-035","fire-109-1-fire-science-035",109,1,35,"有關引火性液體的敘述，下列何者正確？",{"A":16,"B":17,"C":18,"D":19},"蒸氣比重小於 1，滯留低窪區著火危險","閃火點低，易著火爆炸","不易累積靜電","液體比重大，不易浮於水面","B",null,[],false,"本題考點：引火性液體的物理危險特性，包括閃火點、蒸氣比重、液體比重與導電度四項指標的正確方向。\n【正解理由】引火性液體之所以被列為高危險物質，關鍵在閃火點低。閃火點是液面上方蒸氣與空氣形成之混合氣達到爆炸下限、遇火源即閃燃的最低液溫，汽油約在攝氏負四十度上下，遠低於常溫，代表在一般室溫下液面就已備妥爆炸下限以上的蒸氣濃度，遇靜電火花或明火即可著火，密閉空間內更可能演變為蒸氣爆炸。故選 B。\n【逐項排除】\n(A) 敘述方向相反。汽油、苯等引火性液體之蒸氣比重多在二至四之間，大於一，洩漏後才會沿地面流動並積聚於低窪處、坑溝與地下室而形成延遲引燃的危險；若蒸氣比重真的小於一，蒸氣會上升擴散，反而不會滯留低窪區，前後半句彼此矛盾。\n(B) 正確。閃火點低代表常溫即可持續供應可燃蒸氣，是引火性液體管制分級的核心指標。\n(C) 敘述錯誤。引火性液體多為非極性有機溶劑，導電度低、體積電阻率高，灌裝、攪拌、輸送摩擦所產生的電荷不易洩漏至大地，屬於極易累積靜電的物質，因此裝卸時才要限制流速並確實接地。\n(D) 敘述錯誤。汽油約零點七、苯約零點八八，多數引火性液體比重小於一而浮於水面，因此直接以水柱射水會使燃燒中的液體隨水漂流擴大火勢。\n【記憶點】引火性液體記八個字：蒸氣重、液體輕、閃火點低、電荷跑不掉。","閃火點與著火點常被混為一談：閃火點是蒸氣濃度剛好達爆炸下限、遇火源可閃一下但火焰無法持續的最低液溫；著火點還要再高約攝氏五到十度，蒸氣供應速率才足以維持連續燃燒。引火性液體的危險性正來自其閃火點多落在常溫以下或附近，等於容器一開蓋，可燃混合氣就已經備妥；防火管理上也是依閃火點高低將這類液體分級，閃火點愈低者管制愈嚴、允許存放量愈小。\n蒸氣比重是以空氣（平均分子量約二十九）為基準的相對值，等於該蒸氣分子量除以二十九。汽油主成分為碳數五到十的烷類，分子量七十以上，蒸氣比重約三到四，洩漏後蒸氣沿地面流動、積聚於地下室、電纜溝與集水井，常在遠離洩漏點之處被引燃再回燒至洩漏源，這是加油站與油庫火災調查的重點。\n靜電方面，判斷是否易累積的指標是體積電阻率，一般以十的十次方歐姆公分為界，超過此值電荷即難以自然洩漏，多數石油系溶劑都在這個範圍以上，所以流動帶電、噴出帶電特別明顯，對策是限制輸送流速、延長靜置時間、接地與跨接，並避免以絕緣性塑膠容器盛裝。\n液體比重則決定滅火劑的選擇：汽油、苯等比重小於一而浮於水面，射水只會造成流動火災，故 B 類火災以泡沫覆蓋液面窒息、或以二氧化碳、乾粉抑制為主；而酒精、丙酮等水溶性液體會破壞一般泡沫的膜，需改用耐酒精型泡沫原液。同一考點的延伸方向包括爆炸範圍與閃火點的關係、蒸氣密度與通風口高度的設計思維，以及重質油品儲槽的沸溢與濺溢現象。此外閃火點的測定分密閉式與開放式兩種杯具，開放式因蒸氣易逸散，測得值通常略高於密閉式；大氣壓力降低時閃火點亦隨之下降，高地環境中同一液體更容易閃燃，這些都是常見的觀念陷阱。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-109-1-fire-science-034","BLEVE 的發生，下列敘述何者錯誤？",34,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-109-1-fire-science-036","房間的體積為 V=6 m×5 m×3 m，其中 O2 占 0.21 V，請問至少要加入多少公升（L）的 CO2 讓燃燒作用無法持續？",36,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-109-1-fire-science-033","乙醇之燃燒化學反應式為下列何者？ 9 3",33,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-109-1-fire-science-037","D 類火災可使用的滅火劑，何者適合？",37,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-109-1-fire-science-032","已知天花板噴流溫度攝氏 135℃，天花板噴流速度 1.8 m\u002Fs，環境初始溫度 20℃，感知撒水頭作動溫度攝氏 72℃，反應時間指數 67(m1\u002F2s1\u002F2)，感知撒水頭作動時間為下列何者？（提示： ln115=4.74, ln63=4.14）",32,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-109-1-fire-science-038","在橡膠中混入碳黑所製成的產品可防止人體帶靜電，其防止靜電發生的方法為？",38,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-113-1-fire-science-035",113,"某鑄造工廠因高溫鋁水洩漏，遇水引發爆炸，此為何種爆炸？",{"webId":58,"year":59,"stem":60,"number":13},"fire-112-1-fire-science-035",112,"相較於氣體爆炸，一般的粉塵爆炸具有下列那種性質？",{"webId":62,"year":63,"stem":64,"number":13},"fire-111-1-fire-science-035",111,"下列何者為乾粉最主要滅火原理？",{"webId":66,"year":67,"stem":68,"number":13},"fire-110-1-fire-science-035",110,"面對廚房油鍋起火燃燒，下列何項應對動作的風險最大？",{"webId":70,"year":71,"stem":72,"number":13},"fire-108-1-fire-science-035",108,"為避免液化石油氣儲槽因外圍起火燃燒，一時無法撲滅而發生 BLEVE 現象，可採取之防救策略下列何者正確？",1785129967412]