[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-112-1-fire-science-028":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-112-1-火災學概要-028","fire-112-1-fire-science-028",112,1,28,"下列那一種前期現象比較可能因後續的消防滅火或救援作為而引發複燃？",{"A":16,"B":17,"C":18,"D":19},"天花板下熱煙層的輻射回饋使可燃物快速升溫","火勢快速成長而呈現旺盛燃燒現象","天花板下熱煙層的濃度處於燃燒範圍內","火場持續處於封閉式高溫悶燒的狀態","D",null,[],false,"本題考點：複燃（backdraft）的前期條件，要與閃燃、滾燃的前兆現象區辨。\n【正解理由】依複燃的成立機制，密閉且高溫的火場因氧氣被消耗殆盡而轉為悶燒，可燃物持續受熱裂解，產生大量一氧化碳等未燃可燃氣體並蓄積於室內，其濃度遠高於燃燒上限而暫時無法燃燒；當滅火或救援作為開啟門窗、破壞開口時，新鮮空氣湧入把過濃的可燃氣體稀釋回燃燒範圍之內，遇高溫或殘火即發生爆炸性燃燒。故選 D。\n【逐項排除】\n(A) 熱煙層的輻射回饋使可燃物快速升溫，是閃燃的典型前期現象，走的是熱蓄積路徑，與後續供氧無關。\n(B) 火勢快速成長而旺盛燃燒，代表氧氣供應仍然充足、屬燃料控制的成長期，不會形成缺氧而蓄積未燃氣體的條件。\n(C) 熱煙層濃度已落在燃燒範圍之內時，只要有引火源當場即會延燒成滾燃，不必等待外部供氧稀釋，因此不是複燃的典型前期狀態。\n(D) 火場持續封閉、高溫悶燒，使未燃可燃氣體大量累積且濃度過濃，正是複燃所需的前期條件，為正解。\n【記憶點】複燃是「悶燒缺氧＋開門供氧」，閃燃是「熱蓄積」；一個在等空氣，一個在等溫度。","複燃又稱回燃（backdraft），是密閉空間火災中最具威脅的突發現象之一。其形成過程可拆成三段：第一段，火災在封閉空間內消耗氧氣，室內氧濃度降到燃燒難以維持的水準，明火轉為悶燒；第二段，高溫使可燃物持續熱裂解，產生一氧化碳、甲烷、氫及各種碳氫裂解物，這些氣體因缺氧而無法燃燒，在室內蓄積成濃度高於燃燒上限的「過濃」狀態，同時保有數百度的高溫；第三段，開口一旦被開啟，空氣以重力流方式湧入，把過濃氣體由上限之上稀釋回燃燒範圍，火焰隨即沿混合區高速傳播，並因氣體受熱膨脹而由開口猛烈噴出。\n文獻歸納的前兆包括：門窗與牆面異常燙手、室內看不到明火卻有濃厚黑煙、煙由縫隙呈脈動式進出、玻璃內側附著油狀凝結物並被燻黑、開口處有吸入氣流的嘯聲。這些徵候的共同點都指向同一件事：室內是高溫、缺氧、可燃氣體過濃的狀態。\n三個常一起考的名詞務必對照清楚。閃燃是熱蓄積達到臨界後全面起燃，發生在通風尚足的成長期末段，觸發因子是溫度與輻射熱通量；複燃是缺氧蓄積可燃氣體後因供氧而爆燃，觸發因子是氧氣；滾燃是天花板下方累積的未燃氣體先行延燒、火舌沿頂棚滾動前伸，常是閃燃的前奏。另有煙氣爆炸，指流入鄰室的煙氣在該處與空氣形成可燃混合後被引燃，與複燃的差別在於發生位置不在原火場。\n條件面可用一組數值互相對照記憶：閃燃以熱煙層達攝氏五百至六百度、地板輻射熱通量每平方公尺約二十千瓦為判準；複燃則以室內氧濃度降到約百分之十五以下、未燃氣體濃度高於燃燒上限、室溫仍維持在數百度為條件，兩者一個看溫度、一個看氧與濃度。本考點常延伸考三者的溫度、氧濃度與可燃氣體濃度條件對照，以及排煙與開口操作時機對火行為的影響。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-112-1-fire-science-027","下列何種措施於室內發生火災時有助於防止或延緩閃燃的發生？",27,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-112-1-fire-science-029","有關重油油槽發生火災時可能產生的大規模沸溢（boilover）現象，下列敘述何者錯誤？",29,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-112-1-fire-science-026","下列何種靜電災害預防措施旨在防止靜電蓄積，而與其他旨在減少靜電產生的措施有所不同？",26,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-112-1-fire-science-030","滅火藥劑的供給率關乎火災初期的滅火成敗、滅火時間與藥劑使用量，下列敘述何者錯誤？",30,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-112-1-fire-science-025","對可燃性氣體而言，下列那一種特性或條件所衍生的燃燒或爆炸風險相對較高？",25,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-112-1-fire-science-031","在長寬高為10×10×4 公尺的密閉空間中以高壓式二氧化碳作為滅火防護設備。若欲將空間中的氧氣濃度降至 15%以下以達到鈍化效果，至少應加入多少立方公尺的二氧化碳？",31,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-113-1-fire-science-028",113,"關於火場中生成的 CO 對人體的危害，下列敘述何者正確？",{"webId":58,"year":59,"stem":60,"number":13},"fire-111-1-fire-science-028",111,"通風控制燃燒下，居室內有可燃物 1200 kg，該居室有一開口面積 6 m2，高度 2 m，則火災持續時間約幾分鐘？",{"webId":62,"year":63,"stem":64,"number":13},"fire-110-1-fire-science-028",110,"下列有關電器用品「焦耳熱」之敘述，何者錯誤？",{"webId":66,"year":67,"stem":68,"number":13},"fire-109-1-fire-science-028",109,"森林火災的種類與敘述，下列何者正確？",{"webId":70,"year":71,"stem":72,"number":13},"fire-108-1-fire-science-028",108,"火場中煙霧的成分複雜且多具毒性，火災時若吸入下列何種氣體，會妨礙細胞中氧化酵素之活性，造成細胞呼吸停止？",1785129966578]