[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-111-1-fire-science-006":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-111-1-火災學概要-006","fire-111-1-fire-science-006",111,1,6,"火災成長歷程中，下列何者非閃燃之現象？",{"A":16,"B":17,"C":18,"D":19},"火場狀況為缺氧燃燒，因某種特殊的原因導致新鮮的空氣衝入之現象","閃燃係從火災成長期移向旺盛期之短暫現象","閃燃時地板的熱通量達 20 kW\u002Fm2","上層煙氣溫度達到 500～600℃","A",null,[],false,"本題考點：閃燃（flashover）的判定特徵，以及它與回燃（backdraft）的機制區別。\n【正解理由】閃燃是室內火災由成長期跨入最盛期的短暫過渡現象，成因是天花板下方熱煙層向下輻射加熱，使室內所有可燃物表面同時裂解放出可燃氣體而全面起火，常用判準為上層煙氣層溫度達 500 至 600℃、地板面輻射熱通量約 20 kW\u002Fm²。選項所述「缺氧燃燒後新鮮空氣衝入」是回燃的定義，並非閃燃之現象，故選 A。\n【逐項排除】\n(A) 非閃燃之現象，為本題應選者。該敘述描述的是回燃：空間通風不良、火勢因缺氧轉為悶燒，室內蓄積高溫未燃氣體，開口破壞後空氣灌入而爆發性燃燒。\n(B) 屬閃燃之現象。閃燃即由火災成長期移向旺盛期的瞬間過渡，歷時僅數秒。\n(C) 屬閃燃之現象。地板面接受的輻射熱通量達約 20 kW\u002Fm²，是判定閃燃發生的常用量化指標。\n(D) 屬閃燃之現象。上層煙氣層溫度達 500 至 600℃，為另一個常用的閃燃判準。\n【記憶點】閃燃缺的是熱，熱到臨界就全面起火；回燃缺的是氧，補進空氣才爆燃。","閃燃的物理過程可拆成三步：起火後熱煙在天花板下方累積成煙層，煙層溫度與厚度增加後向下輻射，當地板面接受的輻射熱通量把室內其餘可燃物同時加熱到裂解溫度並放出可燃氣體，整室便在數秒內全面起火。三個最常考的判定指標是上層煙氣層溫度約 500 至 600℃、地板面輻射熱通量約 20 kW\u002Fm²、以及開口處開始出現火焰噴出。\n回燃的機制完全不同：密閉或通風不良的空間內，火勢因氧氣耗盡轉為悶燒，室內充滿高溫且未燃燒的熱裂解氣體與一氧化碳，此時若門窗破壞或開啟，新鮮空氣瞬間灌入與高溫燃氣混合並落入燃燒界限，即發生爆炸性燃燒並自開口噴出火球。一句話對照：閃燃是熱量累積到臨界，回燃是氧氣補進來。\n前兆對照也常入題。閃燃前可見煙層明顯下降、煙色轉濃、並出現滾燃（rollover，煙層中火舌向前翻滾）；回燃前則見開口處煙呈脈動式進出、玻璃內側附著油狀凝結物、煙自縫隙高速噴出並伴隨哨音。\n延伸考點是通風控制與燃料控制的轉換：閃燃之前室內氧氣尚足，燃燒速率由可燃物本身決定，屬燃料控制；閃燃之後可燃物大量參與燃燒，氧氣成為限制條件，轉為通風控制，燃燒速率改由開口因子（開口面積乘以開口高度平方根）決定，這也是最盛期持續時間與火載量、開口條件相關的理論基礎。\n易混淆概念還有爆燃、複燃與滾燃三個名詞：滾燃是閃燃的前兆現象，複燃常與回燃互用，爆燃則是燃燒學中相對於爆轟的傳播型態，層次不同，答題時要看題幹問的是室內火災階段還是燃燒波傳播。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-111-1-fire-science-005","在苯中置入油酸鎂等金屬鹼，係採取下列何種防止靜電發生的方法？",5,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-111-1-fire-science-007","油類火災為何種火災？",7,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-111-1-fire-science-004","日本東京放映所及精神病診所火災起因為縱火，請問汽油在空氣中的燃燒下限為何？",4,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-111-1-fire-science-008","空氣氧之重量占整體之 23%，故 1 公斤碳完全燃燒需要多少空氣？",8,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-111-1-fire-science-003","實效濕度低於多少時，日本即發布火災警報？",3,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-111-1-fire-science-009","有關粉塵爆炸的敘述，下列何者錯誤？",9,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-114-1-fire-science-006",114,"依據我國公共危險物品之分類，下列有關可燃液體與易燃液體之敘述，何者正確？",{"webId":58,"year":59,"stem":60,"number":13},"fire-113-1-fire-science-006",113,"有關防止靜電災害的方法，下列敘述何者正確？",{"webId":62,"year":63,"stem":64,"number":13},"fire-112-1-fire-science-006",112,"在標準狀態下，下列氣體中何者之爆炸範圍最廣？",{"webId":66,"year":67,"stem":68,"number":13},"fire-110-1-fire-science-006",110,"阿里山發生森林火災，已知火災當天的相對濕度為 60.0%，前一天相對濕度為 50.0%，再前一天相對濕度為 40.0%，試求火災當天的實效濕度？",{"webId":70,"year":71,"stem":72,"number":13},"fire-109-1-fire-science-006",109,"某次閃電的過程中，雲的底部和地面之間，電壓高達 1 千萬伏特，並在約 0.02 秒內輸送 20 庫倫的電量至地面。下列與閃電有關的敘述何者正確？",1785129966714]