[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-110-1-fire-science-020":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-110-1-火災學概要-020","fire-110-1-fire-science-020",110,1,20,"某室內火場的煙層厚度為 1 公尺，若此時光學密度為 0.173，則該場域中避難反光指標之能見度為多少公尺？",{"A":16,"B":17,"C":18,"D":19},"7.5","10","15","20","A",null,[],false,"本題考點：光學密度、減光係數與能見度的換算公式,屬避難安全評估的基本計算。\n【正解理由】能見度 V 與減光係數 Cs 成反比,V = K \u002F Cs;係數 K 依標識種類取值,反光(反射)型避難指標取 2～4、代表值 3,自體發光型則取 5～10。光學密度 OD 與減光係數的關係為 Cs = 2.303 × (OD \u002F L),L 為光程,即煙層厚度。以 OD = 0.173、L = 1 m 代入得 Cs 約 0.4 m⁻¹,再取反光型 K = 3,能見度約 7.5 m,故選 A。\n【逐項排除】\n(A) 7.5 m:以反光型指標的代表值 K = 3 除以 0.4 m⁻¹ 求得,與題目所問的反光指標相符,正確。\n(B) 10 m:相當於取 K = 4,是反光型取值範圍的上限而非代表值,偏高。\n(C) 15 m:相當於 K = 6,已落入自體發光型的取值範圍,用錯標識類別。\n(D) 20 m:相當於 K = 8,為自體發光型的典型取值,高估最多。\n【演算步驟】\nCs = 2.303 × OD \u002F L = 2.303 × 0.173 \u002F 1 m ≈ 0.398 m⁻¹\nV = K \u002F Cs = 3 ÷ 0.398 m⁻¹ ≈ 7.5 m\n【記憶點】反光靠人照 K 取 3、發光自己亮 K 取 8,除以減光係數就是能見度。","公式的來源是朗伯–比爾定律(Lambert-Beer law):光通過含煙介質後,透射光強與入射光強的關係為 I \u002F I₀ = e^(−Cs·L)。光學密度定義為以 10 為底的對數衰減量,OD = log₁₀(I₀ \u002F I),兩式取對數互換即得 Cs = ln10 × OD \u002F L = 2.303 × OD \u002F L。因此 OD 與 Cs 只差一個常數 2.303 與光程 L,單位分別是無因次與 1\u002Fm,考試最常見的失分點就是忘記除以煙層厚度、或把 OD 直接當成 Cs 使用。\n\n能見度公式 V = K \u002F Cs 屬經驗式,K 值反映「標識本身會不會發光」:自體發光型標識靠自己送出光,煙中仍能被辨識,K 取 5～10;反光型標識必須先接收外來光、再反射回觀察者,光線在煙中往返兩次而衰減加倍,K 只能取 2～4。這也解釋了為什麼同樣的煙濃度下,發光型的可視距離約為反光型的兩倍以上。\n\n延伸考點有三:一是煙粒子濃度與 OD 的關係,可用質量光學密度 Dm 乘以質量濃度推估,燃燒產物含碳量越高(如聚苯乙烯、橡膠)減光能力越強;二是避難安全驗證常用的容忍條件,小空間多以能見度 5 m、大空間多以 10 m 作為判定門檻,與本題算出的 7.5 m 屬同一量級;三是本題也可反過來出,給定能見度求 OD 或煙層厚度,只要記住 Cs = 2.303 OD \u002F L 這一條轉換即可雙向運算。另須留意 K 值並非法定數值,而是實驗與工程慣例的取值區間,答題時依題目所述的標識型式選取,題目指明反光或反射者一律走 2～4 這一組。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-110-1-fire-science-019","當發生危害物質災害時，為降低對民眾及搶救人員的危害，應迅速劃定管制區域，下列區域何者一般以黃色標示？",19,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-110-1-fire-science-021","下列物質在常溫時，何者的熱傳導係數（W\u002Fm∙K）較低？",21,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-110-1-fire-science-018","根據「危害物質災害現場搶救標準作業程序」之規定，其首要工作為何？",18,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-110-1-fire-science-022","火災中所產生的輻射熱量與下列何者成正比？",22,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-110-1-fire-science-017","下列惰性氣體類海龍替代滅火藥劑中，何者的比重小於 1？",17,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-110-1-fire-science-023","請問 2 公斤的氫氣（H2）完全燃燒，所需要的理論空氣量為多少公斤？",23,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-111-1-fire-science-020",111,"下列對於燃燒要素的敘述，何者錯誤？",{"webId":58,"year":59,"stem":60,"number":13},"fire-109-1-fire-science-020",109,"某研究院之廠區引發爆燃事件之推進劑，其內含過氯酸鹽類，試問其為公共危險物品中第幾類物質？",{"webId":62,"year":63,"stem":64,"number":13},"fire-108-1-fire-science-020",108,"下列何種滅火劑所含成分之一，於放射後有刺激呼吸之作用，可有效降低場內人員的窒息危害？",{"webId":66,"year":67,"stem":68,"number":13},"fire-107-1-fire-science-020",107,"為防止由窗口噴出的火焰向大樓上層延燒，下列措施何者錯誤？",{"webId":70,"year":71,"stem":72,"number":13},"fire-106-1-fire-science-020",106,"某一混凝土結構之居室，長 20 公尺、寬 10 公尺、高 4 公尺。居室內之可燃物（以木材為主）總重 2000 公斤、總表面積 500 平方公尺，倉庫僅有一開口，寬 5 公尺、高 2 公尺，已知空氣密度為 1.2 kg\u002Fm3 時，下列敘述何者錯誤？（已知√9.8 = 3.13）",1785123162423]