[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-107-1-fire-science-015":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-107-1-火災學概要-015","fire-107-1-fire-science-015",107,1,15,"有一火場之消光係數為 2 m-1，請問發光物體之能見度為多少公尺？",{"A":16,"B":17,"C":18,"D":19},"2 公尺","4 公尺","6 公尺","8 公尺","B",null,[],false,"本題考點：能見度與減光(消光)係數的關係式,以及發光體與反射體的比例常數差異。\n【正解理由】火場煙層造成的視線衰減以減光係數 Cs 表示,單位為每公尺;能見度 V 與減光係數成反比,關係式為 V = K ÷ Cs。比例常數 K 依標的物性質而定:自身會發光的標示或燈具取 5 至 10,慣用 8;僅靠反射環境光的一般物體取 2 至 4,慣用 3。本題問的是發光物體,取 K = 8,代入減光係數 2 得能見度為 4 公尺,故選 B。\n【逐項排除】\n(A) 2 公尺對應 K = 4,那是反射型標的的上限取值,與題目指明的發光物體不符。\n(B) 4 公尺由 8 除以 2 得出,符合發光物體 K 取 8 的慣例,為正解。\n(C) 6 公尺需 K = 12,已超出發光物體 5 至 10 的合理範圍,無對應的取值依據。\n(D) 8 公尺是把 K 值直接當成答案,或誤把減光係數看成每公尺 1 所致,忽略了題給的減光係數為 2。\n【記憶點】能見度等於 K 除以減光係數;發光體 K 取 8、反射體 K 取 3,一除就有答案。","V = K ÷ Cs 的物理基礎是朗伯-比爾定律:光線通過含煙氣層時強度呈指數衰減,I = I₀ e^(−Cs·L),Cs 為減光係數、L 為光程。人眼辨識標的的門檻對兩類標的並不相同——自身發光的標的自己送出光子,只要透過率不致過低即可辨識;僅靠反射的標的,光必須來回穿過煙層,還要與背景亮度競爭,可辨識距離大約只有前者的三分之一,這就是 K 值分成 5 至 10 與 2 至 4 兩組的由來,也是避難方向指示與出口標示採自身發光型式的理由:同樣的煙濃度下,可視距離明顯較長。\n單位與量級對照:減光係數的單位是每公尺,數值越大代表煙越濃、能見度越短,兩者成反比。以發光標的(K 取 8)為例,Cs = 0.1 時可見約 80 公尺、Cs = 0.5 時約 16 公尺、Cs = 1 時約 8 公尺、Cs = 2 時僅約 4 公尺。避難安全的評估常以「能見度不得低於 10 公尺」或減光係數不得高於 0.5 作為可容忍界限,對照上表就能感受到這個門檻其實相當嚴格:煙層只要稍微變濃,可視距離就以反比速度崩跌。\n易混淆對照:減光係數與光學煙密度是相關但不同的量,若題目給的是每公尺光學密度 OD,需先以 Cs ≈ 2.303 × OD 換算再代入;另有以發煙係數描述材料發煙能力者,那是材料性質而非現場煙層狀態。作答前先看單位是每公尺還是無因次,再決定套哪個式子。\n相關考點:同一公式常反向命題——給定能見度求減光係數,或把標的改成反射型逼你換 K 值;選項通常會把兩種 K 值算出的答案同時放進去。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-107-1-fire-science-014","我國在 106 年實施 A1、A2、A3 新式火災認定方式，下列有關 A2 火災認定之敘述，何者錯誤？",14,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-107-1-fire-science-016","下列何者為海龍替代品滅火藥劑 FE-13 之分子式？",16,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-107-1-fire-science-013","假設大氣中氧氣容積為 21%，現在一密閉空間（體積為 V）內，有三分之一體積（V\u002F3）為惰性氣體時（壓力仍為一大氣壓），該空間內氧氣濃度為多少%？",13,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-107-1-fire-science-017","有關地下建築物火災之敘述，下列何者錯誤？",17,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-107-1-fire-science-012","下列何者並非容易悶燒材料之特性？",12,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-107-1-fire-science-018","已知木造倉庫高 6 公尺，如延燒係數為 0.15，依木造建築物火災溫度標準曲線，其鄰棟建築物之理論安全距離應在多少公尺以上？",18,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-111-1-fire-science-015",111,"下列發火源在理化現象歸類上，何者與其他不同類別？",{"webId":58,"year":59,"stem":60,"number":13},"fire-110-1-fire-science-015",110,"下列有關液化天然氣（LNG）與液化石油氣（LPG）之比較，何者正確？",{"webId":62,"year":63,"stem":64,"number":13},"fire-109-1-fire-science-015",109,"下列海龍替代滅火藥劑，何者之化學組成為五氟乙烷？",{"webId":66,"year":67,"stem":68,"number":13},"fire-108-1-fire-science-015",108,"下列何種現象對於局部電阻所產生的效應恰與其他三者相反？",{"webId":70,"year":71,"stem":72,"number":13},"fire-106-1-fire-science-015",106,"粉塵爆炸與可燃性氣體相同，亦須存在有「最小發火能量」始可能引起粉塵爆炸，下列有關粉塵爆炸「最小發火能量」之敘述何者錯誤？",1785123163613]