船上消防訓練手冊 - 第二章 火災的化學原理

船上消防訓練手冊
Shipboard Fire Training Manual 

尚作仁船長 編撰 Compiled by Captain David Shang 

第二章 火災的化學原理
Chapter 2 Chemistry of Fire

2. 一般資訊
General Information

本章解釋了火災是如何發生的，以及為什麼船上火災若不能及時發現和處理，就會變得難以控制，從而威脅到船舶、船員和乘客的安全。

This chapter explains how fire can occur and why a shipboard fire, if not detected and attacked promptly, becomes difficult to control to threaten the safety of the vessel, its crew and passengers.

本章強調了時刻保持警覺並採取有效防火措施的必要性。

It reinforces the need to be continually vigilant and exercise effective fire prevention measures at all times.

2.1 引言
Introduction

除災難性的爆炸外，大多數大型船上火災都是從小型船上火災開始的。因此，及時發現是防止火勢蔓延的關鍵。越早發出警報，就能越早進行滅火行動。

Except for catastrophic explosion, most big shipboard fires start as small shipboard fires. It follows therefore, that prompt detection is the key to preventing fire spread. The earlier the alarm is raised the sooner a fire fighting response can begin.

一旦發生火災，只要還有可燃物，它就會持續構成威脅。但如果了解火災背後的科學原理，就可以透過多種方法撲滅火災。
Once a fire occurs, it will continue to be a threat for as long as there is something to burn. But if there is an understanding of the science behind fire, a fire can be attacked in a number of ways to achieve extinguishment.

本章討論了火災發生的原因、為何火災若不加以控制會繼續燃燒、為何火勢會迅速蔓延以及如何在緊急情況下及早採取正確措施，從而有效控制火勢蔓延。

This chapter discusses what causes a fire to start, why it continues to burn if unchecked, why fires can rapidly spread and how, if the correct measures are taken early in the emergency, the spread of fire can be effectively controlled.

2.2 燃燒的基本知識
Fundamentals of fire

燃燒是一個氧化過程 - 物質與氧氣結合的化學反應。

Fire is a process of oxidation - a chemical reaction where a substance combines with oxygen.

船上未受保護的鐵製或木質配件與空氣中的氧氣結合，導致鐵材生鏽，木材腐爛。生鏽和腐爛是一種被稱為緩慢氧化的化學反應。

Unprotected steel or wooden fittings on the ship combine with oxygen in the air with the result that the steel will rust and wood can rot. Rusting and rotting are chemical reactions termed slow oxidation.

燃燒中也存在類似的氧化過程，只不過過程極為迅速，會釋放出熱量和光，通常以火焰的形式出現。這被稱為快速氧化。

In a fire the same process is at work except that it is extremely quick, causing the emission of heat and light commonly seen as flames. This is known as rapid oxidation.

基礎化學

Basic Chemistry

1. 固體 - 原子或分子通常緊密排列。
Solids - whose atoms or molecules are generally tightly packed.

2. 液體 - 原子或分子鬆散排列，但仍相互結合。
Liquids - whose atoms or molecules are loosely packed but still bound together.

3. 氣體或蒸氣 - 原子或分子可以自由向任何方向移動。
Gases or Vapours - whose atoms or molecules are free to move in any direction.

根據物質的分子結構決定了其氧化能力。物質的原子或分子運動能力越強，它們就越有可能被氧原子包圍。因此，只有氣體或蒸氣才能承受快速氧化，也就是我們所謂的燃燒。

Accordingly the molecular structure of a substance determines its ability to oxidise. The more a substance's atoms or molecules can move about the more they are capable of being surrounded by oxygen atoms. It follows therefore, that only gas or vapour can sustain the rapid oxidation that we call burning.

但如果固體或液體被加熱，其原子或分子的移動速度會加快。如果施加足夠的熱量，其中一些原子或分子便會脫離固體或液體的表面，並在其表面附近形成氣體或蒸氣。
But if a solid or liquid is heated, its atoms or molecules move about more rapidly. If sufficient heat is applied, some of these atoms or molecules will break away from the surface of the solid or liquid and form a gas or vapour just above its surface.

這種氣體或蒸汽可以與氧氣混合，如果有足夠的熱量使氣體或蒸汽達到其燃點，並且如果有足夠的氧氣，氣體或蒸汽將迅速氧化並開始燃燒，有時甚至迅速引起爆炸。

This gas or vapour can now mix with oxygen and if sufficient heat is available to bring the gas or vapour to its ignition temperature, and if sufficient oxygen is available, the gas or vapour will rapidly oxidise and start to burn, sometimes so rapidly as to cause an explosion.

燃燒

Burning

蒸氣分子的快速氧化被稱為燃燒。在燃燒過程中，分子分解並與氧氣重新結合形成新的分子。在這個分解和重新結合的過程中，能量以熱和光的形式被釋放出來。

The rapid oxidation of vapour molecules is called burning. During burning, the molecules break apart and recombine with oxygen to form new molecules. Energy is released in the form of heat and light during this breaking apart and recombining process.

釋放的熱量向四方輻射。其中一些熱量會輻射回火源——即現在已成為燃料的固體或液體，使更多的蒸汽被釋放出來，並加熱到其燃點。同時，空氣被吸入火焰與新釋放的蒸氣接觸的區域。使蒸氣燃燒，火焰範圍擴大。

The heat released radiates in all directions. Some of it radiates back to the seat of the fire - the solid or liquid that has now become the fuel. More vapour is released, and in turn is raised to its ignition temperature. Simultaneously, air is drawn into the area where flames and the newly released vapour meet. The vapour burns and extent of flames increase.

連鎖反應

The chain reaction

隨著燃燒的蒸汽產生更多熱量，進而釋放並點燃更多蒸汽，火勢會越來越大。這稱為連鎖反應。

As burning vapour produces more heat, which releases and ignites more vapour, the bigger the fire becomes. This is called the chain reaction.

只要有充足的燃料和充足的氧氣，火勢就會越燒越旺，火焰也會越大。

As long as there is plenty of fuel and good supplies of oxygen the more the fire will grow and more flame is produced.

如果任其發展，由於蒸汽釋放量有限，火勢最終會趨於平穩。這種情況會持續到燃料耗盡，隨著釋放的蒸氣減少，可用的輻射熱也隨之減少，連鎖反應也會減慢。火勢最終熄滅，固體燃料通常會留下灰燼，而液體燃料則會完全燃燒。

Left to its own devices, a fire will eventually level off in its intensity due to sustainable limits in the amount of vapour being released. This continues until the fuel is consumed and the chain reaction slows as less vapour is released and consequently less radiated heat is available. The fire dies, solids usually leaving an ash deposit, liquid fuels burning completely.

可燃氣體比固體或液體燃燒得更劇烈，因為它們本身就處於蒸氣狀態。所有輻射熱都用於點燃蒸汽，因此蒸汽總是更容易被完全點燃，通常是瞬間點燃 - 因此可燃氣體具有爆炸性和危險性。

Flammable gases burn more intensely than solids or liquids because they already exist in the vapour state. All radiated heat goes into igniting the vapour, so it is always more fully ignited, often instantaneously - hence the explosive and dangerous nature of flammable gases.

2.3 燃燒三角形
The fire triangle

從上述幾節可以清楚看出，燃燒需要三個條件：
From the previous sections, it's clear that three things are needed to support fire:

1. 燃料 - 汽化並燃燒。
Fuel - to vaporise and burn.

2. 熱量 - 將燃料蒸氣的溫度升高到其燃點。
Heat - to raise the temperature of the fuel vapour to its ignition temperature.

3. 氧氣 - 與燃料蒸氣結合。
Oxygen - to combine with the fuel vapour.

這些組成部分可以用一個三角形來表示，以說明預防和滅火的兩個重要事實。記住它們！
These components can be shown as a triangle to illustrate two important facts in preventing and extinguishing a fire. Remember them!

1. 若三角形的任何一邊缺失，火就無法燒起。
If any side of the triangle is missing, a fire cannot start.

2. 如果三角形的任何一邊被移除，火就會熄滅。
If any side of the triangle is removed, a fire will go out.

通常，氧氣成分指的是空氣中的氧氣含量，其體積佔比約為21%。已知約16%(最低11%)的氧氣含量也能燃燒，但即使氧氣含量低至3%也有可能發生悶燒。
Usually the oxygen component means the oxygen content in air, which is about 21% by volume. Volumes of about 16%, but as low as 11%, have been found to support burning, but smouldering can occur as low as 3% oxygen.

熱量總是會引發我們所知的化學反應，即燃燒。燃燒可能由多種原因引起，例如電器產生的火花、短路或鐵質工具的撞擊、火柴、香菸或焊槍的明火，或僅僅是摩擦產生的熱量。

Heat always initiates the chemical reaction we know as burning. It can arise from a multitude of causes such as a spark from an electrical appliance, a short circuit or the striking of ferrous tools, a naked flame from a match, cigarette or welding torch or heat simply generated by friction.

足夠的熱量，即所謂的自燃，也可以由燃料中的化學反應或細菌或真菌作用於有機物產生。

Sufficient heat, known as spontaneous combustion, can also be produced by a chemical reaction in the fuel or by bacterial or fungal action on organic matter.

2.4 燃燒四面體

The fire tetrahedron

燃燒三角形是記住燃燒要素三個組成部分的簡單方法。但它並不能充分解釋燃燒的本質，尤其沒有說明燃料、熱量和氧氣之間發生的複雜化學反應所引發的連鎖效應。

The fire triangle is simple way of remembering the three components of fire. But it doesn't adequately explain the nature of fire, and specifically does not address the chain reaction that results from the complex chemical reactions occurring between the fuel, heat and oxygen.

為了正確地展示燃燒的過程，可以使用四面體(具有四個三邊形的立體圖形)。

To show the fire process properly, a tetrahedron (a solid figure with four triangulated sides) can be employed.

這個圖形可以容納對維持燃燒至關重要的連鎖反應因素。

This figure can accommodate the chain reaction component so vital to maintaining combustion.

從圖形上看，連鎖反應面似乎能阻止其他三個面崩塌。但一旦連鎖反應面被移除，四面體就會崩塌，從某種意義上來說，火就會被撲滅。

Graphically, the chain reaction side appears to keep the other three faces from falling apart. But once the chain reaction face is removed, the tetrahedron will collapse and metaphorically the fire will be extinguished.

這是滅火的一個重要策略，因為許多便攜式滅火器、固定式滅火系統和爆炸抑制系統都是直接攻擊和破壞連鎖反應序列。

This is an important aspect of fire fighting because many portable fire extinguishers, fixed fire extinguishing systems and explosion suppression systems directly attack and break down the chain reaction sequence.

2.5 火勢蔓延

Spread of fire

大多數火災如果能及時發現並撲滅，都可以被控制在爆發區域內。然而，如果任由火勢肆意燃燒，它就會產生巨大的熱量，這些熱量會從火災區域蔓延開來，在有足夠燃料和空氣的地方引發其他火災。

Most fires, if discovered and attacked promptly can be confined to the area of outbreak. However if a fire is allowed to burn unhindered, it can generate huge amounts of heat that will spread from the fire area, causing other fires wherever sufficient fuel and air is available.

如前所述，船上並不缺乏潛在的燃料，儘管鋼製艙壁和甲板以及專門設計的防火門可以阻止或延緩火焰蔓延，但熱量的傳遞往往會促使火勢蔓延到新的燃料源。

As previously discussed, there is no shortage of potential fuel aboard ship and although steel bulkheads and decks and purpose-designed fire doors can stop or delay the propagation of flame, the transfer of heat often promotes fire spread to new fuel sources.

在大多數情況下，對受影響的艙壁、甲板和其他結構部件進行針對性的噴水(稱為邊界冷卻)可以減緩甚至阻止熱量的傳遞。

In most cases the targeted application of a water spray (called boundary cooling) on affected bulkheads, decks and other structural members will slow down or even stop the transmission of heat.

輻射

Radiation

輻射是指能量在不涉及任何其他中介物質而在空間中的傳遞。

Radiation is the transfer of energy across an intervening space that doesn't involve any other material.

火災輻射熱量的方式與太陽輻射熱量和光的輻射方式相同。就像陽光一樣，當它接觸到物體或表面時，熱量會被吸收、反射或透射。

Heat is radiated from a fire in the same way as the sun radiates heat and light. And just like sunshine, when it contacts a body or surface, heat is absorbed, reflected or transmitted.

輻射熱會加熱沿途所有可燃材料，使其釋放蒸汽，並形成點火源，使火勢向四面八方蔓延。

Radiant heat advances a fire in all directions by heating any combustible material in its path, causing the material to release vapour and providing the ignition source.

在船上，輻射熱會使消防員的工作變得異常困難。根據火災的性質，火源附近和遠處的材料都有可能處於高溫狀態。因此，必須穿戴防護服並應考慮使用噴水或乾粉滅火器來保護人員。(乾粉在火焰中也能產生一定的冷卻效果)
In a ship, radiant heat makes the job of the fire fighter difficult. Depending on the nature of the fire, materials both local to the source of the fire and some distance away can be at high temperature. For this reason, protective clothing must be worn. Consideration should be given to shielding personnel through the use of water spray or dry chemical. (Dry powder can also produce a certain cooling effect in the flame.)

對流

Convection

對流是透過分子運動傳遞熱量的過程。對於海員來說，這意味著對流熱量通常會根據船體結構的設計，可預測其傳播的路徑。

Convection is the transmission of heat through the motion of molecular matter. For the seafarer this means that convected heat often moves in predictable paths determined by the vessel's structure.

舉例來說，假設下層甲板發生了一場小型住艙火災。熱量以煙霧、熱氣體和熱空氣的形式上升到該層甲板頂部並沿著通道水平傳播。一直到達開放式艙口、梯子或被防火門屏蔽的樓梯間。隨後，熱氣向上移動到另一層甲板，點燃沿途所有易燃材料。不久之後，一場大火就發生了，將給消防員和船舶帶來了重大損失。

By way of illustration, assume a small accommodation fire has occurred in the lower decks. Heat in the form of smoke, hot gases and hot air rises to the deckheads and travels horizontally along the alleyways. Until it reaches an open hatch or ladder or a stairwell with its fire door chocked open. Whereupon, the heat moves upwards to the next deck, igniting any flammable materials in its path. Before long, a major fire has occurred with major consequences for the fire-fighters and the ship.