火災(zāi)的形成，追根究底不外乎是起火源與火災(zāi)環(huán)境的結(jié)合。也就是說任何的火災(zāi)，總有其脈絡(luò)可循，往往可以從火災(zāi)學(xué)的原理，推敲其中的原因，應(yīng)用科學(xué)的方法，作為火災(zāi)模型的重建。本文章將把火災(zāi)學(xué)中最容易混淆、最難分清楚的轟燃( Flashover )、爆燃( Backdraft )、滾燃( Rollover )以及其他NFPA的相關(guān)名詞一一解釋清楚，我們能在在學(xué)習(xí)這些火勢(shì)發(fā)展現(xiàn)象時(shí)能更好理解。轟然(Flashover)所謂轟燃 (F.O)是指室內(nèi)起火后，火勢(shì)逐漸擴(kuò)大過程中，因燃燒所產(chǎn)生的可燃性氣體，蓄積于天花板附近，此種氣體與空氣混合，正好進(jìn)入燃燒范圍且達(dá)到燃點(diǎn)之際，一舉引火形成巨大之火苗，使室內(nèi)頓時(shí)成為火海的狀態(tài)。NFPA：參考官網(wǎng)內(nèi)容?Reporter's Guide: All about fire?定義如下：Flashover is the sudden, simultaneous ignition of everything in a room. This is how it happens:
轟燃指的是室內(nèi)所有物品被瞬間、同時(shí)引燃。以下說明它是如何發(fā)生的：Hot gases rise to the ceiling and spread out across to the walls.高溫可燃性氣體上升至屋頂并橫向擴(kuò)散至墻壁。Heat radiates downward and intensifies until all combustible items reach their ignition temperatures and burst into flames.熱輻射不斷向下移動(dòng)并加劇，直到所有可燃物到達(dá)引火點(diǎn)，最后導(dǎo)致全部可燃物瞬間燃燒起來。Temperatures soar to as much as 1,000 degrees Fahrenheit in a few seconds. Even a firefighter in full protective gear is unlikely survive a flashover.溫度將在幾秒內(nèi)瞬間提升至華氏約1000度(約攝氏537度)，即使消防人員穿著完整防護(hù)裝備都可能無法在轟燃中幸存。Firefighters are trained to recognize the signs that flashover is about to occur: dense black smoke with tightly packed curls (“black fire”); dense, black smoke that pushes out of a doorway or window opening; smoke that has accumulated as low as a doorknob, with the fire seen below.消防人員會(huì)接受訓(xùn)練，辨識(shí)轟燃即將發(fā)生的征兆：包含翻滾卷曲的濃黑煙(黑火)、竄出門窗開口的濃黑煙、煙層蓄積到門把高度且有火焰伴隨在煙層下方。

滾燃(Rollover)Rollover，我們一般稱為“滾燃”。新聞上?？吹剿^的轟燃前兆“天使之舞”，指的就是滾燃現(xiàn)象。NFPA：參考官網(wǎng)內(nèi)容( Reporter’s Guide: All about fire )定義如下Rollover occurs when ignited fire gases, or incompletely burned fuels, rise to the ceiling, and spread out horizontally. Then smoke appears to suddenly start burning. If nothing is done to ventilate the room or cool the air, this condition leads to flashover.當(dāng)可燃性煙氣或不完全燃燒的可燃物上升到天花板并水平擴(kuò)散時(shí)，煙層會(huì)突然燃燒起來，導(dǎo)致滾燃的發(fā)生。如果沒有適當(dāng)?shù)赝L(fēng)或降溫可能會(huì)導(dǎo)致轟燃。另外參考NFPA數(shù)據(jù)Technical Committee on Fundamentals of Fire Control within a Structure Utilizing Fire Dynamics 2018?針對(duì)Rollover有更進(jìn)一步的定義：Rollover: The condition in which unburned fuel (pyrolysate) from the originating fire has accumulated in the ceiling layer to a sufficient concentration (i.e., at or above the lower flammable limit) that it ignites and burns. Rollover can occur without ignition of or prior to the ignition of other fuels separate from the origin.滾燃：來自于起火點(diǎn)、尚未燃燒的可燃物(熱裂解物質(zhì))，蓄積于天花板且達(dá)到足夠的濃度(達(dá)爆炸下限或超過)時(shí)，這些可燃物起火燃燒的現(xiàn)象稱為滾燃。沒有引火物仍可能發(fā)生滾燃現(xiàn)象。

爆燃(Backdraft)Backfraft，我們把它稱為“爆燃”也有火災(zāi)學(xué)稱“回燃”或“復(fù)燃”。火災(zāi)學(xué)中定義：火災(zāi)在悶燒(Smoldering)狀態(tài)時(shí)期，因空氣中的氧氣量不足，而產(chǎn)生大量之可燃性氣體，充滿整個(gè)室內(nèi)空間。不久之后，由于門窗玻璃或其他處所之破裂或自外部開啟開口，而形成空氣之流通口。此時(shí)，若造成大量空氣涌入時(shí)，將可能使充滿室內(nèi)之可燃性氣體一舉燃燒，火焰從窗口噴出，造成危險(xiǎn)。此種現(xiàn)象一般稱為復(fù)燃(Back Draft)現(xiàn)象。NFPA：參考官網(wǎng)內(nèi)容( Reporter's Guide: All about fire )定義如下：Backdraft is an explosion that occurs when oxygen is introduced into a room full of hot gases.爆燃是一種爆炸現(xiàn)象，當(dāng)氧氣被引入充滿高溫可燃性氣體的房間時(shí)會(huì)發(fā)生。A fire burning in a confined area consumes all the oxygen.密閉空間中所有氧氣消耗完畢時(shí)會(huì)發(fā)生的一種燃燒形式。Visible flames disappear. Solid fuels smolder, and hot flammable gases accumulate and fill the room.明顯可見的火焰消失，固體可燃物悶燒、高溫可燃性煙氣體蓄積并充滿整間房間。The temperature increases, the gases expand, and pressure builds, pulsing against doors and windows. From outside, the building may look like it is breathing or throbbing.溫度上升、可燃性氣體擴(kuò)散、壓力蓄積，使門窗震動(dòng)。從外部觀察，建筑物看起來會(huì)像在呼吸或搏動(dòng)。If an opening is made to admit oxygen, the hot vaporized fuel bursts into flames, and the pressurized gases explode through the opening, resulting in a rolling fireball.如果制造一個(gè)開口讓氧氣進(jìn)入，高溫可燃性氣體會(huì)瞬間燃燒，有壓力的氣體會(huì)從開口處爆發(fā)出來，導(dǎo)致一個(gè)滾動(dòng)的火球。

NFPA其他名詞補(bǔ)充同樣參考NFPA數(shù)據(jù) (Technical Committee on Fundamentals of Fire Control within a Structure Utilizing Fire Dynamics 2018) ，可以發(fā)現(xiàn)轟然燃、爆燃、滾燃等火災(zāi)現(xiàn)象，NFPA統(tǒng)稱為火勢(shì)快速成長(zhǎng)(Rapid Fire Development , RFD)Rapid Fire Development:?A transient phase in fire behaviour accompanied by a rapid increase in heat release rate of the fire & temperature in the environment, sometimes accompanied by the generation of over‐pressure.火勢(shì)快速發(fā)展：一種短暫的火災(zāi)特性，伴隨著環(huán)境中熱釋率、溫度的增加，有時(shí)也伴隨著超壓(很大的壓力)的產(chǎn)生.These RFDs are subdivided into two main categories of phenomena: flashover and smoke ignition. Smoke ignition is then further subdivided into three separate developments: smoke explosion; backdraft; and flash fire (propagating flame fronts including rollovers) 。火勢(shì)快速成長(zhǎng)可分為兩種現(xiàn)象：轟燃和可燃性煙氣引火燃燒?？扇夹詿煔庖鹑紵挚梢栽诜譃槿N：可燃性煙氣爆炸、爆燃、閃火(火焰前緣傳播，包含滾燃)（見下圖）。
根據(jù)上圖，其實(shí)爆燃、滾燃都屬于可燃性煙氣引火燃燒的一種，而滾燃其實(shí)也只是燃燒波傳播的一種方式。以下再針對(duì)可燃性煙氣引火燃燒(Smoke Ignition)、可燃性氣體爆炸(Smoke Explosion)、閃火(Flash Fire)做說明：Smoke Ignition: The ignition of the products of pyrolysis and incomplete combustion interior or exterior to the fire compartment due to the accumulated smoke layer falling within its flammability range and either auto-igniting or igniting due to an ignition source.可燃性煙氣引火燃燒：起火處所內(nèi)、外，煙層中的熱裂解物質(zhì)、未完全燃燒物質(zhì)達(dá)到燃燒范圍(或稱爆炸范圍)時(shí)，透過自然發(fā)火或被引火源引燃的一種燃燒現(xiàn)象Flash fires, where a flame moves through a flammable mixture with considerable speed, but does not develop a significant over-pressure.閃火：火焰快速地移動(dòng)、通過可燃性氣體混合物，但不產(chǎn)生明顯的超壓。Smoke Explosion: A rapid fire development that occurs when a smoke-air mixture falls within its flammable range, either external or internal to the room of origin and is ignited, resulting in a significant pressure front.可燃性煙氣爆炸：起火處所內(nèi)、外，可燃性氣體與空氣的混合物達(dá)到燃燒范圍(或稱爆炸范圍)時(shí)，引火燃燒且產(chǎn)生壓力波的一種火勢(shì)快速成長(zhǎng)現(xiàn)象。

Two manifestations of flame propagation that fall into this category:火焰?zhèn)鞑サ姆绞椒譃閮煞N形式：Flash Fire和Rollover：Flash fires, where a flame moves through a flammable mixture with considerable speed, but does not develop a significant over-pressure.閃火（Flash fires）：火焰快速地移動(dòng)、通過可燃性煙氣混合物，但不產(chǎn)生明顯的超壓。滾燃（Rollovers）, where a flame front or pockets of smoke-air mixture ignite and move slowly through a mixture. Rollovers are also considered as an early and important indication of impending flashover滾燃：燃燒波或可燃性煙氣與空氣的混合物引火燃燒且緩慢移動(dòng)。滾燃可以被視為轟燃發(fā)生前的重要征兆。由上面說明可知，閃火、滾燃都是火焰?zhèn)鞑サ姆绞健lash fire的Flash可以想成是煙層中的可燃性煙氣瞬間燃燒，火焰閃一下就沒了、移動(dòng)很快速。而Rollover可以想成是燃燒波持續(xù)往前移動(dòng)，火焰沿著天花板水平擴(kuò)散，就像海浪往前推移一樣。

最后：
說實(shí)在的，要一次搞懂這么多種火災(zāi)現(xiàn)象確實(shí)不容易，而且雖然是不同的現(xiàn)象，但實(shí)際到火災(zāi)現(xiàn)場(chǎng)觀察時(shí)會(huì)發(fā)現(xiàn)，火焰?zhèn)鞑?、可燃性煙氣體燃燒的狀況沒有太多差別，而這也提高了消防人員在火災(zāi)現(xiàn)場(chǎng)辨識(shí)這些危險(xiǎn)的難度。