シャドーイング練習: An Introduction to Flashover - Episode 9 - 動画で英語スピーキングを学ぶ

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G'day everyone my name is Matt and welcome back to The Fire Show.

So far in the series we've covered a range of different topics including the fact that smoke burns, pyrolysis, formability range, spontaneous combustion and heat transfer.

In today's episode we're going to be talking about flashover which is a combination of all of these elements.

So if you haven't seen those videos I suggest you go back

and have a quick look at them first and then come back to this one.

Now flashover is a term that gets thrown around a lot by firefighters

and sometimes it gets used correctly and sometimes it gets used incorrectly.

Now, without wanting to get too bogged down in the specifics of terminology,

we're going to have a quick look at what the actual term flashover is referring to

and then we're going to have a look at how it actually occurs

and what we can do to start reading it

and what we can do to actually stop it from occurring in the first place.

Now, a textbook example of flashover is the transition from a localised fire to the general conflagration within the compartment

when all fuel surfaces are burning.

and if you're wondering what conflagration means it's basically just a fancy word for fire

if we wanted a much simpler definition for flashover we could say

it's the transition from a fire within a room to a room

that is entirely on fire now for an example of

that transition what we have is a fire burning in the corner of the room here

and as that fire begins to grow it pumps more

and more heat and flames and smoke into that overpressure above the fire

and this is really important because as

that smoke layer begins to build up

it radiates a of heat back down on all the fuels in the room

and as all of those fuels begin to heat up they get closer

and closer to their auto ignition temperature until a point where everything in

that room catches on fire at around about the same time and we see what's called a flashover

so what we're going to do is go ahead

and talk about how this actually happens

and how we can begin to read the signs that are actually indicating that a flashover is imminent

and in fact what we can actually do about it now

flashover is no different to any other fire where it actually relies on a combination of heat,

fuel, oxygen and a chemical reaction so it can actually occur.

But if we think about it in these terms, it does make flashover easier to understand.

Now if we have a look at this room, we can see that the fuel is coming from the couch

and the TV and the carpet and the walls and those kinds of things.

The oxygen is already present in the room when the fire starts, it's coming from the air that's already present in the room,

and in fact it's coming from the air that's being drawn in through the door as the fire burns.

now the heat actually comes from the fire itself

and as it starts to burn it pushes more heat

and smoke and flame up into that over pressure area

and by the process of convection that heat spreads out across the room

and can actually start to move into other rooms because

that convection current takes hold

and what we actually see is cold air being drawn in through the door

while smoke will actually start to push out through the top of the door and

while this process is actually happening what we're seeing is a

lot of heat being radiated back down on everything in the room

which is slowly starting to heat all of these things up

and in fact for most fuels approximately 30 percent of the

heat liberated in the flame is radiated to the environment

and the rest is actually dispersed convectively in the buoyant flume now this actually means

that around about 70 of the heat produced by the fire is actually being transported by the convection current

which means that 70 % of the heat is actually being moved up

and away from the fire and is therefore available to actually heat up other objects throughout

that room and throughout the building

so as the convection current moves through the building it radiates heat down on all of the fuels

that are confined within that area

and as those fuels begin to heat up they then start to pyrolysis

and the fuels will start to pyrolysis at different temperatures depending on what they're made of for instance

if it's a natural fiber, it's going to pyrolicize at a much higher temperature than if it's an artificial fuel,

such as a plastic or a foam.

Now, as they start to pyrolicize, they're releasing more and more fuel into that atmosphere, which is then available for the fire to burn.

Now, some studies have shown that at a ceiling temperature of approximately 600 degrees centigrade, flashover can occur.

And a reason for this can be found in the auto -ignition temperature for carbon monoxide, which is about 609 degrees so as we're seeing

that ceiling temperature get up to around about

that 600 degree level we're seeing the carbon monoxide in the smoke spontaneously combust

which then increases the heat release rate greatly

and then we see a rapid progress towards flashover as a result

now this is actually an early warning sign for flashover flames in the overpressure region is actually showing

that we're reaching that 600 degrees and

that flashover isn't very far away now the next thing we start to see is all of our fuels

which are pyrolysis are starting to reach their auto ignition temperature which means

that we're getting very close to the point where all of

those pyrolysis gases are simply going to burst into flames on their own accord even

if there is no direct flame impinging from the fire itself

now this is where the fire triangle comes back into it

because if we don't have our mixture of heat fuel

and oxygen we simply can't get the chemical reaction

that starts our flashover now in the room we know

that we have our heat because our ceiling temperature is reaching around about

that 600 degrees level we're seeing the flames in

that overpressure our fuel is everywhere it's been readily pyrolysis by the fire

and we're seeing all of our couches and walls and floors

and all these sorts of things releasing all of these pyrolysis gases

so the the final variable is oxygen now oxygen is something

that is very variable within a structure fire whether the fire is in a fuel controlled

or a ventilation controlled state we're going to be talking about fuel controlled

and ventilation controlled more in a later episode but it's important to note

that oxygen is a really key component to a structure fire actually occurring

and a lack of oxygen can actually stop a flashover happening

altogether whereas the addition of more oxygen can actually cause flashover to happen faster

and this is why it's really important that

when we actually make entry to a building we do so

when we're ready to actually get in and apply water to

that fire without actually allowing it to get in excess of oxygen before we actually suppress that fire.

Now our fire has continued to burn and we're seeing more

and more of these pyrolysis gases starting to come out of our fuels

and we're also starting to see more and more of

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that flame activity above the overpressure which is indicating

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that it's at least 600 degrees

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now the next step is we're going to start to see these fuels reach their auto ignition temperature

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and they're going to spontaneously combust

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now they're not necessarily going to do it all at the same time we're going to see the objects

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that are more vulnerable or higher in the room

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spontaneously combust first then we're very quickly going to see the others spontaneously combust

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and we're going to see that transition from the fire within a room to a room

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that is entirely on fire and this is what we refer to as flashover it's

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that transition from a fire within a room which is feeding

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that convection current to a room that is entirely on fire

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and that's where we see our heat release rate increase rapidly to a very large extent

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and in fact after flashover has occurred temperatures of 900 to 1100 degrees celsius can be reached throughout the room

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now after flashover has occurred there is a lot more heat being generated from the fire

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because there's simply a lot more fire being created

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because we've got an entire room that's on fire rather than just a small section of that room.

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Now the result of which is all of these fire gases

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and all of this heat have to go somewhere and

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so they're going to be heading out of whatever openings they can find

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and generally that's going to be a door or a window

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and you can see here that once our room is flashed over all

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that heat that's being generated quickly starts to heat up the next room and then the room after that.

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So flashover isn't a single occurrence.

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What we actually see in a house fire is one room will flash over

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and then another and then another

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and all of this of course is based on how much air

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that is available to allow that combustion process to fully oxidize those fuels.

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Now this means that flashover really does rely on the three sides of the fire triangle,

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meaning we really need that heat to be radiating down on our fuels

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so that they can start to pyrolysis and reach their auto -ognition temperature.

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We also need the oxygen to allow that combustion process to occur

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and of course we need the fuel because without the fuel itself there's nothing for this process to affect.

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Now

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if we were to talk about some important signs of flashover

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we will be talking about a lowering of the neutral plane

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or that smoke layer as some people will call it we're going to be seeing

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that smoke layer become more and more unstable in the process as well

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because it's going to be needing to try

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and even itself out between the hot overpressure gases and the cold or under pressure gases as the air comes in

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we're going to be seeing objects

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and surfaces around the room start to emit pyrolysis gases as they heat up

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and break down and this is a really late sign as well

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if there's things pyrolysis around the room you know

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that they're being heated to a really extreme extent and that flashover isn't far away.

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We've also talked about flames in the overpressure and we know

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that that's a really late indicator that flashover isn't far away

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and it's really important that

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if we're seeing those flames in the overpressure

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we cool those gases down otherwise we're going to start to see a really rapid progression to flashover.

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Now of course with those really high temperatures above the neutral plane

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we're also going to be getting some really intense and painful radiant heat.

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So if we're in a fire and being force down by the heat, that's a really good indicator that flashover isn't far away

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and we really need to cool those gases down so

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that we can try to create a safer environment for ourselves to work in.

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And while cooling these gases down is really important to ensure

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that we can actually maintain our environment and actually have a safer working environment

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while we try and make our way to the fire, once we reach the fire we need to make sure

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that we attack it in an aggressive manner because the longer we leave it,

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the more it's going to be able to pump out these hot fire gases

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and the more that

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that convection current is going to be pushing hot fire gases throughout the building

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and radiating heat down on all of the fuels and allowing that fire to progress

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so now we've seen how flashover works and we know what some of the signs are

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I'm just going to play a video

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so we can actually follow a fire all the way through from a developing fire all the way through to flashover.

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And we'll actually see quite a lot of these indicators as we go through.

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Now bearing in mind outside the box is quite windy

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so we actually do struggle to get a nice stable neutral plane and a number of points of this fire.

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But that's just because the box is really quite small and it was a fairly windy day.

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Transcription by CastingWords Thank you.

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We'll be right back.

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Thank you.

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Transcription by CastingWords Thank you.

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All right, so now we've seen how flashover works, and we've also seen that it's not really a rare occurrence.

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In fact, it happens at pretty well every structure fire that continues on to being fully involved.

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We've also seen that it's not just one flashover.

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In fact, that each and every room in that house or the building can actually flashover, which is why it's really important that as firefighters,

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when we're entering into these buildings, we're actually looking for the signs of flashover so

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that we can predict the fire's growth and actually act accordingly and actually suppress that fire while keeping ourselves safe.

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And it's only through regular training

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that we're actually going to get used to actually looking for these signs and then acting accordingly.

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Alright well that's it for this one thanks very much for watching and I'll catch you in the next one.

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Bye!

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このレッスンの語彙とスピーキングのポイント

このスピーキングレッスンは、動画「An Introduction to Flashover - Episode 9」を教材にしています。繰り返し出てくる語は次のとおりです：flashover, heat, fuel, gases, temperature。この動画には、シャドーイング用の文が182文、単語が2333語あります。音声の長さは14:07です。話す速さは1分あたり約165語で、日常会話に近い自然なペースです。単語の85%は英語の頻出3,000語に含まれます。残りは練習の前に確認しておきましょう。

この動画の重要語彙

動画に出てくる覚えておきたい単語15語を、発音と意味つきで紹介します。

単語	発音	意味
oxygen 名詞	/ˈɑksɪd͡ʒən/	酸素
flame 名詞	/fleɪm/	炎, 火炎
occur 動詞	/əˈkɜː/	起こる, 起る
transition 名詞	/tɹænˈzɪʃ.ən/	遷移, 推移
automobile 名詞	/ˈɔː.tə.məˌbil/	自動車, 乗用車
ignition 名詞	/ɪɡˈnɪʃən/	点火, 発火
layer 名詞	/ˈleɪ̯ɚ/	層, 膜
neutral 形容詞	/ˈnuː.tɹəl/	中立の
ceiling 名詞	/ˈsilɪŋ/	天井
indicator 名詞	/ˈɪn.dɪˌkeɪ.tə(ɹ)/	インジケータ, インジケーター
combustion 名詞	/kəmˈbʌs.t͡ʃən/	燃焼
extent 名詞	/ɪkˈstɛnt/	程度
refer 動詞	/ɹɪˈfɜː/	問い合わせる
rapid 形容詞	/ˈɹæp.ɪd/	速い, 急な
indicate 動詞	/ˈɪndɪˌkeɪt/	示す, 指す

動画に出てくる句動詞

単語	発音	意味
go ahead 動詞	/ˌɡoʊ əˈhɛd/	どうぞお先に
go back 動詞		戻る, 帰る

この動画の文法

話し手がよく使っている文型を、動画の実際の表現とともに紹介します。

文型	動画での表現
現在完了形 have/has + 過去分詞 — 過去の出来事が今も関係している	we've covered · haven't seen · have shown
受動態 be + 過去分詞 — 誰がするかより、何が起きるかに焦点を当てる	being drawn · being radiated · is radiated
関係詞節 who / which + 節 — 人や物について情報を加える	flashover which is · atmosphere, which is · monoxide, which is

注意したい発音

話し手はwe're, we've, they'reなど、短縮形や弱形を54回使っています。聞こえたとおりの短い形で発音しましょう。

「sh」と「zh」の音: transition /tɹænˈzɪʃ.ən/, ignition /ɪɡˈnɪʃən/, flash /flæʃ/, ventilation /ˌvɛntɪˈleɪʃ(ə)n/, transcription /tɹænˈskɹɪpʃən/
長い単語（アクセントの位置に注意）: automobile /ˈɔː.tə.məˌbil/, indicator /ˈɪn.dɪˌkeɪ.tə(ɹ)/, accordingly /əˈkɔɹ.dɪŋ.li/, ventilation /ˌvɛntɪˈleɪʃ(ə)n/, necessarily /ˌnɛs.əˈsɛɹ.ə.li/

日本語話者が苦手な音：

/r/ と /l/ の区別 — /l/ は舌先を歯茎につけ、/r/ はどこにもつけない: neutral /ˈnuː.tɹəl/, rely /ɹɪˈlaɪ/, variable [ˈvæɹ.i.ə.bl̩], accordingly /əˈkɔɹ.dɪŋ.li/, triangle /ˈtɹaɪˌæŋɡəl/
/v/ — /b/ にならないように、上の歯を下唇に当てる: variable [ˈvæɹ.i.ə.bl̩], ventilation /ˌvɛntɪˈleɪʃ(ə)n/, aggressive /əˈɡɹɛs.ɪv/, vulnerable /ˈvʌln(ə)ɹəbl̩/, overpressure /ˌoʊ.vɚˈpɹɛʃ.ɚ/
/f/ — 「フ」ではなく、上の歯と下唇で出す: flame /fleɪm/, flash /flæʃ/, refer /ɹɪˈfɜː/, atmosphere /ˈætməsˌfɪɹ/, fancy /ˈfæn.si/

この動画での練習方法

まず声を出さずに動画を最後まで聞き、知らない単語をメモします。
まず0.75倍速で一文ずつシャドーイングし、慣れてきたら通常の速度に戻します。
自分の声を録音して元の音声と比べます。oxygen, flame, occurなどの単語に特に注意しましょう。

シャドーイングとは？英語上達に効果的な理由

シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。

シャドーイングのやり方: ステップ別の完全ガイドを読む →

シャドーイング練習: An Introduction to Flashover - Episode 9 - 動画で英語スピーキングを学ぶ

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