ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: An Introduction to Flashover - Episode 9
เลือกโหมดฝึก
แต่ละโหมดจะเปิดห้องฝึกแบบเต็มจอ
182 ประโยค
หากประโยคสั้นหรือยาวเกินไป กดที่ Edit เพื่อปรับแก้
1
G'day everyone my name is Matt and welcome back to The Fire Show.
2
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.
3
In today's episode we're going to be talking about flashover which is a combination of all of these elements.
4
So if you haven't seen those videos I suggest you go back
5
and have a quick look at them first and then come back to this one.
6
Now flashover is a term that gets thrown around a lot by firefighters
7
and sometimes it gets used correctly and sometimes it gets used incorrectly.
8
Now, without wanting to get too bogged down in the specifics of terminology,
9
we're going to have a quick look at what the actual term flashover is referring to
10
and then we're going to have a look at how it actually occurs
11
and what we can do to start reading it
12
and what we can do to actually stop it from occurring in the first place.
13
Now, a textbook example of flashover is the transition from a localised fire to the general conflagration within the compartment
14
when all fuel surfaces are burning.
15
and if you're wondering what conflagration means it's basically just a fancy word for fire
16
if we wanted a much simpler definition for flashover we could say
17
it's the transition from a fire within a room to a room
18
that is entirely on fire now for an example of
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that transition what we have is a fire burning in the corner of the room here
20
and as that fire begins to grow it pumps more
21
and more heat and flames and smoke into that overpressure above the fire
22
and this is really important because as
23
that smoke layer begins to build up
24
it radiates a of heat back down on all the fuels in the room
25
and as all of those fuels begin to heat up they get closer
26
and closer to their auto ignition temperature until a point where everything in
27
that room catches on fire at around about the same time and we see what's called a flashover
28
so what we're going to do is go ahead
29
and talk about how this actually happens
30
and how we can begin to read the signs that are actually indicating that a flashover is imminent
31
and in fact what we can actually do about it now
32
flashover is no different to any other fire where it actually relies on a combination of heat,
33
fuel, oxygen and a chemical reaction so it can actually occur.
34
But if we think about it in these terms, it does make flashover easier to understand.
35
Now if we have a look at this room, we can see that the fuel is coming from the couch
36
and the TV and the carpet and the walls and those kinds of things.
37
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,
38
and in fact it's coming from the air that's being drawn in through the door as the fire burns.
39
now the heat actually comes from the fire itself
40
and as it starts to burn it pushes more heat
41
and smoke and flame up into that over pressure area
42
and by the process of convection that heat spreads out across the room
43
and can actually start to move into other rooms because
44
that convection current takes hold
45
and what we actually see is cold air being drawn in through the door
46
while smoke will actually start to push out through the top of the door and
47
while this process is actually happening what we're seeing is a
48
lot of heat being radiated back down on everything in the room
49
which is slowly starting to heat all of these things up
50
and in fact for most fuels approximately 30 percent of the
51
heat liberated in the flame is radiated to the environment
52
and the rest is actually dispersed convectively in the buoyant flume now this actually means
53
that around about 70 of the heat produced by the fire is actually being transported by the convection current
54
which means that 70 % of the heat is actually being moved up
55
and away from the fire and is therefore available to actually heat up other objects throughout
56
that room and throughout the building
57
so as the convection current moves through the building it radiates heat down on all of the fuels
58
that are confined within that area
59
and as those fuels begin to heat up they then start to pyrolysis
60
and the fuels will start to pyrolysis at different temperatures depending on what they're made of for instance
61
if it's a natural fiber, it's going to pyrolicize at a much higher temperature than if it's an artificial fuel,
62
such as a plastic or a foam.
63
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.
64
Now, some studies have shown that at a ceiling temperature of approximately 600 degrees centigrade, flashover can occur.
65
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
66
that ceiling temperature get up to around about
67
that 600 degree level we're seeing the carbon monoxide in the smoke spontaneously combust
68
which then increases the heat release rate greatly
69
and then we see a rapid progress towards flashover as a result
70
now this is actually an early warning sign for flashover flames in the overpressure region is actually showing
71
that we're reaching that 600 degrees and
72
that flashover isn't very far away now the next thing we start to see is all of our fuels
73
which are pyrolysis are starting to reach their auto ignition temperature which means
74
that we're getting very close to the point where all of
75
those pyrolysis gases are simply going to burst into flames on their own accord even
76
if there is no direct flame impinging from the fire itself
77
now this is where the fire triangle comes back into it
78
because if we don't have our mixture of heat fuel
79
and oxygen we simply can't get the chemical reaction
80
that starts our flashover now in the room we know
81
that we have our heat because our ceiling temperature is reaching around about
82
that 600 degrees level we're seeing the flames in
83
that overpressure our fuel is everywhere it's been readily pyrolysis by the fire
84
and we're seeing all of our couches and walls and floors
85
and all these sorts of things releasing all of these pyrolysis gases
86
so the the final variable is oxygen now oxygen is something
87
that is very variable within a structure fire whether the fire is in a fuel controlled
88
or a ventilation controlled state we're going to be talking about fuel controlled
89
and ventilation controlled more in a later episode but it's important to note
90
that oxygen is a really key component to a structure fire actually occurring
91
and a lack of oxygen can actually stop a flashover happening
92
altogether whereas the addition of more oxygen can actually cause flashover to happen faster
93
and this is why it's really important that
94
when we actually make entry to a building we do so
95
when we're ready to actually get in and apply water to
96
that fire without actually allowing it to get in excess of oxygen before we actually suppress that fire.
97
Now our fire has continued to burn and we're seeing more
98
and more of these pyrolysis gases starting to come out of our fuels
99
and we're also starting to see more and more of
100
that flame activity above the overpressure which is indicating
101
that it's at least 600 degrees
102
now the next step is we're going to start to see these fuels reach their auto ignition temperature
103
and they're going to spontaneously combust
104
now they're not necessarily going to do it all at the same time we're going to see the objects
105
that are more vulnerable or higher in the room
106
spontaneously combust first then we're very quickly going to see the others spontaneously combust
107
and we're going to see that transition from the fire within a room to a room
108
that is entirely on fire and this is what we refer to as flashover it's
109
that transition from a fire within a room which is feeding
110
that convection current to a room that is entirely on fire
111
and that's where we see our heat release rate increase rapidly to a very large extent
112
and in fact after flashover has occurred temperatures of 900 to 1100 degrees celsius can be reached throughout the room
113
now after flashover has occurred there is a lot more heat being generated from the fire
114
because there's simply a lot more fire being created
115
because we've got an entire room that's on fire rather than just a small section of that room.
116
Now the result of which is all of these fire gases
117
and all of this heat have to go somewhere and
118
so they're going to be heading out of whatever openings they can find
119
and generally that's going to be a door or a window
120
and you can see here that once our room is flashed over all
121
that heat that's being generated quickly starts to heat up the next room and then the room after that.
122
So flashover isn't a single occurrence.
123
What we actually see in a house fire is one room will flash over
124
and then another and then another
125
and all of this of course is based on how much air
126
that is available to allow that combustion process to fully oxidize those fuels.
127
Now this means that flashover really does rely on the three sides of the fire triangle,
128
meaning we really need that heat to be radiating down on our fuels
129
so that they can start to pyrolysis and reach their auto -ognition temperature.
130
We also need the oxygen to allow that combustion process to occur
131
and of course we need the fuel because without the fuel itself there's nothing for this process to affect.
132
Now
133
if we were to talk about some important signs of flashover
134
we will be talking about a lowering of the neutral plane
135
or that smoke layer as some people will call it we're going to be seeing
136
that smoke layer become more and more unstable in the process as well
137
because it's going to be needing to try
138
and even itself out between the hot overpressure gases and the cold or under pressure gases as the air comes in
139
we're going to be seeing objects
140
and surfaces around the room start to emit pyrolysis gases as they heat up
141
and break down and this is a really late sign as well
142
if there's things pyrolysis around the room you know
143
that they're being heated to a really extreme extent and that flashover isn't far away.
144
We've also talked about flames in the overpressure and we know
145
that that's a really late indicator that flashover isn't far away
146
and it's really important that
147
if we're seeing those flames in the overpressure
148
we cool those gases down otherwise we're going to start to see a really rapid progression to flashover.
149
Now of course with those really high temperatures above the neutral plane
150
we're also going to be getting some really intense and painful radiant heat.
151
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
152
and we really need to cool those gases down so
153
that we can try to create a safer environment for ourselves to work in.
154
And while cooling these gases down is really important to ensure
155
that we can actually maintain our environment and actually have a safer working environment
156
while we try and make our way to the fire, once we reach the fire we need to make sure
157
that we attack it in an aggressive manner because the longer we leave it,
158
the more it's going to be able to pump out these hot fire gases
159
and the more that
160
that convection current is going to be pushing hot fire gases throughout the building
161
and radiating heat down on all of the fuels and allowing that fire to progress
162
so now we've seen how flashover works and we know what some of the signs are
163
I'm just going to play a video
164
so we can actually follow a fire all the way through from a developing fire all the way through to flashover.
165
And we'll actually see quite a lot of these indicators as we go through.
166
Now bearing in mind outside the box is quite windy
167
so we actually do struggle to get a nice stable neutral plane and a number of points of this fire.
168
But that's just because the box is really quite small and it was a fairly windy day.
169
Transcription by CastingWords Thank you.
170
We'll be right back.
171
Thank you.
172
Transcription by CastingWords Thank you.
173
All right, so now we've seen how flashover works, and we've also seen that it's not really a rare occurrence.
174
In fact, it happens at pretty well every structure fire that continues on to being fully involved.
175
We've also seen that it's not just one flashover.
176
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,
177
when we're entering into these buildings, we're actually looking for the signs of flashover so
178
that we can predict the fire's growth and actually act accordingly and actually suppress that fire while keeping ourselves safe.
179
And it's only through regular training
180
that we're actually going to get used to actually looking for these signs and then acting accordingly.
181
Alright well that's it for this one thanks very much for watching and I'll catch you in the next one.
182
Bye!
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คำศัพท์และข้อสังเกตด้านการพูดสำหรับบทเรียนนี้
บทเรียนฝึกพูดนี้ใช้วิดีโอ “An Introduction to Flashover - Episode 9” เป็นสื่อ คำที่ถูกพูดซ้ำบ่อยที่สุด: flashover, heat, fuel, gases, temperature วิดีโอนี้มี 182 ประโยค และ 2333 คำ สำหรับฝึกพูดตาม ช่วงที่มีเสียงพูดยาว 14:07 ผู้พูดพูดด้วยความเร็วเป็นธรรมชาติ ประมาณ 165 คำต่อนาที ใกล้เคียงกับบทสนทนาในชีวิตประจำวัน 85% ของคำอยู่ใน 3,000 คำที่ใช้บ่อยที่สุดในภาษาอังกฤษ ส่วนที่เหลือควรดูไว้ก่อนเริ่มฝึก
คำศัพท์สำคัญในวิดีโอนี้
คำที่ควรเรียนรู้ 15 คำจากวิดีโอ พร้อมคำอ่านและความหมาย:
| คำศัพท์ | คำอ่าน | ความหมาย |
|---|---|---|
| oxygen คำนาม | /ˈɑksɪd͡ʒən/ | ออกซิเจน |
| flame คำนาม | /fleɪm/ | เปลวไฟ, อัคนิคณะ |
| occur คำกริยา | /əˈkɜː/ | เกิด |
| automobile คำนาม | /ˈɔː.tə.məˌbil/ | รถยนต์, รถ |
| layer คำนาม | /ˈleɪ̯ɚ/ | ชั้น |
| neutral คำคุณศัพท์ | /ˈnuː.tɹəl/ | เป็นกลาง |
| ceiling คำนาม | /ˈsilɪŋ/ | เพดาน |
| extent คำนาม | /ɪkˈstɛnt/ | ขอบข่าย, ขนาด |
| indicate คำกริยา | /ˈɪndɪˌkeɪt/ | บ่งบอก |
| pump คำนาม | /pʌmp/ | เครื่องสูบลม, เครื่องสูบน้ำ |
| triangle คำนาม | /ˈtɹaɪˌæŋɡəl/ | สามเหลี่ยม |
| windy คำคุณศัพท์ | /ˈwɪn.di/ | ลมแรง |
| topic คำนาม | /ˈtɑpɪk/ | หัวข้อ, กระทู้ |
| necessarily คำกริยาวิเศษณ์ | /ˌnɛs.əˈsɛɹ.ə.li/ | ต้อง |
| atmosphere คำนาม | /ˈætməsˌfɪɹ/ | บรรยากาศ |
กริยาวลีที่คุณจะได้ยิน
| คำศัพท์ | ความหมาย |
|---|---|
| heat up คำกริยา | อุ่น |
| go back คำกริยา | กลับไป |
ไวยากรณ์ในวิดีโอนี้
โครงสร้างที่ผู้พูดใช้บ่อยที่สุด พร้อมคำพูดจริงจากวิดีโอ:
| โครงสร้าง | ในวิดีโอ |
|---|---|
| Present perfect have/has + กริยาช่อง 3 — เหตุการณ์ในอดีตที่ยังเกี่ยวข้องกับปัจจุบัน | we've covered · haven't seen · have shown |
| Passive voice be + กริยาช่อง 3 — เน้นสิ่งที่เกิดขึ้น ไม่ใช่ผู้กระทำ | being drawn · being radiated · is radiated |
| Relative clauses who / which + อนุประโยค — ข้อมูลเพิ่มเติมเกี่ยวกับคนหรือสิ่งของ | flashover which is · atmosphere, which is · monoxide, which is |
การออกเสียงที่ควรระวัง
ผู้พูดใช้รูปย่อและรูปลดเสียง 54 ครั้ง เช่น we're, we've, they're ให้พูดแบบสั้นตามที่ได้ยิน
- เสียง “sh” และ “zh”: transition /tɹænˈzɪʃ.ən/, ignition /ɪɡˈnɪʃən/, flash /flæʃ/, ventilation /ˌvɛntɪˈleɪʃ(ə)n/, transcription /tɹænˈskɹɪpʃən/
- คำยาว — ลงเสียงหนักให้ถูกพยางค์: automobile /ˈɔː.tə.məˌbil/, indicator /ˈɪn.dɪˌkeɪ.tə(ɹ)/, accordingly /əˈkɔɹ.dɪŋ.li/, ventilation /ˌvɛntɪˈleɪʃ(ə)n/, necessarily /ˌnɛs.əˈsɛɹ.ə.li/
เสียงที่คนไทยมักออกเสียงยาก:
- เสียงท้ายคำ — ออกเสียงให้ครบ ไม่เปลี่ยนเป็นตัวสะกดแบบไทย: automobile /ˈɔː.tə.məˌbil/, neutral /ˈnuː.tɹəl/, flash /flæʃ/, couch /ˈkaʊ̯t͡ʃ/, triangle /ˈtɹaɪˌæŋɡəl/
- /v/ — ไม่ใช่ /w/ ให้ฟันบนแตะริมฝีปากล่าง: variable [ˈvæɹ.i.ə.bl̩], ventilation /ˌvɛntɪˈleɪʃ(ə)n/, aggressive /əˈɡɹɛs.ɪv/, vulnerable /ˈvʌln(ə)ɹəbl̩/, overpressure /ˌoʊ.vɚˈpɹɛʃ.ɚ/
- /z/ — เสียงก้อง ไม่ใช่ /s/: transition /tɹænˈzɪʃ.ən/, whereas /(h)wɛɹˈæz/, oxidize /ˈɒksɪdaɪz/
วิธีฝึกกับวิดีโอนี้
- ฟังวิดีโอให้จบหนึ่งรอบโดยยังไม่ต้องพูด แล้วจดคำที่ยังไม่รู้จัก
- เริ่มที่ความเร็ว 0.75× พูดตามทีละประโยค แล้วกลับไปใช้ความเร็วปกติเมื่อเริ่มคล่อง
- อัดเสียงตัวเองแล้วเทียบกับต้นฉบับ โดยสังเกตคำอย่าง oxygen, flame, occur เป็นพิเศษ
เทคนิค Shadowing คืออะไร?
Shadowing เป็นเทคนิคการเรียนรู้ภาษาที่ได้รับการรับรองทางวิทยาศาสตร์ พัฒนาขึ้นสำหรับการฝึกนักแปลมืออาชีพ วิธีการนี้เรียบง่ายแต่ทรงพลัง: คุณฟังเสียงภาษาอังกฤษจากเจ้าของภาษาและพูดตามทันที — เหมือนเงาที่ตามผู้พูดด้วยช่วงเวลาห่าง 1-2 วินาที การวิจัยแสดงว่าเทคนิคนี้ปรับปรุงความแม่นยำในการออกเสียง ทำนองเสียง จังหวะ การเชื่อมเสียง การฟังเข้าใจ และความคล่องแคล่วในการพูดได้อย่างมีนัยสำคัญ