[Narrator] In a high
rise building.
- There was no warning.
[Narrator] At sea.
- Innocent people died.
[Narrator] In a train.
Everything was on fire.
Everything was burning.
[Narrator] Disasters can
begin with the smallest
things.
- Changing the opening
hours of a restaurant.
- The bad glue job.
- A paperwork error.
[Narrator] Now,
combining the latest
research with
every available
source of evidence,
experts will forensically
analyze three disasters
down to each tiny detail.
- You've really got to
think outside the box.
- You have to work
your way back
and understand each
link in the chain.
[Narrator]
State-of-the-art
graphics reveal
every critical detail at
every critical moment.
- This whole disaster
could have been averted.
[Narrator] We can
dissect them,
get inside, or
underneath,
freeze time, and
even reverse it.
To conduct a complete
disaster autopsy.
[Narrator]
Surfside, Florida.
An idyllic vacation
and retirement spot.
- The sea is beautiful.
The sun is shining.
So who doesn't
want to live in a
place like this?
[Narrator]
Champlain Towers,
a high-rise condominium.
For 40 years, it offers
residents a prime spot
on this spectacular
beachfront.
Around 1.22 a.m.
on June 24th, 2021,
with no warning, the
12-story tower collapses.
- 10,000 tons of
concrete and steel
comes crashing down.
[Bystander] Oh my God.
[Narrator] Rescue teams
spend two weeks
desperately searching
for survivors.
The disaster
claims 98 lives.
The oldest victim is 92,
the youngest just a year.
How could it collapse
without warning?
[Dr. Joshua Macabuag]
There's no construction
work going on.
There's no hurricanes.
There are no obvious
external reasons
for the collapse.
[Narrator] Using all the
available evidence,
we will digitally
recreate the disaster
to discover what brought
Champlain Towers down.
The condominium
is located in the town of
Surfside in Miami-Dade
County, Florida.
- Champlain Towers South
was completed in 1981
with 136 units
over 12 stories.
On the top floor, it had
a four-bedroom penthouse.
It had a pool deck
and an underground
parking garage.
[Narrator] The first
question is
why do so many die?
[Dr. Joshua Macabuag]
Remember that
this collapse
was around half past
one in the morning,
meaning that people
would have been
asleep in their beds.
[Narrator] Vital
evidence comes from a
CCTV camera that captures
the disaster.
It provides an
initial timeline
for the collapse.
[Dr. Yasemin Aktas] The
security video show that
the first part
of the building
that collapsed was
the central bit.
And then after
a few seconds,
the northeastern
part came down.
[Narrator] This footage
helps explain
the appalling
number of deaths.
The entire disaster takes
just over 12 seconds.
There is no
time to escape.
And photographic evidence
also helps explain
the lethal nature
of this collapse.
- When you look at the
collapsed buildings,
then you see a number
of mostly intact floors
sat on top of each other.
And that's actually
called a pancake collapse
because the floors look
like a stack of pancakes.
[Narrator] In a pancake
collapse, the higher
floors fall vertically
downwards,
almost in one piece
on the ones below.
This is particularly
lethal.
- For people to survive
in a collapsed building,
they need what is called
survivable voids,
intact spaces where
people can be safe
and relatively uninjured.
But with that
pancake collapse,
those voids just
don't exist,
which is what led
to such tragic
loss of life here.
[Narrator] Pancake
collapses can also be
unusually dangerous
because they often
start at the only point
of escape, the bottom.
Evidence points to
exactly this kind of
failure at Surfside.
- There are eyewitness
testimonies
that actually says
that the pool deck
was the first bit of the
building that collapsed.
[Narrator] Surfside
fatalities are high
because it suffers a
lethal pancake collapse
in the middle
of the night.
And it begins with the
failure of the pool deck.
Why does the pool
deck collapse?
Amateur footage
from just minutes
before the disaster
suggests the pool
deck is already in the
early stages of collapse.
[Prof. Luke Bisby] The
video shows debris in
the bottom of the
parking garage.
And the video
appears to show
that water is already
leaking in from up
on the pool deck.
[Narrator] Amateur cell
phone footage taken a
year before the collapse
suggests this area
of the garage ceiling
has been degrading
for some time.
Is there an
underlying problem
with the design
of the pool deck?
[Dr. Yasemin Aktas]
Under normal
circumstances,
we designed the decks
or large surface areas
that tackle water, that
are exposed to water
to have a slight
inclination
so that the water
can be drained away
from the surfaces as
quickly as possible.
But it wasn't the case
with this building,
the first surfaces,
the pool deck
was entirely flat.
[Narrator] That means
there would have been
pools of standing water
on the deck.
- When you have a
flat slab surface
that is exposed to water,
the water will stay
there for a long time.
And because of the
porosity of the concrete,
it is going to infiltrate
into the structure more.
[Narrator] And Surfside
is built in a location
where water intrusion is
particularly dangerous.
- Being located
on the coast,
the building is
very much exposed
to salty sea water.
[Narrator] Without
proper drainage,
corrosive salt water
on the pool deck
could soak into the
concrete from above.
- We're talking
of course about
reinforced concrete,
which means that
you have concrete
around reinforcing
bars or steel bars.
[Narrator] Salt water
soaking through the
concrete is extremely
corrosive
to the steel
reinforcement.
The red staining
in the phone video
of the garage roof
a year before the
collapse is rust,
evidence that
the steel bars
within the pool deck
above are corroding.
And other evidence
suggests salt water
was also attacking the
structure from below.
According to
news reports,
a 2018 memo to residents
warns that salt water
is seeping up
from underground
as a result of
storm surges.
And this is backed
up by key evidence.
- There's a statement
from a former
maintenance manager
named William Espinosa
to suggest that sometimes
there would be
two feet of sea water in
the parking garage.
[Narrator] Across the
garage is a network of
concrete pillars that
support the pool deck.
During flooding,
salt water will be
soaking into them and
attacking the steel
reinforcement inside.
[Dr. Joshua Macbuag] So
as the steel rebar
rusts, then that
rust expands.
That forces the concrete
around it outwards,
causes it to crack
and fall away.
That's something
called spalling.
You're losing
concrete that's able
to support the load
and carry the weight
it's designed to do.
- An impact report
from 2018 documents
that there is
extensive spalling
on those columns.
- And of course,
as it's cracking
and falling away, it's
exposing that steel
to even more corrosion.
[Narrator] The evidence
suggests the pool deck
is weakened from
above and below.
And photographic evidence
reveals that extra loads
were applied to it
that weren't in
the original plans.
[Dr. Yasemin Aktas] They
put very large planters
on the pool deck,
which is full of
wet soil, whose
weight is very high.
So that actually
exerts additional
loading on the
building in a very
concentrated fashion.
[Narrator] The deck was
never meant to carry
this load.
[Prof. Luke Bisby]
What's really
interesting
is if you look at
the original plans
for the building,
these planters are not
part of the design.
[Narrator] The pool deck
and its supports
have been weakened
by saltwater attack
and extra loads.
Is that the cause of
the pool deck collapse?
Photographic
evidence suggests
there is something
else going on as well.
[Prof. Luke Bisby] If
you look at pictures
of the pool deck
after the collapse,
you can see that
in some places it
looks as though
the columns
have punched
up through the slab,
and this is called
punching shear.
[Narrator] Punching
shear happens when a
concentrated load
is applied by the
columns to a small
area of the slab above.
Engineers avoid it
by placing a beam
at the top of the column
to spread the load.
And the Surfside plans
use this technique.
So why don't they work?
- The beams that are
supposed to be there
to support the pool
deck based on the
original drawings
were not there in
the construction.
[Narrator] The pool deck
that triggers the
disaster has flaws both
in construction and in
its use and maintenance
but what is the
trigger that brings
the towers down?
[sirens wailing]
[Narrator] All the
evidence suggests the
failure of the pool deck
is the first step in
the collapse of the
Champlain towers.
-So it seems that the
pool deck
collapses first and
after that point,
what are our options
for things that could
bring this tower down?
Is it that the collapse
of the pool deck
has knocked some
of the columns at
the lower level and
destabilized them?
Is it that the collapse
of the pool deck
pulls the building
slightly to the side
and that destabilizes
the overall
structural system
for the building?
At this point, we
just don't know.
[Narrator] Whatever the
precise chain of events,
the failure of the
pool deck brings down
the central and eastern
towers in seconds.
But if a key
weakness of the deck
is the long-term
degradation and
saltwater damage,
why isn't it spotted
before the disaster?
[building crashing]
- One of the most
shocking things
about this story is
that all of these
maintenance problems
or design problems
were not unnoticed.
There have been
many complaints,
many inspection
reports written,
and many requests for
proper maintenance
or resolution of
these problems.
[Narrator] Miami-Dade
County requires a
40-year structural
recertification
of condominiums
over three stories.
Champlain Towers
was 40 years old.
- In 2018, the
Condominium Board
hired an external
engineering consultant
to try to help them
understand what they
might need to do in this
recertification process.
[Dr. Yasemin Aktas] The
reports talked about the
heavy deterioration on
concrete
structural members.
They mentioned the
waterproofing problems
with the decking.
They actually mentioned
the planters, et cetera.
And to anyone who
reads it, it should
be really alarming.
[Narrator] Estimates
for the required work
come in at around
$15 million.
It's not pocket change,
and organizing agreements
between the residents
inevitably takes time.
By that point,
it's too late.
In June 2021, Champlain
Towers collapses
with the work yet
to be carried out.
Now we understand
the chain of events
that leads to
the collapse.
[Prof. Luke Bisby] The
seeds of this disaster
are sown all the
way back in 1981
during the original
construction of the
tower.
[Dr. Yasemin Aktas] For
whatever reason, the
original design drawings
were not abided with
during the construction,
and the pool deck was
built with less beams
than it should be.
[Narrator] This includes
at least four beams
at the first point
of collapse.
- Now the pool deck
also has issues.
It's been designed
without a slope,
so it can't drain
properly.
And you've got the heavy
palm tree planters
that have been installed
after the fact,
as well as the corrosion
of the reinforcing steel
within the concrete slab.
[Narrator] At around
1.15 a.m.
on June 24th, 2021,
these issues caused
the pool deck to fall
into the garage below.
Just seven minutes later,
the central portion
of the building suffers
a pancake collapse.
A few seconds later, the
eastern wing follows.
- It seems that there
are so many weaknesses
in this structure
that it's possible
we may never know
exactly what triggered
the collapse.
[Narrator] Emergency
crews arrive on the
scene, and search and
rescue efforts
begin before dawn.
- It's very difficult to
point at any one thing
as the sole cause
of this disaster.
The initial design
wasn't strong enough.
It wasn't constructed as
per the design anyway,
and it wasn't maintained,
meaning that the
strength just further
degraded over time.
All of these things
would have come together
in a very complex
way to eventually
initiate this disaster,
which resulted in
the loss of 98 lives.
[Narrator] The Champlain
Towers collapse shocks
America.
In the aftermath,
local authorities
search for answers.
- Miami-Dade County then
orders the inspection
of all high-rise
buildings over
five stories or
older than 40 years.
[Narrator] The
inspections uncover
serious problems.
[Dr. Joshua Macabuag]
That results in the
immediate evacuation
of another condo
seven miles away,
and the closure of the
Miami-Dade courthouse.
[Narrator]
New regulations
onbuilding
certifications
have been introduced.
They are designed to
prevent a tragedy
like Surfside ever
happening again.
But the danger of
any hidden fault
is that disaster can
strike with no warning,
and those hidden faults
can have
devastating
consequences.
The Barents Sea,
August 12th, 2000.
The Russian nuclear
submarine K-141 Kursk
is on a naval
training exercise.
At over 500 feet long,
she is one of the biggest
submarines ever built,
and a fearsome weapon.
- It was capable of
carrying 24 500 kiloton
nuclear missiles
and crewed by
118 submariners.
[Narrator] By late
morning, the Kursk is at
periscope depth,
ready for her part
in the mission.
- This was a training
exercise firing
a dummy weapon with
no expl*sive warhead.
This exercise should have
been a walk in the park.
[Narrator] But just
before 1130,
the Kursk simply
disappears.
-Radio silence, she
just goes missing.
[Narrator] The Kursk is
never heard from again.
The submarine is later
discovered on the seabed,
350 feet below
the surface.
All 118 crew are lost.
What happened to
the pride of the
Russian fleet?
Now, using images of
wreckage on the seabed,
declassified government
documents and
scientific analysis,
we will digitally
recreate the
disaster to find out
what sank this
cutting edge weapon?
♪
[Narrator] The Kursk
nuclear submarine is
found at the bottom of
the sea in August, 2000,
after a routine
training exercise.
- In October, 2001,
about a year and a half
after the accident, the
wreckage of the Kursk
was finally recovered
from the seabed
during an international
salvage operation.
[Narrator] The submarine
appears intact, except
for one major part.
[Nadia El-Awady] When
the Kursk was lifted,
the bow was missing.
The reason for that
was that it was
cut off the Kursk on
the seabed because
there were some concerns
that there could
still be some live
torpedo warheads
in the bow.
[Narrator] A year later,
this critical
piece of evidence
is destroyed in a
controlled expl*si*n.
- Fortunately, before
that was done,
the rescue and salvage
divers managed
to get a good look
at the bow and even
get some samples for
analysis afterwards.
[Narrator] The reports
and footage contain
vital clues.
[Dr. Andrew Steele]
Reports from salvage
divers describe
a massive hole in
the top of the bow,
about 60 feet in length.
There are also reports
of a large dent
and then scraping
marks along the
length of the hole,
which sounds a lot
like impact damage.
[Narrator] Could a
collision have sunk the
Kursk?
[Dr. Sascha Auerbach] If
you look at statements
on Russian television
just a few days
after the disaster,
Russian officials
are already pointing
the finger of blame
at some kind
of collision.
- And in these
statements, there's
absolute certainty
that the collision
wasn't caused by one
of their own ships.
[Narrator] Russian
naval officials produce
evidence to support
their claim.
- The Russians released
satellite imagery
showing a NATO naval
base at Bergen, Norway,
just outside of the
Barents Sea area.
The image shows two Navy
vessels docked there
and the Russians
assert that the
vessel on the left is
the American nuclear
submarine, the Memphis.
[Narrator] The Russians
claim this image is
taken just after the
Kursk sank.
- Russian officials
were claiming that
this could potentially
be the smoking g*n
they were looking for.
[Narrator] They believe
the American submarine
is being repaired
after a collision.
[Dr. Sascha Auerbach]
This is hardly a crazy
idea.
U.S. subs routinely
shadow Russian subs
quite close behind them.
[Narrator] Does an
American submarine
collide with the Kursk?
- If there was a
collision, one thing
is for certain,
someone would
have heard it.
[Nadia El-Awady] There
are thousands of
seismographic stations
all over the world,
and their role is to
detect the tiniest
of vibrations, to
measure natural
phenomena like
earthquakes, for example.
At around the time that
the Kursk disappeared,
the Norwegian
Seismological Institute
picked up an anomaly
in the data.
You can tell a lot
from these graphs.
They basically act
like a fingerprint
of what actually
happened.
What this fingerprint
is telling us
is that it's not two
things hitting up
against each other.
[Narrator] Instead, it
is the unmistakable
profile of an expl*si*n.
- The expl*si*n was
so huge that the
signal was picked up by
seismographic stations
thousands of miles away.
[Narrator] If an
expl*si*n sinks
the Kursk, what
causes it?
The inner workings
of a Russian
nuclear submarine,
like the Kursk, are
highly classified.
[Dr. Sascha Auerbach]
Fortunately, we have
enough information
from naval experts
and from photographs
and footage
that we can
reconstruct the
structure of the Kursk
with this information.
[Dr. Eddie Blanco-Davis]
We do know that it was
likely to have
nine different
watertight compartments.
[Dr. Sascha Auerbach] At
the bow, compartment
one, has torpedo
launchers,
and we believe
space for around 18
conventional torpedoes.
[Narrator] According to
the evidence,
this was the most badly
damaged part of the sub.
Is it possible a
torpedo exploded?
[Dr. Andrew Steele] Data
from the Norwegian
Seismological Institute
shows an expl*si*n
of a size about two
or three tons of TNT.
[Narrator] That is
enough to cause the
massive hole in the
bow and sink the Kursk.
But there is a problem.
An expl*si*n that big
would need around
seven torpedoes to go
off simultaneously.
Is that really plausible?
[Narrator] Around the
time the Kursk sinks,
seismological
data records a
massive expl*si*n
equivalent to two or
three tons of TNT.
But closer analysis
reveals another
smaller event, 135
seconds earlier.
- The pattern of
that smaller signal
is almost identical.
And what that means
was that the first one
was also an expl*si*n.
[Narrator] We know from
Russian reports that
around this time, the
Kursk is preparing
to launch a dummy
torpedo from tube four.
- Analysis of the
salvage crew's recovery
of compartment one shows
something interesting.
Fragments of a torpedo
from tube four
embedded in the ceiling.
Severely melted
equipment was also found
in the compartment,
suggesting that a
fierce fire must have
broken out in there.
This gives us a clear
sequence of events.
A dummy torpedo
explodes in tube four,
and then the fire caused
by that expl*si*n
heats up the
torpedoes around it,
causing several
of them to explode
simultaneously.
The Kursk took on
water and sank.
[Narrator] But something
about this explanation
doesn't quite fit.
- The torpedo in tube
four was what's called
a dummy torpedo.
It didn't carry
any expl*sives.
So how could a
torpedo that doesn't
carry any
expl*sives explode?
[Narrator] The Kursk's
torpedoes are fueled
by a kerosene
burning gas turbine,
and that also requires
a source of oxygen.
This comes from HTP,
highly concentrated
hydrogen peroxide.
But naval records
reveal that HTP has
a troubling history.
- The US and British
navies had such
problems with HTP,
they had banned it
from use on submarines
long before the
Kursk accident.
HTP is inherently
unstable.
So if it mixes with
other fuels or if it
touches brass or copper,
it goes from liquid stage
to a gaseous stage that's
much, much bigger,
thousands of times
greater, but also
releases a lot of heat.
[Narrator] But for an
expl*si*n to occur,
there would have to be a
leak in the dummy
torpedo's HTP tank.
Is that believable?
- We know for this
torpedo that in the past,
they had problems with
the welds corroding
and leaking HTP.
Now, torpedoes
with warheads had
been modified,
but this torpedo
was a practice,
a dummy torpedo.
It didn't have a
warhead, so it probably
was never modified.
So a potentially faulty
weld. It corrodes.
It causes the HTP to
leak out of the torpedo
into the torpedo
bay, where there's
plenty of copper
and brass items.
If the HTP touches
those, it would
cause the expl*si*n.
[expl*si*n]
- The evidence points
to an expl*si*n
in the torpedo room
that caused a chain
reaction leading
to the deaths of
everyone in the forward
compartments of the sub.
But it doesn't
explain what happened
to the rest of the crew.
[Narrator] Inside
compartment nine,
which was only
partially flooded,
rescue divers find
the bodies of
23 crew members.
Why didn't they survive?
We know they didn't die
in the initial expl*si*n,
because one of them
leaves a note.
[Dr. Sascha Auerbach]
"It's dark here to
write, but I'll
try by feel.
Let's hope that at least
someone will read this.
Do not despair."
[Narrator] It is clear
the initial blast hasn't
k*lled the trapped men.
So what does?
[Nadia El-Awady] All of
the men had burns,
some of them
quite significant.
But some also only had
burns on their backs,
which indicates that
their backs were
probably the parts that
were exposed to a fire.
[Narrator] Postmortem
results suggest those
who survived the fire
die from
carbon monoxide
poisoning.
How could a fire start
in the unpowered sub?
[Nadia El-Awady]
They found potassium
superoxide
containers in
the compartment.
These are used to
produce oxygen through
chemical reactions and
absorb carbon dioxide.
The men were probably
using these to
produce oxygen for them
to be able to breathe.
[Narrator] Unluckily for
the survivors, they're
trapped in a compartment
half full of oily water.
[Nadia El-Awady] When
potassium superoxide
mixes with oil and water,
it creates a
devastating flash fire.
What that suggests is
that one of the men
probably dropped the
superoxide container
into the water.
[Dr. Andrew Steele] The
reason that some men
were only
burnt on their back is
probably because they
ducked below the surface
to avoid the fire.
But when they came
back to the surface,
they would have
been greeted with
an atmosphere which
had had a lot of
the oxygen removed
from it by the fire
and replaced with
deadly carbon monoxide.
[Narrator] With no
breathable oxygen, there
was only one outcome
for the 23 souls
trapped in
compartment nine.
♪
[Narrator] We now know
enough to put together
a likely timeline of the
whole Kursk disaster.
- On the morning of
August 12, 2000,
during a naval
exercise, the Kursk
positions itself
at periscope depth
and prepares to fire
a dummy torpedo.
- The dummy torpedo
leaked HDP into
a torpedo tube.
[Narrator] The resulting
chemical reaction
causes a massive
expansion of hot gas,
rupturing the
torpedo's fuel tank
and triggering
an expl*si*n.
- After the first
expl*si*n, the heat
in the torpedo
compartment cooks off
several other torpedoes
with live warheads.
The expl*si*n tears a
gaping hole in the bow,
flooding the submarine
and k*lling everyone
forward of the
fifth compartment.
[Narrator] 23 surviving
crew end up in the
ninth compartment.
But in all likelihood,
a dropped
superoxide cartridge
reacting with oily water
causes a flash fire.
It consumes the remaining
oxygen and kills
the last surviving
crew members.
♪
Following this tragedy,
the Russian Navy
withdraws the hydrogen
peroxide heavy
torpedoes from service.
- In the end, the
evidence points
to the nearly
invincible Kursk.
The submarine that was
supposed to be unsinkable
by enemy torpedoes
was, in fact, undone
by one of its
own torpedoes.
And 118 men lost
their lives in a
training exercise.
♪
[Narrator] The Kursk
disaster was a tragedy
that could have
been avoided.
And it is far from
the only one.
London, King's Cross
Underground Station.
[Dr. Sascha Auerbach]
King's Cross is one of
the busiest
subway stations.
It carries millions
of people in and
out every year.
[Narrator] One November
night in 1987, a minor
fire breaks out.
- It's really not
very big, but as a
matter of precaution,
they begin
evacuating the public.
- And then out of
nowhere, a jet of flame
explodes into an
enormous fireball.
♪
[Narrator] It is the
deadliest blaze in the
history of the city's
underground train system.
Thirty-one people are
k*lled.
Britain is in shock.
How could this happen?
What starts the fire?
How does it transform
into a lethal fireball?
♪
Now using all the
available evidence
and the latest imaging
technology, we will
digitally recreate the
scene of the disaster
in minute detail.
What happens at
King's Cross?
Some of the most vital
pieces of evidence
are witness statements
from people
who are there at
the outbreak.
[Dr. Andrew Steele] The
first sign that
anything's amiss is at
7:29, when a passenger
called Mr. Squire notices
a small fire,
and he rushes to
the ticket office
to let the staff
know what he's seen.
♪
[Narrator] His statement
suggests escalator four
is where the first signs
of fire are seen.
It connects the
Piccadilly line with
the main ticket hall.
In the days after the
disaster, extensive
photographic evidence
is collected.
It contains clues that
help zero in on exactly
where the blaze began.
[Dr. Sascha Auerbach] If
you look at the
scorch marks and
the char patterns
that show the
fire's progression,
we can trace its
origins to right
underneath escalator
number four.
[Narrator] Not on the
escalator,
but underneath it.
This fits with a
second eyewitness.
They describe a
glow and smoke
beneath escalator four.
But how does a
fire start there?
[Newscaster] When the
fire broke out,
the station was
packed with crowds.
[Narrator] Operational
records for the
train network
contain vital clues.
[Ada McVean] Fires on
the London Underground
are not unprecedented
at all.
There have been
around 400 in the
decades leading up
to this disaster.
[Dr. Andrew Steele] The
records between
1956 and 1988
show that about 70%
of them are caused
by discarded
smoking materials.
So discarded bits
of cigarettes after
people have finished
with them, for example.
[Dr. Sascha Auerbach]
Until the mid-1980s,
smoking was actually
allowed on the
London Underground
on the subway.
And though it was
banned in 1985,
people who worked
in the stations
reported that passengers
routinely ignored
these regulations
and lit their
cigarettes immediately
on leaving the train
as they were going
up the escalator
to leave the station.
[Narrator] The builders
of the escalators are
clearly aware
of this risk.
[Dr. Andrew Steele] If
you look at the design
of this escalator,
you can see that at
the edges, there
are little L-shaped
pieces of metal.
And one of the
things these can do
is catch those bits of
falling smoking material
and hopefully stop
them from getting
underneath the escalator.
[Narrator] These are
called fire cleats.
They are fitted on
every tread when the
escalator is built.
But number four escalator
has been in service
for almost half a
century.
[Dr. Andrew Steele]
Staff who worked at the
station reported
that about 30%
of these L-shaped bits
of metal were missing,
providing plenty of space
for a match or a
cigarette to make it
underneath the escalator.
[Narrator] But there
must be more to the
start of this fire.
- A single match
or a lit cigarette
being dropped onto
the escalator or
underneath the escalator
is not really going
to necessarily ignite
the dense, heavy wood
that the escalator
is made from.
[Narrator] Does the
answer lie in the hidden
area beneath the moving
treads, where
eyewitnesses say
the fire begins?
- So if you look
at the schematic
of the escalator,
we can see that
underneath the tread,
there are wheels
and tracks.
And they're all covered
in lubricating grease
to keep things
moving smoothly.
[Narrator] Could this
grease be the source of
the fire?
[Narrator] Grease has
quite a high ignition
point.
You have to get it to
quite a high temperature
before it catches fire.
So it seems unlikely that
just a discarded match
or a discarded cigarette
would have enough energy
to bring it up to
that ignition point
and start a
blaze that way.
[Narrator] Maintenance
records suggest the age
of the escalator may
be significant in
the origin of the fire.
[Dr. Rory Hadden] This
grease has accumulated
over the years.
There's debris and
dirt and rat fur and
all sorts of things.
And that scenario is very
similar to a candle.
And those bits of debris
will act as a wick,
which could be easily
ignited by a match
or possibly a
lit cigarette.
[Narrator] This fits the
evidence.
But is it more than just
a convincing theory?
They find something
else beneath the treads,
a lot of
discarded matches.
♪
[Narrator] There is
evidence that previous
escalator fires have
started in the same way.
But there is one
very big difference
at King's Cross.
[Dr. Sascha Auerbach]
All these previous
fires,
or smolderings, as
the staff called them,
had not been
particularly serious.
There had been no deaths
or serious injuries.
And they'd been put
out quite easily.
This suggests that with
the King's Cross fire,
there was something
else involved.
[Narrator] What is so
different about the
King's Cross fire?
How can a dropped match
become a fireball
that claims 31 lives?
[Narrator] To understand
the King's Cross fire,
we need to establish
the timeline of
its evolution.
- By chance, there
happened to be two
police constables
on duty that day.
And as a precaution,
they start
evacuating passengers
out of the station.
[Narrator] The
evacuation route leads
people out through
the ticket hall
that is at the top of the
smoking escalator four.
But at this stage,
there is no sign
of serious trouble.
- The first fire crew
arrive around 7:42.
And they observe
quite a small fire,
perhaps not something
they would be
overly concerned by.
[Dr. Andrew Steele] A
few minutes later,
something completely
unexpected happens.
An enormous jet of flame
comes up the escalator
and into the ticket hall,
engulfing firefighters
and escaping passengers,
and ultimately
k*lling 31 people.
[Narrator] One of the
fire crew who assesses
the fire just minutes
earlier, 45-year-old
father of two
Colin Townsley,
is overcome by the
smoke and fumes
while trying to
help a burned
passenger to safety.
He loses his life.
How can a small
fire become so
lethal so quickly?
The unique environment
offers several
possibilities.
[Ada McVean] Because
this is happening
in an underground
station, it's prone to
something called
the piston effect,
which is a theory that
the media raises at
the time as a
possible explanation.
[Dr. Rory Hadden] As
trains move through
the underground tunnels,
as they move,
they push air
ahead of them.
And you often feel
this if you're
standing on the platform
of an underground system
as the wind that kind
of rushes by before
the train arrives.
And this piston
effect is something
that will drive or
will push a fire
up the escalator.
[Narrator] But this
theory doesn't stand up
to scientific
investigation.
- Closer analysis
reveals that the system
reveals that the speeds
of wind, the air
speed that you would
get from that, is
really not enough.
It's on the order of 10
or 11 miles per hour.
And the witness evidence
is that the fire
spread much faster
than that up
the escalator.
[Narrator] There is one
phenomenon well
known to firefighters
that fits this
description
a flashover.
- It's where we go from
having a fire in a room
to a room on fire.
As the fire grows,
everything inside
the room gets hot.
Eventually, it
reaches a point where
it will spontaneously
ignite, resulting
in almost simultaneous
ignition of all
of the combustible
materials.
[Narrator] A flashover
requires a large source
of combustible material
that can be heated
to its flashpoint.
Unfortunately,
on the oldest
underground network
in the world, there
is no shortage of
flammable material
right above the
source of the fire.
[Ada McVean] Although
modern escalators are
made of metal, these
were installed in 1939.
They are almost
entirely made of wood,
from the side panels
to the cleats.
They're just a giant mass
of combustible material.
[Narrator] But a
flashover doesn't fit
with a key witness
statement from
a policeman on the scene.
- A flashover requires
quite a lot of heat.
It needs quite a
big fire for the
space that it's in.
And the observations
made are that the
fire is quite small,
about 10 square
feet, and reaching the
top of the handrail.
So it's not easy to
explain how a flashover
could have resulted in
the rapid fire spread.
[Narrator] What else
could it be?
- There's a fairly
well-known phenomena
in fluid mechanics,
which is called
the Coanda effect.
[Narrator] In the Coanda
effect, a flow of liquid
or gas follows
the curvature of
a solid surface.
What we see as a
fire is actually
a flow of fast-moving
luminous gas,
and in physics, moving
gases obey the same
laws as liquids.
The reason the
Coanda effect may
be significant here
is because the fire,
the flow of hot
gas, is on a sloped
surface, an escalator.
[Dr. Rory Hadden]
Normally in a fire, you
see the hot
smoke and the gases
rising straight up.
But that's not
really the scenario
that we have at King's
Cross, because the fire's
at the bottom of the
escalator, which is
inclined at around
30 degrees.
[Narrator] As the flame
gets hotter, the gases
flow faster, increasing
the force of the
Coanda effect,
making the flame
cling to the treads
instead of rising
straight up in the air.
The Coanda effect cooks
the wooden surface
of the escalator, and the
shape of the escalator
itself makes
things worse.
- Unfortunately,
the vertical sides
of the escalator
channel these hot
gases upwards.
They can't escape
out to the sides,
and that only
amplifies the effect.
And that's going to
mean the treads further
up get heated up
incredibly rapidly
until they ignite.
[fire burning and
crackling]
[Narrator] Now we can
explain the chain of
events that leads to the
King's Cross disaster.
- Sometime around
7:25 PM, a passenger
on escalator four lights
a cigarette.
They drop the lit match
on the escalator,
and it falls
down underneath.
[Narrator] The match
sets fire to the
contaminated grease
beneath the escalator.
Then as the fire grows,
the Coanda effect
changes everything.
[Dr. Andrew Steele] The
hot gases begin to lie
down along the surface of
the escalator steps.
The superheated
gases rapidly raise
the temperature of
the combustible wood
further up the escalator.
[Narrator] The wooden
steps further up the
escalator reach the point
of ignition.
- Around 7:45 PM, the
fire begins to
accelerate up those
steps of the escalator,
constrained by the
U-shaped sides,
to emerge as a
jet of flame
into the ticket hall.
[Narrator] It is a
deadly combination of
a flashover-like
fire driven
by the Coanda effect.
- This demonstrates
a previously unknown
phenomenon, which
is now known as the
Trench effect.
[Narrator] The King's
Cross fire is the first
time the Trench effect
is ever documented.
And scientific analysis
reveals that there
is a good reason
for that.
- The conditions at
King's Cross
escalator four were
perfect for a
lightning fast,
Coanda-driven
fire to spread.
Firstly, you need
a ready supply of
combustible material.
And that wooden
escalator provided that.
Secondly, the angle
of that escalator
is really crucial.
Because if the
angle is too steep,
then the hot air will
just rise too quickly
before it sets fire to
the combustible stuff.
And finally, the
length of the treads
is really important, too.
Because if they're
too long, then again,
that hot air can
rise before it sets
fire to the wood
further down its path.
And it's this
combination of factors
that allowed for that
jet of flame to happen.
[Narrator] All it takes
to trigger it is a
discarded match
or cigarette.
- 31 innocent people
died because someone
couldn't wait until
they got outside
to strike
their cigarette.
- In the years following
the King's Cross fire,
there were sweeping
changes to the
operational practices of
the London Underground,
starting with strictly
enforcing the
smoking ban.
[Narrator] It is also
decided to replace the
aging wood escalators
with metal ones.
- It might seem like
an obvious move
to tear out all of these
archaic wooden escalators
from the tube network.
But it wasn't until
2014, 27 years later,
that the last one was
finally removed from
Greenford Station on
the Central Line.
[Narrator] One final
piece of evidence from
the King's Cross fire
reveals just how
safety critical this
decision really is.
- So after the
investigation, they
look at the escalator,
and they see lots
of scorched marks
beneath the escalator.
And this suggests
there have been
many near misses
in the past.
[Narrator] The fatal
King's Cross fire was
an accident
waiting to happen.
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01x05 - Surfside, Kursk, Kings Cross
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Expert analysis recreates real-world disasters in 3D graphics to uncover hidden causes like paperwork errors, bad glue jobs, or changed restaurant hours.
Expert analysis recreates real-world disasters in 3D graphics to uncover hidden causes like paperwork errors, bad glue jobs, or changed restaurant hours.