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in a crowded london underground station a small routine fire suddenly erupts into a deadly inferno and kills 31
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people dozens more are injured a team of forensic experts searches for clues to the cause of the blaze and
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finds that the fire seemed to defied the very laws of physics to unravel the cause of the mysterious
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fire investigators would need to recreate a historic train station inside a modern
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computer [Music] [Applause] [Music] [Applause] the sprawling london underground is the
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largest and oldest subway rail system in the world but on the evening of november 18 1987
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commuters are unaware that disaster lurks beneath them at 7 30 p.m a passenger at the historic
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king's cross station sees a flicker of flame underneath a heavily varnished 50-year-old wooden escalator
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the london fire brigade is dispatched it seems to be a routine call an everyday call to a fine and escalator
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something we were receiving probably 20 or 30 times a month so it was no big deal
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fire captain roger kendall one of the first to reach the scene waits above ground for his supervisor to report
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we will wait for message to come back to say either we're all going home or we
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may need a bit of equipment trains continue to come and go despite the minor commotion
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musician ron lipsius arrives at the station on one of those trains we've noticed these two
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men i don't think they were in uniform but they were blocking physically blocking
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entrance to the wooden escalators on our left which are the ones that directly go to piccadilly train
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so we thought oh that's strange and it was actually a tiny bit hazy in there too we noticed that too
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a little bit smoky firemen see a small fire burning about halfway up one of the escalators bringing passengers from the
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tracks up to the ticket hall a very experienced fire officer looked down the escalator
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and assess the fire as being it's about the size of a cardboard box but firefighter colin townsey spots
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something he believes is dangerous he calls firefighters above ground asking for more equipment and saying
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people are in danger he through his experience had seen something going on above the fire around
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the fire whatever he could see he knew that something bad was about to happen on the train platform below
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passengers are now being urged to get out the quickest escape route is up another
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bank of escalators near the fire these two lead directly to the ticket hall as soon as we got near the top
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we noticed it was really dark and smoky at that time there was this policeman with a
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flashlight and saying hurry up don't don't just stand there but the warning comes too late
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as soon as i went through that turnstile some kind of explosion happened when i was halfway up that escalator a
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sheet of flame erupted and shot across the top of the whole of the top of the exit from that escalator so i was just
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moving up towards a wall of fire searing flames rip up the escalator and into the ticket hall incinerating
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everything in their path they were like these living things in up in the corner by the ceiling and they
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were huge and it was awesome and i just took one look at that thing and i just i felt like an ant i mean it felt like
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this thing is like a monster there was just a complete rush of thick black smoke from the subways
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right all the subways leading out onto the main roads around the station and it was right at that moment we realised
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that the flashover would occur flashover is a virtually instantaneous spread of fire everything flammable
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ignites simultaneously so from two minutes it had gone apparently the size of a cardboard box
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to a major disaster firefighters tried desperately to get inside the station but are driven back
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by the intense heat and smoke firefighters were collapsing left right and center
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the heat down there had made some of them urinate themselves with fear and when they came out to the top they
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weren't capable of moving again a lot of them were collapsing in the heaps ron lipsia stumbles into the chaos
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outside and for the first time realizes he is badly burned i looked at my hands and there was this
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skin just hanging down like like when a snake sheds its skin firefighters battled the blaze for an
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hour when it is finally out 31 people are dead and more than 70 others are injured
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among the dead is firefighter colin townsley colin was found with two two members of
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public that he'd obviously pulled along the tunnel trying to get him out to safety
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two people that he'd obviously tried desperately to get out of that inferno and it cost him his life
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the king's cross station is shut down the london underground is crippled thousands of commuters are stranded
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through the smoky haze of the ruins a mystery emerges why did a fire the size of a cardboard box explode into a deadly
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inferno in a matter of seconds in the hours following the deadly king's cross fire
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investigators from england's health and safety executive sifted through the charred station looking for clues
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but finding them in the ruined ticket halls and tunnels wasn't easy there is nothing quite like seeing a
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fire scene firsthand to give you a full appreciation of the the devastation that
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has taken place and also to give you a feel for how the fire might have developed
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they needed to answer two critical questions what sparked the fire and how could it appear so suddenly and erupt
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into a fatal blaze that claimed 31 lives nearly a million people relied on the underground each day
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they needed to know if the system was safe this is the stuff of nightmares being
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trapped by fire underground i mean it really is something that tugged at the heartstrings of ordinary londoners it
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was on the front pages of every newspaper obviously for several days and there was enormous demand to find
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out why it had happened investigators started where the flames were first spotted the escalator this
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was the lowest point of the fire indicating the fire had started there and burned upward
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no accelerants or other indications of arson were found underneath the escalator investigators
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found accumulated grease litter and debris ideal fuel for starting a fire they also found evidence of many
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previous small fires started by smoldering matches and cigarettes the actual source of ignition
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is assumed to be a dropped match which had not been extinguished and if that had come in contact with the
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grease on the running track of the escalator the grease would have ignited very very
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easily investigators speculated that someone on the escalator lit a cigarette and
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carelessly tossed away a burning match but could one match cause such a deadly fire
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they tried dropping matches from heights they found that a match would be able to
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in certain circumstances to light the grease on the escalator but in the tests the fire was slow
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burning and didn't explode up the escalator there was all sorts of theories as to
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how this could have happened so fast and amongst those theories everyone was desperately searching for the truth
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meanwhile journalists uncovered dozens of previous escalator fires in the london underground
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to some extent the underground had been extremely lucky for 50 years they had a lot of these wooden
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escalators they all suffered from similar problems there'd been a series of escalator fires
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it was reasonably predictable that there was going to be a serious one after a fire two years earlier at
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another station investigators said the system's aging wooden escalators were a disaster
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waiting to happen but why did this fire turn into a deadly inferno there was a lot of thoughts about the
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the trains actually fanning the flames because it was extremely clear whenever a train came into that station that the
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smoke that was bellowing out of the subways where i would increase but measurements of air flow in the
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escalator area showed this would not affect a small fire on the steps other theories blamed the varnish on the
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wooden escalator and multiple layers of paint on the ceiling there are examples of fires in
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old buildings in in the uk which have been painted regularly every three or four years and these buildings
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are 100 years old and if the paint becomes involved it becomes an inferno very very quickly because paint
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delaminates blisters and burns rapidly when they did some tests when the hse did some tests on the ceiling page
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something that was not damaged they couldn't make the flame spread fast enough along it and that's when they
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started to question what else could be the main fuel and that's when they came
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to talk to us to see if we could do anything to help what do you think of these results
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now turned to a team of forensic mathematicians at the investigative firm of cfx
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their goal was to create a computer simulation of the deadly fire using computation fluid dynamics or cfd
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this was the first time it would be applied to the behavior of fire but they believed it would work because
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heat and air flow like fluids hot air causes the the fluid to expand and it makes it lighter and then it
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tends to rise relative to the other ambient fluid around and so then you see smoke rising smoke plumes
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and that's the kind of thing that we can simulate with the software because it
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really is just simple fluid mechanics but could it solve the mystery of the king's crossfire
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[Music] to recreate the deadly king's crossfire in a virtual world the station was
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measured and mapped onto a computer grid then factors such as the fire's point of
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origin air flow and types of wood and paint were added to the simulation but the result showed
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something unusual according to the computer model the king's cross fire had literally defied
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the laws of physics the hot air around the fire did not rise instead it clung to the steps
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we saw that the hottest air seemed to be lying down in the escalator trench which
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was unexpected to me anyway and the other people from hse who came to look at those early simulations
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i think the initial reaction was it was possible that i've got gravity upside
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down which you can do in the computer so maybe i'd made things go the wrong way
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was it a human error could we have input the data incorrectly could there be a bug in the program
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the investigators entered all the data again the results were the same we did all the checking and did more runs and
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and still found that the hottest air was lying down in the trench eventually spiraling up over the ceiling but
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initially lying down in the trench it was a startling but significant clue the hot air and gases should have risen
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up to the ceiling but the escalator stairway appeared to channel them into the ticket hall
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and that made us start to think about maybe the wood of the escalator could be the main fuel if the flames are lying
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down in the trench they're preheating the wood ahead of the main flame front
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and therefore once it gets going it could move very very rapidly they called what they saw
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the trench effect but it was merely a theory using untested computer simulations and it was
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inconsistent with typical fire behavior if you have a fire burning in the open on a flat surface
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the fire feeds itself with air by drawing it in from the outside it's created by the dynamics of
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the flame itself the buoyant gases rise creating slight pressure differences which draw air into low at a low level
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but on an incline that airflow is restricted on the uphill side to examine this a rough model one tenth the size of the
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escalator shaft was placed flat on the ground the result was a slow vertical burn
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but at a 30 degree angle the angle of the king's cross escalator the flames leaned into the shaft at an angle and
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raced upwards in the confined trench the fire could only draw air from below creating a draft
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because the air can't come round the fire it has to come effectively through
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the fire investigators then ran a bigger test on a one-third size model of the complete
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king's cross station if the trench effect worked this time it would prove their theory was right
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in the match of three or four seconds the flames went from the upright to being lying uh along the escalated
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trench and from then on it was just as we predicted which is very gratifying it was clear
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that the previously unknown phenomenon called the trench effect was real people suddenly saw
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a fire and said now we understand you've got an explanation of what it is it's now all
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obvious it fits together the jigsaw fits together perfectly the investigative team now had
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compelling evidence that would reveal the deadly sequence of events [Music] for months a government inquiry into the
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disaster at the king's cross station fire had struggled to find out how a small fire had exploded so quickly and
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killed 31 people [Music] now a team of forensic experts said new computer technology provided the answers
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the computer graphics helped us to understand what had taken place and also to present the results to people
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who were maybe not as familiar with the technology that we were using so we could explain the results to them very
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simply sometime around 7 15 p.m a smoker at king's cross carelessly dropped a match on the wooden escalator
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the match fell between the steps and the side of the escalator into the gear bed
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below it was lined with years of grease and debris a slow burning fire began at 7 30 p.m
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the flames became visible and underground staff called the fire brigade at 7 40 p.m
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two firemen saw the low-lying flames and at first assumed it could be easily extinguished
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the fireman who was walking down escalator number six and looked across to escalator number four approximately
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one minute before flashover and described the fire as being relatively small but then the fire spread across the
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steps the bottom of the trench it could only draw oxygen from one direction from below
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this was the trench effect and once you had established a fire across the width of the escalator it meant that the
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flames were deflected into the trench and began to flow up the treads the risers and exposing the
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balustrades to very high levels of heat flux then it just switches and flips over to stick to the floor
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of the escalated trench from there it pre-heats the wood the hot gases are going up the escalator trench ahead of
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the flame they're heating the wood quite considerably gets quite hot even though there's no flame there it's
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sucking up the air from below like a chimney wood which is what it needs to do and that would tend to flatten the
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flames down in the early stages as well which would start this effect off of the
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trench effect the escalator trench acted as a chimney made not of brick but of highly
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flammable wood at 7 45 a torrent of superheated gas rushed up the escalator priming everything in its
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path to burn it was called a flush over the sudden movement of the fire up up the escalator
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was called the flashover as it burst into the booking hall at the top the hot gases and flames exploded into
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the ticket hall feeding off years of thick paint on the walls and three tons of varnished wood
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on the escalator below the cavernous room was a death trap those people would have died extremely
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quickly and if there's anything if there's any comfort there it is the comfort that they didn't suffer for very
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very long at all they were taken extremely quickly the government's board of inquiry
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accepted the new science of the trench effect and found it had caused the disaster
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there was a general sense amongst people that really the underground should and could have prevented this
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i mean there were resignations of course but um i think there was a sense that the underground
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hadn't really been on top of the problem of fire underground to ensure such a tragedy would never
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happen again all wooden escalators were eventually removed from the system flammable grease and debris
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are regularly removed from beneath escalators and the underground staff is now required to be trained in fire
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evacuation procedures those directly affected by the fire can take some comfort that science
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explained the mystery that changed their lives it ruined the life that i was having
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my life was going certain ways perfectly happy with it and it totally ruined that life but i
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i got onto a different life i don't use the underground i've used the underground since
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that night at king's cross i'm not saying it's not safe because i believe it's far safer now than it ever
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was but for me personally i'm happy to avoid it those who solved the mystery of the
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king's crossfire no their intensive efforts will help save lives there's also plaque in the booking hall
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to the memory of the people that died then you know i often just stop there and stand and read it and just spend a
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quiet moment in reflection because there was a human tragedy there which sometimes can easily be forgotten
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so i feel strange going back there and a little shiver i enjoyed seeing the computer model be
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used in a way that was good so people could understand what had happened and therefore try and prevent it happening
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again it's opened a whole new line of study on flame spread that perhaps we've taken much longer to
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achieve if we hadn't had the experience of kings cross [Music] god [Music] you