from it and then make changes in rules, regulations and procedures, i've done a lot to prevent that next one from happening. in a crowded london underground station a small routine fire erupts into a deadly inferno and kills 31 people. dozens more are injured. a team of forensic experts searches for clues to the cause of the blaze and finds that the fire seemed to defy the very laws of physics. to unravel the cause of the mysterious fire, investigators would need to recreate a historic train station inside a modern computer. the sprawling london underground is the largest and oldest subway rail system in the world.

but on the evening of november 19th, 1987, commuters are unaware that disaster lurks beneath them. at 7:30 p.m., a passenger at the historic king's cross station sees a flicker of flame underneath the heavily varnished 50-year-old wooden escalator. the london fire brigade is dispatched. it seems to be a routine call. >> an everyday call to a fire in an escalator. something we were receiving probably 20 or 30 times a month. so it was no big deal. >> fire captain roger kendall, one of the first to reach the scene, waits above ground for his supervisor to report. >> we were waiting for message to come back to say that we're all going home, or we may need a bit of equipment. >> trains continue to come and go despite the minor commotion. musician ron lipsius arrives at the station on one of these trains. >> we notice these two men, i

don't think they were in uniform, but they were blocking, physically blocking entrance to the wooden escalators on our left, the ones that directly go to the train. we thought, that's strange. it was actually a tiny bit hazy in there, too. we noticed that, too. a little smoky. >> firemen see a small fire burning halfway up the escalators bringing passengers from the tracks up to the ticket hall. >> a very experienced fire officer looked down the escalator and assessed the fire as being, it is about the size of a cardboard box. >> but firefighter colin townsley spots something he believes is dangerous. he calls firefighters above ground, asking for more equipment and saying, people are in danger. >> he, through his experience, had seen something going on

above the fire, wherever he could see, he knew something bad was about to happen. >> on the train platform below, passengers are now being urged to get out. the quickest escape route is up another bank of escalators near the fire. these, too, lead directly to the ticket hall. >> as soon as we got near the top, we noticed it was really dark and smoky. >> at that time, there was this policeman with a flashlight saying, hurry up, don't just stand there. >> but the warning comes too late. >> as soon as i went through that turnstile, some kind of explosion happened. >> when i was halfway up that escalator, a sheet of flame erupted and shot across the top of the hall of the top of the exit from that escalator. i was moving up toward a wall of fire. >> searing flames rip up the escalator and into the ticket hall, incinerating everything in their path.

>> this thing is like a monster. >> there was just a complete rush of thick, black smoke from the subways and it was right at that moment we realize that the flashover occurred. >> flashover is a virtually instantaneous spread of fire. everything flammable ignites simultaneously. >> from two minutes it had gone apparently the size of a cardboard box to a major disaster. >> firefighters try desperately to get inside the station but are driven back by the intense heat and smoke. >> firefighters were collapsing left, right and center. the heat down there had made some of them urinate themselves with fear. and when they came out into the top, they weren't capable of moving again. a lot of them were collapsing into heaps. >> ron lipsius stumbles into the chaos outside, and for the first time realizes he is badly burned. >> i looked at my hands and

there was this skin just hanging down like when a snake sheds its skin. >> firefighters battled the blaze for an hour. when it is finally out, 31 people are dead, and more than 70 others are injured. among the dead is firefighter colin townsley. >> collin, he'd obviously tried desperately to get out of that inferno and cost him his life. >> the king's cross station is shut down. the london underground is crippled. thousands of commuters are stranded. through the smoky haze of the ruins, a mystery emerges. why did a fire the size of a cardboard box explode into a deadly inferno in a matter of seconds? [ female announcer ] new fiber one protein cereal. ♪ yeah, yeah, yeah, yeah! ♪ we are one, under the sun

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in the hours following the deadly king's cross fire, investigators from england's health and safety executive sifted through the charred station looking for clues. but finding them in the ruined ticket halls and tunnels wasn't easy.

>> there was nothing quite like seeing a fire scene firsthand to give you a fill appreciation of the devastation that has taken place. and also to give you a feel for how the fire might have developed. >> they needed to answer two critical questions. what sparked the fire, and how could it appear so suddenly and erupt into a fatal blaze that claimed 31 lives? nearly a million people relied on the underground each day. they needed to know if the system was safe. >> it was on the front pages of every newspaper, obviously, for several days, and there was enormous demand to find out why it had happened. >> investigators started where the flames were first spotted. the escalator. this was the lowest point of the fire. indicating the fire had started there and burned upward. no accelerants or other indicates of arson were found. underneath the escalator, investigators found accumulated

grease, litter, and debris, ideal fuel for starting a fire. they also found evidence of many previous small fires started by smoldering matches and cigarettes. >> the actual source of ignition is assumed to be a topped match which had not been extinguished. and if that had come in contact with the grease on the running track of the escalator, the grease would have ignited very, very easily. >> investigators speculated that someone on the escalator lit a cigarette and carelessly tossed away a burning match. but could one match cause such a deadly fire? >> they tried dropping matches from heights. they found a match would be able to in certain circumstances to light the grease on the escalator. >> but in the test, the fire was slow burning and didn't explode up the escalator.

>> there was all sorts of theories as to how this could have happened so fast, and amongst these theories everyone was desperately searching for the truth. >> meanwhile, journalists uncovered dozens of previous escalator fires in the london underground. >> some extent, the undergrounds have been extremely lucky for years. they had a lot of these wooden escalators. they all suffered from similar problems. there have been a series of escalator fires. it was reasonably predictable that there was going to be a serious one. >> after a fire two years earlier at another station, investigators said the system's aging wooden escalators were a disaster waiting to happen. but why did this fire turn into a deadly inferno? >> there was a lot of thought about the trains actually fanning the flames because it was extremely clear, whenever a train came into that station, that the smoke that billowing

out of the subways would increase. >> but measurements of air flow in the escalator area show this would not effect a small fire on the steps. multiple layers of paint on the ceiling. >> when they did some tests, when the agencies did some tests on the ceiling paint, some of it that was not damaged, they couldn't make the flames spread fast enough along it. and that's when they started to question what else could be the main fuel? that's when they came to talk to us to see if we could do anything to help. >> what do you think of these results? >> investigators now turn to a team of forensic mathematicians at the investigative firm of cfx. their goal was to create a computer simulation of the deadly fire using computation fluid dynamics or cfd. this was the first time it would be applied to the behavior of fire.

but they believed it would work because heat and air flow like fluids. >> hot air causes the fluid to expand and it makes it lighter and then it tends to rise relative to the other ambient fluid around. and so then you see smoke rising, smoke plumes, and that's the kind of thing that we can simulate with the software, because it really is simple fluid mechanics. >> but could it solve the mystery of the king's cross fire? pay my bill. phone: your account is already paid in full. oh, well in that case, back to vacation mode. ♪boots and pants and boots and pants♪ ♪and boots and pants and boots and pants♪ ♪and boots and pants...

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to recreate the deadly king's cross fire in a virtual world, the station was measured and mapped on to a computer grid. then factors such as the fire's point of origin, air flow, and types of wood and paint were added to the simulation. but the results showed something unusual. according to the computer model, the king's cross fire had literally defied the laws of physics. >> bit of a hot temperature. >> the hot air around the fire did not rise. instead, it climbed to the steps. >> we saw that the hottest air seemed to be lying down in the

escalator trench which was unexpected, to me, anyway, and the other people from hse who came to look at those early simulations. i think the initial reaction was it was possible that i got gravity upsidedown which you can do in the computer, so maybe i made things go the wrong way. >> was it a human error? could we have input the data incorrectly? could there be a bug in the program? >> investigators entered all the data again. the results were the same. >> we did all the checking and did more runs and still found that the hottest air was lying down in the trench. eventually spiraling up over the ceiling. but initially lying down in the trench. >> translator: it was a startling but significant clue. the hot air and gases should have risen up to the ceiling. but the escalator stairway appeared to channel them into the ticket hall. >> and that made us start to think about maybe the wood of the escalator could be the main fuel. if the flames are lying down in the trench, they're preheating the wood ahead of the main flame

front, and, therefore, once it gets going, it would move very, very rapidly. >> they called what they saw the trench effect. but it was merely a theory using untested computer simulations and it was inconsistent with typical fire behavior. >> if you have a fire burning in the open, on a flat surface, the fire feeds itself with air by drawing it in from the outside. it's created by the dynamics of the flame, itself. the buoyant gases rise, creating slight pressure differences which draw air in at a low level. >> but on an incline, that air flow is restricted on the uphill side. to examine this, a rough model, one-tenth the size of the escalator shaft, was placed flat on the ground. the result was a slow, vertical burn. but at a 30-degree angle, the angle of the king's cross escalator, the flames leaned

into the shaft at an angle and raced upwards. in the confined trench, the fire could only draw air from below, creating a draft. >> because the air can't come round the fire, it has to come effectively through the fire. >> investigators then ran a bigger test on a one-third sized model of the complete king's cross station. if the trench effect worked this time, it would prove their theory was right. >> in three or four seconds the flames were from upright, then lying along the escalator trench. from then on, it was just predicted which is very gratifying. >> it is clear the previously unknown phenomenon called the trench effect was real. >> now we understand. it's now all obvious. it fits together. the jigsaw fits together perfectly. >> the investigative team now

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provided the answers. >> the computer graphics helped us to understand what had taken place and also to present the results to people who were maybe not as familiar with the technology that we were using, so we could explain the results to them very simply. >> some time around 7:15 p.m., a smoker at king's cross carelessly dropped a match on the wooden escalator. the match fell between the steps and the side of the escalator into the gear bed below. it was lined with years of grease and debris. a slow-burning fire began. at 7:30 p.m., the flames became visible and underground staff called the fire brigade. at 7:40 p.m., 2 firemen saw the low-lying flames and at first assumed it could be easily extinguished. >> the fireman who was walking down escalator number 6 and looked across to escalator

number 4 approximately 1 minute before flashover had described the fire as being relatively small. >> but then the fire spread across the steps. the bottom of the trench. it could only draw oxygen from one direction, from below. this was the trench effect. >> the flames were deflected into the trench and began to flow up the treads, the risers, and exposing the balustrades to high levels of heat flux. >> from there, the gases are going up the escalator trench ahead of the flame. they're heating the wood quite considerably. gets quite hot even though there's no flame there. >> it's sucking up the air from below like the chimney would, which is what it needs to do, and that would tend to flatten the flames down in the early stages as well which would start this effect off of the trench effect.

>> the escalator trench acted as a chimney, made not of brick, but of highly flammable wood. at 7:45, a torrent of superheated gas rushed up the escalator, priming everything in its path to burn. >> the sudden movement of the fire up the escalator was called the flashover. it burst into the booking hall at the top. >> the hot gases and flames exploded into the ticket hall, feeding off years of thick paint on the walls and three tons of varnished wood on the escalator below. the cavernous room was a death trap. >> those people would have died extremely quickly. if there's anything, if there's any comfort there, is the comfort that they didn't suffer for very, very long at all. >> the government's board of inquiry accepted the new science of the trench effect and found it had caused the disaster. >> there was a general sense amongst people that rarely the underground should and could have prevented this. i mean, there were resignations,

of course, but i think there was a sense that the underground hadn't really been on top of the problem of fire under ground. >> to ensure such a tragedy would never happen again, all wooded escalators were eventually removed from the system. flammable grease and debris are regularly removed from beneath escalators. and the underground staff is now required to be trained in fire evacuation procedures. those directly affected by the fire can take some comfort that science explained the mystery that changed their lives. >> my life was going a certain way. i was perfectly happy with it. and it totally ruined that life, but i got on to a different life.

>> i don't use the underground. i haven't used the underground since 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 was. for me, personally, i'm happy to avoid it. >> those who solved the mystery of the king's cross fire know their intensive efforts will help save lives. >> there's also a plaque in the booking hall to the memory of people who died there. i often just stop there and stand and read it and spend a quiet moment in reflection, because there was a human tragedy there which sometimes can easily be forgotten. so i feel strange going back there and a little shiver. >> i enjoyed seeing the computer model be used in a way that was good, so people could understand what had happened and, therefore, try to prevent it happening again. >> it's opened a whole new line of study on flame spread that perhaps we've taken much longer to achieve if we hadn't had the

experience of king's cross. when firefighters found an entire family dead inside their home, it looked like a murder-suicide. but there were several inconsistent clues in the rubble. could ballistics, a time card and some secret audio tapes unravel the mystery? just before daybreak on august 29, 1994, firefighters in venton, virginia, were called to a house fire on virginia avenue. when the fire was extinguished, rescuers found the bodies of all four members of the hodges