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Just before lunchtime on May 4th, 1988, at a facility near Henderson, Nevada, a panicked maintenance crew could be seen dashing away from the site of the Pacific Engineering Production Company, also known as PEPCON. Behind them, a moderate but ambitious-looking fire was establishing itself in a large storage lot.
The crew had been repairing a wind-damaged steel-and-fiberglass building when a stray spark from their welder somehow managed to set fire to the structure. The men fetched some nearby water hoses and attempted to douse the flames, but the flourishing fire mocked their efforts, and soon began to fondle the 55 gallon drums stored nearby. With this alarming development, the crew abandoned their hoses and gave up the fight in favor of a hasty departure. The workers knew exactly what was in these barrels, and they didn’t wish to be present to observe how it would react to the flames.
At that time, PEPCON was one of the only US producers of the chemical ammonium perchlorate, a key ingredient in the rocket fuel used for space shuttle boosters and Titan missiles. This white granular compound is a powerful oxidizer, and its purpose is to accelerate rocket fuel combustion. Also present at the facility were bulk quantities of other hazardous materials used in manufacturing, such as hydrochloric acid and nitric acid.
There were over four thousand tons of ammonium perchlorate in the storage area that day, so the anxiety-stricken workers fled with great enthusiasm. The Challenger explosion fifteen months earlier had prompted NASA to freeze the space shuttle program pending investigation, yet the United States government continued to contract PEPCON at pre-Challenger quantities. Consequently, the containers full of the unused fuel component had slowly accumulated, making the site pregnant with stored energy.
Over the years, the entire facility had become peppered with residue from the ammonium perchlorate. Stiff winds on the day of the maintenance workers’ visit conspired against them, and quickly turned a small welding accident into a brilliant orange fireball. As news of the fire spread, most of the employees rushed to evacuate the six buildings, but a man named Roy Westerfield stayed behind and called 911:
Dispatcher: Fire department.
Westerfield: Emergency. We need the fire department, all you can get here. Immediately.
Dispatcher: What’s the problem?
Westerfield: Oh, we’ve got… everything’s on fire.
At about the same time, the chief of the Clark County Fire Department noticed the column of smoke on the horizon, and ordered his units to go to the location immediately. He and a passenger climbed into his car and raced to the scene ahead of the fire trucks. The intense fireball became visible from about a mile away, belching its column of acrid smoke into the sky. Soon the pair began to see dozens of fear-stricken PEPCON employees on the roadsides; men and women hurrying away from the burning facility on foot in spite of the mid-day desert heat.
A few minutes later, as the chief neared the cluster of flaming buildings, he and his passenger were blinded by an abrupt flash. The car rocked and windows exploded as the vehicle was slammed by a deafening shock wave. As the explosion’s echoes slowly faded, the fire chief stopped the car to assess the situation and tend to a few cuts caused by the hail of broken glass. Moments later a badly damaged vehicle approached from the direction of the plant, and its driver paused alongside the chief just long enough to warn him that the worst of the explosions were probably yet to come. Realizing that the inferno had grown far beyond his department’s fire-suppression capabilities, the chief turned his car around and headed back towards Henderson.
The fire engine crews had reached the same dismal conclusion when they observed the explosion during their approach. It was clear that there were serious safety concerns in moving any closer, so the firefighters pulled their trucks off the road about a mile from the disaster-in-progress, and watched the towering flames from afar.
A mile away in another direction, an engineering crew had been performing routine maintenance on a television tower on Black Mountain when they spotted the fire and began filming. About four minutes after the first major explosion, the engineers watched in awe as the PEPCON site completely disappeared in a spectacular burst of energy that dwarfed the initial blast.
Their vantage point afforded them a perfect view of the compression wave as it recklessly radiated across the desert, mowing down brush and demolishing a marshmallow factory adjacent to PEPCON. Due to the distance the sound of the blast didn’t reach them for several seconds… but when it did, it was thunderous.
The Clark County fire chief was still trying to put distance between himself and the facility when the violent detonation struck. The blast wave swept in rapidly from behind and clobbered his wounded car, momentarily smothering him in an avalanche of noise and pressure. When the moment passed, he was astonished to find that the vehicle was still somewhat operational in spite of the significant bruising. He continued his retreat and eventually limped his injured automobile past the columns of idling fire engines, their pulverized windows littering the roadway. By the time he reached town and found his way to the hospital, there were already hundreds of people there awaiting treatment. The explosion one and a half miles away had dislodged parts of buildings and shattered windows in town, causing many instances of trauma and lacerations.
On the horizon, a plume of smoke rose 1,000 feet into the sky, and the column was said to be visible from as far as one hundred miles away. Some distant observers reportedly wondered whether this mushroom cloud indicated that the long-running Cold War had finally progressed into the Hot War that Americans feared.
The frenzied inferno at PEPCON finally calmed once the explosions had consumed the majority of the fuel. The cataclysmic blasts had ripped a hole in the ground and ruptured a gas line, but the resulting 200-foot-tall flame was easily starved to death by shutting off the gas feed from a station a mile away. Investigators arrived to survey the damage, and they found utter devastation. PEPCON’s six buildings were totally destroyed, and where they had stood was nothing but twisted metal and a fifteen-foot-deep crater. The neighboring marshmallow factory fared no better, having been unable to absorb the incredible pressure wave. Many structures in Henderson also suffered damage, mostly in the form of shattered windows, cracked walls, and doors that were blown from their hinges. Some buildings as far as ten miles away were affected.
Though there were almost 400 injuries reported— both from ground zero and from Henderson residents— surprisingly there were only two deaths. One was a worker confined to a wheelchair who had been unable to exit from the PEPCON building quickly enough. The other was Roy Westerfield, the very man who had made the original 911 call. He had been handicapped by the effects of polio, leaving him unable to walk very well. It is generally believed that he opted to stay behind and alert the authorities, knowing that escape was unlikely.
Further investigation into the event found that the destructive energy from the larger explosion was roughly equivalent to 1,000 tons of TNT, or one kiloton. It caused seismograph needles to dance as far away as Colorado, where the sensitive equipment measured the distant tremor as a 3.5 on the Richter scale.
PEPCON lawyers responded quickly, attempting pin the blame on Southwest Gas company. The lawyers claimed that the natural gas fire occurred first, subsequently causing the ammonium perchlorate explosions. Three days after the disaster, one of these attorneys claimed, “Nothing ignites ammonium perchlorate. It does not burn. It is not flammable.” Though the compound was not considered to be an extreme explosive threat before the PEPCON disaster, chemists pointed out that the attorney’s grasp of chemistry must be as flimsy as his grasp of ethics. They described the chemical as “unstable and highly flammable.”
PEPCON had only $1 million in insurance, a policy which was grossly insufficient to pay for the damage to others’ property. A colossal courtroom battle ensued, involving dozens of insurance companies and over fifty law firms. The outcome of this massive orgy of justice was one million pages of depositions, and a $71 million settlement which was divided among the victims and their families.
PEPCON never rebuilt the Henderson site. The company changed its name to Western Electrochemical Co. and built a new ammonium perchlorate plant in Cedar City, Utah which remains in operation today. But their safety record has certainly improved since the 1988 disaster; to date, there has only been one deadly explosion at the new facility.
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Great article as usual.. man i love this site
Only one explosion at the new facility? hmmmm
I recall seeing the video. Simply awful in the destruction, but extremely fantastic watching the concussion wave racing across the desert.
“pregnant with stored energy”
that’ll learn em
Very interesting Alan. However the first sentence of paragraph 13 needs to be revised.
Though there were almost 400 injuries reported– both from ground zero and from Henderson residents– but surprisingly there were only two deaths.
The “though” or the “but” needs to be removed. Thanks for the great article.
This was featured on Modern Marvels awhile back. They reported that the gas line that was ruptured was 16 inches in diameter… wow! Damn interesting!
lfsmith said: “The “though” or the “but” needs to be removed. Thanks for the great article.”
D’oh… thanks. That’s what I get for writing when I should be sleeping.
No problem, just figured you might want to know. Good luck with your sleep.
You can tell by the amount they eventually zoom out, the scale this must have been on…impressive/scary.
My bad…I didn’t see it was already linked. >_
Wow,DI! and shocking.
I find the lawyers weak surmise appalling. You do not have to be a rocket scientist to know that rocket fuel is flamable or explosive.
Just goes to show how ignorance and greed will always raise it’s ugly head before common sense gets a grip.
Good that the folks were compensated with the 71 mill. But wonder after all this:
PEPCON had only $1 million in insurance, a policy which was grossly insufficient to pay for the damage to others’ property. A colossal courtroom battle ensued, involving dozens of insurance companies and over fifty law firms. The outcome of this massive orgy of justice was one million pages of depositions,
Where did that money come from? And how were the firms, lawyers etc. paid?
A bit of topic, but it is a big explosion and it is DI I thought, it came up when I looked at the PEPCON video.
yeah that’s pretty funny about the lawyers alright did they REALLY think that would work lmao
Yeah, I wonder who told those lawyers that it wasn’t flammable, as if there wasn’t a single chemist in the world who could prove otherwise…
Tink said: “Where did that money come from? And how were the firms, lawyers etc. paid?”
I’m guessing that the Henderson plant was only one of their sites, and they only had $1 million insurance on that site but had other funds with which to pay. I’m not sure, though.
Excellent anthropomorphising Alan!
I think the worst part was that the innocent marshmallow plant next door was destroyed too.
I don’t know about anybody else, but I was thoroughly amused by the description of the resulting trial as a “massive orgy of justice”.
kls-1 said: “”pregnant with stored energy””
…yep, that caught my eye right away as well. Never heard the term “pregnant” used to describe an inanimate object. Live and learn.
And yes, this was on Modern Marvels a few months ago. The video of the pressure wave following the first major explosion was, in a word…awesome. Perhaps I should say, the after effects of the pressure wave. Hard to believe that you can pack more oxidizing agents into a solid material than you can get from natural atmosphere.
Of course, this is why in the industrial world today, you’re supposed to have such things as “confined space monitoring” (when warranted), but more importanlty, a “hot work permit” program any time open flames or sparks are involved for cutting, welding, etc.
So I guess the PEPCON incident supports the Big Band Theory, eh?
What happened to the folks in the marshmallow plant?
Teeny said: “I don’t know about anybody else, but I was thoroughly amused by the description of the resulting trial as a “massive orgy of justice”.”
Superlative articulation, Mr. Bellows.
I’ve always thought the shockwave in this video is absolutely amazing. As an aside, back in ’88 I was a young engineer at Thiokol, the rocket motor company that contracted with PEPCON for the Ammonium Perchlorate. We constantly saw AP drums being trucked on to plant. If I remember right (It’s been 10 years since I worked there) the AP was packed in water to minimize their explosive potential, and since that wasn’t enough, significant steps were taken to electrically ground the drums during transport, unloading, and storage, so they wouldn’t explode due to static electricity. This is nasty stuff. After the Henderson explosion we saw the video often as part of the extreme safety training we were required to have. And rightly so. When it goes into making rocket fuel, it is combined with a binder and an oxygen source so that it can continue to burn without an external oxygen source. The mixing is done in a huge mixer, just like your kitchenaid, only about 10 feet in diameter. This is dangerous in its own right, given all the moving parts, heat and friction involved. Once it starts burning, it is impossible to extinguish. …and yes, even with all the precautions, mixer buildings have exploded too.
jubripley said: “What happened to the folks in the marshmallow plant?”
…S’mores! Need I say more? And please pass the graham crackers…
[joke] Not many people today know the explosions were timed to coincide with a live performance of the 1812 overture in nearby Las Vegas… [/joke]
If PEPCON’s lawyers claimed “Nothing ignites ammonium perchlorate. It does not burn. It is not flammable.” they were correct. I don’t know what chemists were consulted but ammonium perchlorate is an oxidizer, not a fuel, as gutterball is claiming. When combined with a fuel, such as finely powdered aluminum (the rocket fuel you speak of) or a preexisting natural gas fire, the mixture would be considered quite flammable. gutterball, in your post you mentioned mixing it with a binder and an oxidizer; it is the oxidizer.
No doubt the compound is still dangerous because almost anything can be a fuel, but as far as we know it was confined nicely in 55 gallon drums until provoked by massive natural gas flames.
Flash point, explosion limits, and autoignition temperature are all blank, and there is the phrase ” Explosive when mixed with combustible material.” ‘When’ being the key word.
Ammonium perchlorate isn’t flammable. The laywers were right, in a way.
Oxygen isn’t flammable either.
Both substances, pure oxygen, and an oxidizer like ammonium perchlorate, greatly increase the fire risk. A fire will burn very fiercely in the presence of them.
To be honest, no one knew that large quantities of oxidizer could explode in this manner, when they weren’t mixed with something combustible. A huge uncontrollable fire would be expected, but a detonation type explosion wasn’t an expected outcome.
I enjoyed the article a great deal. This is the first damn interesting article I’ve read, about something I lived through myself. My home (I was living in a mobile home at the time) was just on the other side of Black Mountain from Pepcon– maybe ten miles away. The big blast blew out my bedroom window, cutting both my wife and me with flying glass (not seriously).
A couple of noteworthy things:
Kerr McGee Chemicals is the second ammonium perchlorate producer in Henderson, Nv. It still manufactures ammonium perchlorate at their plant several hundred feet away from Henderson’s main street. (called Water St.)
I am sure that there were many more injuries than 400. I know that my wife and I weren’t on any injury list.
The marshmallow plant rebuilt.
Wow. This all happened the day before I was born.
…”the flourishing fire mocked their efforts, and soon began to fondle the 55 gallon drums stored nearby”. ha!
CoryP said: “…”the flourishing fire mocked their efforts, and soon began to fondle the 55 gallon drums stored nearby”. ha!”
Hahaaaahhh! That caught my eye, too!
In an odd bit of synchronicity, my 14-year-old daughter, who plays African drums (which are made from antelope hide), yesterday described the drumming as actually “fondling antelope behinds.”
Now I suppose I will be hearing the word “fondling” everywhere I go! Word of the week! LOL ;)
As others have said, ammonium perchlorate is an oxidiser and can use almost anything as a fuel (a lot of things that normally won’t burn, will, if fed enough oxygen).
Once the gas-line ruptured, there came the fun.
Gas is actually pretty safe, in that it has a very limited burn range of between 7% and 10% gas/air ratio (from memory). Not enough gas, and it is too weak to burn, too much gas (as in the case of a rupture) and it won’t burn at the source (it will as it spreads out, that’s where it gets nasty) – there isn’t enough oxygen. Unless you add a LOT of ammonium perchlorate.
A lot of fuel (a pressurised gas-line) + a lot of oxygen (in the form of ammonium perchlorate) = BIG BOOM.
KiriBlack said: “Hahaaaahhh! That caught my eye, too!
In an odd bit of synchronicity, my 14-year-old daughter, who plays African drums (which are made from antelope hide), yesterday described the drumming as actually “fondling antelope behinds.”
Now I suppose I will be hearing the word “fondling” everywhere I go! Word of the week! LOL ;)”
Be sure to check out DI Baader Meinhof….it is one of my all time favorite DI articles.
oh…and what the hell is a marshmallow plant doing in the middle of Nevada?…….rocket fuel and marshmallows seems like the most odd combination I’ve ever heard of…God bless DI for educating me.
The breakup of the perchlorate radical is strongly exothermic, as is that of the nitrate radical used in most explosives. If the spark from the welder started the breakup in some of the perchlorate that, as Alan wrote, was all over the place, it could have started a high-energy chain reaction just in the perchlorate.
However, it is quite likely that there were enough flammable substances in the area, even before the gas line broke, to join in the fire right away; with the amount of energy being liberated, they need not even have been close to the original outburst.
I’m amazed that PEPCON was ever allowed to operate with just $1M in insurance!
jubripley said: “What happened to the folks in the marshmallow plant?”
They were all evacuated before the explosions occurred (one of the lines was down that day as well, so fortunately there were less people there than normal.) None were injured there. See:
Tales of Vegas Past: PEPCON explosion was Henderson turning point
The nearby chocolate factory and graham cracker factory were also evacuated in time. However, results of the explosion did lead to the origin of the s’more. ;-)
That was interesting but not DAMN interesting. I was reminded of the more impressive 3 kiloton Halifax Explosion.
i saw something on the ole boob tube about this the other day, the shockwave was amazing, kinda cool to read the whole story now, only a few days later.
and this craks me up:”to date, there has only been one deadly explosion at the new facility. ”
My family was in henderson the day pepcon blew up. i was up in northern nevada in tonopah when i heard the news that afternoon. i immmediately called my boss in vegas and told him i was coming back so “cancel the slot route for northern nevada this week..” and he agreed because he was watching the fire from the shop and said it looked serious. he said there’d been a big explosion in the desert between vegas and henderson and nobody knew what it was… i tried to call home but got a message saying i was trying to call into an “emergency area” and all communications were suspended.
Being more than a little upset i jumped into my car (a nice 1985 red prelude) and put the pedal to the metal on the way back to vegas. i did the 90 miles from tonopah in about 45 minutes. all the way i was listening to kdwn radio(am) out of vegas to hear the reports. it was horrifying. the announcer was saying ” and to all you spectators out there—do NOT go near the cloud because it is highly toxic!!” and i heard the smoke was heading towards boulder highway-henderson and i knew home was gonna get hit. by the time i got to vegas the same announcer was pleading with people to not panic because the cloud was NOT toxic.
I got into town about 230pm and managed to make it home through roadblocks and unbelievable destruction. the shock wave from the explosion had blown windows out all over town. i saw houses moved off their foundations, billboards blown down, and front doors and garage doors blown off their hinges. my family’s home on west atlantic in henderson got hit hard enough to shift the house an inch off its foundation; as well as blowing in the front door and living room picture window. there were shards of glass stuck in the wall on the other side of the room. everything smelled of ammonia and gunpowder. there was a frosty-looking coating on all the lawns and gardens (which soonafter died) It was surreal. thankfully my family was okay.
two months after the blast i went to the main pepcon site with a crew dismantling the wreckage and was stunned to see the force of that explosion. in the chain-link fencing around the blast site were peices of thick metals stuck in the fence. peices of propane tanks and storage tanks and barrels just splatted into the fence. the center was barren, nothing left.
And i thought to myself—they let this operate in the middle of the vegas valley? things could have been a lot LOT worse. i sure hope this made our government a little wiser about these things. but i doubt it.
In parting let me add: about two miles from the pepcon plant was kerr-mcgee, right in the center of henderson. many more barrels of ammoniun perchlorate were being stored there at the time. if it had gone up too—-? probably wouldnt be a vegas anymore…
robo said: “That was interesting but not DAMN interesting. I was reminded of the more impressive 3 kiloton Halifax Explosion.
And WTF with leaving the guy in the wheelchair behind?
Talk about a weapon of mass destruction! Seems to me ammonium perchlorate plants don’t just need top-notch fire safety, but top-notch security measures too.
Just to clarify.
Could I put large quantities of ammonium perchlorate in, say a wooden house and cause a serious explosion?
The ammonium perchlorate by itself wouldn’t burn but with the relatively easy burning wooden structure it would cause a serious explosion.
Is this correct or have I misunderstood?
Flames fondling the drums? Orgy of justice? Did the author have some other type of explosion on his mind? Great article.
Chair said: “Flames fondling the drums? Orgy of justice? Did the author have some other type of explosion on his mind? Great article.”
…perhaps it was just another “shot in the dark”. Strange things happen late at night when you’re tired, deprived of sleep and trying to beat a deadline.
Chair said: “Flames fondling the drums? Orgy of justice? Did the author have some other type of explosion on his mind? Great article.”
Orgy of justice might make this the best article anywhere. It might be more creative than Karl Rove.
I totally have to check this site more often. I was all ready to make the whole fuel/oxidizer clarification and then three people had already done it. Good job Flamethrowa, GigsTaggart and badpauly. However, ammonium perchlorate has enough hydrogen in the structure to function as a mono-propellant, so technically the lawyer was wrong, though it is still not flammable in the traditional sense. Good job, Silverhill.
Man said: “Just to clarify.
Could I put large quantities of ammonium perchlorate in, say a wooden house and cause a serious explosion?”
Short answer: Large quantities of ammonium perchlorate anywhere can cause a serious explosion.
Fire safety folks like to talk about the fire triangle: you need a fuel, an oxidizer and an ignition source to cause a fire. In general, we work on eliminating ignition sources since we like to build with wood and we can’t live in a vacuum. In the case of ammonium perchlorate, its products of decomposition have a lower energy than the initial compound, so it can be its own fuel and oxidizer. It can do a much better job, however, if additional fuel is provided since it produces a lot of spare oxidizer – only the hydrogen atoms in the structure function as fuel.
An explosion is a different beast than a fire. What you would think of as an explosion occurs when there is a very rapid rise in local pressure. As this high pressure gas expands, it generates a blast wave. When a boiler ruptures, you get a steam explosion because all the water rapid flashes over to vapor creating a large amount of gas in a very small space, even though you don’t have anything in the system you would traditionally consider an explosive.
For the case you describe, simply storing ammonium perchlorate in a wooden structure is insufficient because there is no ignition source. You could sprinkle the stuff on the floor and be fine. It will start to decompose into chlorine, nitrous oxide, water and oxygen if it reaches 200-300 F (95-150 C). This would be poisonous, but not result in a risk of fire. At 380 F (195 C), the products change a little and the reaction becomes self sustaining and above 450 F (230 C) it will support a deflagration. This means that the heat released by decomposition is enough to cause neighboring ammonium perchlorate to react, resulting in a self-sustaining wave moving through the medium (a flame). My expectation is that a 55 gallon drum of ammonium perchlorate heated to 400 F would explode, as opposed to just busting a seam and leaking out the products of reaction. All this data is from a 1969 Royal Society of Chemistry article.
Since combustion of wood takes a lot of oxygen, most building fires are oxygen starved – this is why you see flames coming out of windows (reaching toward the exterior oxygen source) and why burning homes rapidly become death traps even though they take a long time to burn all the way to the ground. On the other hand, if your wooden house caught fire and you had a large source of oxidizer stored in the family room, that house will be ashes real fast. Still might not explode though.
So, let’s say you 55 gallon drum is the center of a room when an electrical outlet shorts and lights up some nearby furniture, ultimately, the whole room goes up. The temperature of the room shoots up to 1100 F near the ceiling and a little less at the floor. It rapidly depletes the oxygen in the room, transitioning to a compartment fire, where the flames are limited to whatever openings there are for the fire to get oxygen. Meanwhile, our drum starts heating up (it weighs a lot, so the temperature rise will be slow even though the air temperature is high). The ammonium perchlorate inside will start to decompose into gases, which in turn cause the pressure in out drum to rise. The seal at the drum lid gives way, causing a jet of oxidizer into the room gases, which are by now filled with fuel from decomposing wood. Obviously, this jet ignites and we now have a jet of flame shooting out of our leak. This in turn causes the drum to heat faster, increasing the decomposition rate inside and causing a faster pressure rise inside. This causes jets to shoot out of the drum in a few other places, making our problem worse. Eventually, we get a massive failure of the barrel, maybe with the lid blowing off. The expanding gases from the escaping oxidizer also carry some ammonium perchlorate crystals with them. The oxidizing gases and powder now rapidly mix with the fuel-rich, hot room gases, causing a huge energy release and you get your explosion. And if you had just left it in a pile on the floor, you’d probably just burn your house down.
“key ingredient in the rocket fuel used for space shuttle boosters and Titan missiles”
Not quite correct concerning the Titan Missiles/Rockets. Titan I and Titan IIs were ICBMs (missiles) and were liquid fueled. Titan IIIs and Titan IVs also were primarily liquid fueled, and used two solid fuel boosters that contained Aluminum Perchlorate. Titan IIIs and IVs are not considered missiles, but rather rockets given their mission of boosting satellites into orbit.
I remember watching this on Modern Marvels as well. The first time I saw the second explosion, well… it blew me away.
rbb said: “”key ingredient in the rocket fuel used for space shuttle boosters and Titan missiles”
Aluminum powder and ammonium perchlorate. Aluminum perchlorate would make a pretty bad propellant. How dare you submit a comment that contains a typo!?!
I was reading the first two paragraphs, and cringed as soon as I read “ammonium perchlorate”.
I, too, was ready to point out the difference between oxidizers and fuel, but it looks like a few people have done that already.
another viewpoint said: “So I guess the PEPCON incident supports the Big Band Theory, eh?”
It was the choice of the new Michael Jackson generation.
By the way, nice elaboration, FireDude.
What’s sad is all of these accidents still happen these days, even with regulations and safety inspections.
long time reader… first comment.
I dug the writing of this article – so much so that I was inspired to finally get myself a DI account. Kudos!
Will no one congratulate lfsmith on his hilarious first post? I thought it was grand.
In this article we have fondling, pregnancy and an orgy. Does anyone else think the author is having a little fun with us?
Who in his good conscience leaves an handicap and an disabled man behind?
And… how does the person in charge allowed the repairs to proceed knowing that not far away were stored some big nasty drums with something capable to fire rockets into space!!!
Thats not a mistake, its just stupidity. At least it was in the midle of the desert were the fire can’t spread out as easy.
That´s exactly why i dont want a nuclear powerplant in my country.
“We don´t need the water let the MotherF****r burn”
“The neighboring marshmallow factory fared no better, having been unable to absorb the incredible pressure wave. “
If a marshmallow factory couldn’t absorb the blast, nothing could.
Fine exposition by firedude, but he may have forgotten one factor for a fire — a chain reaction. Irrelevant for the PEPCON fire, I think, but I was once stuped by an exhibition fire in a can that was extinguished by putting a metal screet on top of the can. Fuel, oxygen, and the ignition source were all there. The screen dissipated the heat and extinguished the fire. The fire triangle has grown a new side (for one OSHA instructor, at least).
The poor attorney read an MSDS that said it was not flammable. So is gasoline in its liquid form, but try to get a lit match into the liquid!
Thank god it was in such a remote location. Wow.
Yeah, but the location wasn’t really that remote. As someone who has a wife and numerous friends who lived through this event, let me put a few things into perspective. First, all jokes about the Marshmallow factory aside, a lot of people there were injured, nothing like flaming sticky molten marshmallow to cause serious burns. My wife was in her school cafeteria at the time and the roof of the cafeteria lifted up and MOVED, with debris raining down on her and other terrified school children. Another friend of mine had his home split in half at the foundation. Imagine that for a moment…the house was split at its foundation.
Of course, then there was the rush of parents trying to get to their children’s schools, unsure of what had happened. So many roads were snarled and clogged that some parents ended up taking their cars across the desert while racing to get to their children.
The Pepcon disaster left a lot of deep scars in the Las Vegas area. Yes, it is fortunate that more people didn’t die. It is fortunate that there weren’t things closer to the plant when it exploded
As for the article itself though? Very nice. Well written and wonderfully researched.
Thank you, BrianTung and telkontar. I didn’t mention flame arrestors (that’s what those screens are called), but they really are part of the flame triangle. The “ignition source” is really a question of providing enough input energy to start the chain reaction, and flame arrestors work by pulling enough energy away from the chemical reaction to stop it. But accounting being what it is, you are just moving the energy elsewhere and not getting rid of it. If a flame sits on top of an arrestor long enough, the arrestor will heat up and no longer be effective.
You’ll notice in my description I never had flashback into the barrel – this is what flame arrestors are really designed to stop. If the gases in a room on fire are at 1000 F and stays there, eventually everything in the room will be at 1000 F. And once the ammonium perchlorate reaches 200 F, it will start releasing oxidizing gases and pressurization of the barrel will begin.
Oh, and telkontar, thank you for protecting our working men and women. The history of industrial accidents is truly gruesome.
Very nice input FireDude! I’ve seen a lot of discussions about PEPCON and AP in general, especially in terms of model rocketry and amateur pyros complaining about the regulations on AP being a little overbearing (especially considering similar oxidizers are not regulated so heavily).
I wasn’t aware that AP can be a monopropellant, and your … oxidizer BLEVE scenario is actually pretty plausible.
I’ve read a similar study of the fireworks factory fire that resulted in a not-totally-expected huge detonation, they came to a similar conclusion. It wasn’t so much that the black powder and flash powder itself detonated, but rather the tons of cardboard and paper the fireworks were encased in provided a ready fuel rich environment as they burned and gave off fuel gasses, which allowed the pressure to build to a spectacular detonation, instead of just exploding relatively slowly as the fireworks detonated individually.
Wow, Ceronomus… your account was very poignant. Thank you.
It seems like a lot of people on DI live or lived in that area, doesn’t it? That always makes things more interesting!
brienhopkins said: “If a marshmallow factory couldn’t absorb the blast, nothing could.”
You forgot about the feather pillow factories! Surely they could!
If I remember right, PBS, maybe Secrets of the Dead, had a show where a guy proved that the Hindenburg’s skin was coated with ammonium perchlorate and powdered aluminum. The point was that the hydrogen didn’t cause the fire but a static spark ingited the skin.
Could be wrong on some details
fecalmatters, check the Wikipedia article on that disaster; the issue is still undecided, with several competing theories: Hindenburg: Cause of Ignition
Fortunately my home in Las Vegas was far enough away not to suffer any damage, and I was over in Albuquerque, NM, when the blast occurred. Some of the facilities that were located in this industrial site have since moved to the Apex site about 20 miles north of Las Vegas. It’s a very good thing the blast happened before that area became highly populated as it is now. Since 1988 the Las Vegas Valley has been growing by 8 to 12 people per HOUR without letup.
To Jerry Maxwell, I’m sure that this was a scary event for you to go through having your home so close to the explosion. I’d just like to correct a minor statement you made.
“i did the 90 miles from tonopah in about 45 minutes”
Tonopah is 220 miles north of Las Vegas. At 90 miles away you would be about 25 miles this side of Beatty. Still in the middle of nowhere. Back when they were still testing nukes at the Nevada Test Site, they would always make the patrons of the old Beatty Exchange Club go outside and wait across the street in case the nuclear explosion brought this 100+ year old building down. It is still there and is about the only place to eat for 115 miles going north towards Reno. Explosions of great magnitude aren’t new to Las Vegas residents who, in the old days of above ground nuclear testing, could sit on the porch and watch the mushroom clouds appear above the Sheep Mountain range. The tall buildings in town had seismometers to measure the blasts.
Hindenburg wasn’t ammonium perchlorate. It was iron oxide and aluminum powder, the same stuff that goes into thermite. Mythbusters did some experiments with the compositions in question though, and it still seems that hydrogen plays a big role in accelerating the reaction even though the thermite-like paint coatings did accelerate things some too.
The danger of hydrogen is generally overrated, but make no mistake, it is very easily flammable in air.
telkontar said: “The poor attorney read an MSDS that said it was not flammable. So is gasoline in its liquid form, but try to get a lit match into the liquid!”
Seen that done… Just needs to be done FAST.
I usually don’t comment but I must Applaud the Amazingness of this article. It’s so well written and, I don’t know the flow of the words, the amazing use of the English language. I congratulate you Alan!
My dad was stationed at Nellis when that happened. I was 11. It seemed so remote back then… we felt some minor tremors, but that was it. Henderson was 20 minutes away on a two lane highway. Now, it’s practically a suburb. I shudder to think what the damage would have been like if it had happened today.
Like many others, I too had seen this on some television program, (perhaps it was Modern Marvels) and had really not planned on reading this particular DI article until I saw, “The workers knew exactly what was in these barrels, and they didn’t wish to be present to observe how it would react to the flames.” Besides causing me to chuckle at that line, it also inspired me to read the entire article where I was rewarded with, “…”the flourishing fire mocked their efforts, and soon began to fondle the 55 gallon drums stored nearby.” and “orgy of justice”. I just had to get myself a DI account just to say how well written I thought the article was and how much I enjoyed it, well as much as one can “enjoy” a disaster story.
as a welder who has worked around lots of flammables, getting a hot work permit might of helped but i have also seen hot work permits handed out like paychecks, it is the following of proper proceedure of the hot work permit that could of saved this…..very welll written and good read.
Roy Westerfield was my husband’s cousin. He contacted polio early in life. A family man, who thought of others first, he insisted personnel leave the plant while he stayed on the phone to keep in contact with rescuers and to direct evacuation as long as he was able. Unfortunately, the explosions and spreading fire shortened time available for this. He was declared a hero and deservedly so.
I was in high school at the time of this explosion and remember vivid details of the day. Basic High was I guess 3 – 5 miles away from the Pepcon site, but it still caused significant damage to the high school. We had lost ceiling tiles, blown out windows and several hundred panicked and terror stricken teenagers. My first concern was my younger brother who attended Burkholder Junior High (the school closest to the blast site, maybe 1 – 1.5 miles). Anyhow, the article refreshes my memory of one terrifying day that I will not forget for the rest of my life.
haha an ambitious looking fire. It was meant for great things…
Man this is scary. I’m a college kid who works in a big factory that extracts oil from sage plants (I know, a little obscure) during the summers, and this doesn’t make me feel any better about it. I work in a huge building that has about 15 10,000 gallon tanks and boilers full of hexane and methanol, and it sucks to work in a situation where if there is a fire, you’re screwed. And what the heck was the deal with leaving the guy in the wheelchair?!
Explosive. But not unreasonable. It seems they did the right by NOT calling 911 immediately or for sure there would have been more deaths. As far as the attorney, pretty imbecilic to say ammoium percolate is not volatile. If it wasn’t the rockets would not fire, hmm? Remind me of that brain Rosie O’Donnell stating that iron/steel doesn’t melt – referring to 9/11. Obviously she never heard of Bethlehem Steel?
That’s an interesting thought. That the delay and relative remoteness of the plant could conceivably have saved many rescue worker’s lives.
But, as has been stated several times above, ammonium perchlorate is an oxidant, not a fuel. A volatile substance would have a high vapor pressure, which ammonium perchlorate, a solid material, does not. So in the purest sense of the meaning of “volatile,” ammonium perchlorate is not volatile at room temperature. If you mean “volatile” in the sense of a general quality of being dangerous, then yes, it is, because it can allow for many other unexpected materials to act as fuels.
Wow, that is downright scary when you think about it.
a couple of days to go?…like the little kid in the Disney commercial..”I’m SO excited!”
I still tell this story to my friends when they ask me what it was like to grow up in Las Vegas.
I was sitting in the school cafeteria at Woodbury Jr. High (about 7 or 8 miles away from the “blast site”) when the explosion occurred; and, like many of the other people who have posted eyewitness reports, I also have vivid memories of the event. I was eating a cinnamon roll when the doors to the recess area suddenly slammed shut in unison with enough force to knock tiles down from the ceiling. Some people reacted like they thought it was an earthquake and dived under the tables, some people openly stated that it was a bomb, but most of us just sat there in stunned silence. Conversations died quick deaths. Eventually, one of the teachers slowly opened one of the doors outside, and as we students wandered over to the door, we saw the column of smoke on the horizon. In my overwrought imagination, it appeared to be mushroom-shaped.
Most of my memories of that day are tinged with fear, because even the adults that were in the room were terrified, especially after the gas cloud was called “highly toxic” by radio commentators. The school didn’t have anyplace to put all of us, so they carried on as though it were business as usual — after a while the bell rang and they told us to go to our 4th period class. None of us wanted to. My friends and I were most horrified by the prospect of dying at school.
We sat and listened to the radio for an hour, and then were sent to 5th period. Same thing. Sometime during 6th period the principal announced the decision that we wouldn’t be allowed to leave unless we 1) rode the school bus home or 2) our parents picked us up. My dad was teaching at UNLV at the time, and my mom taught at a school on the other side of the city and was stuck there until all of the children under her supervision had been claimed.
My dad was finally able to pick me up sometime around 5:30 that day, and we drove home (“home” was about 1/2 a mile from the school). Our house didn’t sustain much damage — some things were knocked over or broken, and some pictures had been knocked off the walls, but there were no broken windows or busted shingles. I had friends whose houses or businesses were hit much, much worse. If I remember correctly, some of the hotels on Boulder Highway out toward Henderson were shut down for a couple of days to replace the shattered windows.
The other part of the event that sticks out in my mind was the aftermath. Even though Las Vegas is one of the biggest tourist traps in the country, most of the people who live there don’t use the attractions very often. Residents go to other places for their vacations. Strangely, the rocket fuel plant became a “tourist site” for the residents of Las Vegas and Henderson. The first weekend following the explosion, my family drove out to take a look for ourselves, and we were surprised to see hundreds of cars with Nevada plates parked on both sides of the road. Perhaps a thousand people were there, wandering around outside and taking pictures. We joined the throng.
“The neighboring marshmallow factory fared no better, having been unable to absorb the incredible pressure wave.”
Am I the only one that thinks it would have been a great visual for the Stay-Puffed Marshmallow-Man to be caught up in the PEPCON blast?
Damn Interesting article and Firedude’s commest is Damn Interesting as well.
I remember this incident and the one in Cedar City as I am from there and was living there at the time. It is amazing the memories and thoughts that come flooding back after so long. DI!!!
Alan, your link to the explosion footage on YouTube is no longer good – YouTube says they took it down for a Terms of Service violation or somesuch. Fear not though; there are several more videos of the incident still posted there. My personal favorite is this one.
Sta-Puf Marshmallow Man! I had been hoping for a sequel and this looks like a movie that needs to be made!!!!! A DI article and a DI movie, if my wishes come true!!!
For a better understanding of the chemistry of the explosion you might want to take a look at http://www.chemaxx.com/explosion1.htm written by Dr. Fox. Dr. Fox was one of the team members investigating the explosion. He feels the storage containers played a big part in the explosion; “Soon, all the normal aluminum storage bins for the perchlorate were full and additional storage containers were needed. Instead of aluminum bins, high-density polyethylene (HDPE) drums were used. Neither the unconfined perchlorate nor HDPE bins present much of a hazard alone, but together they form a classic fuel + oxidizer scenario.”
The Defense Department used the explosion to do some work on blast damage http://www.stormingmedia.us/90/9006/A900693.html
Youtube pulled the vids any other URLS?
NM Just serached PEPCON on utube found it
I like some of the others who have posted comments lived in Henderson the day of the Pepcon explosion. I was in class at Basic High School at the time the of the first explosion. Unlike some of the other schools the students where lead out to the foot ball fields due to parts of the tiles falling in and there was lights that where falling as well due to the sound wave that the first explosion sent rambling across the desert with nothing in its way to slow it down any. By the time the second explosion happened alot of us stood and watched as the balls of fire shot up into the sky followed by the plumes of smoke whan the second sound wave hit the ground moved under your feet. Everyone was scared no one really new what was happening some of the students thought that it was a bomb that had been dropped as the news reports started to come in about what was happening they where saying for people to stay in doors due to toxic fumes that had been shot up in the air with the balls of fire a toxic cloud that mind you was spreading across miles as a result of the wind caring it. The school dismissed classes in the days following the explosion of Pepcon crews came in to asses the damages to all the homes business and schools in the area. Of course the area around the plant and henderson where hit hard everything around the plant was gone just holes and burned spots where the fire had been many houses and business in the henderson area had a great deal of damage. The school was closed for the rest of te school year due to it being unsafe for us to resume classes the structure of the school had been damaged due to the force of the sound wave you could see where the front doors of the school had been blown in ward the doors wouldnt shut right the big thing though was that in the aftermath as they checked the school over to make sure it was safe it was dicovered that insulation that hadd been used in the school when it was orignally built was not safe to be in the building because it was made with abseptos which if exposed to the dust and particals that covered our school could cause cancer. It was discovered that there was alot of this in the school officals determined that the school was not safe for us to return to class. Shipping us to other schools wasnt possible due to the amount of students that we had and the amount of students that where at the other schools there would have been to many in the schools. The school was dismissed a few weeks early and the school was told that before the classes could resume in the fall that all the contaminated things in the school which was all the insulation most of the ceilling tiles and some other stuff had to be cleaned up and removed from the school before we would be aloud to go back in the school. I remember watching the crews working all summer that year to make the school safe and for a while no one thought that the crews would hav it done in time. The amount of people that where hurt that day was sad and the two who where unable to make it out will live in the hearts forever or at least for those of us who where actually there that terrible day. It was a day that any one who lived through it will remember it like it happened yesterday and those who have read about it will always intrested in the events that unfolded that day.
We hope that appropriate Safety-Measures r taken so that this doesn’t happen in a Big City!?
“Hindenburg wasn’t ammonium perchlorate. It was iron oxide and aluminum powder, the same stuff that goes into thermite. Mythbusters did some experiments with the compositions in question though, and…”
This was one of Mythbusters’ worst and most sloppy cringingly bad experiments. They basically just controlled the flow of hydrogen through a valve to try to make the combustion look something like Hindenburg. You can’t accurately replicate combustion with scale models.
I too was there, I went to S.N.V.T.C. about a mile away. I was in the office when it happened and I could remember the dirt and dust falling from the ceiling as the first explosion hit. We thought an aircraft had crashed on our runway.
The second explosion took out a long hall of windows that I was standing next to, I could have been hurt. The entire window frame structure was barely hanging from the ceiling, and all the glass was shattered.
I spoke with a family member who owned a portion of Pepcon a few years later. It appears that Southwest Gas had a gas leak on site that had been reported but nothing was done about it. A welding accident had set the natural gas off first. This didn’t hit the papers because the person that owned a good part of the gas company (Mr. Greenspun) also owned the newspapers.
Her story did coinside with other information I had available and I am sure of its authenticity.
Prior to this disaster, there was a series of arson fires throughout the United States that burned so hot, they could only have been fueled by AP. That sort of fire is less dangerous than you would expect. When showing up to a warehouse fire that’s burning, a fire crew has to decide what can be saved, and then they begin the dangerous call of duty to risk life in protection of property. With an AP fire though, it’s so hot and dynamic that there is no question about whether to save the building. Does anyone else recall the AP arsons of 1988?
Holy crap… if this isn’t the best site I’ve found in quite some time, I don’t know what is. Thank you for this.
PEPCON Disaster 1988.05.04 – Ammonium Perchlorate Explosion
Modern Marvels S10E41 – Engineering Disasters 8
…given that if a picture is worth a thousand words,
a video is worth…
Your ability to be detached,
allowing you to type tongue in cheek,
gives this page a marvelous aire,
that I find refreshing on the web.
Good job. You are the greatest. I did laugh.
PS: Perfection being a lonely art,
if you should feel artistic,
kindly add the word “to”
between this article’s words “attempting pin”,
so that is reads,
“…lawyers responded quickly, attempting to pin the blame…”.
I understand your having made that error.
Bloody lawyers irritate me to distraction also.
When will they not share with us their great secret,
though the key to their fortunes,
you want to talk about amazing i wish the news footage showed the highway a little better because if they did you would see me as a seventeen year old hitchhiker on the side of it with my thumb out when the two major blasts happened. I was picked up and thrown both times first blast threw me into the first lane the second blast picked me up and threw me all the way across the highway and feeling like i was instantly atomized i then almost got ran over by the firetrucks and ambulances!
some guy then stopped and let me cool off in his car because it was really hot that day.
he asked me what happened i told him i think the Russians hit us!
he assured me he didn’t think that was the case and then turned on the radio which explained what had happened and that the local casinos were showing the community they cared
by opening their doors to those evacuated from Henderson and anyone needing to stay could stay for free in the rooms.
i then looked over at the gentleman and said thanks for the air and opened the car door and got out heading back into Vegas i got a room at the casino for two days and when they inquired about my parents i headed out the back door and back on the road thumbing it.
and that was my experience on may 4th 1988
i was there. i was12 & in school. iwas as far a
way as the people video taping. it was huge and frightning. i was down wind from the red smoke. the blast blew in the metal doors made the tiles fall and blew out windows. the roads were like something u would see in a movie. i have lots of flash backs from this day.
Hi my name is sylvia and I am the owner of a property in henderson nv . Is there anything you can tell me about the lawsuit back in 2007..I was never notified of such lawsuit and if anyone can provide me any info in regards to this case I will appreciate it. Thank you……sylvia. cell phone 951 287 0258
I was at the new plant in Utah what a mess I was there to do start up of two Dixon 900 hp boilers was there for 8 month’s what a desater it was built a office but forgot to add a restroom coast another 30-40 grand
Had alot of problems was getting feedback from the mile or so cable trays
Once they were in production they showed how dangerous this crap is.
After that it was time to go
Nice vacation place lol
I was watching Engineering Disasters and saw the Texas City explosion. I was working at Pepcon when the explosion happened. Believe me I ran for my life and knew both of the people that died at the plant.
Am I wrong that there was only one explosion at the Nevada facility as well?
“PEPCON lawyers responded quickly, attempting pin the blame on Southwest Gas company. The lawyers claimed that the natural gas fire occurred first, subsequently causing the ammonium perchlorate explosions.”
I was EXTREMELY surprised to see this comment in the article and can even provide some testimony about it. Southwest Gas was owned by the exact same person who owned the News Papers and other outlets, so they stayed FAR away from this portion of the story for a VERY LONG time.
I was exactly one mile away from the explosion that took place and saw the second and third explosions take place personally, and knew personally a young lady whose family owned the facility. Before this previous fire became known, she told me the story about the natural gas fire. Southwest Gas had been told about the leak that took place but neglected in their duties to come out and fix it. The natural gas ignited when a welding incident was taking place, but this was indeed a situation that Southwest Gas was directly involved in.
Nice read down memory lane. As we are approaching May 4th 2018 I was remembering and thinking back on that incident 30 years ago while driving last night; I’m a truck driver. I was only 18, a dropout from high school, and working at the Wendy’s fast food restaurant on Boulder highway in Henderson. As I was washing dishes in the back the drop ceiling tiles above me suddenly raised with a rushed breeze. As I was looking up at all of the tiles floating out of their frame, I suddenly felt my body jolt from head to toe as if someone had shoved me in every direction all at once at the same time. Then I heard a loud ‘BAM!’ and the pregnant girl from the drivethrough window screamed loudly then I heard glass shattering as the drop ceiling tiles reseated themselves in the framing above my head. I walked around the corner to see everyone in a frantic commotion and then I heard the firetrucks. Everyone was talking at the same time and customers looked dazed. One of the storefront windows had shattered. JoAnn Bower, drive through window girl had mascarra running down here face and was clenching her arm unsure if it was ok. She was handing a customer cash when the blast had jerked her arm. After a few short minutes the manager told us we needed to clock out and leave as the store was now closed. An evacuation order was heard over the local radio so co-worker had offered me a ride-to-nowhere since I didn’t have a car. I remember a chemical scent in the air and as we headed down south Boulder highway towards Boulder City traffic was very busy. I was a bit confused but didn’t feel anything until we turned around and headed back towards Henderson. Then anxiety finally overwhelmed me with feelings of helplessness. There was a very large traffic jam on the way back from Boulder City. I fidn’t get back home at my friends house in Pitman until sunset only to find many houses had windows broke and structural damage. By the next morning many many homes throughout the entire valley had spray paint or card board signs thanking PepCon for the carelessness that led to the damage. The odd thing is, my step dad worked next door at Kerr McGee which also processed the same fuel at that time. He brought some home once approxiamately a couple years before the explosion. It was about a handful. The stuff was like white Play-Do. He had held a lit Bic cigarette lighter to it and chuckled, “See it don’t explode!” It had the same chemical smell that I breathed in the air that day. A couple days later I sculpted a snail out of it and a few days after that it had dried out, just as Play-Do would. It eventually crumbled apart and was thrown away in the kitchen garbage.
Yours is my favourite webpage on the whole internet. I’m dropping by every day I can and have been doing so since the one-armed bandit article. During the years I’ve found plenty of entertainment following the curated links and reading the new occasional article. English is not my mother tongue, so I might not be the most qualified of your readers to say that the sentence ‘By the time he reached town and found his way to the hospital there were already hundreds of people gathered there awaiting treatment’ is not your very bestest. I think it would make for smoother reading if you got rid of one “there”. I’d suggest ‘people awaiting treatment’ but well…. And since I’m already here, I even have the feeling that it needs a comma.
I hope you and yours are ok!
I was in 4th grade at OK Adcock Elementary School in Las Vegas and on my way to the office when I saw the first plume and then noticed something odd. Several seconds later I saw a second plume forming and then heard an explosion and the ground shake like nothing I ever felt before.
I had formerly lived in San Diego a couple of years earlier and experienced 2 earthquakes, but I was not sure what to think.
I had office staff come out to see what was going on and after they saw what I did, I was immediately brought into the office and sat in a back room, away from windows, until they could figure out what was going on.
Shortly after then. I was escorted back to class and our school was ordered to keep all students indoors. No recess or lunch. We stayed in class until they let us out to go home. I honestly can not remember if we were let go early or at regular time. The news on the radio and tv stations were saying the plant exploded and to stay indoors that evening due to fears of hazardous chemicals in the air. The next day we were given the all clear and life went on for us.
I will NEVER forget that day…
Note to self: Finished.