CRTphobia

April 27, 2007 8:01 AM

Can my computer kill me without warning?

In Cryptonomicon, there's a scene where a hacker sets up someone's computer to overdrive their (CRT) monitor, causing it to explode and send glass shrapnel into their eyes, brain, etc. Ever since then, I can't use a CRT-connected computer without thinking about it. Particularly the monitor I have at home, which makes these loud clunky clicking sounds whenever it switches modes, comes out of screensaver or turns on. Sometimes I even squint and cover my eyes, even though I know this is probably not very likely, if it's even possible.

I haven't been able to find anything about this online and sometimes the absence of evidence IS evidence of absence.

I would like to get an LCD (not just for this reason--I'm far from debilitated by this) but they are still too expensive.

posted by DU to technology (45 comments total)

It must be true, I read it in the Weekly World News.
posted by mr_crash_davis at 8:11 AM on April 27, 2007

In Bernard Werber's Les Fourmis, there's a bit in which the citizens of a computer life simulation achieve sentience, revolt at their 'god' (the computer user) and do the same. As a result, I've always wondered about this as well.

I mean, I know it's very very implausible, that the safety checks inherent in the design of the monitor as well as the hardware/software would take care of things, but I do wonder. It's a nice question to ask, about software manipulation within a closed system to affect the hardware outside of that system...
posted by suedehead at 8:13 AM on April 27, 2007

You can be killed by an exploding CRT. I've seen other occurrences. But it's so rare that you should be more worried about being killed by an airplane crashing through your ceiling.
posted by solid-one-love at 8:14 AM on April 27, 2007

Even assuming that someone could program a computer to send too much information to the CRT, what would make it explode? What does it have inside it that would explode? How would the computer force the screen to draw extra electricity? It seems to me that the computer might be able to force the monitor to fry itself (theoretically), but this wouldn't produce an explosion. You need something explosive to explode. I don't think that many companies build in explosives to home electronics, for obvious reasons. There's a reason they call it science fiction.
posted by Dasein at 8:15 AM on April 27, 2007

I'm sure a fuse somewhere in the monitor or power supply would blow before the monitor overloaded enough to explode that forcefully. They'd have to fit a safety feature in case a mains power surge caused the same thing to happen.
posted by EndsOfInvention at 8:24 AM on April 27, 2007

Good link, s-o-l, and it reminds me that I wince whenever I get a shock from the TV for the same reason. IT'S GONNA BLOW!!!!
posted by DU at 8:26 AM on April 27, 2007

Ah, yes, the old "can your computer injure its own hardware" question.

This has been a popular question to ask since the TRS-80 Model 1 came out in about 1981 or so. ;-)

Short version: no.

Longer version: about the only thing that is under programmatic control of a PC that can cause any physical damage to anything is the sync controllers in the video adapter.

Early non-multisync monitors could be overdriven by programming those sync pulses to occur too fast, but the worst that would *typically* occur is that you'd burn out horizontal sync components, or, rarely, the flyback transformer. The latter is pretty spectacular, but exceedingly unlikely to be able to shatter the CRT.

CRTs are *STRONG*.

If you're really feling froggy, take an old 25" TV set out to a safe place, dress appropriately, and start hitting it with a hammer. Or shoot it with a .22.

But I would relax about your computer violating one of the three laws of robotics.

Or get an LCD. :-)
posted by baylink at 8:36 AM on April 27, 2007 [1 favorite]

CRTs are remarkably mature technology, with literally billions of units in operation. If death by exploding CRT was a common event, CRTs would be a lot less common than they clearly are. The reason for that is that CRTs have been extensively enginneered to protect users, when operated in normal ways, and even when exposed to projectiles and many instances of being abused or dropped on their faces. The glass face of a CRT is its thickest, and, by intention, the thinnest glass is in the enclosed "neck" or electron gun area of the tube, which is generally enclosed in most consumer devices. If the tube is mechanically damaged, it is designed to implode with most of the released force and shard glass being retained by the tube face and the secondary enclosure. Also, most CRTs larger than about 9" diagonal measure have additional safety features, such as a steel rimband around the perimeter of the picture face, that vastly improves structural integrity even in implosions.

There are other risks associated with CRT use, not the least of which is high voltage leakage and excess X-ray production, particularly with larger color tubes. But I don't think there is any use scenario where a pattern of display information could be reliably programmed to cause failures of CRT assemblies such that users could be readily killed under programmatic control. If there was, I suspect many system administrator tool kits would contain such routines, as, after all, it would be the ultimate LART. :-)
posted by paulsc at 8:37 AM on April 27, 2007 [1 favorite]

Right, because the engineers who designed modern crts put a secret overload circuit into them which can be triggered by sending a specific signal.

Look both ways before crossing the street. Oh, and the tube is evacuated. It'll IMplode.
posted by defcom1 at 8:43 AM on April 27, 2007

I suppose if you sleep near your computer desk the monitor could fall off the table and crush your head if in the right position and then a small earthquake happened, but that's the most plausible, and that's not very plausible at all.

There have been recorded instances of CD-drives malfunctioning and sending flying disc shrapnel but I don't believe there have ever been recorded fatalities.

In other words, the most likely way your monitor will kill you is if you decide to plug it in and and take a bath with it. As long as you avoid that I'm pretty sure you'll be fine.
posted by XQUZYPHYR at 8:48 AM on April 27, 2007

It is for this very reason that I wear a visored motorcyle helmet while at the PC.

Oh, crap.
posted by Clyde Mnestra at 8:51 AM on April 27, 2007

Yes. I think the most probable scenario involves a lightning strike and a set of headphones.

Because of the high voltages involved in CRTs (ionization etc.), I believe the chances of fatality would be greater for a given lightning bolt with one of them than a LCD.
posted by jamjam at 8:54 AM on April 27, 2007

My cat pushed my LCD monitor off my desk by landing on it during a miscalculated jump from the window to the floor. If I would have been sitting at my desk, I would have been injured. If I'd had a CRT, there would be no way the cat's velocity could have pushed it off the desk.

So you're really no safer buying a LCD. Presuming you have a really clutzy cat, that is.
posted by desjardins at 8:55 AM on April 27, 2007

P.S. Both the cat and the LCD were basically unharmed, though I do have a "bruise" on the screen. The desk has been moved to the opposite side of the room, away from the window.
posted by desjardins at 8:57 AM on April 27, 2007

I'm seeing a lot of handwaving about how unlikely it is, but the only hard facts in evidence are a link showing that it definitely is possible. Maybe I should upgrade to an LCD after all and save some power and desk space.
posted by DU at 9:09 AM on April 27, 2007

I don't think it could ever explode, but it can damn sure ASSPLODE! And if that happens, GAME OVER.
posted by spicynuts at 9:12 AM on April 27, 2007

CRTs indeed implode, but implosion can still mess you up.
posted by MtDewd at 9:21 AM on April 27, 2007

Am I the only one who doesn't remember this scene from Cryptonomicon?
posted by odinsdream at 9:38 AM on April 27, 2007

if you're going to spend money, and not a small amount of it, either, worrying about your crt exploding, then may i also suggest that you remove everything flammable from your house, throw out your microwave and all sharp cooking and eating utensils. You are far more likely to be harmed or killed by fire, an exploding microwave or accidental stabbing than you are from your crt exploding. in fact, it might be a good idea to turn off the hot water in your house to prevent scalding, and also to discourage taking baths during which you might drown.

the answer to your question is yes, a crt monitor can explode, and yes an exploding crt monitor can kill you if you're close enough to it. but no, it is not likely, no the technology in cryptonomicon does not exist, and no you should not base any significant purchases in your life on the ever so slight possibility that something like this could happen. you are more likely to be killed or injured doing any number of other daily household activities than you are by your monitor (or CRT tv!!!!!!!!!!) exploding that "just being safe" isn't an actual possibility.

for instance, the material inside an lcd monitor (if it cracks in any way) is unhealthy for you.
posted by shmegegge at 9:50 AM on April 27, 2007

I'm seeing a lot of handwaving about how unlikely it is, but the only hard facts in evidence are a link showing that it definitely is possible. Maybe I should upgrade to an LCD after all and save some power and desk space.

If you want an LCD, just buy an LCD. They're inexpensive consumer electronics that don't need to be justified with the odds of a 1" thick piece of glass shattering outwards at you via software.
posted by mendel at 9:50 AM on April 27, 2007

on lack of preview, i don't remember that scene in cryptonomicon either.
posted by shmegegge at 9:51 AM on April 27, 2007

There was a similar scene in Cryptonomicon - but it was not a malicious attack, simply an accident where a CRT monitor did explode severly injuring a side-character.
posted by jkaczor at 10:46 AM on April 27, 2007

Now that we've allayed your fears, a 17" Acer LCD can be had for $139.00. That's about as much as a nice dinner for two.
posted by DefendBrooklyn at 11:07 AM on April 27, 2007

In Crypotnomicon the Monitor was rigged to explode by a terrorist. Even in a fantasy world with magic gold and dotcoms that make money the author felt that having "the Finn that blew up" blow up without help was implausable.
posted by Megafly at 11:14 AM on April 27, 2007

The relevant bit from Cryptonomicon:

Before Pekka became known around Silicon Valley as the Finn Who Got Blown Up, he was known as Cello Guy, because he had a nearly autistic devotion to his cello and took it with him everywhere, always trying to stuff it into overhead luggage racks. Not coincidentally, he was an analog kind of guy from way back whose specialty was radio.

When packet radio started to get big as an alternative to sending data down wires, Pekka moved to Menlo Park and joined a startup. His company bought their equipment at used-computer stores, and Pekka ended up scoring a pretty nice nineteen-inch high-res multisync monitor perfectly adequate for his adaptable twenty-four-year-old eyes. He hooked it up to a slightly used Pentium box jammed full of RAM.

He also installed Finux, a free UNIX operating system created by Finns, almost as a way of proclaiming to the rest of the world "this is how weird we are," and distributed throughout the world on the Net. Of course Finux was fantastically powerful and flexible and enabled you, among other things, to control the machine's video circuitry to the Nth degree and choose many different scanning frequencies and pixel clocks, if you were into that kind of thing. Pekka most definitely was into it, and so like a lot of Finux maniacs he set his machine up so that it could display, if he chose, a whole lot of tiny little pixels (which displayed a lot of information but was hard on the eyes) or, alternatively, fewer and larger pixels (which he tended to use after he had been hacking for twenty-four hours straight and lost ocular muscle tone), or various settings in-between. Every time he changed from one setting to another, the monitor screen would go black for a second and there would be an audible clunk from inside of it as the resonating crystals inside locked in on a different range of frequencies.

One night at three A.M., Pekka caused this to happen, and immediately after the screen went black and made that clunking noise, it exploded in his face. The front of the picture tube was made of heavy glass (it had to be, to withstand the internal vacuum) which fragmented and sped into Pekka's face, neck, and upper body. The very same phosphors that had been glowing beneath the sweeping electron beam, moments before, conveying information into Pekka's eyes, were now physically embedded in his flesh. A hunk of glass took one of his eyes and almost went through into his brain. Another one gouged out his voicebox, another zinged past the side of his head and bit a neat triangular hunk out of his left ear.

Pekka, in other words, was the first victim of the Digibomber. He almost bled to death on the spot, and his fellow Eutropians hovered around his hospital bed for a few days with tanks of Freon, ready to jump into action in case he died. But he didn't, and he got even more press because his startup company lacked health insurance. After a lot of hand-wringing in local newspapers about how this poor innocent from the land of socialized medicine had not had the presence of mind to buy health insurance, some rich high-tech guys donated money to pay his medical bills and to equip him with a computer voicebox like Stephen Hawking's.
posted by dmd at 11:26 AM on April 27, 2007

but the only hard facts in evidence are a link showing that it definitely is possible.

I would hardly call a story in WWN a "hard fact".

The other story was a TV set from 1990. Is your CRT monitor from 1990?

Look, I've dismantled a CRT. I've dropped one from the second story of a window. I've beaten one with a baseball bat. None of those things caused any sort of explosion. I know a kid who tried to set one on fire - the worst part was the toxic fumes. No explosion.

Just get an LCD monitor if you want one.
posted by muddgirl at 11:37 AM on April 27, 2007

$139 for a dinner for two....3 times. But maybe my wife and I are just cheapskates.
posted by DU at 11:59 AM on April 27, 2007

i think the movie maximum overdrive answers this one.
posted by andywolf at 11:59 AM on April 27, 2007

unless of course you haven't seen it (which is sad). the soda machine kills a guy when everything electronic gains sentience. so, if your computer is harboring some resentment (say, a bit of jealousy with the internet porn) and feels dejected you may have to watch your back.
posted by andywolf at 12:07 PM on April 27, 2007

No.

However you seem to be pretty wound up about this despite everyone else saying "no".

Exactly what evidence would convince you? Because CRT's don't kill people by exploding. Therefore there are no statistics we can point you to to show how unlikely it is. Just like there are no statistics showing how many cattle drives there are at the top of the Empire State building, no one keeps statistics on things that don't happen.

What you witnessed is a work of fiction. Not fact.

Know the difference.
posted by Ookseer at 12:12 PM on April 27, 2007

Also, unless I've understood something wrong, the exploding TV set did not kill the woman by way of flying shrapnel, it caused a fire. There's no reason to assume that CRT monitors are more fire-prone than other electric appliances in your home.
posted by pravit at 12:23 PM on April 27, 2007

However you seem to be pretty wound up about this...

Not really, though I am a little ticked that the best people can come up with is "nuh-uh, Batman could TOTALLY beat a CRT". Presumably this has been tested at some point (glass pressure vessel at high voltage about 18 inches from a person's face--Bueller?).
posted by DU at 12:35 PM on April 27, 2007

Having shot at CRTs before (old ones, IMO more likely to send glass everywhere), I know from experience that it's very difficult to get them to do much of anything.

With a BB gun, it took about 20 shots to get one to implode. It was rather underwhelming. There was a pile of glass extending a couple inches high a couple of inches in front of the monitor. There might have been some tiny shards I couldn't see that went farther.

Being teenagers in Arkansas, with that completed, we went and got a .22 and shattered another one in one shot. Still no huge explosion.

Maybe they would have done more if we had removed the tension band, but with it on there, it was more like breaking a window. Most of the glass ended up inside the tube.

As far as your computer causing your CRT to explode, that's simply not possible. As someone mentioned upthread, if your monitor does not have the appropriate protection circuitry, it could certainly fry the inputs, but that will in no way cause it to explode. Modern CRT monitors will not pass through out of range sync pulses to the sensitive circuitry in the first place.
posted by wierdo at 12:44 PM on April 27, 2007

check out this thread on snopes, which links to this Old Man Murray article (OMM! CLASSIC)

I *know* KNOW KNOW i read somewhere about this sort of thing before, where a person said, "no, you can't make it explode, but you can write software that causes the monitor to flip the thingy shooting the beams to the side, so the monitor is basically trying to excite pixels where there are none, effectively breaking your monitor". Obviously, though, that recall is not enough to search on. Maybe someone else knows what I'm talking about? (or i'm crazy).
posted by fishfucker at 12:54 PM on April 27, 2007

It is, theoretically possible for your PC to render your CRT monitor non-functional. There are all sorts of clock timings and old-school bits to flip on video adapters that can send out of range data to the monitor and cause it to no longer work. In fact, old Linux xf86config settings included warnings to not just guess at values for exactly that reason.

However, most CRTs made after (say) 2000 have a far smarter controller than the dumb vga terminals this fact relies on. My CRTs will simply go black and complain if an impossibly high refresh rate or timing is asked of them.

Even allowing for ancient hardware, malicious software, AND that perfect storm of unluck, no your computer cannot kill you without any physical help on your part.
posted by Skorgu at 1:29 PM on April 27, 2007

Just a what-if here, for the sake of nerd-dom:
I notice that the SVGA interface has a line for both H & V sync. Can you control this directly?
(I don't know anything about video adapter programming)

If you can, could you write a ML routine to cause it to set up some kind of resonant frequency in a CRT? Something outside of the normal 17kHz and 30 Hz (NTSC) ranges? I'm thinking the V might be better than the H for this- bigger flyback?

If you can, what would happen? My guess would be it blows a fuse.
posted by MtDewd at 2:40 PM on April 27, 2007

There used to be an old story floating around UseNET (can't you just feel the quality of my comment already?) that old IBM computers could be made to "walk" off desks via computer code that made the dual floppy drive systems spin up and down in a particular manner creating some sort of "harmonic resonance" that edged the computer forward till it lept off the desk to its death (I guess possibly resulting in a broken foot for any sucker at the desk who hadn't noticed a big old computer system slowly vibrating towards them).

Almost certainly complete nonsense.....but I have always placed my computers on the floor next to my desk to be safe.......but mostly just so I could kick them more easily when they crash.
posted by inflatablekiwi at 3:02 PM on April 27, 2007

It is most definitely possible for your computer to break your monitor as it happened to one of mine. The computer power supply became faulty and sent too much current to the monitor and fried it (as far as I can tell, the problem was definitely the power supply). A few flickers, some weird colours then the monitor didn't go any more. No explosion, no implosion, no burning, nothing at all exciting. I replaced the power supply, my boyfriend bought me a sweet 19 inch replacement monitor and all is well.

I'd be more worried about a faulty power supply in your computer killing you via electric shock than a monitor exploding. And I doubt either is able to be controlled by outside programming or is at all likely.
posted by shelleycat at 3:17 PM on April 27, 2007

Oh. I meant break as in 'make no longer working' not as in breaking glass or anything that dramatic.
posted by shelleycat at 3:17 PM on April 27, 2007

I've never read Cryptonomicon, and always thought I was missing out on something special. After reading dmd's quote, I now know I'm not (unless you consider bad science, bad sci-fi, and bad writing "special"...)

DU: Don't ever watch Murder By Phone, Ghost In The Machine, or The Cars That Ate Paris.
posted by Pinback at 5:38 PM on April 27, 2007

Don't judge it on that paragraph. It is, quite possibly, the most boring and badly written piece of writing in the whole book.
posted by dmd at 8:29 PM on April 27, 2007

In that section of Cryptonomicon, I always thought the resolution switch was a trigger for explosives. Otherwise, monitors just don't work that way.
posted by Pronoiac at 9:11 PM on April 27, 2007

For it to kill you, there needs to be two things: a physical mechanism for it to cause you harm (implosion? doubtful...) and some way for the software to control that mechanism.

An implosion requires damage to the glass envelope and the software certainly doesn't control any little robotic arms inside the monitor for the purpose of smashing the back of the tube.

As has been mentioned, the worst you can do is burn out the horizontal sync driver on an OLD (pre-1996 or so) monitor that doesn't have a smart controller. What happens there is that too-high hsync frequencies cause the current in some capacitors to be so high that they vaporise. So you get a puff of very acrid white smoke and the monitor ceases to function.

Now obviously if you wire the detonator of a bomb to your parallel port, the computer can kill you without warning. One of our dodgy old machines sends a handful of characters to the printer (wastes a page) on bootup; if there was a bomb wired to that machine I'd be dead.... but I'm guessing you don't have bombs wired to your computer. Which makes it a big fat "no".
posted by polyglot at 2:20 AM on April 28, 2007

inflatablekiwi- when they're talking about old IBM computers, they're not talking about the kind you put on your desk. We're talking Eisenhower-era 1401s and 7090s. I have worked with guys who have seen some of this stuff. (Sorry, no videos of disks walking). Also, the IBM 5225 printer could walk off a desk (if you could get it up on one) just in normal operation, it shakes do much.
posted by MtDewd at 3:35 AM on April 28, 2007

(glass pressure vessel at high voltage about 18 inches from a person's face--Bueller?).

What are you talking about? That sentence simply doesn't make sense. Why would there be a study of this?

The voltage has nothing to do with this, in any case. The malfunction described in this thread is related to the scan frequency overdriving certain circuitry in the monitor, causing these components to fail. This is completely unrelated to the glass vacuum tube.

You have caught on so far to the fact that it's a vacuum tube, not a "pressure vessel," right? You do understand the difference, right? One would implode, that is - it would collapse inward, while the other would explode, which you understand.

And, in any case, the whole reason the monitor would fail is because of old technology. Even relatively new monitors will simply go dark and show you a message that says something like "Out of Frequency" They won't be damaged by incorrect video signals because they watch for them.

So - are you just not reading this thread?
posted by odinsdream at 8:09 AM on April 30, 2007