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Are Airport X-Rays Harmful To Certain Hard Drives? 12

An Anonymous Coward wishes to put this curious query before you all: "I have been through the airport many many times w/ my laptop and have never had any problems w/ losing my data on my 2.5" hard drive, but two work associates of mine have not had the same good fortune: they had both traveled and brought their destkop 3.5" drives with them and had their data compromised/destroyed as a result of having had them go through the standard carry-on luggage x-ray machine. The drives were not defective mechanically before having gone through just to clear up any misconceptions. Were these just fluke incidents or does the x-ray system @ airports actually destroy data on certain types of hard drives? Let's hear your opinions!" Any thoughts on this? Personally, I would think that desktop HDs would be more sensitive to the shocks and bumps inherent in travel than the X-ray machines at the airport.
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Are Airport X-Rays Harmful to Certain Hard Drives?

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  • by Lazarus Short ( 248042 ) on Friday November 17, 2000 @10:24PM (#616279) Homepage

    Actually, it's much, much more likely that the x-ray machine is not the culprit at all. Remember that hard drives are magnetic in nature. X-rays are no more magnetically charged than the light from the light bulbs in your house. X-rays will erase highly sensitive photographic film, but that's about the sum total of damage that they could ever do to any of your stuff.

    However, in close proximity to the X-ray machine is a device that makes use of strong magnetic fields: the metal detector. Carrying a laptop though one would almost certainly mess with the data on it (note that it wouldn't totally wipe the drive beyond recovery. If you think it'd do that, put down the Neal Stepenson book [cryptonomicon.com] and take a break).

    Now, metal detectors are supposed to be shielded from interfering with devices not going through them, but, needless to say, that's not always the case. It's more than possible a more sensitive than usual hard drive could be corrupted by just passing next to one.

    For further reference, see Here [computerproblems.com], Here [atomicboy.com], and Here [orlingrabbe.com]

  • by rjh ( 40933 ) <rjh@sixdemonbag.org> on Saturday November 18, 2000 @12:14AM (#616280)
    Older X-ray machines used higher levels of radiation, which means that your risk increases with the age of the airport.

    The other risk factor is the HD itself. How dense is the media? Is it set up to do software RAID? Is it a name brand, or is it a fly-by-night? Speaking generally, Big Name manufacturers are more resistant to stresses of all kinds than a HD which just fell off the back of a turnip truck.

    To summarize--let your modern laptop go through modern X-ray machines without too much worry. But if either of them aren't modern, you might want to ask Security to hand-check it.
  • A few years ago, I was working at a very large company and a number of the big-shot execs went on a trip. While on the road, their laptop hard drives got completely scrambled.

    As it turns out, the little seat-back (or whatever) tables on the plane had magnets in them to keep the meal-service stuff in place. The put their laptops on the tray tables, turned them on, and saw...a mess.

    Not sure if they still do this, but it's worth asking a flight attendant.

  • by Detritus ( 11846 ) on Saturday November 18, 2000 @04:33AM (#616282) Homepage
    X-rays are not going to damage a hard drive. The problem is the electric motors that are used for the conveyor belt. These generate strong magnetic fields that can erase or corrupt magnetic media. I've heard of similar problems with subway cars, big electric motors under the car that have been known to erase tapes in boxes that were set on the floor.
  • As manufacturers have become more sophisticated, the energy levels of the x-ray machines have dropped. If fact, it's more of a fluoroscope than a 'real' x-ray machine -- the difference is that photographic plate x-rays require higher energy levels than video fluoroscopy.

    However, recent events and paranoia about airline safety have seen new x-ray devices introduced which can image soft materials like plastic explosives and other things that would not have shown up with a 'conventional' machine. These devices (synthetic aperature x-rays, IIRC?) use a signifigantly higher energy level, and have been proven to fog film. (Remember how the security people will swear up and down that their machine is safe for film? No more!)

    The worst part of it all is, for 'security reasons,' they (most often) won't tell you if they even have one of these higher-energy machines, never mind whether or not you just put your film (or your laptop) on one!

    I guess the moral of the story is 'insist on hand-inspection for film and laptops.'

    Gotta love that security paranoia. What are they expecting? That you're going to go down the hall, plug your super-whizz-bang-space-captain laptop into their PA system and hack the x-ray machine? Well... I've seen some airport security types that would believe that one...

  • A simple solution might be to place things you worry about (such as hard drives) in a lead lined bag. They're generally sold to protect film, but there's no reason you can't stick other things in. Most likely anything inside won't be completely shielded, but it might help some.

    Then of course, one can always request that your bag be hand searched.

  • Most modern hard drives store the low-level volume data (track good/bad, compensation, timing info) in flash ram or eeprom on the printed circuit board.

    There are known problems with using either of these technologies within a high radiation flux. Secondary scattering from the device case may produce particles that can effect flash ram, and soft xrays may be able to produce a similar effect to ultraviolet light that affects eeprom (or even eprom).

    While these technologies are used in spacecraft and radiation area, I know that much effort is placed in shielding such (special "heavy metals free" plastic and ceramics for cases, special epoxies, different device packaging forms).

    Magnetic flux densities used in hard drive with modern evaporated or plated media are fairly high, even though the power required is quite small due to the incredibly tiny spot size. This, plus the shielding of the case, plus distance fom magnetic source, makes it unlikely that the focus coils or power supply of an xray generator would have much of an effect.

    I will have to start wondering about my Visor, though. Has anybody made any tests?

  • It's been noted in a few photography magazines that some new xray machines showing up at airports will streak film. Certain types of film are more EMF sensitive than others (like IR film or other high-speed films), but streaks are showing up on standard b&w/color chrome and negative films and at relatively slow speeds like 200 and 400. One magazine actually suggested that you ask for your film to be hand-inspected. (Which I did on a recent jaunt from Minneapolis to LAX.) This suggests that we're dealing with a new beast, one which is kicking out more EMF than its predecessors.

    What I'm not sure of, though, is if these new machines produce sufficient EMF to screw with a hard drive. I know that most of the problem spots are electric motors, but I still wouldn't toss a laptop to chance like that. (And definitely not Zip disks, etc. Anymore it seems like a Zip will corrupt if you look at it wrong.)

  • It's possible it's not the X-ray machine at all, but vibration on the plane. Planes suffer from really bad high-frequency vibration, and if you place something in a not-very--well-padded bag on the cabin floor, the vibration can cause problems. Typically it will cause very small screws to come unscrewed, and that sort of thing.

    Everyone in our group has a Sony Vaio 505 and travels a lot - the case screws seem to vibrate loose on planes all the time. Also I had a Canon EOS camera stop working the same way. So my guess is that it's just as likely that it's the plane that caused the problem as it is the X-ray machine.


  • I agree that the conveyor belt is a likely culprit. I'd like to add that the major hazard here, though, is travelling in general. Looking at the original posting, he says, that he has never had any problem with his laptop, but these guys were travelling with their 3.5" desktop drives. Perhaps, since laptops are designed for travelling, they can absorb the bumps and bangs and rattles of going over a conveyor belt, being jostled in luggage, kicked under the seat, etc., much easier than a naked desktop drive. He doesn't say how the drives were protected. If they weren't well-protected from jarring, all bets are off.

    Why were they just carrying the drives in a carryon anyway? Wouldn't one _assume_ the need to protect them in _some_ way?

  • I'm not so sure that modern hard-drives are better at surviving x-ray machines than old ones. I happen to have a Toshiba T3200 LABtop computer with a 40MB HDD in it. The drive and computer are so full of shielding that the whole thing weighs 19lbs. It's been through many x-ray machines (as well as dropped, had coffee spilled in it, and innumerable other "don'ts") and still functions. I think it all depends on what the manufacturer's priorities were when designing the HDD.
  • I hope I'm not feeding a troll, but x-rays are EM (electro-magnetic) waves, just like visible light, radio waves, ultraviolet, etc. The only difference is that they have a much higher energy due to higher frequency (shorter wavelenght ~1A instead of ~500nm for visible light).

    The only way you can claim that x-rays are particles is when using the particle nature of light. In that case, they are photons. However, the currently accepted theory is that light (and everything else, for that matter) has a dual nature, both particle and wave, according to the deBroglie relationship.

    It is also true that x-rays aren't particularly related to electricity. However, electricity has very little to do with the fact that we call light Electro-Magnetic waves. We do it because a while ago (anyone correct me if I'm wrong) someone discovered that a lot of the properties of light (and x-rays, UV, IR, etc) could be explained if they were actually waves of an electric field at right angles to, and propagating in the same direction as, waves of a magnetic field. Hence, electro-magnetic fields. I don't think this is the accepted view any more, but the name stuck.

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