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Airport X-Ray Machines
One of the great myths about computer media, such as floppy disks and tapes, and even hard disks and portable computers, is that they will be damaged if put through the X-ray detecting hardware at airports. This is, in fact, not true. Not only will these machines not erase or damage magnetic media, they are in many ways the best place for your floppy disks to be as you pass through the airport security checkpoint. (Seriously... read below.)
I am not entirely sure how this legend got started; I know that at one point I believed it myself. Every time I traveled by airplane and took my laptop and all my disks out of my bags before putting them through the X-ray machine. I did this diligently for years before learning that it was unnecessary. I also found some floppy disks that I had forgotten about, which had been going through the machine for years, and they worked with no ill effects.
The reason that these machines pose no threat to your disks is that X-rays are not magnetic. They are a form of electromagnetic energy, and perhaps it is this name that causes the confusion. Guess what electromagnetic energy is? Light. X-rays are just light waves of a specific wavelength, much like visible light, infrared (radiated heat), microwaves and radio waves. While some of these energy forms can damage media through heating (if exposed to strong enough sources, like the sun on a hot day), none affect magnetic fields. And they are present in much lower energy levels than those required to generate damaging heat.
Some people even think that compact disks are affected by these X-ray devices. This one I really have a hard time understanding, since compact disks do not even use magnetic encoding. Their data is stored using physical structures--minute holes in the surface of a plastic disk. No form of electromagnetic radiation encountered in daily life (short of melting them with heat) will harm CDs.
Quite ironically, those who avoid putting floppy disks through X-ray machines may be inadvertently risking them with exposure to another device that can affect magnetic media, and which is right at the same security checkpoint--the metal detector! One of the properties of metal objects is that they distort the shape of a magnetic field when they pass through it. Metal detectors work by establishing a weak magnetic field and then monitoring disruptions caused by metal objects. These are real magnetic fields and can in theory damage the data on a floppy disk (although it probably would take bad luck or multiple exposures, I am not sure of this.)
By passing the disks through the X-ray machine, you provide the safest route past the metal detectors. If you ask for a hand inspection (or worse, carry the disks through the detector with you) you may be creating the very risk you are trying to avoid.
Warning: The comments above do
not apply to photographic film. This medium is not magnetic, but photosensitive, and some
types of films can be partially exposed when subjected to X-rays. The most susceptible
types are fast films, ISO 800 or higher, since they are more sensitive to light. X-ray
exposure on some of these films shows up as clouding or fogging on the film. I personally
use ISO 400 film and it does not go through the X-ray machine.