Full-Body Scanners 101: The Two Types and How They Work

In the first part of this series, we told at which airports you'll be encountering full-body scanners, and as our week of focusing on this privacy-busting security measure continues, we're getting into the technical bits.

This second lesson in Full-Body Scanning 101, is exactly how these behemoth machines (which can easily break down, apparently) function, and what technology they're using to locate all your nooks and crannies.

First, we have to say that there are two types of full-body screening machine: The millimeter wave machine, and the backscatter machine. It's easy to tell them apart, once you know how they work...

· The Millimeter Wave scanner This is probably the one you'll find at airport right now, since there are 40 of them scattered around the 19 US airports with full=body scanning technology. It appears like a giant cylindrical phonebooth, with mostly clear glass walls and scanning panels that move around you.

How it works: This machine emits small radio waves that pass through your clothing and returns with images of the body underneath. Human skin is all they want to show up, and anything that is not human skin is cause for alarm. Because the panels move around you, this scan can take up to 40 seconds and there is a zoom option. This is the machine that reveals most bodily detail, but software will blur your face...in case you're George Clooney and worried about TMZ getting ahold on your security scan.

· The Backscatter scanner These are one their way to more US airports, with 150 or more scheduled to show up in US airports in 2010. It's not as cool-looking as the millimeter wave's circular glass contraption; you're effectively standing between two giant boxes, with your hands up. But what those boxes are doing is the cool part...

How it works: Two low-level X-rays of you are taken within twenty seconds. If the electromagnetic waves are absorbed, then you're good to go, but if you're hiding foreign objects, then those items will reflect the rays and be visible in the scan. Radiation is not a concern; the amount you'll absorb is the same you get exposed to during everyday life. Images from this sort of full-body scanner appear more skeletal than fleshy, and you'll probably not be able to recognize your own face.