Passing airport security can be stressful. You will probably forget to remove your belt or have too big a bottle of shampoo in your carry-on. Happens to all of us, but what if you have to pass through a body scanner? Will thoughts of radiation risks haunt you throughout your journey? What about the possibility of the operator saving a snap of your naked body? Get ready to learn the secrets behind the mysterious machines that see through your clothes, the main question being – do they actually work?

First, let’s make sure we’re on the same page about one thing: there are two types of scanners used in airports across the globe – millimeter wave (mm-wave) and X-ray (also called backscatter scanners). Both are used for the same reason – to get a (albeit blurry) picture of a person underneath their clothes without actually asking them to strip down. The image is then usually converted into a cartoon-like body outline and presented to the operator. How dangerous can that be?

X-ray vs. mm-wave technology

X-ray scanners were once deemed a safe technology, with some vendors using them in stores to get the client’s foot size without making them remove their shoes. That was, of course, before radiation and its impact on health was discovered. Remember Hiroshima and Nagasaki? Well, more people died of radiation-related illnesses than from the explosions, when the uranium and plutonium bombs were dropped.

With safety regulations getting stricter as we speak, X-ray body scanners have been slowly disappearing from everywhere, airports being no exception. X-ray backscatter scanners have been banned in European airports since 2012. Most recently, in October 2016, China has also discontinued the use of this technology due to radiation risks at its railways terminals and airports.


On the other hand, millimeter wave scanners use a subset of the microwave radio frequency spectrum, which is five orders of magnitude less energetic than X-ray radiation. On the contraty, backscatter scanners do use ionizing radiation, which (in large dozes) is considered carcinogenic and can potentially impact the person’s DNA. Sounds scary? Well, the devil might be not as black as he is painted.

200,000 scans in a row

So, how dangerous is the dose you get after being subjected to an X-ray check? Experts have been debating this same question since the first backscatter scanner was produced in 1992. One is for sure – the radiation dose is surely not comparable with what Marie Curie was exposed to while carrying radium test tubes in her pocket (spoiler alert: her death was caused by radiation). Although ionizing radiation (which what X-rays are) is considered carcinogenic even in miniscule doses, an individual would have to be scanned around 200,000 times in a row to get the same amount of radiation that he would be exposed to during one regular tomography procedure, according to Dr. Andrew J. Einstein from Columbia University.

Similar views are expressed by Julie Accardo and M. Ahmad Chaudhry in their article published in the Journal of Radiation Research and Applied Sciences. According to them, “People are exposed to background radiation on a daily basis and the health effects can take years to appear. If a passenger is truly concerned about their radiation exposure then they should probably think twice before flying as a travel option because flying at high altitudes will expose an individual to much more radiation than from a backscatter unit.”

To be fair, millimeter wave scanners are considered safer, with even the strict European Commission greenlighting them. According to a source in the EC, “The results of scientific studies conducted on behalf of the European Commission indicate that the negative impact on the health of persons when exposed to non-ionising radiation is negligible.”

What if it’s just for show?

Health concerns are only the tip of the iceberg when it comes to the question of X-ray scanner use. Many groups, including the US-based Electronic Privacy Information Center have protested the use of such screening technology due to privacy issues. This is the reason, by the way, that modern scanners convert the nude “chalk picture” to a cartoon-like image. But one thing trumps all other concerns. Namely, the question whether the technology actually works!

In 2014, a group of researchers from UC San Diego, University of Michigan and Johns Hopkins University published their findings after tinkering with Rapiscan Secure 1000, a backscatter scanner that was used in hundreds of US airports. And those findings hit yet another nail in the X-ray scanner coffin, as researchers had no trouble concealing knives, weapons, explosives and detonators. Furthermore, exploiting the scanner’s software, they demonstrated novel ways of smuggling contraband. Specially designed malware would simply swap the image on the screen with a pre-installed one, fooling both the machine and the operator.

An image produced by the mm-wave scanner 
 The image shown to the operator Raw image of a scanned TSA agent

While it is true that mm-wave scanners are considered to be safer in terms of emitted radiation, what can be said about their performance? Unfortunately, in reality they are not much better then X-ray scanners. In fact, a test by undercover US Department of Homeland Security agents in 2015 showed that the screening process failed 95% of the time! As a result, the director of the Transport Security Administration was fired and the ProVision mm-wave scanners removed from airports. Both the human factor and technical imperfections were blamed for the fiasco, but nevertheless no substantial change in the screening process in the US was introduced.

Unfortunately, mm-wave scanners, despite being considered safer health-wise, produce a blurry picture with large dead regions.  Couple that with the fact that the operator is looking at image altered by the program to protect the privacy of the person being scanned, and you get plenty of room for error.

A study conducted in Germany in 2011, for example, showed a 54% false positive rate, meaning that every second person had to go a pat-down after the scan.

There are ways to minimize the margin of error, but they all trade the person’s privacy for safety. One of such examples can be Israel’s Ben Gurion airport, which uses only X-ray scanners that produce higher quality images. On the screen the operator sees the raw image that was was not altered by software. In a way, you could say that it gets as close to the old-fashioned strip search without physical contact.

What to expect?

Health concerns aside, the main decision regarding what kind of technology to use in order to improve airport security depends on how well the technology works. Steven W. Smith, President of Tek84 Engineering Group, which produces airport scanners, claims that X-ray scanners might be re-introduced to Europe if image recognition software gets better.

“If the radiation safety problem is a grape, the software problem is a watermelon,” Smith told AeroTime.

“That’s a huge difference in significance. One is mainly an administrative and a philosophical problem, while the other is that the equipment is essentially nonfunctional.”

All things considered, the situation might change with the advent of AI-powered body scanners, which are currently in development by Boston-based Evolv Technology. The machine still uses mm-wave technology to produce the image, but advanced techniques of machine learning are employed to improve spotting weapons and explosives. With an impressive scanning speed of 800 people per hour, the new scanner will surely surpass the capabilities of human-operated scanners. However, it can still be hacked, which might lead to a worst-case scenario of multiple terrorists passing through compromised security.

Of course, there are several alternatives to full body scanners, but most of them serve purposes that are too narrow. For example, General Electric’s Puffer, a machine that detects chemical particles (think explosives and gunpowder). The name derives from the machine blowing chemically-sensitive air around the person being “puffed”. Other viable alternatives include metal detectors, canine units and classical pat downs, which will probably still be used in combination with even the most modern body scanners of tomorrow.