Backscatter Scanners: How Do Airports Use Them?

Airport backscatter scanners are imaging technology used to detect threats such as weapons or explosives that a person could be carrying under their clothing. They use ionizing radiation to create images of what people are carrying. This technology has been controversial due to concerns about privacy, safety, and time spent in the security line. While the risk of health effects from backscatter X-ray systems is considered very low, some people may still prefer to opt for a pat-down search instead.

Backscatter X-ray machines emit ionizing radiation

The original versions of backscatter X-ray machines were removed in May 2013 due to concerns about the risks associated with ionizing radiation. They have been replaced by Advanced Image Technology (AIT) or millimetre-wave scanning devices in most airports. However, some large US airports still use newer backscatter X-ray machines for some of their security scanners.

Backscatter X-ray machines use rotating collimators to generate low-energy X-rays, which bounce off a person's body. These X-rays have a wavelength of about 0.0000000001 meters or 0.0000001 millimetres. The machines produce a whole-body silhouette of the subject, which can be blurred using privacy algorithms to protect sensitive areas.

While backscatter X-ray machines emit ionizing radiation, the doses used in airport scanners are much lower than those used in medical X-rays. The US Food and Drug Administration (FDA) has deemed the technology safe and does not require the same safety evaluations as medical X-rays.

Millimeter wave scanners use microwaves

Millimeter wave scanners work by directing millimeter wave energy at the subject and interpreting the reflected energy. They can create 3D images that reveal a person's unique topography, although these images are often blurred for privacy. The scanners have a high false-positive rate, often mistaking folds in clothing, buttons, and sweat for suspicious objects.

Millimeter wave scanners have been adopted in airport security as a safer alternative to backscatter X-ray machines, which use ionizing radiation. Ionizing radiation has the potential to cause adverse health effects by removing electrons from atoms and altering biological molecules. While millimeter wave scanners are considered safer, some concerns have been raised about their efficacy in detecting threatening objects.

Millimeter wave scanners are one of the common technologies used for full-body imaging at airport security checkpoints. They are designed to detect objects concealed under clothing, ensuring the safety of travelers by identifying hidden weapons and other hazards. The use of millimeter wave scanners in airports is part of the efforts to prevent potential disasters and enhance security.

Advanced Image Technology (AIT) is safer and less intrusive

Advanced Imaging Technology (AIT) is a safer and less intrusive alternative to backscatter X-ray machines. Unlike backscatter X-rays, AIT uses millimetre wave scanning technology, which is a non-ionizing source of radiation. This means that the waves emitted by AIT scanners are much larger and, therefore, have less impact on smaller human proteins and DNA. As a result, the risk of health effects from AIT scanners is very low, and the technology meets all known national and international health and safety standards.

AIT scanners also enhance passenger privacy by producing a generic, cookie-cutter-like image of all passengers, regardless of their gender, height, or weight. This is in contrast to backscatter machines, which produce a whole-body silhouette that reveals some details about a person's build and shape. With a privacy algorithm applied, the software blurs these details and only highlights potential threats.

In addition to being safer and less intrusive, AIT is also effective in detecting both metallic and non-metallic threats, including weapons, explosives, and other objects concealed under layers of clothing. This makes it an essential tool for airport and flight security. Furthermore, AIT has been shown to reduce wait times at TSA checkpoints and provide passengers with an alternative screening option to walk-through metal detectors and pat-downs, which some travellers may find more intrusive.

While AIT has been criticised for its inability to differentiate between threatening and non-threatening objects, resulting in secondary searches, it has been suggested that continued use of AIT would enhance detection of non-metallic weapons and reduce the number of pat-downs. Overall, AIT provides a safer, less intrusive, and more efficient means of screening passengers at airports.

Backscatter machines produce 2D images

The resulting image is a whole-body silhouette that resembles a chalky sketch, with some details of the person's build and shape visible. To address privacy concerns, software has been implemented to blur these details and only highlight potential threat items. If no threat is detected, the screen will display the word "OK" with no image.

The use of backscatter X-ray technology has been controversial due to concerns about the potential health risks associated with ionizing radiation. This type of radiation is considered carcinogenic even in small doses, but the doses used in airport scanners are believed to have a negligible impact on individuals.

In response to these concerns, the original versions of backscatter X-ray machines were removed in 2013 and replaced with Advanced Image Technology (AIT) or millimetre-wave scanning devices in most US airports. However, some airports still rely on newer backscatter X-ray machines for their security scanners.

TSA uses x-ray machines to screen carry-on items

The Transportation Security Administration (TSA) uses x-ray machines to screen carry-on items and checked luggage. The use of x-ray machines helps to identify hidden weapons and other hazards that are not approved for airline travel. The x-ray machines used by the TSA include backscatter x-ray machines, cabinet x-ray machines, and advanced imaging technology (AIT) machines.

Backscatter x-ray machines use ionizing radiation to create images of what is in luggage and detect objects that may be hidden by passengers. These machines emit low-energy x-rays that are reflected back to the machine, creating a detailed full-body image of the passenger. The amount of radiation received from a backscatter machine is considered very low risk, equivalent to the amount of cosmic radiation received during two minutes of flight. However, due to concerns about the potential health effects of ionizing radiation, the original versions of backscatter x-ray machines were removed in 2013, and many airports have replaced them with AIT or millimeter-wave scanning devices.

Millimeter-wave scanning devices use non-ionizing radiation and produce images using ultrahigh-frequency millimeter waves rather than x-rays. These waves are similar to microwaves and are less likely to negatively impact smaller human proteins and DNA. The TSA has also equipped these machines with automated target recognition (ATR) software, which produces a generic outline of a person and highlights any areas that may require additional screening.

AIT machines are another type of whole-body scanning device used by the TSA. They use electromagnetic radiation to detect weapons, explosives, and other threats that may be hidden on a person's body. AIT machines were installed at over 200 U.S. airports as of 2012, with about 30% of them being backscatter machines.

In addition to x-ray machines, the TSA also utilizes metal detectors, which use non-ionizing radiation to identify metal objects. These machines create a magnetic field using a pulse of electrical current, which is reflected back to the machine if metal objects are present.

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