Airport Security: Scanning Checked Bags, What To Know

Airport security is a complex and multifaceted operation, employing various advanced technologies to ensure the safety of passengers. One crucial aspect of this security protocol is the screening of checked bags, which play a pivotal role in detecting threats and preventing dangerous items from being transported onto aircraft. Utilizing sophisticated scanners, security personnel can effectively inspect the contents of each bag, identifying potential hazards and contraband items. This process is designed to maintain aviation security and facilitate a smooth travel experience for passengers.

Scanners use X-ray technology to detect threats

X-rays are a form of electromagnetic radiation with higher energy than visible light, allowing them to pass through most objects, including the human body. When X-rays pass through the body, they are absorbed in different amounts by different tissues, depending on the radiological density of the tissues they pass through. This density is determined by the density and the atomic number of the material being scanned. For example, bones contain calcium, which has a higher atomic number than most other tissues, so they absorb X-rays and produce high contrast on the X-ray detector, appearing whiter than other tissues.

X-ray machines used for security screening at airports are typically backscatter X-ray machines, which use very low-energy X-rays that are reflected back to the machine itself. The amount of radiation received from these machines is very low and is comparable to the amount of cosmic radiation received during two minutes of flight. Additionally, safety measures are in place to ensure that workers and travellers are not exposed to high levels of radiation.

X-ray technology is crucial for detecting threats and keeping people safe while travelling. It allows security personnel to identify items that may pose a danger and take appropriate action to ensure the safety of everyone at the airport and on the aircraft.

Scanners can identify metallic and non-metallic objects

Metallic objects, such as guns, knives, and other potential weapons, are easily detected due to the X-rays' interaction with metal, causing a clear and distinct image on the security monitor. These objects appear as dark orange or blue on the screen.

Non-metallic objects, such as those made from plastics, ceramics, or glass, are identified through their density and atomic number, which affect how much they absorb or scatter X-rays. This makes it possible for scanners to detect items such as plastic explosives or other contraband that could pose a threat to aircraft security.

Organic materials, such as drugs, food, explosives, paper, or clothing, are also detectable by airport scanners. These materials are marked with an orange color on the scan and have unique densities and compositions that stand out on an X-ray scan.

Additionally, millimeter-wave scanners are used to detect both metallic and non-metallic objects that may be hidden under clothing. These scanners employ radio waves to generate a 3D image of the passenger and are adept at detecting concealed objects.

Scanners can detect organic materials like food and drugs

Airport security involves a range of measures, including physical checkpoints, baggage scanners, and metal detectors. These security measures are designed to protect passengers and their luggage from potential threats. The Transportation Security Administration (TSA) in the United States, for example, screens approximately 1.3 million checked bags daily for explosives and other dangerous items.

Baggage scanners at airports use X-ray radiation, a high-energy electromagnetic radiation, to detect prohibited items. These scanners can identify both metallic and non-metallic objects, including organic materials like food and drugs. The X-rays penetrate through the surface of the luggage to create detailed images of the items inside, allowing security officers to calculate the density of each object and spot contraband.

Organic materials such as drugs, paper, food, and explosives are typically marked with an orange color on the scanner, while metals and glass are indicated in blue or green. The denser the object, the darker the color. While scanners cannot determine the exact composition of an object, they can distinguish between organic and inorganic (metallic or non-metallic) materials.

In addition to visual cues, the scanners use two detectors to record the energy and position of the contents. The first detector collects low-energy X-rays, while the second detector collects high-energy X-rays. By comparing the outputs, the machine constructs an image that helps identify the position and potential material of the objects inside the luggage.

While airport scanners are effective at detecting organic materials, it is important to note that the detection process also depends on how items are packed and the presence of other objects in the luggage. A cluttered or overstuffed bag may require additional screening time, and certain items, such as food, powders, and electronics, may need to be separated for clearer X-ray images.

Scanners use density and shape to identify potential threats

Millimetre wave scanners are a common technology used for body imaging and to detect objects concealed underneath clothing. They come in two varieties: active and passive. Active scanners direct millimetre wave energy at the subject and interpret the reflected energy. Passive systems create images using only ambient radiation and radiation emitted from the human body or other objects.

In active scanners, the millimetre wave is transmitted from two antennas simultaneously as they rotate around the body. The reflected wave energy is used to construct a three-dimensional image, which is displayed on a remote monitor for analysis.

The first millimetre-wave full-body scanner was developed at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington. In 2002, Silicon Valley startup SafeView, Inc. obtained an exclusive license to PNNL's intellectual property and commercialized the technology. From 2002 to 2006, SafeView developed a production-ready millimetre body scanner system and software, including scanner control, algorithms for threat detection, and object recognition.

In 2006, SafeView was acquired by L-3 Communications, which continued to make incremental enhancements to the scanner systems while deploying thousands of units worldwide. In 2020, Leidos acquired L3Harris, including their body scanner business unit.

Millimetre wave scanners have faced criticism for their efficacy in detecting threatening objects. Some studies suggest that the cost-benefit ratio of these scanners is poor. As of January 2011, there had been no report of a terrorist capture as a result of a body scanner. Additionally, millimetre wave scanners have problems reading through sweat and can yield false positives from buttons and folds in clothing.

Scanners are used for both checked and carry-on luggage

Checked baggage scanners are large machines located behind the scenes at airports. They use high-energy X-rays to penetrate dense materials and create detailed images of the contents. These scanners focus on identifying potential threats by analysing the density and shape of objects. In the United States, major airports often employ computer tomography (CT) scanners, which use revolving X-rays to create a detailed tomogram (slice) of the bag. CT scanners calculate the mass and density of objects, warning operators of any potentially hazardous items.

Carry-on luggage scanners, on the other hand, are smaller machines found at security checkpoints. They are designed to scan personal items and smaller bags that passengers bring onto the plane. These scanners prioritise speed and efficiency by using automated algorithms to assess whether an item is safe or requires further inspection. While they also employ X-ray technology, the key difference is in the processing of images, with carry-on luggage scanners optimised for efficiency in the security checkpoint process.

The use of scanners for both checked and carry-on luggage is essential for maintaining aviation security. They help detect metallic and non-metallic objects, as well as organic materials such as drugs and explosives. The advanced imaging technologies provide security officers with clear images of luggage contents, enabling them to quickly identify potential threats. This not only enhances security but also contributes to a smoother travel experience by expediting security checks.

Frequently asked questions