Airports: Scanning All Bags Or Just Some?

Airport security has become increasingly stringent, with advanced technology being leveraged to ensure the safety of passengers and staff. A crucial aspect of this security apparatus is the scanning of bags, which utilises X-ray technology to detect potential threats. While the specifics of bag scanning vary across airports and countries, it is standard procedure for all bags, including checked-in luggage and carry-on items, to undergo some form of screening. This process is designed to identify prohibited items, such as weapons, explosives, and illegal substances, by creating detailed images of bag contents based on density and atomic number.

X-ray technology

Backscatter X-ray machines are used to scan passengers and their luggage, detecting metallic and non-metallic objects hidden under clothing or in shoes, as well as in body cavities. These machines use low-dose radiation, and the amount of radiation received is typically between 0.05 and 0.1 μSv. However, the use of these machines has sparked debates about safety, leading multiple countries to ban them.

Cabinet X-ray systems, on the other hand, are used to screen luggage and carry-on items. These machines have thick walls and lead curtains to prevent radiation from escaping. Strict standards are in place to limit radiation exposure, and the equipment is regularly tested to ensure compliance with safety regulations.

CT scanners, another form of X-ray technology, are used in major airports in the United States. These scanners are hollow tubes that surround a bag, with an X-ray mechanism slowly revolving around it, emitting X-rays and recording data. The data is used to create detailed tomograms, or slices, of the bag, allowing the calculation of the mass and density of individual objects inside. CT scanners are used selectively, scanning bags flagged as "suspicious" due to anomalies during the reservation or check-in process.

Millimeter-wave technology, which does not use X-rays, is another important component of airport security. This technology employs non-ionizing radiation in the form of low-level radio waves to scan individuals. It creates a 3D image, which is sent to a remote monitor for analysis. Millimeter-wave machines can detect hidden threats such as guns and knives, ensuring a comprehensive security screening process.

CT scanners

The use of CT scanners at airports is becoming increasingly common, particularly in the United States, where most major airports have adopted this technology. CT, or computer tomography, scanners are used to inspect checked baggage. The scanners are hollow tubes that surround bags, with an X-ray mechanism revolving around the bag, emitting X-rays and recording the resulting data. This data is used to create a detailed tomogram (or slice) of the bag and its contents. The mass and density of individual items in the bag can be calculated, and if an object's mass or density falls within a certain range, the operator is alerted to a potential hazard.

CT technology offers significant advantages over traditional X-ray systems. It provides a more detailed 3D image, allowing for a thorough analysis of the bag's contents. The technology can automatically detect explosives, including liquids, and other potential threats. This enhanced detection capability is particularly useful in the context of carry-on baggage screening, where the goal is to eventually allow laptops and liquids to remain in bags during screening, reducing physical contact and increasing efficiency.

The adoption of CT scanners at airports brings several benefits beyond security enhancements. The technology helps minimise contact between travellers, screeners, and surfaces, contributing to a safer travel experience in the post-COVID-19 era. It also reduces the time passengers spend in lines and increases operational efficiency. With a false alarm rate as low as 5%, CT scanners can decrease the number of secondary screenings, making the overall process faster and less intrusive.

Manual searches

X-Ray Scanner Flags Suspicious Items

X-ray scanners are commonly used to screen carry-on and checked baggage. If the scanner detects something suspicious, such as an object with a high density, security personnel may manually search the bag to identify the item. This could include asking the passenger to remove specific items or conducting the search themselves.

Unusual Travel Circumstances

Unusual travel circumstances, such as a one-way ticket purchased with cash, can trigger additional security measures. In such cases, checked baggage may be immediately sent through a CT scanner, and security personnel may conduct a manual search to identify any potential hazards.

Prohibited or Suspicious Items

Certain items are prohibited from being carried onto an aircraft, and if detected during screening, may result in a manual search. This includes items such as firearms, ammunition, sharp objects, and flammable liquids. Even obviously fake weapons, such as foam swords or water guns, are banned from carry-on luggage and may require a manual search to be removed.

Dense or Metallic Objects

Objects with high density or metallic content can be difficult for X-ray scanners to penetrate. Examples include stacks of books, microphones, electronics, and metal sheets or objects. In these cases, security personnel may manually search the bag to identify and inspect these items separately.

Large Amounts of Electronic Devices or Cables

A large number of electronic devices or a tangled mess of cables can attract extra scrutiny. Passengers may be asked to remove these items from their bags and place them in separate bins for X-ray screening or manual inspection.

Powdery Substances

White powders or powdery substances can arouse suspicion and may require a manual search to identify. It is recommended to place such substances in checked baggage to avoid confusion with illegal substances.

Unusual Contours or Shapes on X-Ray

Sometimes, harmless items can appear suspicious on X-ray scans due to their shape or contour. In these cases, security personnel may ask the passenger to identify and remove the item for further inspection. An example is a drawing compass that resembled a butterfly knife mechanism on the X-ray image.

Locks and Restricted Access

If a checked bag is locked and security personnel need to access its contents, they may cut the lock if it is not a TSA-approved lock. TSA has master keys for certain branded locks, but they may still need to be removed if necessary. Some countries may require the passenger's presence during the search if the lock needs to be cut.

International Flights and Varying Security Protocols

Different countries may have varying security protocols, and international flights can result in additional screening procedures. For example, passengers flying into the United States may experience a more extensive screening process, including additional screening of personal electronic devices.

Full-body scanners

Three distinct technologies are used in full-body scanners: millimeter wave scanners, X-ray-based scanners, and infrared thermal conductivity scanners. Millimeter wave scanners use electromagnetic radiation in the extremely high frequency (EHF) radio band, which is a lower frequency than visible light. This technology does not generate ionizing radiation, but the health risks posed by these machines are still being studied, and the evidence is mixed.

X-ray-based scanners include backscatter X-ray scanners and transmission X-ray scanners. Backscatter X-ray scanners use low-dose radiation to detect suspicious metallic and non-metallic objects hidden under clothing or in body cavities. The dosage of radiation received is typically between 0.05 and 0.1 μSv, and there has been considerable debate about the safety of this method, leading multiple countries to ban its usage. Transmission X-ray scanners, on the other hand, use higher-dose penetrating radiation to detect objects hidden under clothing or inside the body. The dosage received is usually not higher than 0.25 μSv and is regulated by American radiation safety standards.

Infrared thermal conductivity scanners do not use electromagnetic radiation to penetrate the body or clothing. Instead, they rely on slight temperature differences on the surface of clothing to detect foreign objects. These scanners are less commonly used compared to X-ray-based and millimeter wave-based scanners.

Privacy considerations

• Privacy in Full-Body Scanners: Full-body scanners, including millimeter-wave and backscatter X-ray scanners, are designed to protect privacy by using generic or 'mannequin-like' representations instead of specific images of individuals. This approach ensures that while security personnel can detect concealed items, the privacy of passengers' bodies is maintained.
• Non-Storage of Scan Images: Agencies like the Transportation Security Administration (TSA) have strict protocols in place to handle scan information. Images produced during scans are not stored, transmitted, or retained beyond the duration necessary for security checks. This practice helps protect passengers' privacy and prevents the misuse of sensitive data.
• Advanced Imaging Technologies: The implementation of advanced imaging technologies, such as 3D Computed Tomography (CT) and integrated biometrics, enhances privacy. These technologies improve the accuracy and speed of threat detection, reducing the need for manual searches and physical inspections, which can be invasive.
• Notice of Baggage Inspection: When checked baggage is physically inspected, most airports, including those with TSA procedures, place a notice of baggage inspection inside the bag. This practice informs passengers that their property has been opened and manually searched.
• Privacy in Data Handling: Airport security measures must adhere to privacy standards in data handling. This includes selecting equipment and technologies that respect privacy criteria while effectively screening for security threats, such as CEIA metal detectors used for military operations and border security.
• Continuous Improvement: Privacy considerations are an ongoing process. Stakeholders in air travel safety must remain vigilant in adapting and improving privacy safeguards as technology evolves. This includes exploring innovative solutions, such as artificial intelligence (AI) and machine learning, to enhance privacy while maintaining rigorous security measures.

Frequently asked questions