Most airport passenger scanners today use millimeter wave technology, not X-rays, while baggage scanners typically employ X-ray or CT X-ray systems.
Navigating airport security can sometimes feel like a puzzle, especially with the array of technologies used to keep everyone safe. Many travelers wonder about the specific types of scanners they encounter and what they’re designed to detect. It’s a common question whether the machines we walk through use X-rays, and the answer depends on the specific device and its purpose.
Unpacking Passenger Screening Technologies
When you approach the security checkpoint, you’ll generally encounter one of two primary types of passenger screening equipment: Advanced Imaging Technology (AIT) scanners or traditional walk-through metal detectors. These systems operate on fundamentally different principles to identify potential threats without direct contact.
Millimeter Wave Scanners: The Modern Standard
The most prevalent type of full-body scanner at airport checkpoints is the Advanced Imaging Technology (AIT) machine, which primarily uses millimeter wave technology. These scanners emit extremely low-power radio frequency waves, similar to those used in cell phones, but at a much higher frequency. The waves reflect off the body and any concealed objects, creating a generic outline for security officers to review.
- How it Works: Millimeter wave scanners create a 3D image by detecting the energy reflected from the body’s surface and anything hidden underneath clothing. The system processes this data to highlight potential anomalies.
- Privacy Features: Modern AIT scanners use Automated Target Recognition (ATR) software. This means the system generates a generic, non-specific outline of a person, indicating only the location of a detected item with a box or highlight. The actual body image is never displayed to the officer, maintaining passenger privacy.
- Safety Aspects: Millimeter wave technology uses non-ionizing radiation, which means it does not carry enough energy to remove electrons from atoms or molecules, unlike X-rays. This makes it a very low-energy process, comparable to common radio signals.
The Legacy of Backscatter X-Ray Scanners
While less common today, some travelers may recall or still encounter backscatter X-ray scanners. These machines did use very low-dose X-rays to create an image of items concealed under clothing. The technology worked by detecting X-rays that “scattered” back from the passenger’s body.
- Former Use: Backscatter X-ray scanners were deployed in airports for a period but have largely been phased out from passenger screening by the TSA in favor of millimeter wave technology.
- Image Generation: These scanners produced a “naked” image of the person, which raised significant privacy concerns despite measures taken to obscure facial features and have officers view images remotely.
- Radiation Type: Backscatter X-ray scanners utilized ionizing radiation, albeit at extremely low levels. The doses were considered negligible, but the presence of any ionizing radiation, coupled with privacy issues, contributed to their replacement.
Traditional Metal Detectors and Their Role
Walk-through metal detectors remain a fundamental component of airport security. These devices use electromagnetic fields to detect metallic objects on a person. They do not use X-rays or millimeter waves, focusing solely on the presence of metal.
- Detection Principle: When a metallic object passes through the electromagnetic field, it disrupts the field, triggering an alarm. The sensitivity can be adjusted to detect various types and sizes of metal.
- Limitations: Metal detectors are highly effective at finding metallic weapons or devices but cannot detect non-metallic threats such as plastic explosives, ceramics, or certain liquids. This is why they are often used in conjunction with AIT scanners or lead to secondary screening.
- Common Use: Many passengers still pass through metal detectors as a primary screening method, or as a secondary check after an AIT scan if an alarm is triggered.
Comparison of Passenger Screening Technologies
| Technology | Radiation Type | How it Works |
|---|---|---|
| Millimeter Wave (AIT) | Non-ionizing radio waves | Emits waves, detects reflections, forms generic outline |
| Backscatter X-Ray | Low-dose ionizing X-rays | Detects X-rays scattered back from the body (largely phased out for passengers) |
| Walk-Through Metal Detector | Electromagnetic fields | Detects metallic objects by disrupting a field |
What Happens During Baggage Screening?
The technology used for screening luggage is distinct from passenger screening and almost exclusively relies on X-ray technology. This allows security personnel to see inside bags without opening them, identifying objects that might pose a threat.
Carry-On Baggage Scanners
For carry-on bags, you’ll encounter two main types of X-ray scanners. The traditional X-ray machine provides a 2D image, while newer Computed Tomography (CT) scanners offer a more detailed 3D view.
- Conventional X-Ray: These machines pass X-rays through your bag, and a detector on the other side creates a 2D image. Different materials absorb X-rays differently, allowing security officers to distinguish between organic and inorganic items, and identify shapes of objects.
- CT Scanners: Increasingly deployed at checkpoints, CT scanners for carry-ons are similar to medical CT scans. They rotate around the bag, taking multiple X-ray images from different angles to construct a detailed 3D image. This allows officers to rotate and inspect objects virtually, often eliminating the need to remove liquids or electronics from bags.
- Screening Protocols: Regardless of the scanner type, items like liquids (following the 3-1-1 rule) and large electronics often need to be placed in separate bins for clearer imaging.
Checked Baggage Scanners
Checked luggage undergoes a more intensive screening process, primarily using advanced CT X-ray systems. These are known as Explosive Detection Systems (EDS).
- Explosive Detection Systems (EDS): These large machines are designed to automatically detect explosives by analyzing the density and atomic composition of objects within bags. They use powerful CT X-rays to generate highly detailed 3D images, which can be automatically analyzed by software and reviewed by security personnel.
- Prohibited Items: Due to the nature of checked baggage handling and the potential for hazards in the cargo hold, certain items are strictly prohibited in checked bags. For example, according to the FAA, loose lithium-ion batteries and power banks must be carried in carry-on luggage only, due to fire risks.
Common Items and Screening Requirements
| Item Type | Carry-On Permitted | Checked Bag Permitted |
|---|---|---|
| Liquids (3-1-1 rule) | Yes (under 3.4 oz/100ml) | Yes (larger quantities) |
| Laptops/Large Electronics | Yes (may require removal) | Yes (recommended carry-on) |
| Lithium Batteries/Power Banks | Yes (carry-on only) | No (strictly prohibited) |
| Sharp Objects (knives, scissors) | No (blades over 2.36 inches) | Yes (must be sheathed securely) |
Navigating Health Concerns at Security Checkpoints
Understanding the technology helps address common health-related questions, particularly concerning radiation exposure and medical devices. Security agencies prioritize safety while maintaining effective screening.
Radiation Exposure: A Closer Look
For passenger screening, the primary concern is radiation exposure. Millimeter wave scanners use non-ionizing radio waves, which are considered safe with no known health risks from exposure at airport security levels. The energy levels are significantly below international and national safety standards.
- Ionizing vs. Non-Ionizing: The key distinction is that X-rays are ionizing radiation, capable of altering atoms, while millimeter waves are non-ionizing, similar to radio or Wi-Fi signals.
- Comparison to Background Radiation: Even with the very low-dose X-ray backscatter scanners previously used, the radiation exposure from a single scan was often compared to just a few minutes of natural background radiation exposure at sea level.
- Official Guidance: Security agencies and health organizations consistently state that the exposure levels from airport screening technologies are minimal and pose no health risk to the public.
Medical Devices and Pregnancy
Travelers with medical devices or those who are pregnant often have specific questions about scanner safety. Security protocols are in place to accommodate these situations.
- Pacemakers and Implants: Millimeter wave scanners are generally safe for individuals with pacemakers, defibrillators, cochlear implants, or other medical devices. The non-ionizing radio waves do not interfere with these devices. However, you can always inform a security officer about your device if you have concerns.
- Pregnancy: Pregnant individuals can safely use millimeter wave scanners as the technology does not use X-rays and is considered safe. If you prefer, you can always request an alternative screening method, such as a pat-down.
- Alternative Screening: Any traveler can request a pat-down instead of going through an AIT scanner. This is a standard procedure, and you have the right to request a private screening with a witness if desired.