How Millimeter Wave Technology Actually Works

Millimeter wave scanners operate in a frequency band between 30 and 300 gigahertz, occupying the spectrum between microwave and infrared radiation. Unlike traditional X-ray machines, these scanners bounce radio waves off the body’s surface rather than penetrating it with ionizing radiation. The reflected waves create a detailed three-dimensional image that security personnel can analyze for anomalies.

The science behind these systems is remarkably elegant. When a passenger enters the scanning booth and assumes the position—arms raised, feet slightly apart—the machine emits waves that travel at the speed of light and reflect differently depending on what they encounter. Human skin, clothing, metal objects, ceramic materials, and even liquids all produce distinctive reflection patterns. Advanced algorithms then process these reflections to construct an image highlighting potential threats while attempting to maintain privacy.

Modern systems have evolved significantly from early versions. Today’s scanners incorporate automated threat detection software that identifies suspicious areas without generating explicit anatomical images. This technological refinement addresses many of the privacy concerns that plagued first-generation systems while maintaining security effectiveness.

The Privacy Evolution From “Naked” Scans to Gingerbread Figures

When millimeter wave scanners first appeared in airports around 2007-2008, they generated remarkably detailed images of passengers’ bodies. These early systems effectively created what critics described as “electronic strip searches,” revealing anatomical details that raised serious privacy objections from travelers and civil liberties organizations alike.

The public backlash was swift and powerful. In response, manufacturers and security agencies collaborated to develop privacy-enhancing algorithms. Modern systems now display generic “gingerbread figure” outlines rather than detailed body images. These cartoon-like representations show only the location of potential threats—indicated by yellow boxes—without revealing physical characteristics of the person being scanned.

This technological evolution represents an important case study in how public pressure can shape security technology implementation. The Transportation Security Administration now employs these privacy-enhanced systems exclusively, with all image viewing occurring via automated systems rather than human review of detailed body scans. The images are not stored, transmitted, or printed, addressing many initial concerns about potential misuse of sensitive personal data.

Detection Capabilities and Limitations

Despite their sophisticated technology, millimeter wave scanners aren’t perfect. These systems excel at detecting metallic objects like guns, knives, and conventional explosives. They can also identify dense non-metallic items that might evade traditional metal detectors. The waves reflect differently off various substances, allowing the scanners to distinguish between normal body contours and concealed objects.

However, certain limitations remain. The technology struggles with items that have similar density to human tissue or that can be molded thinly against the body. Critics have demonstrated that determined adversaries can potentially exploit these weaknesses by strategically positioning threatening items. Additionally, some medical implants, prosthetics, or certain types of clothing can trigger false alarms, requiring additional screening measures.

System performance also varies based on environmental factors. Moisture on clothing from rain or perspiration can affect scan results. The accuracy depends on proper passenger positioning—one reason travelers are instructed to stand with arms raised in a specific stance. When passengers move during scanning or fail to follow positioning instructions, effectiveness decreases significantly.

Security agencies continuously refine detection algorithms to address these limitations, but the technology remains part of a layered security approach rather than a standalone solution. This explains why airports continue to employ multiple screening methods, including traditional metal detectors, explosive trace detection, and behavioral observation.

Health Concerns: Separating Facts From Fears

Unlike backscatter X-ray scanners, which emit low doses of ionizing radiation, millimeter wave technology uses non-ionizing radiation similar to the radio waves produced by cell phones—though at different frequencies. The radiation exposure from a single scan is approximately 10,000 times less than a typical cell phone call, making it extremely low-risk according to most scientific assessments.

Multiple health organizations have evaluated these systems and concluded they pose negligible health risks. The World Health Organization classifies non-ionizing radiation at these frequencies and power levels as safe for human exposure. The millimeter waves penetrate only about 1/64 inch into the skin, primarily interacting with the outer epidermal layer rather than reaching internal organs.

Despite these reassurances, some medical researchers advocate for ongoing monitoring, particularly for vulnerable populations like pregnant women, children, and individuals with certain medical conditions. While no credible evidence suggests harmful effects from occasional exposure, some scientists recommend prudent avoidance for those with electromagnetic hypersensitivity claims, though this condition remains controversial in medical literature.

The $120,000 Question: Economic Impact and Global Adoption

A single millimeter wave scanning unit typically costs between $120,000 and $170,000, representing a significant investment for airports and security agencies. Beyond the initial purchase, these systems require regular maintenance, software updates, and operator training. For major international airports processing tens of thousands of passengers daily, deploying enough units to prevent bottlenecks means investing millions in this technology.

This substantial price tag has influenced global adoption patterns. Wealthy nations like the United States, Canada, Australia, Japan, and European Union members have widely implemented these systems. The U.S. alone has deployed over 1,000 units across approximately 200 airports. In contrast, many developing nations continue to rely on traditional metal detectors and physical pat-downs due to financial constraints.

The economic impact extends beyond purchasing costs. These systems can significantly affect airport operations. When properly implemented with sufficient units and trained staff, they can actually increase passenger throughput compared to older screening methods. However, when understaffed or poorly deployed, they create frustrating bottlenecks that increase passenger stress and potentially impact airline schedules.

For manufacturers like L3Harris Technologies and Smiths Detection, which dominate the airport security scanner market, these systems represent a multi-billion dollar revenue stream that continues to grow as aviation security standards tighten globally. As the technology matures and production scales increase, prices may gradually decrease, potentially broadening adoption in regions currently priced out of the market.