When you travel by plane, train, or subway, you encounter various security screening devices – X‑ray baggage scanners, millimeter‑wave body scanners, terahertz scanners, and metal detectors. They keep us safe, but many people wonder: do they affect our health? Let’s break down how each type works and what the science says about safety.

1. X‑ray Baggage Scanners – The Workhorse for Luggage

How they work
X‑ray scanners use high‑energy electromagnetic waves to penetrate luggage. Different materials absorb X‑rays to different degrees, allowing the system to distinguish between organic and inorganic objects. On the monitor:

Orange/yellow – organic materials (food, plastics, paper, clothes)

Blue/light blue – metals (iron, copper, etc.)

Green – mixtures (stainless steel, ceramics)

Red – very dense or thick substances (lead, large amounts of gold)

These colour codes help security officers quickly identify prohibited items such as knives, firearms, and explosives.

Is it safe?
The radiation dose from X‑ray baggage scanners is extremely low. For example, even security staff working near the exit conveyor belt receive an annual effective dose of only about 0.39 mSv – far below the natural background radiation we all get (around 2.4 mSv per year). The lead curtains at the entrance and exit prevent radiation leakage. However, never reach your hand inside the curtain while the machine is running – that could expose you to unnecessary radiation.

2. Millimeter‑Wave Scanners – Fast, Contact‑Free Body Screening

How they work
Millimeter‑wave scanners use non‑ionising electromagnetic radiation (millimetre‑length waves). They emit waves and read the reflected signals, then use advanced algorithms to construct an image. They can detect both metallic and non‑metallic items – including plastics, liquids, powders, explosives, lighters, and other contraband – without physical contact.Security Inspection Door MDAJ-TCT-AJ710A | Fanyue

Are they safe?
Because millimetre waves are non‑ionising, they do not have enough energy to alter DNA or harm cells. They are completely safe for human use and are widely deployed at airports, stadiums, and large events.

3. Terahertz Scanners – The Detail Master for Advanced Security

How they work
Terahertz scanners operate at even higher frequencies than millimetre waves, providing exceptional resolution. They can penetrate clothing and reveal hidden objects with remarkable clarity. Their sensitivity makes them ideal for detecting:

Metals and non‑metal weapons

Electronic devices

Explosives, drugs, and powders

Biological macromolecules and composite materials

Due to their high precision, terahertz scanners are often found in research labs, specialised material inspection, and high‑level security checkpoints.

Are they safe?
Like millimetre waves, terahertz radiation is non‑ionising and poses no known health risk. No harmful effects have been observed at the power levels used in security applications.

4. Metal Detectors – Simple, Effective, and Totally Harmless

How they work
Metal detectors use a combination of magnetism and electromagnetic induction. When a metal object enters the detection field, it disturbs the electromagnetic field and triggers an alarm. They do not produce any ionising radiation – their operation is purely based on magnetic field changes.Handheld Metal Detector MDAJ-TCB-GP3003B1 | Fanyue

Are they safe?
Absolutely. Metal detectors are completely harmless to humans and are commonly found at schools, courthouses, museums, and sports venues.

Final Verdict: Safety First – Both in Detection and Health
All four types of security scanners are designed with strict safety standards:

Scanner Type Radiation Type Health Impact
X‑ray baggage Ionising (very low dose) Safe when used properly; do not bypass lead curtains
Millimetre‑wave Non‑ionising Safe
Terahertz Non‑ionising Safe
Metal detector No radiation Safe
The security measures we encounter daily protect us from potential threats without posing any significant risk to our health. Understanding how they work can help us appreciate the technology and cooperate more confidently during screenings.