Ruth Haines
Metal detectors are a common feature of airport security, with all public access to an airport channelled through them. They are used to identify metal objects on a person's body, ensuring that weapons are detected before entry. These detectors are extremely sensitive and can identify even the smallest metallic items with precision. They use pulse induction to send powerful bursts of current through a coil of wire, creating a magnetic field. When a metal object passes through, it creates an opposite magnetic field, causing a beeping noise to alert the TSA agent. While these detectors are safe for all passengers, including those with medical devices, they can cause concern for travellers with metal implants. Certain items, like keys, jewellery, and belt buckles, can trigger alarms, leading to potential delays. However, small amounts of metal, like buttons or earrings, are usually ignored.
| Characteristics | Values |
|---|---|
| Purpose | To keep people safe while travelling by checking passengers and personal items for dangerous items such as weapons, chemicals and liquids that are not allowed as carry-on items. |
| Technology | Most airport metal detectors are based on pulse induction (PI). PI systems use a coil of wire on one side of the arch as the transmitter and receiver. This technology sends powerful, short bursts (pulses) of current through the coil of wire. Each pulse generates a brief magnetic field. |
| Metal objects | If a metal object passes through the metal detector, the pulse creates an opposite magnetic field in the object. |
| Metal implants | Orthopaedic implants will set off the metal detectors at the airport. |
| Metal detectors ignore | Very small amounts of metal, like the button on your jeans or small earrings. |
| Items to remove | Bobby pins, large watches, jewellery made from cheap metals, hats, mobile phones, wallets with metal, etc. |
| Items that can be worn | Underwire bras, jeans, smartwatches, religious head coverings, etc. |
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What You'll Learn
Metal implants in the body
If you have a metal implant, you should inform a Transportation Security Officer (TSO) about your implant before screening begins. You can request to be screened by imaging technology (X-ray machine) instead of a metal detector to reduce the likelihood of a pat-down. Millimeter-wave scanners use radiofrequency (non-ionizing) radiation, while backscatter X-ray machines use very low levels of ionizing radiation. If you choose not to be screened by imaging technology, or if you set off a walk-through metal detector, you will be screened by pat-down.
If you set off the metal detector, airport security will prompt you to complete a full-body scan if one is available. This security scan takes an image of your entire body to pinpoint where the detection is, ensuring nothing is missed. If a full-body scan is not available, or if they need to conduct additional checks, airport security may request to give you a body pat down to verify the presence of any items that might have caused the alarm. This process is routine and is conducted to ensure everyone's safety.
There is no official document you can carry to prove that you have metal implants, and you will still be required to have a second scan if you set off the alarms. However, you can carry a note from your doctor explaining that you have metal implants.
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Metal detectors' technology
Metal detectors are a common device used in airports to ensure the safety of passengers and staff. They are used to identify metal objects on a person's body as they pass through security checkpoints. Almost all airport metal detectors use pulse induction (PI) technology, which involves sending short bursts of electrical current through a coil of wire, generating a magnetic field. When this magnetic field interacts with metal objects, it creates a reflected pulse that is detected by the machine, indicating the presence of metal.
Recent advancements in metal detection technology have improved sensitivity, detection speed, and false alarm reduction, making the screening process more efficient and less intrusive. Modern metal detectors feature adjustable sensitivity settings, allowing TSA officers to fine-tune the detectors to reduce disruptions caused by harmless metal objects, such as keys, jewellery, or belt buckles. Additionally, walk-through metal detectors are now often paired with hand-held metal detectors, enabling security guards to conduct secondary, more targeted searches when necessary.
Metal detectors use non-ionizing radiation, which has enough energy to move atoms in a molecule or cause them to vibrate but not enough to remove electrons from atoms. This type of radiation is considered safe and is used to scan travellers and their carry-on items for hidden metal objects. Airports may also use other screening equipment, such as millimeter wave machines, backscatter X-ray, and cabinet X-ray machines, each serving a different purpose in ensuring the safety of travellers and staff.
It is important to note that not all metal objects will trigger a metal detector. Small metal items like buttons, zippers, or earrings are usually ignored by the detectors. Additionally, certain types of jewellery made from non-magnetic metals like gold, silver, or platinum are less likely to set off the alarms. However, large and bulky jewellery or jewellery made from cheaper, magnetic metals may trigger the detectors. Similarly, smartwatches and fitness trackers usually do not set off alarms, but some airports may request that you remove them.
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Clothing with metal
Metal detectors at airports are sensitive to metals, including orthopedic metal implants inside the body. The most common types of metal implants include stainless steel, cobalt chrome, and titanium. As airport security measures have been heightened and metal detectors have become more sophisticated, people with metal implants may face greater and more frequent inconvenience with more invasive security checks.
If you have a hip replacement, knee replacement, metal plate, screws, or one of the many other types of orthopedic implants, you may set off the airport metal detector. It is recommended that you alert the TSA officer that you have metal in your body and where it is located, and be prepared to step aside for further screening with a metal-detecting wand. While every country handles security screening a little differently, the same protocol exists: inform the security staff that you have a medical implant and be prepared for another level of screening.
Metal detectors ignore very small amounts of metal, like the buttons on your jeans or small earrings. However, metal buckles almost always trigger metal detectors and must be removed. Jeans with metal studs or rivets may sometimes set off scanners, so if you're wearing heavily embellished clothing, you may be asked to undergo a pat-down. Hats are not allowed to be worn through the scanners, and you will be asked to remove them before walking through the metal detectors.
Underwire bras rarely cause issues at airport security, and smartwatches usually do not set off alarms and can be worn through scanners. However, some airports may still ask you to remove them due to different policies.
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Metal objects in carry-on items
Metal detectors and other screening equipment at the airport are used to keep people safe while travelling. They are used to check carry-on items and checked luggage for items that are not approved for air travel.
Metal detectors use magnetic fields to identify metal objects. When a metal object passes through the metal detector, the pulse creates an opposite magnetic field in the object. When the pulse's magnetic field collapses, causing the reflected pulse, the metal object makes it take longer for the reflected pulse to completely disappear. This change in duration is what alerts the TSA agent to the presence of a metal object.
However, metal detectors ignore very small amounts of metal, like the button on your jeans or small earrings. So, you don't need to worry about removing all metal items before passing through a metal detector. For example, underwire bras are fine to wear through airport security. Similarly, jeans are fine to wear through airport security. Even though they may have metal buttons, zips, or studs, the amount of metal is so small that it is unlikely to be picked up by the metal detectors.
That being said, there are some metal objects that are larger or made of cheaper metals that you should avoid bringing in your carry-on items or on your person. For example, jewellery will only set off metal detectors if it is made from magnetic or cheap metals. Similarly, watches made from cheap metals or that are large and chunky should be removed. If you are unsure about your watch, it is better to be safe and remove it, as some airports will ask you to do so anyway. Additionally, if you have a lot of bobby pins in your hair, you should remove them, as these can set off the metal detectors.
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Other types of security screening
Metal detectors are a common feature of airport security. They are used to screen passengers entering the secure area of the airport. Almost all airport metal detectors are based on pulse induction (PI). This technology sends short bursts of current through a coil of wire, generating a magnetic field. When the pulse ends, the magnetic field collapses, creating a sharp electrical spike. This process allows metal objects to be detected.
Pat-Downs
Pat-down procedures are used to determine whether prohibited items or threats are concealed on a person. They may be required if the screening technology alarms, as part of unpredictable security measures, or as an alternative to other types of screening. A pat-down may include the inspection of the head, neck, arms, torso, legs, and feet, including sensitive areas such as the breasts, groin, and buttocks. Sufficient pressure is applied during the pat-down to ensure detection, and areas may be checked more than once.
X-Ray Systems
X-ray machines are used to screen carry-on baggage, personal belongings, and checked luggage. They help detect prohibited items and ensure they do not board the plane. X-ray systems are also used to screen cargo and packages tendered for air transport.
Explosives Trace Detection (ETD)
ETD devices are used to screen passengers and their carry-on items for traces of explosives. This is part of the pre-board screening process to ensure the safety of the aircraft and passengers.
Biometric Scanning
Biometric scanning is used at certain checkpoints for non-passenger screening. This includes individuals who work at the airport but are not passengers, such as pilots, flight attendants, baggage handlers, and customer support representatives. Biometric scanning helps identify individuals who may pose a security risk.
Closed-Circuit Television (CCTV)
CCTV systems are used at airports to monitor activities and address any questionable conduct. These systems employ facial recognition technology to track individuals and flag potential security risks. Dedicated staff monitor the recordings around the clock to ensure timely identification and response.
Other Screening Methods
In addition to the above, airports may also employ hold baggage security screening (HBSS) systems, computed tomography (CT) scans, and physical searches of baggage. These methods help detect prohibited items, including weapons, chemicals, and liquids, ensuring the safety of passengers and aircraft.
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Frequently asked questions
Metal detectors at airports are extremely sensitive and can detect even the smallest metallic items. Jeans are fine to wear, but if your jeans have metal studs or rivets, they may set off the metal detectors. Hats are not allowed to be worn through the scanners, and you may be asked to remove your watch, regardless of the materials it is made from. If you have metal implants, you should be prepared for the detectors to go off.
You will be asked to place your mobile phone, wallet, and any other electronic devices in a separate tray for screening. You can keep your jewellery on if it is made from non-magnetic metals like gold, silver, or platinum. However, large and bulky jewellery with lots of metal may set off the metal detectors.
If a walk-through detector signals an alert, security staff may use hand-held metal detectors for a more detailed inspection. They will then decide whether additional screening is necessary.
