Swabbing tests to detect traces of explosives at airports: what they are and how they work

  • 28.08.2023 20:36
  • Bruno Arcos

In this article, we’ll dive into the world of explosive trace detection (ETD) and reveal the science behind swabbing tests at airports.

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If you’ve traveled frequently, you’re probably familiar with the routine swabbing that takes place during airport security checks. Whether it’s your hands, your waist or your luggage that undergoes this process, you might have wondered about its purpose and the technology behind it. Is it a precaution against explosives or simply a show of security?

Detecting dangerous explosives: The need for ETD

Heading straight to the point, security officers at airports conduct swabbing tests to detect extremely tiny traces of dangerous explosives. When individuals come into contact with explosive materials, even in small amounts, their bodies and belongings can retain tiny particles or residues of these explosives, which can linger on the skin, clothing, and items like bags, laptops or electronic devices. As such, ETD methods are employed to identify these traces, allowing security personnel to identify passengers who may have harmful intentions, and serving as an important layer of security to mitigate potential threats.

Although it’s not a foolproof system by all means, it nonetheless improves the overall safety of air travel.

Why some passengers get selected for the ETD swab test

Swabbing tests aren’t administered to every passenger due to limitations in resources and time, so, certain individuals are selected for these tests based on several factors:

  • Suspicious Items: Baggage containing suspicious or unusual items may trigger further inspections. The same goes for items that appear strange on X-ray scans, which may prompt security agents to conduct a swabbing test.
  • Behavioral Cues: Passengers who display nervous or suspicious behavior while waiting in line might be selected for swabbing. Agents are trained to identify individuals who seem unusually apprehensive.
  • Refusal of Full Body Scanners: Opting out of full-body scanner screenings often leads to additional security measures, including swabbing tests and pat-downs.
  • Random Selection: Some passengers are chosen randomly for additional screening, either without warning or based on specific markers on their boarding passes.
  • Traveling with Pets: Passengers accompanied by pets may have their hands swabbed as well, as per aviation security guidelines.
  • Medical Equipment: Individuals with mobility aids, external medical devices or equipment might undergo swabbing tests to ensure safety.

Swabbing Process: How it Works

Once chosen for swabbing, passengers are directed to a designated area, where they are asked to extend their palms while their luggage is set aside for swabbing. This process, though potentially stressful, is relatively quick, as agents wearing nitrile gloves use fabric strips or handheld swabs, sliding them through your hands, waist and luggage. The swabbing process requires precision in applying the right amount of pressure to gather a sample, which is why, depending on the material, a single swab may be used up to 10 times, after which it’s replaced due to contamination concerns.

The collected sample is then subjected to an ETD instrument that employs ion mobility spectrometry (IMS) to analyze the substance. IMS ionizes the sample, transforming it into gas particles, which are then moved through a tube via an electric field, with a detector recording their transit time. The results are compared to a library of known substances to identify any matches that took the same time to get through the tube. If there are any matches, the ETD machine will beep and light up a red light.

Common substances that trigger alarms

Swabbing tests may cause false alarms due to the presence of various substances unrelated to explosives. Some common triggers include:

  • Glycerin: Found in lotions, makeup and soaps.
  • Fertilizers
  • Medications: Nitroglycerine pills, often used for heart conditions, can lead to false positives.
  • Fireworks and Pyrotechnics

Plus, if you happen to be around firearms and ammo regularly, this may also trigger positive results during ETD tests, even if you’re not carrying while at the airport. This can be quite common, as traces of explosives and powder can easily contaminate your skin and belongings. Finally, it’s definitely worth mentioning that unmaintained ETD machines might produce false alarms.

If you happen to test positive due to a false trigger, do not panic. You will be accompanied to a separate area of the airport, where security agents will perform further testing, patting you down, inspecting every item of your baggage thoroughly and possibly asking you a few questions.

The Purpose of ETD swabbing tests

Swabbing tests for explosive trace detection form an integral part of airport security protocols. While they might occasionally inconvenience travelers, the aim is to ensure the safety of all passengers. That being said, if you find yourself frequently selected for swabbing, consider that you might be carrying unusual items in your baggage, or displaying some kind of behavior that can be seen as nervous/anxious. If it still doesn’t make sense, then you might simply be the unfortunate target of random selection markers – be that as it may, by understanding the purpose and science behind swabbing tests, you can navigate security checkpoints with a better grasp of the process.

Remember, at the end of the day, these measures are in place to safeguard all travelers.

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