Traveling by plane involves going through different control stages before arriving at the boarding area. Some are well known to all passengers, such as going through the metal detector or checking luggage, but there are less publicized procedures that can surprise even the most common travelers, like this strip of paper that is passed into the hands or waist of passengers chosen at random by airport security.
Strip of paper on hands or waist
One of these procedures can occur when, after passing through the metal detector, a security agent approaches and passes a small strip of paper over the hands and around the waist.
This action is part of a specific test aimed at strengthening airport security and preventing threats, both for passengers and infrastructure, says the website dedicated mainly to Pplware technology.
This method is known as explosive trace detection testing, or Explosive Trace Detection (ETD). This is a measure used in airports around the world and which, in Portugal, is part of a set of protocols designed to identify residues of potentially dangerous substances.
How the ETD test works
The procedure is based on collecting particles that may remain on the hands, clothing, luggage or other personal objects of someone who has been in contact with explosive material. For this purpose, a cloth or strip of specific material is used, which is passed over the surfaces to be analyzed, normally on the hands and waist.
The collected samples are then placed in a detection machine that uses, in most cases, ion mobility spectrometry technology (Ion Mobility Spectrometry – IMS).
This technique heats the sample to release the molecules present and analyzes their mobility when subjected to an electric field. Each substance has its own chemical signature, which allows for quick and effective identification, says the same source.
The result is obtained in a few seconds. If a substance considered suspicious is identified, the passenger or object is subjected to additional checks. It is important to note that a positive result does not necessarily mean that the person is carrying explosives, as false positives may occur due to compounds with a similar chemical composition.
The main advantage of this method is, according to the previously mentioned source, its high sensitivity, which allows very small amounts of material to be detected. However, effectiveness depends on correct sample collection and regular equipment maintenance.
Who is selected for the test
The selection of passengers for the ETD test can be done completely randomly or based on suspicious behavior or circumstances. This control works as a complement to x-ray scanners and body detection systems, contributing to a more comprehensive and effective security system.
According to , in modern airports, ETD is considered essential to maintain the balance between security and fluidity in passenger processing, ensuring that potential threats are identified without compromising the pace of operations.
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