Airport Security

1989/02/01 Elhuyar Zientzia Iturria: Elhuyar aldizkaria

The case of the plane that exploded in the sky of Scotland before Christmas has again questioned the security measures of the airport.

X-ray equipment is used at airports for the exploration of bags and bags. The problem is that X-ray devices in airports are not able to detect plastic explosives. These explosives are very stable before the explosion and barely have gas leaks.

Plastic explosives are mainly composed of two compounds (cyclotrimethyl trinitramine and pentaerite tetranitrates). The Semex, supposedly used in the Scottish explosion, contains 44.5% of the two and the rest is plasticizer.

The security systems currently in place at airports are designed to deal with the kidnappings that occurred in the last decade. Two types of tools are used: X-ray devices and metal detectors. In some areas, such as Seoul, there are also explosive detection equipment.

X-ray devices provide the shadow of objects inside the suitcase and the technique has limitations. The device emits x-rays through the suitcase. On the other side of the case a diode battery detects X-rays. It depends on the amount, thickness, density and chemical nature of the x-rays that a material absorbs. Therefore, the compact metal of a pistol absorbs a lot of X-rays and on the detector screen you see the defined shade. Plastic absorbs very little X-rays and gives no defined shade.

The British Airport Agency is testing a new X-ray tool at London Gatwick Airport. This device uses high and low energy x-rays and can be used to detect plastic explosives.

However, alternative technologies are proposed. One is based on the different capacity of all substances. In the 1970s it was used to detect pump packages and it seems that, after small changes, it can also be used at airports.

It has also been proposed as an alternative the study of suitcases with infrared rays or the detection of aromas to explosives. The detection of aromas is not easy, since plastic explosives are very few. It is very useful for nitroglycerin or dynamite.

A detector of this type has been used in Seoul at the Olympic Games and the manufacturers of the apparatus claim that one billion is able to detect an explosive molecule in molecules. The system is based on the presence of nitrous vapors in explosives, which can be identified based on the electrical charge they generate.