Trade secrets... Explosive detection

The threat posed by terrorist explosive devices and landmines are an unfortunate fact of life in many areas of the world. Explosive devices can be disguised inside everyday objects such as bags, shoes and even underwear. Security staff at airports and other vulnerable public places therefore depend on specialised scientific techniques to detect explosives and keep the public safe. The standard detection set-up is an X-ray machine for luggage and a walk-through metal detector. In some places, items of concern can also be swabbed and rapidly analysed using a portable mass spectrometry machine. Handheld metal detectors are normally used when searching for landmines but they are no use if the devices don’t contain metal. They also suffer from frequent false positives, setting off an alarm every time they encounter metallic rubbish. However, an interesting technique called nuclear quadrupole resonance (NQR) is showing promise in tackling some of these issues.