An explosive cat-and-mouse game

CONFLICT creates arms races. As in the struggle against computer hacking or drug detection, stopping bomb-makers is a race between two kinds of innovation: creating the bad stuff and detecting it. Intelligence agencies regularly draw up lists of “substances of interest” and pass them on to firms that design and supply detection technology, says Kevin Riordan, of Smiths, an aviation-security firm. But once a substance can be routinely detected, terrorists will either attempt to conceal it better, or make something else.

A dog’s nose is still a good detector for many explosives. Some have suggested bomb-sniffing bees as a further step. But technology is the basis of the explosive- detection business and it usually works either by examining the density of material using X-rays or by using spectroscopy to detect the mass and mobility of molecules. For more advanced machines, detecting a new explosive can be as simple as upgrading the software. First, the new target is characterised, then an algorithm (a series of rules programmed into a computer) is devised to detect it in scanned samples. …