How It Works: The Mechanical Bomb Sniffer
Mechanical Sniffer Trevor Johnston A guide to the machine that could change how we screen for explosive threats Last fall, David Atkinson and a team at the Pacific Northwest National Laboratory announced that they had "sniffed" certain explosives in ambient air for the first time. Most common explosives-RDX, PETN, blasting gels-exist in very low ambient concentrations, often in the parts-per-quadrillion range. Existing detectors are not that sensitive, meaning security forces need to test suspects directly, as in airports. A version of Atkinson's machine could simply sniff targets, speeding the process. "It could change the way we do screening for explosive threats," he says. Scientists spike a glass slide with residue from a few known explosives. A vacuum pump within the detector sucks air through a one-inch wide opening at a rate of between one and five liters per minute. The vapor passes through a copper tube toward an ionization source. Nitrate ions,...