Explosive detection is a non-destructive process to determine whether something contains explosive materials, these inspections are commonly used at airports. There are quite a few ways officials inspect packages for explosives, they use dogs, mechanical scent detection, spectrometers, x-rays and neutron activation machines.
In the field, specially trained dogs are used to identify the scents of several common explosive materials and notify their handlers when they do. Dogs are perfect for this line of work since they have sensitive noses and the chosen dogs are rigorously trained by certified handlers. These dogs are very effective; however their usefulness degrades a bit if they become tired or too bored.
Mechanical scent detection machines can pick up the trace signatures for various explosive materials with a quick swab of the item and analysis can be completed in less than a minute. Spectrometers utilize UV lights to measure the residue left from explosive materials. X-ray machines pick up explosive devices based on the items density. Neutron activation machines bombard the suspect item with neutrons to read the gamma radiation decay signatures to determine the chemical composition of the item in question. Explosive materials have very similar ratios of carbon, hydrogen, nitrogen and oxygen, which the machines are able to easily detect.
Mechanical means were developed for more accurate and much faster detection of explosives for use in more controlled environments. A lot of these techniques are not portable, like the dogs are, and are used more commonly for border patrol or airport security.
~TeCHS
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