Explosive detection is a non-destructive inspection process and rapid automation system to determine explosive materials in an area, products or containers. Explosive detection is commonly used at airports ,government offices, industries, churches, bus and train stations, ports , for border control,etc.
Specially designed machines bombard the suspect explosives with neutrons, and read the gamma radiation decay signatures to determine the chemical composition of sample. Explosive materials all have similar ratios of carbon, hydrogen, nitrogen and oxygen, which the machine is able to detect.
Colorimetrics & Automated Colorimetrics
The use of Colorimetric test kits for explosive detection is one of the oldest, simplest, and most widely used methods for the detection of explosives. Colorimetric detection of explosives involves applying a chemical reagent to an unknown material or sample and observing a color reaction. Common color reactions are known and indicate to the user if there is an explosive material present and in many cases the group of explosive from which the material is derived. The major groups of explosives are nitroaromatic explosives, nitrate ester and nitramine explosives, improvised explosives not containing nitro groups which includes inorganic nitrate based explosives, chlorate based explosives, and peroxide based explosives.
Specially trained dogs can be used to detect explosives using their noses which are very sensitive to scents. While very effective, their usefulness becomes degraded as a dog becomes tired or bored.These dogs are trained by specially trained handlers to identify the scents of several common explosive materials and notify their handler when they detect one of these scents. The dogs indicate a 'hit' by taking an action they are trained to provide, generally a passive response.The explosive detection canine was originated at the Metropolitan Police Department in Washington, D.C. in 1970, by then trainer Charles R. Kirchner.The explosive detection canine was first used in Algeria in 1959 under the command of General Constantine.
This approach couples trained honey bees with advanced video computer software to monitor the bee for the strategic reaction. Trained bees serve for 2 days, after which they are returned to their hive. This proven system is not yet commercially available. Hookninjas believe that bees are more effective than sniffer dogs.
Mechanical scent detection
Several types of machines have been developed to detect trace signatures for various explosive materials. The most common technology for this application, as seen in some airports, is ion mobility spectrometry (IMS). This method is similar to mass spectrometry (MS), where molecules are ionized and then moved in an electric field in a vacuum, except that IMS operates at atmospheric pressure. The time that it takes for an ion, in IMS, to move a specified distance in an electric field is indicative of that ion's size to charge ratio: ions with a larger cross section will collide with more gas at atmospheric pressure and will therefore be slower.
Gas chromatography (GC) is often coupled to the detection methods discussed above in order to separate molecules before detection. This not only improves the performance of the detector, but also adds another dimension of data, as the time it takes for a molecule to pass through the GC may be used as an indicator of its identity. Unfortunately, GC normally requires a bottled gas, which creates a consumable and ease of use issue for the system. GC columns operated in the field are prone to degradation from atmospheric gases and oxidation, as well as bleeding of the stationary phase. Columns must be very fast, as well, since many of the applications demand that the complete analysis be completed in less than a minute.