Explosive detection is a non-destructive inspection process to determine whether a container contains explosive material. Explosive detection is commonly used at airports, ports and for border control. Detection tools Colorimetrics & automated colorimetrics The use of colorimetric test kits for explosive detection is one of the most established, 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 explosives from which the material is derived. The major groups of explosives are nitroaromatic, nitrate ester, and nitramine explosives, as well as inorganic nitrate-based explosives. Other groups include chlorates and peroxides which are not nitro based explosives. Since explosives usually contain nitrogen, detection often is based around spotting nitrogenous compounds. As a result, traditional colorimetric tests have a disadvantage: some explosive compounds (such as acetone peroxide) do not contain nitrogen and are therefore harder to detect. Dogs 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, such as sitting down and waiting. 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. Recent studies suggest that mass spectrometric vapor analysis techniques, such as secondary electrospray ionization (SESI-MS), could support canine training for explosive detection. Honey bees 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. Biotechnology firm Inscentinel claims 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