Explosives are devices intended to change to an environment in the process of construction, for example, or cause damage and loss of life through a sudden expansion of gases with violence, heat, and noise due to a reaction that may be chemical or nuclear. Explosives are divided into high explosives and low explosives — which are divided into propellant, atomic, and fuel and air explosives. The transportation of explosives is regulated in many countries, for example, by the Explosives Regulatory Division of Natural Resources Canada, in Canada and by the Bureau of Alcohol, Tobacco, Firearms, and Explosives — as well as state law — in the United States. Explosives Trace Detection (ETD) is technology designed to detect the smallest amounts, or traces, of explosives, for the purpose of safety and security.
Explosives Trace Detection has been developed in a variety of formats. There are hand-held modules, portals for screening people, and tabletop models. There are also swab-based Explosives Trace Detection technologies and document scanners.A variety of detection approaches are used in Explosives Trace Detection. Some types include Ion Mobility Spectroscopy (IMS), ChemiLuminescence (CL), Electron Capture Detectors (ECD), and Surface Acoustic Wave (SAW). The use of Mass Spectrometry (MS), long used in laboratory settings, is being developed for the field.In seeking an ETD that does not require contact with the explosive substance, MIT (Massachusetts Institute of Technology) scientists are exploring a method using lasers, as is QuantaSpec, a research and development company working under a grant from the US Department of Homeland Security.
There are a variety of circumstances in which Explosives Trace Detection is used. It is employed at airports to screen passengers and baggage and at mail facilities to ascertain the safety of questionable packages. Bomb search teams and building security teams at high-risk facilities use ETDs. For the military in the field, portable Explosives Trace Detection devices are used to detect threats such as liquid and plastic explosives and other components that find their way into Improvised Explosive Devices (IEDs).
Concerns in the use of Explosives Trace Detection devices include false-negative rates and false-positive rates. The Detection Limit (DL), a measure of the smallest detectable amount of material that can be identified, is also a matter of concern. Processing time can also be an issue in a volatile situation, and developers are working on this issue. Some devices promise analysis of all varieties of explosives in 30 seconds or less.