Explosive detection is a non-destructive
inspection process to determine whether a container contains
explosive material. Explosive detection is commonly used at
airport
An airport is an aerodrome with extended facilities, mostly for commercial air transport. Airports usually consists of a landing area, which comprises an aerially accessible open space including at least one operationally active surfa ...
s,
port
A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as H ...
s 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
In organic chemistry, a nitrate ester is an organic functional group with the formula , where R stands for any organic residue. They are the esters of nitric acid and alcohols. A well-known example is nitroglycerin, which is not a ''nitro'' com ...
, and
nitramine
Nitramide is a chemical compound with the molecular formula H2NNO2. Organyl derivatives of nitramide, RNHNO2 are termed nitroamines, and are widely used as explosives: examples include RDX and HMX. It is an isomer of hyponitrous acid.
Struct ...
explosives, as well as inorganic nitrate-based explosives. Other groups include
chlorates
The chlorate anion has the formula ClO3-. In this case, the chlorine atom is in the +5 oxidation state. "Chlorate" can also refer to chemical compounds containing this anion; chlorates are the salts of chloric acid. "Chlorate", when followed by ...
and
peroxides
In chemistry, peroxides are a group of compounds with the structure , where R = any element. The group in a peroxide is called the peroxide group or peroxo group. The nomenclature is somewhat variable.
The most common peroxide is hydrogen p ...
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
Secondary electro-spray ionization (SESI) is an ambient ionization technique for the analysis of trace concentrations of vapors, where a nano-electrospray produces charging agents that collide with the analyte molecules directly in gas-phase. In t ...
(SESI-MS), could support canine training for explosive detection.
Honey bees
This approach couples trained
honey bee
A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosm ...
s 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 Inscentinel was a firm based at Rothamsted Experimental Station in Hertfordshire. They specialise in the development of insect olfaction technologies for the detection of trace chemicals, specifically Hymenoptera training techniques and technologie ...
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 most common technology for this application, as seen in US airports, is
ion mobility spectrometry
Ion mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized molecules in the gas phase based on their mobility in a carrier buffer gas. Though heavily employed for military or security purposes, such as detect ...
(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 bottled gas, which presents logistical issues since bottles would have to be replenished. 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.
Spectrometry
Technologies based on
ion mobility spectrometer
Ion mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized molecules in the gas phase based on their mobility in a carrier buffer gas. Though heavily employed for military or security purposes, such as detect ...
(IMS) include
ion trap mobility spectrometry
Ion mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized molecules in the gas phase based on their mobility in a carrier buffer gas. Though heavily employed for military or security purposes, such as detect ...
(ITMS), and
differential mobility spectrometry
Differential may refer to:
Mathematics
* Differential (mathematics) comprises multiple related meanings of the word, both in calculus and differential geometry, such as an infinitesimal change in the value of a function
* Differential algebra
* ...
(DMS).
Amplifying fluorescent polymers
Amplification or Amplified or Amplify may refer to:
Science and technology
* Amplification, the operation of an amplifier, a natural or artificial device intended to make a signal stronger
* Amplification (molecular biology), a mechanism leading t ...
(AFP) use molecular recognition to "turn off" or quench the
fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
of a polymer.
Chemiluminescence was used frequently in the 1990s, but is less common than the ubiquitous IMS. Several attempts are being made to miniaturize, ruggedize and make MS affordable for field applications; such as an
aerosol polymer that fluoresces blue under UV but is colorless when it reacts with nitrogen groups.
One technique compares reflected
ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...
,
infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
and
visible light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
measurements on multiple areas of the suspect material. This has an advantage over olfactory methods in that a sample does not need to be prepared. A patent exists for a portable explosive detector using this method.
Mass spectrometry is seen as the most relevant new spectrometry technique. Several manufacturers have products that are under development, both in the US, Europe and Israel, including Laser-Detect in Israel,
FLIR Systems
Teledyne FLIR LLC (an acronym for "forward-looking infrared"), a subsidiary of Teledyne Technologies, specializes in the design and production of thermal imaging cameras and sensors. Its main customers are governments and in 2020, approximately ...
and Syagen in the US, and SEDET in Europe.
X-ray machines
Specially designed
X-ray machine
An X-ray machine is any machine that involves X-rays. It may consist of an X-ray generator and an X-ray detector.
Examples include:
*Machines for medical projectional radiography
*Machines for computed tomography
*Backscatter X-ray machines, used ...
s using
computed axial tomography can detect explosives by looking at the density of the items.. These systems that are furnished with dedicated software, containing an explosives threat library and false-color coding to assist operators with their dedicated threat resolution protocols. X-ray detection is also used to detect related components such as
detonators, but this can be foiled if such devices are hidden inside other electronic equipment.
Recently,
machine learning
Machine learning (ML) is a field of inquiry devoted to understanding and building methods that 'learn', that is, methods that leverage data to improve performance on some set of tasks. It is seen as a part of artificial intelligence.
Machine ...
algorithms have been developed that can automatically detect threats in x-ray scans.
Neutron activation
Specially designed machines bombard the suspect explosives with neutrons and read the resulting
gamma radiation decay signatures to determine the chemical composition of the sample. The earliest developed forms of
Neutron Activation Analysis use low-energy neutrons to determine the ratios of nitrogen, chlorine, and hydrogen in the chemical species in question and are an effective means of identifying most conventional explosives. Unfortunately, the much smaller thermal
Neutron cross section
In nuclear physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. The neutron cross section σ can be defined as the area in cm2 for which the number of ...
s of carbon and oxygen limit the ability of this technique to identify their abundances in the unknown species, and it is partly for this reason that terror organizations have favored nitrogen absent explosives such as
TATP in the construction of
IEDs. Modifications to the experimental protocol can allow for easier identification of carbon and oxygen-based species, (e.g. the use of
inelastic scattering In chemistry, nuclear physics, and particle physics, inelastic scattering is a fundamental scattering process in which the kinetic energy of an incident particle is not conserved (in contrast to elastic scattering). In an inelastic scattering proces ...
from
fast neutron
The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term ''temperature'' is used, since hot, thermal and cold neutrons are moderated in a medium with ...
s to produce detectable gamma rays, as opposed to simple absorption occurring with the
thermal neutron
The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term ''temperature'' is used, since hot, thermal and cold neutrons are moderated in a medium wi ...
s), but these modifications require equipment that is prohibitively more complex and expensive, preventing their widespread implementation.
Silicon nanowires for trace detection of explosives
Silicon nanowire Silicon nanowires, also referred to as SiNWs, are a type of semiconductor nanowire most often formed from a silicon precursor by etching of a solid or through catalyzed growth from a vapor or liquid phase. Such nanowires have promising applications ...
configured as
field effect transistor
The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs contro ...
s have been demonstrated to detect explosives including
TNT
Trinitrotoluene (), more commonly known as TNT, more specifically 2,4,6-trinitrotoluene, and by its preferred IUPAC name 2-methyl-1,3,5-trinitrobenzene, is a chemical compound with the formula C6H2(NO2)3CH3. TNT is occasionally used as a reagen ...
,
PETN
Pentaerythritol tetranitrate (PETN), also known as PENT, PENTA, (ПЕНТА, primarily in Russian) TEN, corpent, or penthrite (or, rarely and primarily in German, as nitropenta), is an explosive material. It is the nitrate ester of pentaerythri ...
and
RDX
RDX (abbreviation of "Research Department eXplosive") or hexogen, among other names, is an organic compound with the formula (O2N2CH2)3. It is a white solid without smell or taste, widely used as an explosive. Chemically, it is classified as a ...
in sensitives superior to those of canines. The detection in this method is performed by passing a liquid or vapor containing the target explosive over the surface of a chip containing tens to hundreds of silicon nanowire sensing elements. Molecules of the explosive material interact with the surface of the nanowires and induce a measurable change in the electrical properties of the nanowire.
Detection aids
A
detection taggant
A taggant is any chemical or physical marker added to materials to allow various forms of testing. Physical taggants can take many different forms but are typically microscopic in size, included at low levels, and simple to detect. They can be u ...
can be added when explosives are made to make detection easier. The
Montreal Convention 1991 is an international agreement requiring manufacturers of explosives to do this. An example is with
Semtex
Semtex is a general-purpose plastic explosive containing RDX and PETN. It is used in commercial blasting, demolition, and in certain military applications.
Semtex was developed and manufactured in Czechoslovakia, originally under the name B 1 ...
, which now is made with
DMDNB
DMDNB, or also DMNB, chemically 2,3-dimethyl-2,3-dinitrobutane, is a volatile organic compound used as a detection taggant for explosives, mostly in the United States where it is virtually the only such taggant in use. Dogs are very sensitive to ...
added as a detection taggant.
DMDNB
DMDNB, or also DMNB, chemically 2,3-dimethyl-2,3-dinitrobutane, is a volatile organic compound used as a detection taggant for explosives, mostly in the United States where it is virtually the only such taggant in use. Dogs are very sensitive to ...
is a common taggant as dogs are sensitive to it. In the UK, the relevant legislation is the Marking of Plastic Explosives for Detection Regulations 1996.
Bogus detection devices
The
US Department of Justice
The United States Department of Justice (DOJ), also known as the Justice Department, is a federal executive department of the United States government tasked with the enforcement of federal law and administration of justice in the United Stat ...
warned in a
National Institute of Justice publication, "Guide for the Selection of Commercial Explosives Detection Systems for Law Enforcement Applications (NIJ Guide 100-99)," about the ongoing trend of "bogus" explosives detection equipment being sold to unsuspecting consumers. The report mentions by name the
Quadro Tracker
The Quadro Tracker, also known as the Positive Molecular Locator, was a fake "detection device" sold by Quadro Corp. of Harleyville, South Carolina between 1993 and 1996. Around 1,000 were sold to police departments and school districts around the ...
, an apparent
dowsing rod with a freely pivoting radio antenna rod with no functioning internal components. On August 8–9, 2005 the
Naval Explosive Ordance Disposal Technical Division via the United States Counter-Terrorism Technology Task Force conducted testing on the
SNIFFEX
Sniffex and Sniffex Plus are fake explosive detection systems produced by Homeland Safety International, debunked as ineffective. Also availablhere
Performance
An article in ''The Dallas Morning News'' in April 2007 explained that Sniffex is a ...
and concluded that "the SNIFFEX handheld detector does not work".
A number of fake dowsing rod-style detection devices have been widely used in
Iraq
Iraq,; ku, عێراق, translit=Êraq officially the Republic of Iraq, '; ku, کۆماری عێراق, translit=Komarî Êraq is a country in Western Asia. It is bordered by Turkey to the north, Iran to the east, the Persian Gulf and K ...
and
Thailand
Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...
, notably the
ADE 651
The ADE 651 is a fake bomb detector produced by the British company Advanced Tactical Security & Communications Ltd (ATSC). Its manufacturer claimed it could detect bombs, guns, ammunition, and more from kilometers away. However, it was a sca ...
and
GT200
The GT200 is a fraudulent " remote substance detector" that was claimed by its manufacturer, UK-based Global Technical Ltd, to be able to detect, from a distance, various substances including explosives and drugs. The GT200 was sold to a number ...
, where they have been reported to have failed to detect bombs that have killed hundreds of people and injured thousands more.
Additional names of fake dowsing rod style detectors include ADE101, ADE650,
Alpha 6, XK9, SNIFFEX, HEDD1, AL-6D, H3TEC, PK9.
See also
*
Bloodhound
The bloodhound is a large scent hound, originally bred for hunting deer, wild boar and, since the Middle Ages, for tracking people. Believed to be descended from hounds once kept at the Abbey of Saint-Hubert, Belgium, in French it is called, ...
*
Counter-terrorism
Counterterrorism (also spelled counter-terrorism), also known as anti-terrorism, incorporates the practices, military tactics, techniques, and strategies that governments, law enforcement, business, and intelligence agencies use to combat or ...
*
Scent hound
Franz Rudolf Frisching in the uniform of an officer of the Bernese Huntsmen Corps with his Berner Laufhund, painted by Jean Preudhomme in 1785
Scent hounds (or scenthounds) are a Dog type, type of hound that primarily hunts by scent rather than ...
*
Terrorism
Terrorism, in its broadest sense, is the use of criminal violence to provoke a state of terror or fear, mostly with the intention to achieve political or religious aims. The term is used in this regard primarily to refer to intentional violen ...
*
Gambian Pouched Rat
The Gambian pouched rat (''Cricetomys gambianus''), also commonly known as the African giant pouched rat, is a species of nocturnal pouched rat of the giant pouched rat genus ''Cricetomys'', in the family Nesomyidae. It is among the largest m ...
*
Explosives trace detector
References
{{DEFAULTSORT:Explosive Detection