Defining liquid explosives
There are several types of liquid and gel explosives which law enforcement should be familiar with. Some of these explosives are very volatile — even picking up a bottle of say, nitroglycerine, and shaking it could cause an explosion. Force safety must be of paramount concern when answering a call to a suspected bomb-making site. When bomb-making activity is suspected, untrained officers should never touch anything at the scene without having bomb techs clear the area before the investigation begins.
Familiarization with the types of explosives is also vital in detecting activity in bomb IED labs. You may answer a call about suspicious activity and fail to recognize the substances.
WaterGel explosives were developed to replace dynamite. They are packaged in plastic and look like very large sausages. They require a detonator and are not subject to heat, friction or electrical detonation.
Astrolite G and Astrolie A-1-5 (basically the addition of one additional component are extremely dangerous but stable liquid explosives). There are simple formulas for putting these together for anyone with an Internet connection. Both are claimed to be the most powerful non-nuclear explosive (Astrolite G) and A-1-5 version is claimed to be the world's highest detonation velocity explosive. Both are clear liquid. These use mechanical or electrical detonation.
Two-component Kinepak is commercially available and looks like a syrupy red liquid, which when mixed with a white powder substance creates a very powerful explosive.
Nitroglycerin is the most instable of explosives, but extremely powerful and detonation with explosion makes it much more powerful. It is a combination of sulphuric and nitric acid. It can be stabilized by a combination of freezing or re-constitution (cotton balls soaked and then dried) or the addition of compounds that can then be removed. The liquid looks clear but with aging becomes brown.
Incendiary chemicals are widespread and in a suitable container may cause large-scale damage. Gasoline, gelled gasoline, chlorate sugar and thermite are some examples.
Middle Eastern terrorists favor Triacetone Triperoxide (TATP) largely because of its ease of preparation. It is not a liquid explosive, but rather a crystal solid form explosive made up of readily available liquids. All it takes is acetone, hydrogen peroxide (3-percent medicinal peroxide is not concentrated enough), and an acid-like hydrochloric or sulfuric acid.
It is important to realize new substances have the property of releasing large quantities of gas at high velocity (the essentials of an explosive) are being developed in terrorist bomb labs regularly so the effort of classification and description is difficult.
Detecting liquid explosives
There are several problems with detecting liquid explosives. For this reason they have become more popular with terrorists. Solid explosive detection is relatively advanced. Also, just like Youssef, terrorists are constantly experimenting with different substances that will be useful to their aims either as rapid inflammation or explosive compounds. The most critical problem is the difference between organic and inorganic liquid explosives. This means two types of detection need to be used.
The publicity of the August 10 plot has given rise to an entire industry determined to fill the holes left to terrorists to deploy these weapons.
Rapiscan Systems is developing four devices to detect liquid or Gel explosives, but they are relatively expensive. Machines can cost up to $250,000 each.
For high-transit situations the devices have difficulties. Each bag must be placed in a closed compartment — and each and every bag would have to go through this process, something that would cause immense delays whether at an entrance to a football game or airport.
A machine which detects explosives in liquid or solid form, does so by bombarding it with energy such as radio waves or neutrons. Software then processes the result to determine the chemical compound in the innocuous container.
Millimeter wave technology, such as Defendertech's camera system, can detect a bottle hidden under a person's clothing without being invasive.
Despite all efforts, terrorists come up with new compounds and there are certain compounds which have belied testing.
For example TATP has posed special problems for detection because it lacks a metal component or nitro groups that would make them amenable to detection by standard screening or rapid identification methods. Furthermore, since no electrical charge or wires are required to ignite TATP, the "problem" of setting off metal detectors is avoided.