Detect Me Not Covering All the Bases in Explosives Detection

Explosives

detect me not Explosive detection: An overview

Not all explosions are created alike. In general, explosives are classified into two categories: as either low or as high explosives, depending upon their rates of decomposition. Low explosives burn; in contrast, high explosives detonate (Chapter 12, 2011, FAS). Detonation is a different phenomenon from burning. During detonation of a high explosive, the initial reaction is initiated by a shock that generates compression, heat, and finally chemical decomposition. Every component of a high explosive has its own equation of state (EOS) with a unique relationship of pressure, density, and internal energy (Walter 1996). When the temperature of a substance increases, molecules of the different components travel faster and hit the surface of the exterior of the bomb casing with greater and greater force, finally causing an explosion when the interior surface of the casing can no longer resist (Moorcraft 2001). The speed with which this occurs depends upon the nature of the substance.

The increased concern about chemical-style explosives has caused the Transportation Safety Authority (TSA) and most major air carriers worldwide to institute the 3-1-1 rule for carry-on liquids. The rule stands for the fact that every passenger can carry a 3.4 ounce (100ml) bottle or less (by volume) of liquid in a single, quart-sized, clear, plastic, zip-top bag. Only one bag per passenger is allowed, which is placed in screening bin before the passenger is allowed on the flight (Make your trip better using 3-1-1, 2011, TSA). The 3.4 ounce (100ml) limit and one container limit means that this is the maximum amount of liquid passengers can bring. The amount of liquid and container size is limited given the potential dangers of a travel carrying a substance that could be hazardous but masked as an apparently innocent bottle of water or shampoo.

However, there have been many complaints about security procedures, which some travelers claim are excessively burdensome in terms of searching for chemical explosives. Scientists are working to develop more thorough screening procedures as a result. New procedures less physically intrusive, such as Near Infrared (NIR) spectroscopy. NIR can ferret out hidden hazardous chemicals even when they are hidden behind clothing without body searches (Nolan-Neelan 2010). NIT technology is especially useful because it allows for detection at a remote distance. A light transmits through the passenger's clothing and signals are reflected by the chemical and back through the clothing to a NIR detector. "The signal was then passed into a spectrometer, which analyzed the intensity of the light at each wavelength. By comparing the intensities of light diffused by the clothing material and the hidden chemicals, the group was able to work out a 'fingerprint' for the chemical" (Nolan-Neelan 2010).