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The Proper Application of Explosives Detection Kits (As published in the May/June 2006 issue of The Detonator)

Craig Johnson

Field Forensics, Inc.

St. Petersburg, Florida, USA

Because of the drive for better and less expensive methods, explosives detection

technology is constantly pushed forward. Instrumental methods for laboratory analysis of

explosives, bench top systems for detection, field-portable instruments equipped with

new types of sensors, and stand-off detection ideas, are continuously introduced. The

design of disposable explosives detection kits has advanced as well, and, as with

detection instruments, their proper use must be part of an application-specific explosives

detection protocol.

Basic Considerations

The detection “protocol” is the complete definition of how explosives are to be detected

in a given application and would include a primary detection method, a secondary

detection method, procedures used when explosives are indicated, instrument response

checks, frequency of calibration and periodic maintenance procedures – everything that

will completely explain and define how detection of explosives will take place in a given

scenario or application.

As of this writing there is no perfect explosives detection instrument or kit and it’s likely

that there will never be one. Any detection protocol, whether it makes use of instruments

or scanners or test kits or K-9s as the primary detection method, must account for such

technical issues as interfering substances, calibration, training, availability, shelf-life,

maintenance, consumables, and so on. It is the responsibility of the practitioner to

develop explosives detection protocols that will yield high-confidence results because

high-confidence results are necessary in order to take action. Explosives detection kits

can be used with great success in improving confidence in any detection protocol.

Explosives detection kits are generally colorimetric. That is, the user is required to look

for the color changes that result from explosives reacting with the chemical reagents in

the kit. There are typically a few steps to a test kit’s procedure through which the user

may not only make a determination as to whether energetic material is present, but, also,

what type of energetic material is present. Results can sometimes be obtained with some

specificity and excellent reliability based on the particular color observed and the step of

the test procedure in which the color change is observed.

Basic Applications

All types of detection methods are brought to bear on a variety of sub-applications within

the broad practice of explosives detection. The number of possible applications is

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virtually unlimited but there are two major categories under which all of them can be

grouped. These two major categories are:

1) Point-detection

2) Field-detection

Point-detection includes situations where all of the explosives detection is performed in a

fixed location. Field detection includes all applications where portable explosives

detection is required, both indoors and outdoors. Even these categories are very broad

when one considers the many different situations where explosives detection is necessary.

(Note: For the purposes of this article analytical equipment used in a laboratory for

detailed explosives analysis will not be discussed.)

Point-Detection

Point-detection includes applications such as baggage screening, passenger screening,

screening of pedestrians, objects entering buildings, etc. To the average person the most

familiar point-detection application is security screening of passengers and their carry-on

baggage at air terminals, so we shall use it here as an example.

In this example application, in addition to x-

ray scanning of carry-on baggage, some bags

are randomly selected for additional

explosives screening. There are several

considerations in selecting the primary

detection method including cost, reliability,

and sensitivity. When considering cost one

has to take into account the initial cost of the

device (whether a kit or an instrument) and

the cost of the consumables that both

instruments and kits require for operation. In

some cases it may be appropriate use explosives detection kits as the primary detection

method but usually explosives screening is carried out with an instrument based on some

sort of ion mobility spectrometry (IMS). A basic reason for using an instrument instead

of a kit is specificity – the ability to identify specific explosives. Another reason is that

old-style kits are prone to user error because of their complexity. With most of these kits

the user is confronted with a miniature chemistry set with bottles of reagent and limited

shelf-life or reliability of reagents; next-generation long-shelf-life kits, as in the

photographs below, are designed as integrated units and offer the advantage of far greater

simplicity.

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When an instrument is chosen as the primary detection

method, it is important to understand that every type of

instrument has weaknesses its strengths and. For the purposes

of this article the type of instrument doesn’t really matter. The

important thing is that any point-detection protocol where an

instrument is used as the primary detection method, the

protocol must compensate for the instrument’s weaknesses

while making use of its strengths. An excellent use of

explosives detection kits is in compensating for these

weaknesses.

For example, many instruments might have the benefit of high sensitivity but with the

negative side-effect of a high incidence of false positives. Instruments also require

calibration, maintenance, and will sometimes encounter samples that require the

instrument to be taken off-line for cleaning (baking-out). In other words, there will

always be some amount of scheduled and unscheduled downtime. These issues should

be taken not as criticisms of instrumental methods but considerations in the development

of rational and objective detection protocols. Some instruments are prone to systematic

errors, which will lead to the same error no matter how many times the measurement is

repeated. Explosives detection kits, when used as a back-up, or secondary detection

method, can reduce or eliminate systematic errors by providing an alternative method of

looking at the same object. When an instrumental method gives a positive indication for

explosives a secondary measurement with a detection kit can either confirm or make

suspect the primary measurement. Then too there are situations where an instrument

must be taken offline for either routine or unscheduled maintenance and an explosives

detection kit can provide a convenient and effective backup.

Field-Detection

Field-detection includes such applications as presumptive testing by police, searches on

ships and aircraft, random screening, and roving searches at large public venues. The

field-detection application is where explosives detection kits are the most useful because

of their portability, and, in next-generation kits, ease-of-use, tolerance of a wide range of

environmental conditions and long shelf-life. Of course, portable instruments and K-9s

are often used in these applications as well.

As with point-detection applications, field-detection applications require complete

protocols to define how explosives will be detected and what steps are to be taken should

a positive for explosives be indicated. Unlike most point-detection applications, field-

detection applications often combine routine and non-routine explosives detection

scenarios. In other words, some of these applications are employed on in searches only

when the policeman or soldier has reason to suspect that further investigation is required

but hasn’t identified a particular suspicious package as when there is not enough

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suspicion to warrant calling in the bomb squad or an EOD team. For example, during a

traffic stop a policeman wouldn’t normally test for explosives on the door handle of the

car or the hands of the driver, but, given some suspicion the officer might decide to

perform a quick check. Or, perhaps the application is post-blast (or shooting) and

explosives detection will be used to segregate suspicious bystanders from innocent

bystanders. In other cases, the explosives detection step is a routine part of an

installation’s security.

Consider for example the application of roving searches at a nuclear power plant. In this

case, security personnel have reason to conduct routine tests for explosives on vehicles at

many different locations of the site including receiving areas and remote areas.

Explosives detection kits are perfect for this application because most kits are small and

very portable and do not require calibration or periodic maintenance. Next-generation

kits are simple to use without a great deal of training.

Conclusion

There is no single best solution for explosives detection. The goal of managers, whether

police, military, or commercial security, should be to institute explosives detection

protocols as part of an overall security plan that has the highest degree of confidence. In

order to achieve this confidence, technical strengths and weaknesses of various detection

methods must be considered and different methods used to make up for the other’s

weaknesses. In any practical situation cost is always a concern. It should be kept in

mind that the most expensive explosives detection method is the one that is purchased

and not used. Explosives detection kits should play a part in any detection protocol,

whether as the primary, or, as a back-up detection method.