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Guide to Buying the RIGHT Explosives Detector

AI Publication - June 2010
By, American Innovations, Inc.

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Whether your job is Military EOD, Police or Fire Bomb Squads, Security Personnel responsible for screening for various threats crossing your checkpoint, or a Corporate Agent trying to protect your building and people from harm, you will eventually need to add a good explosives detection system. But how do you do that, exactly? As a matter of fact, what IS a "good explosives detector?"

With all that has been written and said about what is "required", the speed at which technology evolves and improves, and with the dozens of offerings on the market, how do you know what you really need? Do you judge on price? Size? Speed? What others are using? Doesn't every manufacturer claim to have the "best" system? Doesn't every peer claim that what they bought is the "best" technology available?

This article won't answer the question of what meets YOUR particular need, but we hope it does at least help you know the questions you should ask and answer in order to know what is best for your situation.

1. How do you buy the right Explosives Detector? This is a question that has many other questions within it, but what you essentially have to know is what you are looking for. If you need to detect contamination or residue left on surfaces from contact with a person who has handled explosives, and the quantity of residue or contamination is invisible to the naked eye, you have defined the broadest criteria for Trace Detection. If, on the other hand, you come across visible quantities of unknown substances (powders, liquids, gels, solids) such as during drug raids or other contraband interdictions, and you need to know quickly if any of these substances are explosive in nature, you have met the broadest criteria for Bulk Detection. If you encounter both needs, well, that is a whole class by itself, since most Trace Detectors cannot also handle bulk explosives and vice versa.

Trace Detection typically means detecting a quantity that is invisible to the naked eye, and is usually categorized as less than a microgram (millionth of a gram). Most trace detectors are capable of detection levels in the low nanograms range (billionths of a gram). Bulk detection, therefore, typically means detecting a quantity that is visible to the naked eye, and is categorized as more than a microgram, even pounds of a substance.

Many detectors that are sensitive enough to detect trace quantities are too sensitive to handle bulk quantities also, since they become "overwhelmed" or "clogged" and must be cleared out before testing can resume. This can cause real problems if you have only one detector and lots of people or items to screen, since the clear-down process can take minutes, hours or even require a service call. Bulk detectors are, by definition, inadequate for detection at post-blast scenes, or for Gun Shot residue testing, for example, since they are not designed to be sensitive enough to meet these requirements. Know your requirement before deciding on what detector works best for you.

2. False Positives and False Negatives. False Positives or "false alarms" represent the number of times that an explosives detector indicates that it has detected explosives when in fact none are present. If this rate is too high, the user loses confidence in the detector, or begins ignoring alarms that might be actual explosives. Some systems claim a low rate of false positives, but fail to disclose that there are many commonly encountered substances producing those false alarms, such as fuel, skin lotions, hair gels, perfumes, etc.

False Negatives represent the number of times that an explosives detector fails to indicate that an explosive is present when it actually is. False Negatives are dangerous since that means missing people or devices that are dangerous and may cost lives. Any system with a false positive rate of 2% or less is considered excellent. False negatives, at least for the substances you typically encounter on the job, should be virtually 0.

You should carefully examine how the "False Negative" percentage was arrived at, since being able to wave a system around in the air inside a car or room and not getting any alarms is certainly NOT a good determinant of whether any threats were present. Some systems trumpet their "sniffer" capability and speed of analysis, and some of those are quite good, but others are not so good. Let the buyer beware.

3. Probability of Detection. This is the ability of the system to detect explosives when other confusants, interferents or masking agents are present. The detector you choose should have the ability to detect not only pure laboratory samples of explosives, but actual explosives the way they are found in the field: powdered, solid, liquid, dry, wet, aluminized, plasticized, or mixed with other explosives and/or non-explosives materials.

Some of these non-explosive materials are very effective at preventing certain technologies of seeing past them and detecting actual explosives present. You should carefully examine test results for detectors you are considering to see what the success rate for detecting real-world explosives samples is. Manufacturer testing can be considered, but third party testing is always preferred.

4. What explosives need to be detected? Of course it is always preferable to detect every type of explosive, but some explosives are more commonly encountered than others. For example, the most common type of explosive material used in mail bombings in the US has been black powder.

If your security plans include screening mail or packages, you might focus on a detector that works very well on black powder, even though it might not detect peroxide explosives, for example. If you work in an area where there is a high level of background contamination of explosives, such as a firing range, it might be best to seek a detector that is not so sensitive that it alarms continuously on propellants, or which is easily "clogged" or "overwhelmed" by larger samples of explosives. A detector that is too sensitive in this situation would be virtually useless in such an environment.

5. What are the system costs? There are actually three parts to the “cost” of a system. First you must consider the purchase cost. There are very inexpensive, disposable single-use kits which cost as little as a few hundred dollars for 50-100 tests but which have limited capabilities. There are also systems that cost $20,000, $30,000 or more, even up to $100,000 per system. Budgets will dictate the quality, capabilities and features you can afford.

The second consideration is consumables and other life cycle costs. These can include consumables such as dopants, membranes, reagents, sampling swipes, scheduled maintenance contracts, etc. These are ongoing costs that also have to be considered, since finding dollars to purchase equipment can be difficult enough, but finding substantial additional dollars later on for sustainment can be nearly impossible.

The last consideration is training costs. Some systems require minimal initial training and no ongoing training, whereas others require extensive operator, preventative maintenance, and corrective maintenance training.

6. Ease of use. Systems can vary widely in their capability and complexity. Some systems are designed to be used by technical lab staff in controlled forensic environments. Others are field durable which can be operated proficiently with just a few hours of training. If a system requires significant set-up time, and/or has a warm-up time, consider how practical it is to use in all the scenarios you will encounter.

Another consideration is calibration and re-calibration time. Certain systems require time to not only "warm-up" but also time to be calibrated to background conditions. Some systems require the operator to make the calibration adjustments, while others are self-calibrating. The time and expertise required to conduct the calibrations should factor in to your decision making. Calibrations may also have to be repeated as ambient conditions change (temperature rises or drops, humidity goes up or down, altitude changes, winds increase, etc.) in order to keep the system reading accurately. This is yet another cost to operating this type of equipment that must be considered.

An additional consideration is how easy is this system to use by someone who has not been trained? Given the way personnel turnover can occur in some jobs and agencies, the person currently assigned the equipment may not have been in that position when the manufacturer's training was first conducted. Lack of training is one of the leading reasons equipment falls into disuse, becoming a very expensive paperweight.

7. Portability. First, what is portability? Does it mean you can quickly unplug a system, pick it up from a desk and move it to another desk where it can be powered up, warmed-up and calibrated again? Or, does it mean a device that is light, able to be held in one hand, and hangs from a belt or MOLLE vest? Your definition of portability will determine just how 'portable' your system needs to be.

If you are operating a fixed checkpoint where people must come to you to enter an area, then a fixed system that sits on a desk doing its job might be fine. However, if you are on patrol, checking people or vehicles, etc., it is not very convenient to have to take a sample and then run inside to conduct the test, only to find the person/car/item you were screening has left the area.

Modern systems are able to be held in a single hand, operated quickly and safely with instant-on and no calibration requirements, then shut down and put away just as easily after the test is done, regardless of environmental conditions or types of surfaces being tested. Don't be fooled. Size used to be an indicator of capability...big desk systems were better and more powerful than small hand-held systems. THIS IS NO LONGER THE CASE! The world of Explosives Detectors has been just as driven by miniaturization as any other technology, and today the size of a system has virtually no bearing on what that system can or cannot do.

8. Sampling method. The vast majority of explosives detectors available either sample air for explosives content, detect explosives material from a sample collection swipe, or both. In fact, the majority of air sampling systems ("sniffers") demonstrate swipe sampling as their primary means of collecting a sample. The goal is to increase the Probability of Detection while being as un-intrusive as possible [NOTE: Neither of these collection methods qualify as "stand-off" detection, which is defined as the ability to detect explosives or explosives contamination in/on a vehicle, package, person, or item from a distance as little as a few meters away to hundreds of meters away..often while that object is moving (like a homicide bomber moving through a crowd, or a vehicle borne IED being driven to a checkpoint.)

True stand-off detection is the "Holy Grail" of IED detection and defeat right now, and unfortunately, we have not seen any stand-off systems that are proven and currently in large scale production.] The discussion of swipe vs. vapor sampling all by itself is a significant debate. One that is too involved for this single paragraph, so watch for future articles from American Innovations on this subject.

The bottom line is that a wide variety of options, variables and requirements must be considered when evaluating explosives detectors. Tradeoffs are inevitable, and some features will be more important to you and your mission than others. Certain criteria will remain priority throughout the search, like sensitivity, or portability, while others may be important but less so. The goal is to make the best decision for your particular situation.


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