How Do Explosives Detection Systems Work

How do I use Expray or DropEx explosive detection kits?

Most explosives are not water-soluble and traces can be found long after the explosives have been removed. Directions are printed on each can and inside cover of the each kit carrying case. The steps for using Expray and DropEx are quite similar. It is important that they be applied in order.

1. Remove a collection paper from the dispenser. The collection paper (#C0530) is laminated on one side and have a protective cover on the other to prevent either pre- or cross contamination
2. Peel the protective layer exposing the sticky surface. The collection papers are covered with a thin layer of glue to ensure good specimen collection. Be sure not to touch and potentially contaminate the exposed adhesive collection surface.
3. Wipe suspected surface (e.g., hands, door handles, objects) with the sticky side of the collection paper. (A small amount of suspected material, soil or extract can be placed on the collection paper.)
4. Test the paper with a light application of Expray-1 or a drop of DropEx-1. Always shake the Expray reagents first, direct the spray away from the body and apply from a distance of about six inches. Apply DropEx from a distance of about three inches.
5. Observe for an immediate color change. If a dark brown color appears (similar to the color on the label) this indicates the presence of GROUP A explosives. Some compounds may give other colors. Refer to the color chart provided with the kit.
6. If after applying the first reagent there is no color change, then test the same spot on the collection paper with Expray-2/DropEx-2.
7. Observe for an immediate appearance of a pink color (similar to the color on the label) indicating the presence of GROUP B explosives. Most plastic explosives, including Semtex, belong to this group,. [Tetryl belongs to both Groups, so it will change from orange (color change caused by Expray-1/DropEx-1) to pink after being tested with Expray-2/DropEx-2.]
8. It is especially important that reagent 3 be well shaken immediately prior to use.
9. If there is no color change after using the 1 and 2 reagents, but presence of explosives is still suspected, test the same spot on the collection paper with Expray-3/DropEx-3.
10. Observe for an immediate appearance of a pink color (similar to the color on the label) indicating the presence of inorganic nitrates, which could be part of an improvised explosive.
11. If other explosives are suspected, repeat steps 1 to 3 (do not use a sample that was tested with other reagents) and apply DropEx-A to the fresh sample. Observe for an immediate appearance of a dark-blue color indicating chlorates or bromates are present.
12. If there is no color change after using DropEx A, but presence of explosives is still suspected, test the same spot on the collection paper with DropEx B. Observe for the immediate appearance of a dark-blue color indicating peroxide based explosives are present.
    

Explosive Detection Kit Verification: Both Expray and DropEx performance can be checked by using the verification paper provided with each kit. Tear one verification paper from the pad. Do not wipe anything. On the non-glossy side of the verification paper, apply Expray-1/DropEx-1 followed by Expray-2/DropEx-2 as described above. Observe for the immediate appearance of the letters “EX” indicating the validity of the reagents.

Note: Only an immediate color change should be considered a positive test result. A treated paper left in open air, may gradually turn pink. This delayed color change should be disregarded.

How can I be sure the detection kit is working properly?

The kits are equipped with verification papers that allow the technician to confirm that the reagents are reacting properly. To test the reagents, simply use Expray/DropEx-1 followed by Expray/DropEx-2 on an unused verification paper. If the letters EX appear, then the reagents are still good.

Do I have to use the collection papers?

No, the collection papers are provided as a convenient way to collect samples. Any clean white paper can be used. It is recommended that all of the reagents used be applied to any alternative paper used to assure that no contaminants that might react with the reagents are present. Although not recommended the reagents can be used on any surface that contrasts with the developed color.

How sensitive is the kit?

Laboratory tests found the kit can detect particles as small as 20 nanograms. Such small particles can be found on hands, on working surfaces (tables, desk) and on the outer side of envelopes or parcels in which explosives were sent. Even after an explosion, unexploded particles can be found in the area, which can give an immediate clue about the nature of the explosion. Refer to the links provide to see published test results.

For detection of plastic explosives only, can "Expray/DropEx-2" be used without "EXPRAY/DropEx-1"?

No, the reagents must be used sequentially in order to ensure accurate results.

How long after handling the explosive can traces be found?

Most explosives are not water soluble, and it is very hard to get rid of traces on the hands even after washing with water and soap. Explosive traces can be found on undisturbed objects even months and years after the actual explosive has been removed.

Is the result of the testing with EXPRAY accepted as evidence in court?

No, in order to gain evidence for court, further laboratory examination of the material is necessary.

If so, why use the kit?

Without a field kit, the technician performing an investigation cannot know which object should be sent for laboratory examination or which suspects to question further. The result is usually flooding the laboratory with numerous samples suspected of having explosive contamination, resulting in increased time and expense for testing. By using the kit, the technician can screen several samples/objects and send to the laboratory only those that give a positive result.

Note: Some propellants and explosives are mixed with plasticizers (such as Bis(2-ethylhexyl)phthalate) that can mask the presence of some of the compounds, a solvent may be necessary in these circumstances to properly expose the energetic material and allow detection.