Particles of explosives or drugs are usually acquired from surfaces by direct swiping the surface with the sample card or through a filter, which then is heated to release the trace into the analyzer unit. In the case of RDX and PETN from plastic explosives the particles are often mixed with binder material and grease from the hands of handlers. These greasy materials tend to stick the particles to the surface, to a degree which also depends on the nature of the surface. The function of the sampling system is to remove the particles from the surface and transfer them, usually in the vapor form to the analyzer.

One approach is to heat up the surface to vaporize the trace and collect vapors on the sample card. Another approach is direct swiping the surface with a filter or the sample card itself and processing the card into the analyzer unit.

Another approach is based on the use of hand held sampler or high volume sampler to suck particles of surfaces and trap them on the sample card. The card is then analyzed.

Parameter Affecting Sampling of Particles

  • Type of contraband sampled
  • Surface type and surface loading
  • Surface to sampler distance (closer is better)
  • Type of sampler used: wipe versus vacuum
  • Humidity and wet condition