The saturated vapor pressure of an explosive or drug determines the maximum concentration of that substance’s vapor that can be expected be available for collection. Some contraband has relatively high vapor pressure like NG, DNT and TNT, whereas, plastic explosives such as RDX, PETN have low vapor pressuresat ambient air temperature. This means that vapor sampling at ambient temperature may not be very effective for detecting plastic explosives or non-volatile salt forms of hard drugs like cocaine or heroin. The alternative strategy is to collect any available particles of the contraband by surface swabbing or aspiration which have the tendency to be transferred to surface during handling, packaging and generally careless contamination of the contraband package.

It is important to mention that soak time is critical in the availability of vapors after contraband is placed inside the container.

Another effective strategy is to sample volatiles emitted from the contraband. Such volatiles are characterized as follow:

  • Volatile solvents or/and starting materials used in the extraction and the preparation process of the contraband.
  • Impurities and/or decomposition products which are structurally related to the contraband and which may be present from the extraction and/or preparation of the contraband. These are of high interest since their presence in a vapor sample would provide a strong indication of the presence of the smuggled contraband.
  • Generally, drugs are cut or diluted with other substances. These substances are relatively much more volatile and permeate through packages and again are far more manifested in the air space of the package then the contraband itself.

TSI sampling and detection equipments take advantage of all these features available in various degrees of smuggled contrabands, in order to increase the probability of detection and reducing false and nuisance alarms when examining complex environments like marine containers.