Particle sampling is often thought to be less attractive option than vapor sampling, but both techniques have their advantages and drawbacks, summarized in following table.
Vapor versus Particulate Detection
Vapor Detection |
Particle Detection |
| Good for volatile explosives and drugs | Good for non-volatile explosives and drugs |
| Consistent vapors emitted from concealed target | Erratic- particle transfer depends on many chance factors |
| Reproducible to some extent | Not reproducible |
| Dependent on temperature | Not dependent on temperature |
| Easy to sample – Vapors may be collected anywhere near target | Harder to sample if surface swiping not accessible |
| Countermeasures- Contraband may be concealed in airtight vessel | Countermeasures- Hard to avoid particles transfer |
| Not affected by humidity | May be affected by humidity if contraband is highly hydroscopic like some drug salts |
| Enclosure agitation not necessary | Agitation is helpful and necessary to lift particles to airborne status |
| Some vapors can permeates through barriers like plastic, packaging etc. | Outside package surface contamination and distribution by handling, movements and agitation |
| Longer soak time is better for volatiles | Not required if particle is airborne or container is agitated |