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