A large flow of air is sucked through or over an adsorbent thin film of solid phase micro-extraction coated sample card, which retains the vapors. The material is then desorbed by heating it whilst a smaller volume of air or a carrier gas passes through the adsorbent and sweeps the desorbed vapor into the analyzer. This process occurs automatically in the desorber module of the analyzer system TSI-3000 and involves simple insertion of the sample card into the heated desorber to startup sample processing and detection.

Generally, sampling longer time would mean more sample collection and enrichment. This is effective for relatively volatiles and semi-volatiles substances but much less effective for non-volatile contrabands as mentioned earlier.

Long soak time (several hours) is required from the time the contraband is placed inside the container. This would allow for the volatiles to permeate the packaging and diffuses into the air space of the container.