Portal trace detection systems for detection of imbedded particles

Abstract

A portal trace detection apparatus is provided for detecting minute particles of interest, such as traces of narcotics, explosives and other contraband. The apparatus includes a portal through which a human suspect will pass. A detection apparatus is disposed at least partly in the ceiling of the portal, and hence above the human subject in the portal. Particles of interest will be entrained in the human thermal plume that exists in the boundary adjacent the suspect, and will flow upwardly from the suspect to the detection apparatus in the ceiling of the portal. The ceiling is coated with an anti-static material so that particles are more likely to flow towards the detector and less likely to be affixed electrostatically to the ceiling.

Description

[0001] This application is a divisional of U.S. patent application Ser. No. 10 / 774,004 filed Feb. 6, 2004, which is a divisional of U.S. patent application Ser. No. 10 / 033,874, filed Dec. 20, 2001, now issued as U.S. Pat. No. 6,708,572.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The subject invention relates to a detection apparatus for dislodging particles from clothing and skin of a person and then testing the dislodged particles for the presence of substances of interest. [0004] 2. Description of the Related Art [0005] Detection systems exist for detecting traces of materials, such as narcotics and explosives. Such systems are marketed by Ion Track Instruments, Inc. and are shown, for example, in U.S. Pat. No. 5,491,337. [0006] Prior art detection systems rely upon the fact that trace amounts of contraband will be transferred to the body of a person who handled the contraband, and subsequently will be transferred from the body to any article that the perso...

AI Technical Summary

Benefits of technology

[0015] The jets may be connected to a high pressure (40-100 psi) air supply and may be operated sequentially by solenoid valves that are connected to and operated by a controller. Each jet is operative to deliver a short puff of air which disturbs the clothing of the human suspect sufficiently to release trapped particles. The air flow created by the jets necessarily disturbs the body plume somewhat, and hence conceivably could cause a turbulence that could direct particles of interest out of the portal. However, the effect of the jets on the human thermal plume can be minimized substantially by operating each jet only for a very short duration. Thus, each jet functions essentially like a smoke ring with a local disturbance, but a minimum effect on air flow patterns in the human thermal plume. Furthermore, the effect of the short puffs of air produced by the jet can be used cooperatively with the human thermal plume by actuating the jets sequentially from bottom to top in each of the vertical arrays of jets. The jets preferably are switched on for about 10-80 ms, and each level of jets is switched off before the next level is switched on. It has been determined that longer periods of operation for the respective jets adversely affects the human thermal plume without significantly increasing the release of particles from the clothing of the human suspect passing through the portal.

[0016] The portal apparatus of the subject invention provides still a further advantage. In particular, it has been determined that small dander particles that are given off from the skin gradually migrate into the clothing. These dander particles can act as vapor traps for very low volatility materials, such as explosives and narcotics which may be hidden under the clothing of under the human subject passing through the portal. These dander particles are released by the jets, and hence become entrained in the human thermal plume. More particularly, the dander particles effectively become tiny traps that are released by the jets and transported in the human thermal plume to the detection system where the trapped vapors are desorbed. Thus, the incorporation of the jets into the portal detection system creates the possibility of detecting vapors that normally would be below the threshold of sensitivity of the system.

[0017] It also has been determined that particles of interest often affix themselves to the hood or ceiling of the portal due to static electricity, in much the same way that dust accumulates on a television screen. This phenomenon can be reduced or eliminated by coating the hood or ceiling with an anti-static material. Thus, fewer particles become affixed to the hood, and sensitivity is increased.

Problems solved by technology

The air flow created by the jets necessarily disturbs the body plume somewhat, and hence conceivably could cause a turbulence that could direct particles of interest out of the portal.

It has been determined that longer periods of operation for the respective jets adversely affects the human thermal plume without significantly increasing the release of particles from the clothing of the human suspect passing through the portal.

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