Explosive and narcotics detection dog training with vapour or aerosol air impregnation

Abstract

The present invention provides devices and methods for the impregnation of air with the vapor or aerosol of a substance in a ‘controllable manner to enable the testing or training of detection means to evaluate and quantify the presence of the substance in an enclosed volume, and iη• particular to enable production of training aids and quality assurance test items for use in canine-olfaction based security screening.

Claims

1. A method for the impregnation of air with the vapour or aerosol of a substance in a repeatable and controlled manner to enable the testing or training of means for detecting to evaluate and quantify the presence of the substance in an enclosed volume in a real environment, comprising arranging for an airflow from said enclosed volume in said real environment to pass over a predetermined volume or predetermined surface area of the substance supported within a conduit having an inlet and an outlet for passage of the airflow at a predetermined flow rate for a predetermined period of time thereby impregnating air of said airflow with said vapour or aerosol of said substance in a repeatable and controlled manner, and further arranging for delivery of said impregnated air to said means for detecting the substance, wherein said real environment is the environment found at a real situation, as opposed to a simulated environment which is a fake or mock environment that seeks to emulate the characteristics of said real environment.

2. The method according to claim 1, wherein the substance comprises an explosive.

3. The method according to claim 1, wherein delivery of impregnated air comprises adsorption of said impregnated airflow onto a substrate.

4. The method according to claim 1, wherein said real environment is a cargo hold, and the enclosed volume is cargo.

5. The method according to claim 1, wherein the conduit is within a device, and the conduit comprises a means for supporting a predetermined volume or predetermined surface area of substance within the conduit such that in use the air flowed through the device is impregnated with the vapour or aerosol of the substance.

6. The method according to claim 5, wherein said conduit comprises two interconnecting flow channels, a first and second flow channel, wherein the means for supporting the predetermined volume or predetermined surface area of substance is within the second flow channel, such that in use air entering the conduit is divided between the two flow channels, impregnated with the vapour or aerosol of the substance in the second flow channel, and then recombined prior to exiting the conduit.

7. The method according to claim 5, wherein the means for supporting a predetermined volume or predetermined surface area of substance comprises a chamber.

8. The method according to claim 7, wherein said chamber comprises a removable cylinder.

9. The method according to claim 7, wherein said chamber further comprises a mesh material wherein said mesh material is capable of containing a substance but which does not restrict the airflow significantly.

10. The method according to claim 5, comprising dimensions such to accommodate an airflow compatible with the use of REST approved equipment for the production of detection dog training aids.

11. The method according to claim 1, for the production of training aids for detection dog training, wherein the detection dog training is the REST procedure.

12. A method for producing a training aid for detection dog training, comprising arranging for an airflow from an enclosed volume in a real environment to pass over a predetermined volume or predetermined surface area of a substance supported within a conduit having an inlet and an outlet for passage of the airflow at a predetermined flow rate for a predetermined period of time thereby impregnating air of said airflow with a vapour or aerosol of said substance in a repeatable and controlled manner, and adsorbing said impregnated air onto a substrate, wherein the substrate comprising the substance is the training aid, and wherein said real environment is the environment found at a real situation, as opposed to a simulated environment which is a fake or mock environment that seeks to emulate the characteristics of said real environment.

Description

(1) The present invention will now be described with reference to the following non-limiting examples and figures in which:

(2) FIG. 1 is a Computational Fluid Dynamics (CFD) image showing one embodiment of a device of the first aspect (V1);

(3) FIG. 2a is an image of the CFD model of a second embodiment of the device (V2a)

(4) FIG. 2b is an image of the CFD model of a third embodiment of the device (V2b);

(5) FIG. 3 is a photograph of an embodiment of the device (V2a) connected to the REST pump and filter holder, and a polyethene tip for insertion into the genuine environment;

(6) FIG. 4 is a graph showing the effect of sampling time on the emission of Substance A from devices V2a and V2b. The error bars represent one standard deviation;

(7) FIG. 5 is a graph showing stability of emissions on three separate days from device V2a. The error bars represent one standard deviation;

(8) FIG. 6 is a graph showing stability of emissions on three separate days from device V2b. The error bars represent one standard deviation;

(9) FIG. 7 is a graph showing the effect of sampling time on the emission of Substance B from devices V2a and V2b. The error bars represent one standard deviation;

(10) FIG. 8 is a graph showing the stability of emissions of Substance B on three separate days from device V2a. The error bars represent one standard deviation; and

(11) FIG. 9 is a graph showing stability of emissions of Substance B on three separate days from device V2b. The error bars represent one standard deviation.

(12) FIG. 10 is a drawing of one embodiment of the device.

EXAMPLES

(13) A device has been produced to enable production of training aids having a range of concentrations of a substance to train detection dogs. The device is required to produce training aids of concentrations that are comparable to that potentially encountered by sampling air from an enclosed volume in a genuine environment.

(14) Having regard to FIG. 1, the device comprises a first flow channel 1, a second flow channel 2, a chamber 3 for retaining a substance, an inlet 4 and an outlet 5. Air can be drawn through the device by use of a pump, such as the REST pump, connected to outlet 5. In the case of the REST method, a REST filter would also be located at outlet 5 Tubing (not shown) connected to inlet 4 can be inserted into a genuine environment, such as cargo. The majority of the sampled air passes through first flow channel 1 with a smaller proportion diverting along second flow channel 2 and through chamber 3. The proportion of air that passes through chamber 3 is controlled by the dimensions of the first flow channel 1, the second flow channel 2 and chamber 3 itself.

(15) Having regard to FIGS. 2a and 2b, two devices (V2a and V2b) were produced, one where the substance could be retained in chamber 3 within a porous cylinder 6 (V2a) and the other where the substance could be retained in chamber 3 within a recessed well 7 (V2b).

(16) CFD modelling was used to refine the dimensions of the designs. In particular refinements to the diameter of the second flow channel 2 were investigated, especially sections 2i and 2ii of the second flow channel, either side of chamber 3. Refinements to the diameter of the first flow channel 1 were also investigated, especially utilisation of variable diameters 1i, 1ii and 1iii. Other potential refinements included angling sections 2i and 2ii.

(17) It was found that reducing the diameter of second flow channel 2, in particular section 2ii on the outlet side of the device, with respect to the diameter of the first flow channel 1 and/or section 2i, could reduce the rate of airflow through second flow channel 2 and chamber 3, achieving control of the amount of substance vapour exiting the device whilst maintaining the overall flow rate through the device, and consequently leading to more consistent sampling.

(18) Having regard to FIGS. 2a and 2b, devices at least partially optimised for use with the REST method and instrumentation had the following dimensions. The second flow channel 2 has a diameter of 13 mm throughout. The first flow channel 1 has a variety of diameters along its length, with sections 1i and 1iii of 9.5 mm, and sections 1ii of 13.5 mm. It was observed that the wider diameter of section 1ii of 13.5 mm, situated at junction 8 and junction 9 between the first flow channel 1 and second flow channel 2, had the effect of reducing the airflow rate through that section of first flow channel 1, with the further effect that the airflow has a greater chance of diverting along the second flow channel 2, and so increases the airflow through chamber 3. Having regard to FIG. 2a, at an overall flow rate through the device of 60 L.Math.min.sup.−1, a CFD model predicted that the flow rate through chamber 3 of device V2a would be 13.9 L.Math.min.sup.−1 and that through chamber 3 of device V2b would be 14.3 L.Math.min.sup.−1. This flow rate could then be adjusted in a controllable manner though the utilisation of an adjustable flow restrictor located in section 2ii of second flow channel 2.

(19) An adjustable flow restrictor may comprise a length of acrylic 14 mm by 130 mm, with holes of a variety of diameters centrally aligned along its length. The adjustable flow restrictor may interrupt the path of a flow channel across the flow channel's diameter, the adjustable flow restrictor at all times engaged with the walls of the flow channel, such that no air escapes the device. Air can then be forced through the chosen hole within the adjustable flow restrictor. Such a restrictor may provide for the restriction of, for example, a 13 mm diameter flow channel at a point after the chamber outlet (and, in a multiple channel embodiment, prior to rejoining the other flow channel) to, for example, 1.63 mm in diameter, and so increase the pressure and decrease the rate of airflow through the chamber, thus providing greater control over air impregnation. The effects of adjustments to the diameter of section 2ii, which could be provided by a flow restrictor, are shown in Table 2.

(20) Having regard to FIG. 2a (V2a), cylinder 6 has a 30 mm diameter and is 15 mm high V2a has the advantage over V2b that the cylinder is self contained and so could easily be removed for storage etc. Having regard to FIG. 2b (V2b), recessed well 7 has a 30 mm diameter and is 10 mm deep Device V2a would be easier to use operationally because substances could be pre-prepared in the cylinder 6 in a controlled environment and then be placed in the device with a minimum of difficulty by the user. Sample chamber 3 in both V2a and V2b is 60 mm diameter and 15 mm deep. Such dimensions advantageously provide a chamber of small volume which is capable of enhancing consistency and control in the production of training aids. A device comprising a chamber of small volume was shown to effectively eradicate the effect of certain time variables in the production of training aids, such as the time that the substance is retained in the device prior to impregnation, or the time between production of each training aid. Such a small chamber is also capable of essentially overcoming variabilities in the vapour pressure of substances due to fluctuations of temperature, since the production of vapour from a substance will rapidly reach a state of equilibrium, consequently minimising the effect of any such variability.

(21) Having regard to FIG. 3, device 10 is illustrated connected to the REST pump and filter holder 11, and polyethene tip 12. The device 10 includes threaded fittings at inlet 4 and outlet 5 for simple removal/fitting of 11 and 12.

(22) The applicant has observed that the material the device is made from may have an effect upon its ability to impregnate air with only scent characteristics from a selected genuine, environment. Following analysis of a range of materials, the limited scent characteristics of an inert polymer such as acrylic were found to have the least detrimental effect in producing training aids.

(23) A mesh can be incorporated into the chamber 3 in order to enable use of the device with powdered or particulate substances. The mesh would need to be fine enough to contain the powder but coarse enough so as to not restrict the flow of the vapour significantly.

(24) A range of different meshes (from Goodfellow, Huntingdon, UK) were tested and the coarsest was found to contain the powder. The mesh had the following properties: Material—Polyethylene terephthalate Nominal aperture—100 μm Monofilament diameter—70 μm Threads/cm—55 Open area—33% Plain weave mesh

(25) Experiments were conducted to assess the impact of the mesh's inclusion in device V2a, arranged around the inner surface of the porous cylinder, and V2b, fixed over the opening of the recessed well, upon impregnation and thereby adsorption onto a substrate. Having regard to FIG. 2a, the inside of the cylinder 6 was lined with a single sheet of plastic mesh and rolled into a cylinder to enable retention of a substance. Having regard to FIG. 2b, the opening of well 7 was covered with the plastic mesh. The variation in output was however minimal, with a reduction of only 2.4%.

(26) Two explosive substances were tested in devices V2a and V2b, substance A and substance B, with dimensions and masses indicated in Table 1.

(27) TABLE-US-00001 TABLE 1 Substances evaluated using devices V2a and V2b Substance A Substance B Dimensions mass Dimensions mass Probe dia × h (mm) (g) dia × h (mm) (g) V2a 25 × 15 9.6 23 × 15 7.5 V2b 25 × 7  6.1 23 × 7  3.9

(28) Having regard to FIG. 3, laboratory air was drawn through the device by the REST pump in the conventional manner for 10 s, 30 s, 60 s, 120 s and 180 s, and impacted on a REST filter. During experiments air was sampled orthogonally from the main airflow using a personal air sampler (Universal model, SKC) to draw vapours onto a Tenax™ trap which was then analysed by thermal desorption gas chromatography mass spectrometry (TD GC-MS) A limitation of the technique was that it was only possible to sample 2 L min.sup.−1 from a total airflow of 60 L min.sup.−1. Thus the technique was limited to substances which release a large amount of vapour. The ratio of vapour pressures of some example compounds over a temperature range 5° C. to 30° C. were found to be up to 100.

(29) Measurements for each substance and sampling time were repeated five times. A comparison was also made on the day to day stability of the emissions from a single substance by comparing the levels produced on three different days (1, 12 and 22 days after placement of sample in the device) at similar ambient temperatures.

(30) Cylinder 6 in device V2a was found to present a larger surface area of substance to the airflow and consequently produced higher levels of target vapour than recessed well 7 in device V2b.

(31) Substance A

(32) The effects of sampling time of 10, 30, 60, 120 and 180 seconds on the amount of target vapour produced by both devices V2a and V2b are shown in FIG. 4

(33) All data points recorded represent one thirtieth of the total vapour that has impregnated the airflow. The amounts produced at 60 seconds sampling time from device V2a (approximately 60 ng×30=1800 ng) are similar to the levels provided by the “fish tank method” (approximately 524 ng×10/4=1310 ng, to convert from a 2 L.Math.min-.sup.1 sample collected for 2 min to a 60 L.Math.min-.sup.−1 sample collected for 10 seconds). Device V2b also produced approximately the same amount of vapour as that of the “fish tank method”.

(34) A demonstration of the stability of emissions from substance A produced from device V2a and device V2b on 1, 12 and 22 days after placement of the substance is shown in FIGS. 5 and 6 respectively.

(35) Substance B

(36) The effect of sampling time on the amount of Substance B impregnating the airflow from device V2a and V2b are shown in FIG. 7.

(37) The long term stability of emissions of the target vapour for substance B from device V2a and V2b on 1, 12 and 22 days after placement of the substance in the device was monitored with sampling times of 10 s, 30 s and 60 s shown in FIGS. 8 and 9 respectively.

(38) Control of Sample Concentration

(39) Having regard to FIG. 2a, following the demonstration that the device was producing sample concentrations at the upper end of the required range, CFD was used to assess how restricting the diameter of second flow channel 2 and varying sample times could reduce the amount of vapour output and investigate to what degree the output could be regulated. Table 2 shows the results from the CFD models. The restricted diameter in this instance was in section 2ii of the device, i.e. in the second flow channel subsequent to the outlet to the chamber.

(40) TABLE-US-00002 TABLE 2 Mass of vapour output from the device V2a for two sample times and five section 2ii diameters. Chamber Second flow outlet channel flow Mass samples after diameter rate 30 seconds 300 seconds (mm) (L .Math. min.sup.−1) (ng) (ng) 13.00 14.4 332 3336 9.75 13.3 317 3185 6.50 8.8 238 2397 3.25 2.9 153 1547 1.63 0.8 83 869

(41) By restricting the diameter of section 2ii, the flow could be reduced by a factor of 28 but the mass of sample output only reduced by approximately 4. Additional ways to increase the concentration range include:

(42) 1. Varying the mass of substance in the chamber, though too small a mass of substance could be highly susceptible to drying out and so the consistency of the samples could be compromised.

(43) 2. Varying the type of mesh in the chamber to slow the vapour transfer into the airflow.

(44) Device V2a can produce training aids that have a mass of vapour that is comparable to that produced with the fish tank method. Experiments have confirmed that the device is capable of delivering reproducible quantities of the vapour associated with an explosive substance. Device V2a, in which the substance is contained in a cylinder, produced consistently higher levels of target vapour than device V2b. The day-to-day stability of emissions from the probe as indicated by the standard deviation was good. Tests with explosives showed a linear relationship between sample time and mass output for shorter sampling time (60 seconds or less) but at longer times the emissions reduced.