Abstract:
Embodiments of the invention provide novel, industrially applicable, and non-obvious apparatus and methods for automatically, routinely, and accurately calibrating a trace detection portal. Embodiments of the apparatus include a calibrant container; a substance (or substances) uniquely identifiable by a trace detection portal as a calibrant; unique placement of the calibrant container&#39;s outlet relative to a substance collection port of a sample collection chamber; and/or computer executable instructions that, when executed by a computer processor, cause a consistent release of a measured amount of calibrant into the sample collection chamber upon command and/or at pre-determined time intervals.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The field of the invention relates to threat detection systems generally and, more particularly, to an apparatus and method for calibrating a trace detection portal. 
         [0003]    2. Description of Related Art 
         [0004]    Extant threat detection systems check persons and objects for traces of substances of interest, such as narcotics and explosives. Such systems operate on the basis that trace amounts of substances of interest tend to be transferred to the body of a person who handles them, and from the person&#39;s body to any article the person&#39;s body may touch. Attempts have been made to test persons without physically touching them, but articles such as suitcases and handbags are tested by swiping them with a small piece of material that is then inserted into a known type of threat detection apparatus, which tests for the presence of the substance(s) of interest. 
         [0005]    A trace detection portal is a known type of threat detection system into and/or through which a person can walk. U.S. Pat. No. 6,073,499 (the “&#39;499 patent”) illustrates a known type of trace detection portal. A trace detection portal, such as the one described in the &#39;499 patent, operates based on the principle that a person&#39;s body heats the boundary of air surrounding it, and that the heated air, being less dense than ambient air further away from the body, flows upwardly to create a thermal plume about the body. The rising thermal plume entrains particles comprising a substance of interest present on the person&#39;s body and carries them up and away from the body. A fan or other airflow generator positioned in a portion of the trace detection portal above the person operates at a speed that approximates the airflow rate of the rising thermal plume. The fan thus directs the thermal plume to a detector without drawing significant volumes of ambient air into the detector. Consequently, a significant concentration of particles comprising the substance of interest is created. 
         [0006]    Some types of trace detection portals route the thermal plume directly to a detector for analysis. Other types first route the thermal plume through a trap that collects particles of interest from the thermal plume. The trap is then inserted within a desorber. Within the desorber, the trap is heated rapidly to temperatures of about 200 degrees Celsius to desorb and volatize the trapped particles comprising the substance of interest collected from the thermal plume. Clean air is injected into the desorber at a low rate and suction is applied to draw the clean air and the particles on the trap into the detector. The detector then detects and identifies the presence of the particles comprising the substance of interest. The trap will remain in the desorber until it is time for the next sample collection. The trap is then removed from the desorber, and repositioned across the airflow inlet at the upper portion of the sample collection chamber and rapidly cooled in preparation for the next sample collection. U.S. Patent Application Publication No.: 2004/0131503 illustrates such a known type of desorber and trap. 
         [0007]    Calibrating a trace detection portal to accurately and consistently test for particles comprising a substance of interest is difficult, and typically involves misting differing amounts of a calibrant into the trace detection portal&#39;s sample collection chamber by hand. For example, calibrant can be delivered into the portal detection chamber using a hand-held container such as a pistol-grip sprayer, aerosol spray can, nasal spay bottle, etc. Delivering an effluence of calibrant into the portal detection chamber in this manner is imprecise for several reasons. First, the amounts of calibrant released will differ from person to person depending on how long each person actuates the hand-held container. Second, if the calibrant is released too far from the upper portion of the detection chamber, ambient airflow turbulence will reduce the concentration too much for calibration purposes. Other challenges include ensuring a trace detection portal is calibrated on a routine basis, for example, at the beginning of each shift, which may be once every eight hours of usage that the trace detection portal is used. Non-calibration can create regular periods during which the portal cannot be used. Such periods decrease the trace detection portal&#39;s throughput. 
         [0008]    Long-felt needs thus exist for: an apparatus and method that can calibrate a trace detection portal automatically, simply, and accurately; an automatic and accurate calibration apparatus that can be easily retrofitted to existing trace portal detection systems; and a calibration apparatus and method for consistently dispersing a predetermined amount of calibrant into a sample collection chamber at a predetermined distance from a calibrant collection area of the trace detection portal. 
       SUMMARY OF THE INVENTION 
       [0009]    Embodiments of the invention disclosed herein overcome the disadvantages associated with the related art and meet the needs discussed above by providing novel, industrially applicable, and non-obvious apparatus and methods for automatically, simply, and accurately calibrating a trace detection portal. Embodiments of the apparatus include a calibrant container; a substance (or substances) uniquely identifiable by a trace detection portal as a calibrant; unique placement of the calibrant container&#39;s outlet relative to a substance collection port of a sample collection chamber; and/or computer executable instructions that, when executed by a computer processor, cause a consistent, repeatable release of a predetermined amount of calibrant into the sample collection chamber upon command and/or at pre-determined time intervals. 
         [0010]    Newly manufactured or retrofitted trace detection portals comprising an embodiment of the claimed calibration apparatus and/or using an embodiment of the claimed calibration method may be installed in airports, courthouses, schools, military installations, and any other government, commercial, industrial, or private venue where it is desired to detect threats posed by various types of explosives and/or other substances. 
         [0011]    A technical effect afforded by an embodiment of the invention is the output from a component of the trace detection portal of a signal that causes calibrant to be expelled from the calibrant container and into a trace detection portal&#39;s sample collection chamber. Another technical effect afforded by an embodiment of the invention is the output from a component of the trace detection portal of a signal that causes the trace detection portal&#39;s detector to perform a calibration routine upon detecting and uniquely identifying a substance of interest as a calibrant. Yet another technical effect afforded by an embodiment of the invention is the output from a component of the trace detection portal of a signal that causes a display panel and/or other communication means to indicate the trace detection portal is ready to process a person. 
         [0012]    Broadly, an embodiment of the invention includes an apparatus for calibrating a trace detection portal. The apparatus may include a calibrant container having an outlet configured to couple with a sample collection chamber of the trace detection portal. Additional components that may be included in the apparatus described above include means for releasably containing a calibrant, and means for coupling the means for releasably containing a calibrant with a sample collection chamber of the trace detection portal. Means for initiating a release of a predetermined amount of the calibrant into the sample collection chamber, and means for automatically self-calibrating one or more of its components upon detecting and uniquely identifying the calibrant may also be components of the above-described apparatus for calibrating a trace detection portal. 
         [0013]    Broadly, another embodiment of the invention provides a method for calibrating a trace detection portal. The method may include the step of providing a calibrant container having an outlet, and the step of releasably storing a calibrant within the calibrant container. The calibrant is a substance the trace detection portal is configured to detect and uniquely identify, and which (upon detection and identification by the trace detection portal) causes one or more components of the trace detection portal to automatically self-calibrate. Self-calibration of a trace detection portal component may include automatically performing one or more steps designed to improve and/or restore the component&#39;s operation and/or sensing accuracy. 
         [0014]    Additional method steps that may be included as part of the method described above, include the step of receiving a signal from a control means coupled with the trace detection portal; and the step of releasing a predetermined amount of a substance from a calibrant container into the sample collection chamber in response to the signal received from the control means. Other steps may include detecting, analyzing, and identifying the substance. Yet another step may include automatically initiating a self-calibration of one or more components of the trace detection portal upon identifying the substance as a calibrant. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The above and other aspects of the various embodiments of the claimed invention will become more apparent when the following detailed description is considered together with the accompanying drawings in which: 
           [0016]      FIG. 1  is a front, perspective, cut-away view of a trace detection portal fitted or retrofitted to include an embodiment of a calibration apparatus; 
           [0017]      FIG. 2  is an enlarged, cross-sectional view of an upper portion of the trace detection portal of  FIG. 1  more clearly depicting an embodiment of the calibration apparatus; 
           [0018]      FIG. 3  is a flowchart illustrating an embodiment of a method of operating an embodiment of the calibration apparatus; 
           [0019]      FIG. 4  is another cross-sectional view of the upper portion of the trace detection portal of  FIG. 1  more clearly depicting another embodiment of the calibration apparatus; 
           [0020]      FIG. 5  is another flowchart illustrating an embodiment of a method of fitting or retrofitting an embodiment of the calibration apparatus to a newly manufactured or existing trace detection portal; and 
           [0021]      FIG. 6  is a perspective view of an embodiment of a calibrant container and an embodiment of a bracket used to detachably or fixedly couple the calibrant container to a component of the trace detection portal of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    Reference is made herein to the accompanying drawings briefly described above, which show by way of illustration various embodiments of the claimed invention. Persons of ordinary skill in the above-referenced technological field will recognize that other embodiments may be utilized, and that structural, electrical, and procedural changes may be made without departing from the scope of the claimed invention. As used throughout all of the specification, figures, and claims, the singular (illustratively, “substance”) includes the plural (illustratively, “substances”), and the plural includes the singular. 
         [0023]      FIG. 1  is a front, perspective, cut-away view of an exemplary trace detection portal  100  originally fitted (or retrofitted) with one or more components of an embodiment of a calibration apparatus  150 .  FIG. 2  is an enlarged cross-sectional view of an upper portion of the trace detection portal  100  further illustrating the calibration apparatus  150  of  FIG. 1 . 
         [0024]    Referring to  FIGS. 1 and 2 , an embodiment of the trace detection portal  100  has two vertical sidewalls  112  and  114  that are spaced apart from each other at a distance “W” to form a sample collection chamber  116  through which a person may pass. The sidewalls  112  and  114  each have a length “L” that is sufficient to bracket the width or depth of a person standing in the center of the sample collection chamber  116 . A ceiling  118 , which is disposed at a height “H” above the floor or other surface that supports the trace detection portal  100 , also forms part of the sample collection chamber  116 . The height “H” of the ceiling  188  is sufficient to permit persons to pass easily into and through the sample collection chamber  116 . 
         [0025]    Additionally, the upper and lower portions of the trace detection portal  100  are defined by a horizontal axis (e.g., a horizontal plane)  105  that passes through a center point  106  of the trace detection portal  100 . In an embodiment, the upper portion of the trace detection portal  100  is at or above the axis  105 ; and the lower portion of the trace detection portal  100  is at or below the axis  105 . The upper portion of the sample collection chamber  116  gradually tapers from wide dimensions proximate the axis  105  to narrow dimensions proximate the sample collection port  120 . In an embodiment, the sample collection port  120  is a hollow conduit extending from an interior upper surface of the sample collection chamber  116  into (and/or through) the ceiling  118  of the trace detection portal  100 . 
         [0026]    The sample collection port  120  collects and condenses the rising thermal plume of a person present within the sample collection chamber  116 . A movable trap  122  provided within the smaller cross-sectional dimensions of the sample collection port  120  collects particles comprising a substance of interest that are entrained in the rising thermal plume. Non-limiting examples of articles comprising a substance of interest include particles, airborne trace chemicals in vapor form and skin flakes having adsorbed compounds thereon, among others. 
         [0027]    A fan  124  provided at the upper portion of the sample collection port  120  rotates at a speed required to draw air in at about the same flow rate as the rising thermal plume. The suction provided by the fan  124  directs the thermal plume through the trap  122 . A conveyor  126  provided on a substrate  102  moves the trap  122  into and out of a desorber  128 , which is also provided on the substrate  102 . The desorber  128  rapidly heats the inserted trap  122  to about 200 degrees Celsius to free the entrapped particles of interest. Contemporaneously, clean air injected into the desorber  128  is suctioned to draw the vaporized particles comprising a substance of interest into a detector  130 , which detects and identifies the particles comprising a substance of interest. 
         [0028]    In the embodiment shown in  FIGS. 1 and 2 , a calibration apparatus  150  is coupled with substrate  102 , which has opposing first and second surfaces. A conveyor  126  and the desorber  128  may be disposed on the first surface of the substrate  102 , and the detector  130  may be supported on the second surface of the substrate  102 . A hollow conduit may link the desorber  128  to the detector  130 . Particles comprising a substance of interest may be aspirated from the desorber  128 , through the hollow conduit, and into the detector  130  for analysis. 
         [0029]    An embodiment of the calibration apparatus  150  may comprise a calibrant container  160  that releasably contains a substance the detector  130  is configured to uniquely recognize as a calibrant. The calibration apparatus  150  may further comprise an actuator  170  coupled with a calibrant container  160  and a control means  180  configured to operate the actuator  170 . In an embodiment, the actuator  170  may include an air pump  196 , a first solenoid valve  185 , a second solenoid valve  180 , and/or conduits  181 ,  182 , and  183 . The actuator  170  may be configured to discharge a predetermined amount of calibrant into the trace detection portal&#39;s sample collection chamber  116  in response to a signal generated by the control means  180  and relayed to the actuator  170  via a wired or wireless communications link  190 . A power source  195  provides electrical power to the control means  180 , the first solenoid valve  185 , the second solenoid valve  186 , the air pump  196 , the conveyor  126 , the desorber  128 , the detector  130 , and/or other components of the trace detection portal  100 . The power source  195  may be a generator, a battery, a photovoltaic cell, a hydrogen fuel cell, and the like. 
         [0030]    In an embodiment, the conduit  181  connects the air pump  196  with the first solenoid valve  185 . Additionally, the conduit  182  connects the first solenoid valve  185  with an inlet of a calibrant container  160 . The conduit  183  connects an outlet of a calibrant container  160  with the second solenoid valve  186  and with the sample collection chamber  116 , and the conduit  184  connects the first solenoid valve  185  with the desorber  128 . Any suitable type of flexible or inflexible conduit may be used for each of conduit  181 ,  182 ,  183 , and  184 . Non-limiting examples of suitable conduit materials include metal, metal alloys, glass, plastic, polymers, and the like. 
         [0031]    An end of the conduit  183  (or, alternatively, the outlet of the calibrant container) that connects with the sample collection chamber  116  may be suitably positioned at a predetermined distance from the trap  122  that permits the trap  122  to consistently collect all or a majority of the predetermined amount of calibrant that is released from the calibrant container  160  and infused into the sample collection chamber  116 . The exact placement of the conduit  183  (or the outlet of the calibrant container  160 ) will vary depending on a number of factors, including, but not limited to: the size of the sample collection chamber  116 , the configuration of the sample collection port  120 , whether the sample collection chamber  116  is fully or partially enclosed, and the like. 
         [0032]    The control means  180  is coupled with one or more components of the apparatus  150  described above. Non-limiting examples of the control means  180  include a computer subsystem  189 , a computer input means  188 , and a button, toggle, or slider switch  187 , among others. The computer subsystem  189  may comprise a data bus that links a computer processor with a memory, a transceiver or modem, and the computer input means  188 . The computer input means  188  may include, but is not limited to, a computer keyboard, a computer mouse, a computer touch screen, and the like. 
         [0033]    In the embodiment illustratively shown in  FIGS. 1 and 2 , each of solenoid valves  185 , 186  occupies a first default closed position, which prevents hot air from the air pump  196  from entering the inlet of a calibrant container  160  and prevents calibrant from reaching the sample collection chamber  116 . Each of solenoid valves  185 ,  186  moves to a second open position in response to a signal generated by the control means  180 . 
         [0034]    When opened, the solenoid valves  185 , 186  allow a predetermined amount of heated air and calibrant to infuse the sample collection chamber  116 . Inside the sample collection chamber  116 , at least the calibrant is drawn upwards into the sample collection port  120  by the fan  124 . Particles comprising a substance of interest that forms the calibrant are captured and concentrated by the trap  122 . Conveyor  126  inserts the trap  122  into the desorber  128 , which rapidly heats the trap  122  to free the particles comprising the substance of interest. Clean air provided by the air pump  196  via conduit  181  and  184  is injected into the desorber  128 . The clean air and the particles of interest freed from the trap  122  are then aspirated into the detector  130 . 
         [0035]    In an embodiment, the detector  130  is an ion mobility spectrometer (“IMS”), but other types of detectors known to a skilled artisan may also be used. (i.e., ion trap mobility spectrometer (“ITMS”), mass spectrometer, etc). Within an IMS detector  130 , the particles comprising the substance of interest may be ionized (via a weak radioactive source or other means known to a skilled artisan) and caused to drift through a weak electric field. The time a particle takes to drift through the weak electric field is known as “time of flight.” Experiments have shown that particle time of flight is a distinct “fingerprint” that enables the detector  130  to uniquely identify many different kinds of substances of interest. 
         [0036]    In an embodiment, the substance of interest may be a calibrant releasably contained within the calibrant container  160 . The calibrant may have a unique, predetermined “time of flight” different from the “times of flight” associated with other substances of interest, which may include, but are not limited to, explosives and narcotics, among others. In an embodiment, when an IMS detector  130  detects the “time of flight” uniquely associated with the calibrant, a calibration signal may be output to one or more components of the trace detection portal  100 . The calibration signal may cause such components to automatically self-calibrate. One of these components may be an IMS detector  130 , which may automatically self-calibrate using one or more peak values from (current) IMS spectra data. 
         [0037]      FIG. 3  is a flowchart illustrating an embodiment of a method  300  (hereinafter, “the method  300 ”) of calibrating a trace detection portal  100 . It will be appreciated that the method steps shown in  FIG. 3  and described herein may be performed in any suitable order, and that variants of the method  300  may include one or more steps in addition to the ones herein shown and described. 
         [0038]    Referring to  FIGS. 1 ,  2 , and  3 , the method  300  is initiated by transmitting a signal from the control means  180  to the calibration apparatus  160  (block  301 ). As previously described, the control means  180  may generate and transmit this signal. The method  300  further comprises releasing a predetermined amount of a substance contained in a calibrant container  160  into the sample collection chamber  116  (block  303 ). As noted above, this step may be accomplished by opening both solenoid valves  185 ,  186 . The method  300  further comprises analyzing the measured amount of substance released into the sample collection chamber  116  (block  305 ). As previously noted, this step may be accomplished using the detector  130  and/or a trap  122  located in the sample collection port  120 . The method  300  yet further comprises identifying the measured amount of substance as a calibrant (block  307 ). As mentioned above, this step may be accomplished in an embodiment using ion mobility spectrometry (or other suitable detection method known to a skilled artisan), and/or by comparing the analysis data with the data on the above-referenced threat and/or calibrant lists. The method  300  further comprises automatically initiating a self-calibration of one or more components of the trace detection portal in response to the identification of the substance as a calibrant (block  309 ). As described above, this step may further include outputting a calibration signal to one or more components of the trace detection portal  100 . One such component may be the detector  130 . 
         [0039]    The method  300  further comprises generating a “clear” signal if the components of the trace detection portal  100  are each functioning properly (block  311 ). Alternatively, the method  300  further comprises generating a “fault” signal if one or more components of the trace detection portal  100  are malfunctioning (block  313 ). If the “clear” signal has been generated, the method  300  further comprises indicating via a display panel, or other communication means, that the trace detection portal  100  is ready to process persons (block  317 ). If the “fault” signal has been generated, the method  300  further comprises resetting and/or repairing the malfunctioning component(s) (block  315 ). Following the reset and/or repair, the method  300  may loop back to the step of transmitting a signal to the calibration apparatus  150  (block  301 ) and proceed as described above. If the trace detection portal  100  has been indicated to be ready to process a person, the method  300  may optionally comprise the step of setting a timekeeping device to transmit the signal to the calibration apparatus after the expiration of a predetermined period of time (block  319 ). After the timekeeping device is set, the method  300  may loop back to the step of transmitting the signal to the calibration apparatus (block  301 ). Alternatively, the method  300  may end after performing the steps represented by either (block  317 ) or (block  319 ). 
         [0040]      FIG. 4  is a cross-sectional diagram of an upper portion of the trace detection portal  100  illustrating another embodiment of a calibration apparatus  450  in which a calibrant container  460  containing a calibrant in an initial liquid, vapor, or aerosol state is insulated from receiving heat generated by the desorber  128 . The heating effects of the desorber  128  may be minimized or eliminated by locating the calibration apparatus  450  away from the desorber  128 , as illustratively shown in  FIG. 4 . 
         [0041]    In an embodiment where the calibration apparatus  450  is positioned near the desorber  128 , insulation may be provided by an insulator disposed between the calibration apparatus and the desorber  128 . The insulator may be air disposed between the calibrant container  460  and the substrate  102  and/or the desorber  128 . Alternatively, the insulator may be any suitable material having heat-insulative properties. Non-limiting examples of suitable insulator materials include fiberglass, foam, ceramic fibers, microporous insulation, high temperature cloth, insulative laminates, insulative woven tapes, high temperature paper/felt (e.g., a blend of fibers, binders, and additives that can resist or contain heat), and the like. Additionally (or alternatively), a calibrant container  460  may be formed of plastic or another material having heat-insulative properties. 
         [0042]    Referring to  FIGS. 1 ,  2 , and  4 , the calibration apparatus  450  also includes an actuator  470 . In an embodiment, the actuator  470  is a plunger/piston that is directly coupled with an inlet of a calibrant container  460 . The actuator  470  may also be coupled with the control means  180  via wired or wireless communication link  190 , and optionally with the power source  195 . In response to a signal received from the control means  180 , the actuator  470  operates to discharge a predetermined amount of calibrant into the sample collection chamber  116  for collection by the trap  122  and analysis by the detector  130 . 
         [0043]    In an embodiment, the control means  180  may be configured to initiate and execute a calibration of the trace detection portal upon receipt of a signal from a timekeeping device. The timekeeping device may be configured to automatically transmit the signal to the calibration apparatus upon expiration of a predetermined period-of-time. 
         [0044]    Referring to  FIGS. 1 ,  2 , and  4 , each of a calibrant containers  160 ,  460  are formed of metal, plastic, or other suitable material, and are either single-use, disposable, or rechargeable. The phrase “single-use container” refers to a calibrant container  160 , 460 , the contents of which are designed to last the operational lifetime of the trace detection portal  100  in which it is used without replacement. The phrase “disposable container” refers to a calibrant container  160 , 460  designed to be thrown away after being emptied of its contents. The phrase “rechargeable container” refers to a calibrant container  160 , 460  designed to be refilled with a calibrant after being emptied of its contents. In an embodiment, a single-use container may be fixedly attached to the substrate  102 . In another embodiment, either a disposable container or a rechargeable container may be detachably coupled with the substrate  102 . 
         [0045]      FIG. 5  is another flowchart illustrating an embodiment of a method  500  (hereinafter, “the method  500 ”) of fitting or retrofitting to a trace detection portal  100  an embodiment of the claimed calibration apparatus  150 , 450  shown in  FIGS. 1 ,  2 , and  4 . It will be appreciated that the method steps shown in  FIG. 5  and described herein may be performed in any suitable order, and that variants of the method  500  may include one or more steps in addition to the ones herein shown and described. 
         [0046]    Referring to  FIGS. 1 ,  2 ,  4 , and  5 , a first step of the method  500  may be providing a calibrant container  160 , 460  (block  501 ). The method  500  may further comprise releasably storing a calibrant within the calibrant container  160 , 460  (block  503 ). The method  500  may further comprise configuring a trace detection portal  100  to detect and identify a calibrant and to automatically self-calibrate upon identification of the calibrant (block  505 ). The method  500  may further comprise detachably or fixedly coupling the calibrant container  160 , 460  with the sample collection chamber  116  of the trace detection portal  100  (block  507 ). The method  500  may further comprise insulating a calibrant container  160 , 460  from heat generated by a component of the trace detection portal  100  (block  509 ). Alternatively, the method  500  may further comprise thermally connecting a calibrant container  160 , 460  to absorb heat generated by a component of the trace detection portal  100  (block  511 ). After performing either the step represented by block  509  or by block  511 , the method  500  may end (block  515 ) or may optionally perform the steps represented by blocks  301 ,  303 ,  305 ,  307 ,  309 ,  311 ,  313 ,  315 ,  317 , and  319  of method  300 , as shown in  FIG. 3  and described above. 
         [0047]      FIG. 6  is a diagram illustrating a quick-release bracket  670  that may be used to detachably couple a calibrant container  660  with a substrate  102  of a trace detection portal. Referring to  FIGS. 1 ,  2 ,  4 , and  6 , during manufacture of a new trace detection portal  100 , for example, the bracket  670  may be integrally formed as part of the substrate  102  or formed separately from the substrate  102  and attached thereto using a fastener. Similarly, in an embodiment of the invention directed to retrofitting a previously manufactured trace detection portal  100 , the bracket  670  may be attached to the substrate  102  using a fastener. Non-limiting examples of fasteners include: clips, screws, bolts, nails, adhesives, and the like. 
         [0048]    In  FIG. 6 , the bracket  670  is illustratively depicted as a quick-release bracket that has a “c” shape with opposing ends  672 , 674  separated by a gap. The quick-release bracket  670  and a calibrant container  660  may take any suitable shape and/or configuration, and are not limited to those illustratively depicted in  FIG. 6 . For example, the bracket  670  may comprise a first strip of hook-and-loop material adhered to the substrate  102  and a second opposing strip of hook-and-loop material adhered to an exterior portion of a calibrant container  660 . In another embodiment, the bracket  670  may comprise a half-cylinder or a four-sided box attached to the substrate  102 , and into which a calibrant container  660  removably fits. It will be appreciated, however, that other variants of the bracket  670  and a calibrant container  660  are possible. 
         [0049]    As shown in  FIG. 6 , an embodiment of a calibrant container  660  having a generally cylindrical shape with an inlet  662  and an outlet  664  formed at opposing ends thereof is gripped by the bracket  670 . A calibrant container  660  may be inserted within the bracket  670  by positioning a calibrant container  660  adjacent the gap between the opposing ends  672 , 674  of the bracket  670  and compressing a calibrant container  660  until the opposing ends  672 , 674  spread apart and allow a calibrant container  660  to enter the interior of the bracket  670 . A calibrant container  660  may be detached from the bracket  670  by pulling a calibrant container  670  towards the gap between the opposing ends  672 , 674  of the bracket  670  until the opposing ends  672 , 674  spread apart and allow a calibrant container  660  to exit the bracket  670 . 
         [0050]    Embodiments of the invention illustrated in the appended drawings and illustratively described above position a detector  130 , a sample collection port  120  coupled with the detector, and a calibration apparatus  150  in an upper portion of a trace detection portal  100 . In an embodiment, the upper portion of a trace detection portal includes regions of the trace detection portal that are at or above a horizontal plane (e.g., a plane that substantially parallels the floor or support surface on which the trace detection portal is placed) that passes through a center point of the trace detection portal. Alternative embodiments of the invention, however, position the detector  130  (and/or a sample collection port  120  coupled with the detector  130 ) and/or the calibration apparatus  150  in a lower portion of the trace detection portal  100 . In an embodiment, the lower portion of the trace detection portal  100  includes regions that are at or below the horizontal plane that passes through the center point of the trace detection portal. In such alternative embodiments, for example, the detector  130 , a sample collection port  120  coupled with the detector  130 , and/or the calibration apparatus  150  may each be located in the floor or lower sidewalls of the trace detection portal  100 . 
         [0051]    A detailed description of various embodiments of the invention has been provided; however, modifications within the scope of the invention will be apparent to persons having ordinary skill in the above-referenced technological field. Such persons will appreciate that features described with respect to one embodiment may be applied to other embodiments. Thus, the scope of the invention is to be properly construed with reference to the following claims.