Abstract:
A device for detecting human body odors produced from ammonia and amino acids—chemicals naturally excreted through the skin and sweat glands. Unless eliminated, such odors can alert game animals to a hunter&#39;s presence. Worn on the exterior of odor-absorbing clothing, the device includes both a packet and an indicator chemical sensitive to extremely low concentrations of nitrogen-containing compounds. The packet defines first and second openings which, in use, are directed away from and toward the wearer&#39;s body, respectively. Affixed to the packet, a transparent tape forms an airtight window through which one can continually view the indicator chemical, held in place within the first opening by the tape&#39;s adhesive backing. Accessible only to substances which pass through the wearer&#39;s clothing and then into the packet&#39;s interior via the second opening, the indicator chemical undergoes a permanent color change, once odor-producing chemicals begin to break through the clothing.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a non-provisional application of the earlier filed provisional application Ser. No. 61/135,758, filed Jul. 23, 2008, and claims the benefit of the priority of the filing date of Jul. 23, 2008, pursuant to 35 U.S.C. Sec. 119(e). 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to devices for indicating the presence of airborne chemicals and especially to such devices which change color when exposed to compounds present in human body odor. 
     BACKGROUND OF THE INVENTION 
     It is unavoidable that humans emanate odor. This odor is produced by a chemical mixture, excreted through the skin and sweat glands, which contains ammonia and amino acids. It is well known that wild game animals have a keenly developed sense of smell and can readily distinguish odors that are not indigenous to their natural habitat. Hunters seeking to get into close proximity to game animals have sometimes tried special clothing in an attempt to either mask or absorb their natural body odor. In the related prior art, Sesselmann, U.S. Pat. No. 5,539,930, discloses a system of special clothing for hunters designed to absorb body odor. Fore, U.S. Pat. No. 5,891,391, discloses a clothing deodorizer for deer hunters. 
     Devices designed for personal protection against environmental hazards caused by ammonia fumes are also well known in the prior art. However, none of these devices is suitable for detecting gaseous ammonia when it is present in only parts per billion, which is the order of magnitude of those concentrations of ammonia found in human body odor. The American Gas Co., for example, markets ammonia detectors used for personal protection. When exposed to gaseous ammonia in the sensitivity range of 25 ppm for five minutes, the indicator chemicals in them change color from yellow to blue. However, when American Gas &amp; Chemical Co. detectors were tested to see if they could be used to detect ammonia and amino acids at the concentrations at which they are found in human body odors, no change of color occurred. Further, after these detectors had been exposed to high concentrations of ammonia which changed the color of their indicator chemicals to blue and after they were then removed from these high concentrations, their color changed back to yellow. 
     Like the indicator chemicals in the American Gas &amp; Chemical Co. detectors, those used in the paint or coating compositions disclosed by Mallow et al., U.S. Pat. Nos. 5,183,763 and 5,322,797 (hereinafter “Mallow”), when incorporated into such a detector, have proven themselves to be useful only for indicating the presence of ammonia and/or amino acid vapors in relatively high concentrations. 
     Indeed, this situation exists, notwithstanding Mallow&#39;s teaching that his chemical composition, when applied to selected surfaces as a paint, can serve as a passive detector for extremely low concentrations of vapor or liquid reactants, such as ammonia. 
     Specifically, tests were done by the applicant on detectors in which one of Mallow&#39;s compositions served as the indicator chemical, with this composition being sealed within the detector in such a way that it could not be activated by airborne chemicals from the atmosphere/outside environment. Rather, because of the manner in which the detector was attached to the test subject&#39;s body, the composition could only be activated by compounds released through the wearer&#39;s skin, thereby limiting the exposure of Mallow&#39;s composition to the constituents of human body odor. These tests showed no color changes in Mallow&#39;s compositions when they were exposed, for intervals of up to four hours at a time, to ammonia and amino acids at the concentrations at which they are found in human body odor. 
     Moreover, each of Mallow&#39;s compositions, once it has changed color as a result of exposure to sufficiently high concentrations of ammonia or other nitrogen-type compounds, is known to revert back to its original color (e.g., yellow) after a period of time. Consequently, valuable information may be lost before a user realizes that a spike in the release of ammonia or the like has occurred. 
     SUMMARY OF THE INVENTION 
     I have discovered when testing Mallow&#39;s compositions that not only did they fail to change color when they were exposed to the concentrations of odor-producing chemicals which are found in human body odor but also two of the solvents (butyl acetate and toluene) which Mallow included in each of his compositions attacked certain transparent, nonabsorbent polymer films, otherwise suitable for use as window material in a visual detector, and actually dissolved these films. 
     I have further discovered that the failure of Mallow&#39;s compositions to change color is caused, in part, by the presence of ethyl cellulose which functions, in each of them, as a combination water insoluble binder and highly permeable membrane through which odor-producing gases, such as ammonia vapor, can pass. Unfortunately, the ethyl cellulose also acts to coat amorphous silica, a substrate for the dye bromophenol blue in these compositions, and in the process inhibits reaction between the odor-producing gases and the indicator chemical. Indeed, this reaction is slowed to the point that Mallow&#39;s compositions cannot be used as the indicator chemical in an odor detector in a hunting environment. 
     The present invention solves these problems by providing an improved detector which includes an indicator chemical consisting of a dry powder which reacts quickly, undergoing a color change, when it is exposed to nitrogen-containing compounds at extremely low concentrations, the dry powder being held in place within a detector packet which, when affixed to the outside of a hunter&#39;s clothing properly worn, is capable of trapping, with its indicator chemical, a portion of the odor-producing gases escaping through the hunter&#39;s clothing, without interference from such gases and/or other nitrogen-containing compounds generated by outside sources. 
     More specifically, there is provided a dry reactive chemical powder and a two-sided detector packet for holding it, the detector packet having an outer face which defines a first opening, a window fabricated of a transparent, nonabsorbent tape stretched across the first opening and affixed to the outer face forming an airtight seal with it, and an inner face which defines a through opening. The two sides of the detector packet are joined together along their contiguous outer edges so as to form a continuous airtight seal and define a centrally-located void fluidly connected to the through opening. Mounted within the detector packet is a thin layer, preferably measuring at most 1/10,000th inch in thickness, of the dry reactive chemical powder. This thin layer is held in place, behind the window, by the adhesive backing of the tape which is stretched across the first opening-and is visible through the window. A nonhydroscopic filter media sheet permeable to gaseous, odor-producing chemicals, also mounted within the detector packet, covers the thin layer of dry reactive chemical powder in such a way that this thin layer is juxtaposed between the transparent, nonabsorbent tape and the filter media sheet and is accessible to such chemicals diffusing through the filter media sheet from the centrally-located void. 
     The dry reactive chemical powder itself is prepared by blending together, so as to form a slurry, only three substances: the solvent acetone, the dye bromophenol blue, and amorphous silica, the latter functioning both as a substrate for the dye and as a dye sensitizer, and then evaporating off the acetone, leaving, as a dry residue, a yellow powder, ready for use as an indicator chemical which permanently changes color whenever it adsorbs an extremely low threshold amount of gaseous ammonia or amino acids. 
     Accordingly, it is an advantageous feature of the present invention that an odor detector is provided which, when its inner face is adhesively affixed to the outside surface of odor eliminating clothing for hunters such as that developed by Sesselmann, gives a permanent visual indication that the concentrations of odor-producing chemicals escaping through said clothing are sufficiently high that the user&#39;s human body odor might be detectable by game animals. 
     A related advantageous feature of the invention is that an odor detector constructed in accordance with the present invention can be fabricated from relatively low cost materials, making practicable a “one time use only” visual detector which, once its indicator chemical has been activated to change its color, does not revert to its original color, thereby creating a permanent record which a hunter can use to decide whether sufficient human body odor has escaped from his clothing that he needs to take preventive action. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a partially finished frame of the detector packet according to the present invention, which shows a transparent, nonabsorbent tape affixed to an exterior surface of the frame and covering one of its openings; 
         FIG. 2  is a plan view of the partially finished frame according to  FIG. 1 , which shows the frame&#39;s other side and a dry reactive chemical powder added thereto, the latter being shown as a thin layer adhering to the adhesive backing side of the transparent, nonabsorbent tape; 
         FIG. 3  is a plan view of the partially finished frame according to  FIG. 1 , which shows the frame&#39;s other side and a filter media sheet added thereto, the latter covering the same opening as does the transparent, nonabsorbent tape but, unlike it, being affixed to the interior surface of the frame; the filter media sheet, in this view, obscuring the thin layer of dry reactive chemical powder which is juxtaposed between the filter media sheet and the tape; 
         FIG. 4  is a plan view of the two-sided detector packet according to the present invention, which shows its outer face and the opening therein sealed by the transparent, nonabsorbent tape, the tape forming a clear window through which the dry reactive chemical powder adhering to the tape&#39;s adhesive backing is visible; the finished frame having been constructed by folding the partially finished frame according to  FIG. 2  so as to align the two openings in it; 
         FIG. 5  is a plan view of the two-sided detector packet according to the present invention, which shows its inner face and both a two-sided tape and a protective backing, the two-sided tape which is affixed to the frame being sandwiched between the frame and the protective backing, the two-sided tape and the protective backing being peeled back to expose a corner of the frame and a portion of a perforated plug formed in the two-sided tape, respectively; and 
         FIG. 6  is a transverse cross-section, on an enlarged scale, taken along line  6 - 6  of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, a body odor detection device according to the present invention is indicated generally by the reference numeral  10 . The device  10  includes a generally planar dry chemistry unit  11  and a frame  21  which supports the chemistry unit. 
     The chemistry unit  11  comprises a strip of transparent, nonabsorbent tape  13 , a thin layer of a dry reactive chemical powder  12 , and at least one sheet  15  of a non-hydroscopic filter media. Affixed to the exterior surface of the frame  21  and forming a continuous airtight seal with a portion thereof which defines a view aperture  22 , the tape strip  13  covers the latter opening. Partially embedded within an adhesive coating  14  backing the tape  13 , the dry reactive chemical powder  12  is held in place within a window well surrounded by the peripheral edge of the opening  22  and a thin annular ring  28  which is mounted on the interior surface of the frame  21  ( FIGS. 1 ,  2  and  6 ). Most of the particles of the dry reactive chemical powder  12  not adhered to the adhesive coating  14  are kept within the window well by the filtering action of the sheet  15 ; the latter element, generally centered on the view aperture  22 , is bonded by adhesive to the interior surface of the frame  21  ( FIG. 3 ). 
     Unfinished, the frame  21 , which is fabricated from a sheet of pressed paper, plastic, metal or the like, resembles, in its shape, a pair of side-by-side rectangular forms from each of which a generally circular hole  22 ,  23  has been cut out ( FIG. 1 ). Once the chemistry unit  11  is in place on the unfinished frame  21 , it is then folded in such a way that the centers of the view aperture  22  and through opening  23 , which is preferably about ⅛th inch greater in diameter than the view aperture, are generally aligned ( FIGS. 4 and 5 ). Simultaneously, as the frame  21  is being so folded, the two newly-formed sides of its interior surface, precoated with adhesive, are pressed together, sealing their edges. 
     Assembly of the two-sided detector packet  10  is then complete except for the application, to the packet&#39;s inner face  30 , of backing material such as a two-sided tape  31  with adhesive coatings  32 ,  33  and a protective covering  35 . Prior to their being applied to the packet  10 , both the two-sided tape  31  and the protective covering  35  are cut to size so that they can cover substantially the entire surface area of the inner face  30 . A circular perforation  36  positioned in such a way that it can be centered over the through opening  23  and having a ⅛th inch greater diameter than the latter opening is also punched into the tape  31 , forming a plug  34  which can be disengaged from the remainder of this tape ( FIG. 5 ). 
     Immediately prior to use, the protective covering  35  is peeled off in order to expose the outer adhesive coating  33  so that the detector packet  10  can be sealed to a hunter&#39;s clothes. The orientation of the detector packet  10  is then such that the transparent, nonabsorbent tape  13  through which the dry reactive chemical powder  12  is visible faces away from the user. 
     During the process of peeling off the protective covering  35 , the plug  34  stays attached to it, leaving the remainder of the two-sided tape  31  affixed to the inner face  30  and uncovering the through opening  23  so that odor-producing chemicals which escape from the outer surface of the hunter&#39;s clothes can diffuse into the packet  10  and come into contact with the dry chemistry unit  11 . Moreover, in the event the level of exposure from odor-producing chemicals which so escape proves to be too low to trigger a permanent color change in the dry reactive chemical powder  12 , the user has the option of reapplying the protective covering  35 , with the plug  34  still attached, to the packet&#39;s inner face  30 , thereby sealing off its through opening  23  so that the packet  10  can be stored for reuse. 
     The dry reactive chemical powder  12  of the present invention is prepared from a slurry which consists of only three substances: the solvent acetone, the dye bromophenol blue, and amorphous silica. Remaining structurally unchanged in the slurry, the amorphous silica, which in the preferred embodiment, exists in the form of powder granules in the 9 to 11 micron size range, readily absorbs the acetone and the bromophenol blue molecules dissolved it. Not only does the low viscosity of acetone allow it to penetrate these powder granules with their very small pore size but also it insures that the acetone evaporates quickly leaving little, if any, residual solvent to outgas from the dry reactive chemical powder  12 . The acetone, which can be evaporated off the slurry at room temperature, leaves behind, as a dry residue, a yellow powder, which is believed to be the product of amorphous silica granules absorbing bromophenol blue molecules. 
     The ingredients and ranges of each ingredient in parts by weight for the slurry from which the dry reactive chemical powder  12  of the present invention is prepared are illustrated in Chart A hereinbelow: 
     
       
         
               
               
               
             
           
               
                 CHART A 
               
               
                   
               
               
                   
                 Ingredients 
                 Range (Parts by Weight) 
               
               
                   
               
             
             
               
                   
                 Amorphous Silica 
                 26 to 40 
               
               
                   
                 Bromophenol Blue 
                 0.01 to 0.19 
               
               
                   
                 Acetone 
                  50 to 120 
               
               
                   
               
             
          
         
       
     
     The following examples are presented to illustrate the composition of the slurry from which the dry reactive chemical powder  12  of the present invention is prepared in a more detailed manner: 
     EXAMPLE 1 
     
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
               
               
                   
                   
                   
                 Percentage 
               
               
                 Ingredients 
                 Quantity 
                 Parts by Weight 
                 by Weight 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Amorphous Silica 
                 26  
                 grams 
                 26 
                 20.63%  
               
               
                 Bromophenol Blue 
                 0.19  
                 grain 
                 0.01 
                 0.01% 
               
               
                 Acetone 
                 100  
                 grams 
                 100 
                 79.3% 
               
               
                   
               
             
          
         
       
     
     EXAMPLE 2 
     
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
               
               
                   
                   
                 Parts by 
                 Percentage 
               
               
                 Ingredients 
                 Quantity 
                 Weight 
                 by Weight 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Amorphous Silica 
                 30  
                 grams 
                 30 
                 23.08% 
               
               
                 Bromophenol Blue 
                 0.19  
                 grain 
                 0.01 
                 0.008% 
               
               
                 Acetone 
                 100  
                 grams 
                 100 
                 76.92% 
               
               
                   
               
             
          
         
       
     
     EXAMPLE 3 
     
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
               
               
                   
                   
                 Parts by 
                 Percentage 
               
               
                 Ingredients 
                 Quantity 
                 Weight 
                 by Weight 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Amorphous Silica 
                 30  
                 grams 
                 30 
                 23.04% 
               
               
                 Bromophenol Blue 
                 0.3  
                 grain 
                 0.019 
                 0.015% 
               
               
                 Acetone 
                 100  
                 grams 
                 100 
                 76.91% 
               
               
                   
               
             
          
         
       
     
     EXAMPLE 4 
     
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
               
               
                   
                   
                 Parts by 
                 Percentage 
               
               
                 Ingredients 
                 Quantity 
                 Weight 
                 by Weight 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Amorphous Silica 
                 50  
                 grams 
                 50 
                 33.32% 
               
               
                 Bromophenol Blue 
                 1.0  
                 grain 
                 0.065 
                 0.043% 
               
               
                 Acetone 
                 100  
                 grams 
                 100 
                 66.64% 
               
               
                   
               
             
          
         
       
     
     EXAMPLE 5 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                   
                 Parts by 
                 Percentage 
               
               
                   
                 Ingredients 
                 Quantity 
                 Weight 
                 by Weight 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Amorphous Silica 
                 40  
                 grams 
                 40 
                 44.43% 
               
               
                   
                 Bromophenol Blue 
                 0.31  
                 grain 
                 0.020 
                 0.022% 
               
               
                   
                 Acetone 
                 50  
                 grams 
                 50 
                 55.54% 
               
               
                   
                   
               
             
          
         
       
     
     As the applicant&#39;s tests have shown, the sensitivity of the dry reactive chemical powder  12  can be varied by varying the percentage of amorphous silica in the slurry. Specifically, when this percentage drops below approximately 18%, the dried reactive chemical powder  12  takes at least 3 hours to change color; and it may turn to only a yellow green, not a blue, or give no definite indication at all. On the other hand, when the percentage of amorphous silica in the slurry goes above 44% (as in Example 5 hereinabove), the powder  12  is too sensitive and turns an olive green with only minimal stimulus from outside sources such as atmospheric nitrogen. It is believed that when the percentage by weight of amorphous silica is around 35%, the dry reactive chemical powder  12  exhibits an optimum sensitivity for use in the detector packet  10 , subject as it is to the time constraints of hunters. 
     Another critical factor which must be taken into account in selecting preferred embodiments of the powder  12  is the ratio between the quantity of bromophenol blue and the quantity of amorphous silica in the slurry. The applicant has found that the shelf life of the powder  12  is substantially enhanced when this ratio is maintained at approximately 0.01 grain of bromophenol blue to 1 gram of amorphous silica or higher ratios. In the case of Example 2, for instance, this ratio fell to only 0.006; and the powder  12  turned blue in less than 1 year. But in the case of Example 3, where the slurry from which the dried powder  12  was prepared closely resembles that in Example 2 except for the fact that this critical ratio was 0.01 instead of 0.006, the dried powder has thus far had a shelf life in excess of 1-½ years. If one were to select the composition of the slurry from which the dry reactive chemical powder  12  is prepared on the basis of stability/extended shelf life alone, EXAMPLE 6 would be a preferred candidate: 
     EXAMPLE 6 
                                                                       Parts by   Percentage       Ingredients   Quantity   Weight   by Weight                                Amorphous Silica   20    grams   20   16.66%        Bromophenol Blue   0.2    grain   0.013   0.01%       Acetone   100    grams   100   83.3%                    
Indeed, this slurry is so stable that the amorphous silica granules settle out in such a way as to facilitate pouring off the excess acetone; but because the percentage by weight of amorphous silica is less than 18%, any dried reactive chemical powder prepared from it would take too long to change color to be of practical value in the detector packet  10 , especially under the time constraints hunting imposes.
 
     Yet another factor which can significantly alter the rate at which the dry reactive chemical powder  12  changes color is the depth of the powder layer through which nitrogen type compounds must diffuse before they can activate bromophenol blue molecules within the viewing range of a would-be observer. In the case of the detector packet  10 , the applicant has found that the greater the depth of the layer of dry reactive chemical powder  12  in the dry chemistry unit  11 , the longer this color change takes before it is observable through the view aperture  22 . In the preferred embodiment, the thin layer of powder  12  has a depth of approximately 1/10,000th inch. 
     It is to be understood that any adhesives employed to bond together components of the dry chemistry unit  11 , as well as adhesives to secure the unit  11  to the frame  21  and bond together elements of the frame itself, must be free of any traces of ammonia or nitrogen type compounds. Otherwise, the dry reactive chemical powder  12  immediately turns color, e.g., blue. In the preferred embodiment, the transparent, nonabsorbent tape  13  is a clear packaging tape with an adhesive backing found, by trial and error, to be free of any nitrogen type compounds including ammonia. The same has been found to be true for the annular ring  28  which is preferably fabricated from a clear vinyl film. 
     The amorphous silica used in preparing the dry reactive chemical powder  12  can be purchased from Sygma Aldrich and is categorized as having a Davisil Grade 710, with a size range of 9.5 to 11 microns. Between 1/10 grain and 2 grains of the dry reactive chemical powder  12  is used in each dry chemistry unit  11 . 
     The non-hydroscopic filter media sheet  15  is preferably a polyester fiber woven fabric which is two layers thick. This double layered filter blocks about 90% of the amorphous silica granules which otherwise would migrate out of the thin layer of dry reactive chemical powder  12  disposed contiguous with the adhesive coating  14  on the tape  13 . The manufacturer of the polyester fiber woven fabric used in the sheet  15  is Hoppe&#39;s. Alternately, a filter media made of glass and having a 5 micron pore size, which is available commercially from Fisher Scientific, can be utilized for the sheet  15 . 
     The two-sided detector packet  10  is preferably square shaped and measures, by way of example, two inches on a side, with the view aperture  22  and the through opening  23  having diameters of 1 inch and 1-⅛ inch, respectively. In addition, the circular perforation in the two-sided tape  31  preferably leaves a 1-¼ inch hole in this tape when the plug  34 , which is approximately 1-⅛ inch in diameter, is pulled out. 
     In use, the dry reactive chemical powder  12  in the packet  10  turns from yellow to light green to blue depending upon the concentrations of nitrogen type compounds such as ammonia and amino acids in the vapors to which the powder is exposed. When the level of human odor escaping from a hunter&#39;s odor absorbing clothing turns the detector blue, it is believed that game animals are able to smell the presence of a human. The powder  12  in the detector packet  10  is extremely sensitive and can detect vapors of ammonia or amino acids, as well as atmospheric nitrogen, when they are present in concentrations of parts per billion. Indeed, once the dry chemical unit  11  has been exposed to nitrogen type compounds which are present in concentrations in the parts per billion range, the color of the dry reactive chemical powder  12  changes from yellow to blue. Moreover, the powder  12  in the unit  11  holds the blue color so that the hunter has a chance to know that his body odor is escaping through his odor eliminating clothes. Unlike the prior art, the powder  12  in the unit  11  will not revert back to its original yellow color. 
     In summary, the improved device according to the present invention not only can detect extremely low levels of airborne amino acids, ammonia vapor or other gaseous nitrogen-type compounds but also is limited to a single “blue” exposure. That is, once the dry reactive chemical powder  12  has been exposed, the powder does not revert back to its unexposed state, thereby giving the user the earliest possible indication that his body odor eliminating clothing is at or near its saturation limit and a breakthrough of odor-producing chemicals has occurred or is about to occur.