a preferred example wearable chemical dispenser 18 is shown in fig1 - 11 . the wearable chemical dispenser 18 includes a top housing section 20 having a generally oblong side wall 22 that extends from a top wall 23 . in use , the wall 23 is typically frontally disposed and acts as a lid . a plurality of spaced apart apertures 24 are radially arranged in the top wall 23 of the top housing section 20 . the apertures 24 provide an inlet for permitting air to enter into an interior space of the wearable chemical dispenser 18 . a tab 26 provides a means to grasp the top housing section 20 when opening the top housing section 20 . the wearable chemical dispenser 18 also includes a slide cover 28 having an on - off button 29 , openings 31 , and a cam projection 32 . a fastener 34 ( see fig6 ) mounts the slide cover 28 to the top housing section 20 such that the slide cover 28 may rotate with respect to the top housing section 20 when a user moves the on - off button 29 along the side wall 22 of the top housing section 20 . in the ‘ off ’ position , the slide cover 28 closes the apertures 24 that are radially arranged in the top wall 23 of the top housing section 20 . in the ‘ on ’ position , the openings 31 of the slide cover 28 align with the apertures 24 that are radially arranged in the top wall 23 of the top housing section 20 . the wearable chemical dispenser 18 also includes a hinge bracket 36 that is mounted to an inner surface of the top housing section 20 as shown in fig5 . the hinge bracket 36 has a flat base plate 37 that mounts to the top housing section 20 , a generally l - shaped arm 38 having an inwardly directed pivot pin 39 at its end , and generally l - shaped arm 40 having an inwardly directed pivot pin 41 at its end . the arm 38 and the arm 40 are spaced apart on the plate 37 as shown in fig5 and 6 . the hinge bracket 36 forms part of a hinge mechanism as described below . a replaceable refill unit 44 is provided with the wearable chemical dispenser 18 . the refill unit 44 has a generally slab - like support structure 45 . in top plan view , the refill unit 44 has an essentially tear - drop shaped overall appearance , with a generally circular portion at one end and a generally triangular portion at another end . there is a spoke support 47 across a circular opening through the refill unit 44 ( see fig5 ). across the spoke support 47 is positioned a fabric substrate 48 . when air is drawn in , the air passes through the fabric substrate 48 . the choice of the fabric , and its porosity , the speed of the air flow , and the vapor pressure of the active , are the main factors in coordinating the speed of use up of the active with the speed of use up of a visual use - up cue 49 ( see fig5 ) that can be viewed through the slot 25 of the top housing section 20 . an example refill unit has a twelve hour life , and the visual use - up cue 49 is designed to evaporate or change in appearance after twelve hours . a suitable visual use - up cue is described in u . s . patent application publication no . 2008 / 0141928 . by impregnating the fabric substrate 48 with an appropriate air treatment chemical , air entering the device will pick up some of the volatile chemical , and dispense it out of the device . active release rates of 0 . 2 milligrams per hour ( mg ./ hr .) or higher are preferred . particularly preferred actives are transfluthrin , prallethrin , vaporthrin , tefluthrin , and esbiothrin or other synthetic pyrethroids . for use in controlling mosquitoes , it is preferred to use metofluthrin from the sumitomo chemical company ( trade name sumione ). the impregnation material can be pure active , or for ease of handling the material can be dissolved in a hydrocarbon or other solvent . alternatively , or in addition , the fabric may also bear a fragrance , a deodorizer , or other air treatment chemical . it is preferred to have the fabric substrate 48 configured so that the pressure drop across the substrate is no more than 40 pascals ( pa ). suitable fabrics can be made of woven or non - woven materials providing only minimal resistance to the airflow . the fabric substrate 48 should also be capable of holding active ingredient dosed onto the material and also allow ready migration of the active to the surface so as to allow its evaporation in response to the airflow . for an active ingredient that is hydrophobic and migrateable at common environmental temperatures between about 10 ° c . and 40 ° c . ( e . g ., metofluthrin ), suitable materials include , only by way of example , polyester , polypropylene , cotton , cellulose , poly - rayon , and other similar fabrics . these can be non - wovens with basis weights ranging from 10 grams per square meter ( gsm ) to 40 grams per square meter ( gsm ), fabricated from synthetic , natural , or combined synthetic and natural polymeric materials . the ideal fabric substrate 48 should also allow for wicking of the active ingredient following dosing so as to ensure efficient distribution throughout the substrate , and thereafter allow migration of active ingredient to the substrate surface to replenish the active ingredient that is being evaporated by the passing airflow . dosing may be by dropping , spraying , printing , or other conventional delivery of a liquid active ingredient to the substrate . a particularly desirable fabric is a non - woven felted material with a basis weight of 20 - 30 gsm fabricated from polyethylene terephthalate . a frame 50 is located below the refill unit 44 in the wearable chemical dispenser 18 . the frame 50 has a generally oblong perimeter , and supports the refill unit 44 ( see fig5 and 6 ). note that one side of the essentially triangular portion of the refill unit 44 is straight and the other is indented . this slight lack of symmetry is designed to accommodate a corresponding slight lack of symmetry along the top side of frame 50 , and to thereby prevent a consumer from installing the refill unit 44 inside - out on the frame 50 . one end of the frame 50 has a pair of slots 51 that form part of a hinge mechanism as described below . a circular opening 52 is provided at the other end of the frame 50 . holes 54 in the frame 50 support a rotating activation button 56 that is biased by a rotary spring 57 into an off position . looking at fig6 and 11 , there is shown a fan 60 of the wearable chemical dispenser 18 . the fan 60 has a rotor 61 having a central vertical wall 63 that joins a top central horizontal wall 64 . the central vertical wall 63 and the top horizontal wall 64 define a recess 65 in the bottom of the rotor 61 ( see fig7 ). the top horizontal wall 64 of the rotor 61 includes a tubular mounting element 66 on the axis of the rotor 61 . the preferred fan 60 includes fourteen fan blades 68 a to 68 n ( see fig1 ). it has been discovered that a fan configuration , which results in an ideal balance of airflow and minimal power consumption for the wearable chemical dispenser 18 , includes twelve to eighteen fan blades . preferably , the fan produces an average volumetric flow rate of air of 1 . 5 to 3 cubic feet per minute ( with the refill unit 44 installed ) over the life ( e . g ., at least eight , and most preferably at least twelve hours ) of a refill unit 44 . typically , the fan will operate at 3000 - 5000 rpm . in one example wearable chemical dispenser 18 , over the life ( e . g ., twelve hours ) of a refill unit 44 , the consumed power from the power supply is 0 . 35 watts or less , preferably 0 . 30 watts or less , more preferably 0 . 25 watts or less , and even more preferably 0 . 20 watts or less . in one example embodiment , over a twelve hour life of a refill unit 44 , the consumed power from the power supply is about 0 . 17 watts while maintaining an average volumetric flow rate of air of at least 1 . 5 cubic feet per minute over the twelve hour period . when using one or more batteries for the power supply , the voltage will vary during discharge . however , the power consumed can be determined from the total energy consumed divided by the total time . each blade 68 a to 68 n has a generally rectangular body 69 defined by an inner edge 70 , an outer edge 71 , a top edge 72 extending from the inner edge 70 to the outer edge 71 , and top surface 73 of the rotor 61 . looking at fig1 , a radial reference line r 1 can be extended from a centerpoint c of the rotor 61 to the inner edge 70 of each blade 68 a to 68 n . likewise , a radial reference line r 2 can be extended from a centerpoint c of the rotor 61 to the outer edge 71 of each blade 68 a to 68 n . the body 69 of each blade 68 a to 68 n forms an included angle a with its associated radial reference line r 1 . it has been discovered that a fan configuration , which results in an ideal balance of airflow and minimal power consumption for the wearable chemical dispenser 18 , includes a range of fan sizes and fan blade angles . preferably , each blade 68 a to 68 n has a length extending from the inner edge 70 to the outer edge 71 in which the length measures 80 % to 130 % of the distance of radial reference line r 1 . preferably , each blade 68 a to 68 n has a length extending from the inner edge 70 to the outer edge 71 in which the length measures 45 % to 75 % of the distance of radial reference line r 2 . preferably , the included angle a in fig1 , which is formed between the body 69 of each blade 68 a to 68 n and its associated radial reference line r 1 , is in the range of 100 to 150 degrees . these example fan sizes and fan blade angles contribute to an ideal balance of airflow and minimal power consumption for the wearable chemical dispenser 18 . thus , among other things , the average volumetric flow rate of air from the fan depends on the outer radius of the rotor , the inner radius of the rotor , the number of blades , the blade angles , and the fan revolutions per minutes . one non - limiting example of the fan 60 has a length extending from the inner edge 70 to the outer edge 71 of about 15 millimeters , a radial reference line r 1 of about 14 millimeters , a radial reference line r 2 of about 25 millimeters , and an included angle a of about 120 degrees . in this non - limiting example , blade thicknesses can range from 0 . 3 - 1 . 0 millimeters , with 0 . 6 millimeters being preferred , and blade height ( from the top surface 73 of the rotor 61 to the top edge 72 of the body 69 ) can range from 5 - 11 millimeters , with about 8 millimeters being preferred . the wearable chemical dispenser 18 includes an electrical power supply . in the example embodiment shown , a microswitch 75 of the power supply is electrically connected to battery contacts 76 . another battery contact 77 completes an electrical circuit with batteries 78 and the battery contacts 76 to provide electricity to the microswitch 75 . when a user rotates the slide cover 28 by rotating the on - off button 29 into the ‘ on ’ position , the cam projection 32 of the slide cover 28 is driven into the rotating activation button 56 which then contacts the microswitch 75 to turn on the power supply . looking at fig6 - 8 , the wearable chemical dispenser 18 includes a chassis 80 for mounting various components of the wearable chemical dispenser 18 . when the top housing section 20 and the chassis 80 are in a closed position ( see , e . g ., fig1 ), a housing having an interior space is formed . the chassis 80 engages the frame 50 in a snap fit . the chassis 80 has a bottom wall 81 with a raised portion 82 that defines a upwardly directed space 83 in the chassis 80 ( see fig6 and 7 ). a battery compartment 84 is also provided in the bottom wall 81 of the chassis 80 ( see fig7 ). the battery contacts 76 , 77 are mounted at opposite ends of the battery compartment 84 . extending upward from the bottom wall 81 of the chassis 80 there is a hinge support 85 having a notch 86 and a hinge support 87 having a notch 88 ( see fig6 and 8 ). the hinge support 85 and the hinge support 87 form part of a hinge mechanism as described below . the chassis 80 also includes a side wall 90 having regularly spaced openings 91 that define an outlet for permitting air mixed with air treatment chemical to exit the interior space of the wearable chemical dispenser 18 . in the non - limiting example embodiment shown in fig5 , the openings 91 extend from point e to point f around the side wall 90 of the chassis 80 . in fig5 , the included angle between point e and point f and point d ( which is on axis x shown in fig6 ) is about 270 degrees . therefore , the openings 91 are regularly spaced around 270 degrees of the side wall 90 of the chassis 80 . preferably , the openings 91 are regularly spaced around at least 180 degrees of the side wall 90 of the chassis 80 . more preferably , the openings 91 are spaced around at least 235 degrees of the side wall 90 of the chassis 80 . one non - limiting example of the total outlet area of the openings 91 is 8 . 5 × 10 − 4 m 2 . advantageously , the battery compartment 84 is isolated from the openings 91 . these example opening configurations contribute to an ideal balance of airflow and minimal power consumption for the wearable chemical dispenser 18 . preferably , a flow path from the fan to the openings 91 is unobstructed . some other devices included a slide cover designed to shut off air flow by blocking the inlet vents and the exhaust vents . the intent was to minimize loss of actives while the unit is not in use by blocking off airflow across the dosed pad . the walls blocking the exhaust vents and the geometries supporting them occupied large space and caused the device to increase in size . these blocking walls are eliminated in the present invention without increased loss in actives ingredient . a motor 93 is positioned in the space 83 in the chassis 80 , and a wire 94 connects the motor 93 to the microswitch 75 for powering the motor when the rotating activation button 56 contacts the microswitch 75 to turn on the power supply . the motor 93 includes a drive shaft 95 that is connected to the tubular mounting element 66 on the rotor 61 . as a result , the motor 93 can rotate the fan 60 . a battery door 96 covers the battery compartment 84 in the bottom wall 81 of the chassis 80 . the battery door 96 includes mounting tabs 97 . a bottom cover 102 is fastened to the chassis 80 by way of fasteners . looking now at fig6 , 9 and 10 , means for clipping the wearable chemical dispenser 18 to a user &# 39 ; s clothing ( e . g ., a belt ) are shown . the bottom cover 102 includes a throughhole 103 partially surrounded by an arcuate well 104 in a bottom surface 105 of the bottom cover 102 . the bottom surface 105 of the bottom cover 102 further includes five spaced apart oblong depressions 106 a , 106 b , 106 c , 106 d , 106 e arranged in a semicircle around the throughhole 103 . the wearable chemical dispenser 18 also includes a clip 110 having a front section 112 that is spaced at its upper end from a rear section 113 by a top section 114 that connects the front section 112 and the rear section 113 . at the lower end of the clip 110 , the front section 112 and the rear section 113 are in contact until flexed apart by a user . the rear section 113 of the clip 110 has an arcuate projection 116 , a tubular mounting element 117 , and a movable tab 119 having a protrusion 120 on its end . the movable tab 119 is formed by a cutout 121 in the rear section 113 of the clip 110 . a fastener 122 ( see fig6 ) is inserted through the throughhole 103 of the bottom cover 102 and into the tubular mounting element 117 of the clip 110 to connect the bottom cover 102 and the clip 110 . still looking at fig6 , 9 and 10 , a rotation feature of the clip 110 can be explained . when the clip 110 is connected to the bottom cover 102 , the clip 110 is positioned as in fig9 . the fastener 122 secures the tubular mounting element 117 of the clip 110 in the throughhole 103 of the bottom cover 102 such that the clip 110 can rotate with respect to the bottom cover 102 . when the clip 110 is rotated clockwise from its position shown in fig9 , the arcuate projection 116 moves in the arcuate well 104 in a clockwise direction thereby guiding rotation of the clip 110 . the protrusion 120 of the movable tab 119 moves out of the depression 106 c by way of flexing of the movable tab 119 . the clip 110 rotates clockwise until the protrusion 120 of the movable tab 119 moves into the depression 106 b of the bottom cover 102 . when the clip 110 is further rotated clockwise from the position in which the protrusion 120 is in the depression 106 b , the arcuate projection 116 moves further clockwise in the arcuate well 104 , and the protrusion 120 moves out of the depression 106 b by way of flexing of the movable tab 119 . the clip 110 rotates clockwise until the protrusion 120 of the movable tab 119 moves into the depression 106 a of the bottom cover 102 . when in this position , the arcuate projection 116 is prevented from moving further clockwise by wall 129 of the arcuate well 104 , and the housing of the wearable chemical dispenser 18 is at 90 degrees in relation to the clip 110 . when the clip 110 is rotated counterclockwise from its position shown in fig9 , the arcuate projection 116 moves in the arcuate well 104 in a counterclockwise direction thereby guiding rotation of the clip 110 . the protrusion 120 of the movable tab 119 moves out of the depression 106 c by way of flexing of the movable tab 119 . the clip 110 rotates counterclockwise until the protrusion 120 of the movable tab 119 moves into the depression 106 d of the bottom cover 102 . when the clip 110 is further rotated counterclockwise from the position in which the protrusion 120 is in the depression 106 d , the arcuate projection 116 moves further counterclockwise in the arcuate well 104 , and the protrusion 120 moves out of the depression 106 d by way of flexing of the movable tab 119 . the clip 110 rotates counterclockwise until the protrusion 120 of the movable tab 119 moves into the depression 106 e of the bottom cover 102 . when in this position , the arcuate projection 116 is prevented from moving further counterclockwise by wall 127 of the arcuate well 104 , and the housing of the wearable chemical dispenser 18 is at 90 degrees in relation to the clip 110 . thus , the arcuate projection 116 and the arcuate well 104 provide a means for controlled rotation of the clip 110 with respect to the bottom cover 102 . specifically , the projection 116 moves in the well 104 when rotating the clip 100 . in the example embodiment of fig9 , the well 104 and the projection 116 are dimensioned such that the clip 110 can rotate 180 degrees ( i . e ., 90 degrees clockwise and 90 degrees counterclockwise ). preferably , the clip 110 can rotate at least 90 degrees . in addition , the movable tab 119 with the protrusion 120 and the spaced apart oblong depressions 106 a , 106 b , 106 c , 106 d , 106 e arranged in a semicircle around the throughhole 103 provide a means for indexed rotational positioning of the clip 100 and the housing relative to each other . the depressions 106 a , 106 b , 106 c , 106 d , 106 e provide a guide and the protrusion 120 of the movable tab 119 travels stepwise in the guide as explained above . often a user will clip the wearable chemical dispenser 18 to a belt with the clip 110 of the wearable chemical dispenser 18 in the position shown in fig9 wherein the outlet openings 91 face down from , to one side , and to the opposite side of the user . this directs a mixture of air and air treatment chemical down from , to one side , and to the opposite side of the user . if a user wishes to direct the mixture of air and air treatment chemical up , down , and to one side , the user can rotate the housing using the rotating clip 110 as described above . a user may also wish to rotate the housing in order to avoid any pinching against the body when sitting . also , by locating a pivot point of the clip 110 in a section of the housing adjacent the outlet openings 91 , more precise control of the direction of the mixture of air and air treatment chemical is afforded when rotating the clip 110 . thus , the housing of the wearable chemical dispenser 18 can be vertical or horizontal when in use . turning now to fig5 , 6 , 8 , 8 a , 8 b , and 8 c , the hinge mechanism of the wearable chemical dispenser 18 can be described further . the hinge mechanism allows a user to open the top housing section 20 to the open position of fig5 , 7 and 8 a so that a new refill unit 44 can be installed on the frame 50 as shown in fig5 . looking at fig8 a , 8 b and 8 c , movement of the pivot pin 39 of the hinge arm 38 in the notch 86 of the hinge support 85 can be explained . the pivot pin 39 has an outer wall 131 having an arcuate section 132 that extends between a first flat section 133 and a second flat section 134 . an intermediate section 135 connects the first flat section 133 and the second flat section 134 . although fig8 a , 8 b and 8 c do not show the pivot pin 41 , the pivot pin 41 has an outer wall with the same shape as outer wall 131 of pivot pin 39 . in fig8 a , the top housing section 20 is in a fully open position . the second flat section 134 of the outer wall 131 of the pivot pin 39 rests on a bottom flat surface 137 ( see fig8 ) of the notch 86 of the hinge support 85 . the mating of the bottom flat surface 137 of the notch 86 and the second flat section 134 of the outer wall 131 of the pivot pin 39 keeps the top housing section 20 in the fully open position . in fig8 c , the top housing section 20 is in a closed position . the first flat section 133 of the outer wall 131 of the pivot pin 39 rests on the bottom flat surface 137 of the notch 86 of the hinge support 85 . the mating of the bottom flat surface 137 of the notch 86 and the first flat section 133 of the outer wall 131 of the pivot pin 39 keeps the top housing section 20 in the closed position . also , a catch 155 ( see fig5 ) of the top housing section 20 engages a slot 157 ( see fig5 ) to keep the housing closed . in fig8 b , the top housing section 20 is in a partially open position . the intermediate section 135 of the outer wall 131 of the pivot pin 39 rests on the bottom flat surface 137 of the notch 86 of the hinge support 85 . the mating of the bottom flat surface 137 of the notch 86 and the intermediate section 135 of the outer wall 131 of the pivot pin 39 tends to keep the top housing section 20 in the partially open position . however , movement of the top housing section 20 in direction z will cause the top housing section 20 to quickly return to the fully open position shown in fig8 a as pivot pin 39 will rotate due to gravity until the second flat section 134 of the outer wall 131 of the pivot pin 39 rests on a bottom flat surface 137 of the notch 86 . in contrast , movement of the top housing section 20 in direction y will cause the top housing section 20 to move to the closed position shown in fig8 c as pivot pin 39 will rotate due to gravity until the first flat section 133 of the outer wall 131 of the pivot pin 39 rests on a bottom flat surface 137 of the notch 86 . the pivot pin 41 moves in the notch 88 in a similar manner with flat sections of the outer wall of the pivot pin 40 resting on the bottom flat surface 138 ( see fig8 ) of the notch 88 of the hinge support 87 during opening of the top housing section 20 . during movement of the hinge , the arm 38 and the arm 40 of the hinge bracket 36 move in the slots 51 of the frame 50 ( see fig5 ). the configuration of the outer wall of the pivot pins 39 , 41 of the arms 38 , 40 of the hinge bracket 36 provides an advantageous hinging action when opening the top housing section 20 . when a user first begins to open the top housing section 20 , the user must overcome the tendency of the pivot pins 39 , 41 to return to the closed position where the first flat section of the outer wall of the pivot pin rests on a bottom flat surface of the associated notch ( see fig8 c ). however , once the top housing section 20 has reached the partially open position of fig8 b , a small amount of further movement in direction z will cause the top housing section 20 to quickly move to the fully open position shown in fig8 a as pivot pin 39 will rotate due to gravity until the second flat section 134 of the outer wall 131 of the pivot pin 39 rests on a bottom flat surface 137 of the notch 86 . likewise , the configuration of the outer wall of the pivot pins 39 , 41 of the arms 38 , 40 of the hinge bracket 36 provides an advantageous hinging action when closing the top housing section 20 . when a user first begins to close the top housing section 20 , the user must overcome the tendency of the pivot pins 39 , 41 to return to the fully open position where the second flat section of the outer wall of the pivot pin rests on a bottom flat surface of the associated notch ( see fig8 a ). however , once the top housing section 20 has reached the partially open position of fig8 b , a small amount of further movement in direction y will cause the top housing section 20 to quickly move to the closed position shown in fig8 c as pivot pin 39 will rotate due to gravity until the first flat section 133 of the outer wall 131 of the pivot pin 39 rests on a bottom flat surface 137 of the notch 86 . regarding component construction , the top housing section 20 , slide cover 28 , hinge bracket 36 , support structure 45 of the refill unit 44 , frame 50 , fan 60 , chassis 80 , battery door 96 , bottom cover 102 , and clip 110 may be formed from a suitable polymeric material such as polyethylene , polypropylene , or polyester . in operation , the wearable chemical dispenser 18 will be clipped on a belt , purse or the like using clip 110 for that purpose . when a user moves the on - off button 29 along the side wall 22 of the top housing section 20 into the ‘ on ’ position , the openings 31 of the slide cover 28 align with the apertures 24 that are radially arranged in the top wall 23 of the top housing section 20 . the cam projection 32 of the slide cover 28 is driven into the rotating activation button 56 which then contacts the microswitch 75 to turn on the power supply to power the fan 60 by way of motor 93 . air is sucked by the fan 60 of the wearable chemical dispenser 18 in through apertures 24 and the openings 31 . as the air passes through fabric substrate 48 , the air treatment chemical mixes into the air and a mixture of air and air treatment chemical is then blown radially out openings 91 ( preferably down along pants or dresses ). a user can rotate the clip 110 as described above . while the present device is primarily intended to be used as a wearable item carried with a human when outdoors , it can also be laid flat , with the clip 110 downward and the top housing section 20 upward , on a picnic table or the like . when used in this manner it can provide protection to an area during a picnic or similar outdoor activity . hence , the device is much more compact and lightweight , yet still effective . further , the cost of operation from a battery standpoint is reduced . the device can more comfortably be used when seated , and provides greater control over dispensing direction . also , installing a replacement active refill is easier . these advantages are achieved at lowered cost , and provide a reliable construction . in the wearable dispenser , the intake grill size is designed to work in concert with an improved fan which falls within a specific range of fan blades , size and blade angle . a low current draw motor is recessed into the axial hub of the fan design . the airflow exits through 270 of output vents . this combination of design features results in an ideal balance of airflow and minimal power consumption that results in a highly efficient system , which produces good insect repellency and usage duration in a relatively small , lightweight unit . while an example embodiment has been described above , it should be appreciated that there are numerous other embodiments of the invention within the spirit and scope of this disclosure . for example , the device can be powered by a different source of energy ( e . g . a solar power panel ), other forms of actives can be dispensed along with or in substitution for the insect control ingredients ( e . g . a fragrance or deodorizing chemical ), and even when an insect control ingredient is dispensed it need not be one focused on controlling mosquitoes ( e . g . chemicals for repelling other flying or crawling insects or pests can be used ). hence , the invention is not to be limited to just the specific embodiments shown or described . provided herein are wearable dispensing devices capable of dispensing insect control chemicals and / or other air treatment chemicals adjacent a human body .
wearable devices for dispensing insect repellents , fragrances , and / or other chemicals along the outside of the clothing of a human are disclosed . they are of the type that are clipped onto a belt or the like , and use a powered fan to dispense active . they are configured with fan rotor arrangements to minimize power use while still achieving acceptable air flow rates . these changes permit use of smaller batteries and more compact arrangements for battery positioning . this in turn permits a much more compact and lightweight construction to achieve the desired results . the devices are also provided with a rotatable clip structure to render use of the device more comfortable when the user is seated and to provide greater control over the direction of the dispensing . further , they are provided with modified lids to facilitate active refill replacement .