Patent Publication Number: US-2023141193-A1

Title: Face and Head Shield

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority benefit of U.S. Provisional Patent Applications 63/002,340 filed Mar. 30, 2020; 63/005,140 filed Apr. 3, 2020; 63/020,501 filed May 5, 2020; and 63/059,739, filed Jul. 31, 2020; each of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to personal protective equipment, and more specifically to protective facial shields. 
     BACKGROUND 
     The current COVID-19 outbreak demonstrates the significant demand for adequate personal protective equipment (PPE) for medical personal who risk potential exposure to contagions when treating infected patients. A face shield used in such context is conventionally composed of a panel of transparent polymeric material worn in curtain-like fashion hanging in front of the user&#39;s face via an attached supportive headband or visor worn at forehead level. The panel is curved in a horizontal direction across the wearer&#39;s face, so that a central region of the panel resides anteriorly of the wearer&#39;s face over the eyes, nose and mouth, and lateral regions of the panel curve posteriorly from this central region to at least partially cover the side of the face. The shield itself typically terminates at an upper edge of the panel situated at, or shortly above, the shield&#39;s attachment to the headband or visor, leaving at least part of the forehead and the user&#39;s hairline exposed, especially if a separate protective cap or other head cover is not also worn. Such inadequate coverage at the upper facial area, together with gaps left between the shield and the wearer&#39;s face where the lateral regions terminate at upright lateral edges of the panel, leaves the user at risk of exposure to droplets or aerosol particles emitted by a sneezing or coughing patient. More adequate coverage than that provided the shield itself thus conventionally requires donning of additional protective gear. 
     Accordingly, there is a need for improved solutions to address this and/or other shortcomings of conventional face shields. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, there is provided a face and head shield comprising a transparent non-spherical dome or shell delimiting a hollow interior space for receiving facial and cranial regions of a user&#39;s head therein, said non-spherical dome or shell having a boundary edge thereof that delimits an opening of said hollow interior space through which said facial and cranial regions of said user&#39;s head are admitted into said hollow interior space, said opening having an elongated primary dimension measured in one direction thereacross and configured with sufficient length to accommodate a chin-to-crown measurement of the user&#39;s head in inferior-superior anatomical direction, and a shorter secondary dimension measured cross-wise to said primary dimension and configured with sufficient length to accommodate a narrower width measurement of the user&#39;s head in a lateral anatomical direction. 
     According to another aspect of the invention, there is provided a method of protecting against exposure to a hazard, said method comprising obtaining a plurality of face and head shields each configured to cover both facial and cranial regions of a user&#39;s head, wearing a support frame on said user&#39;s head on an ongoing basis, and during said wearing of said support frame on said ongoing basis, intermittently swapping out a worn one of said plurality of face and head shields for a replacement one of said face and head shields. 
     According to yet another aspect of the invention, there is provided a protective shield for shielding facial and cranial regions of a user&#39;s head, said protective shield comprising a singular unitary piece of transparent material comprising an upper cranial portion arranged to overlie a top of the user&#39;s head, at least at a frontal scalp thereof, a lower facial portion arranged to hang downwardly from the cranial portion over the facial region of the user&#39;s head, and at a transitional region that joins said lower facial and upper cranial portions, at approximately forehead level when said protective shield is worn, a pair of inward protrusions jutting inwardly from the transitional region relative to surrounding inner surface areas thereof, and an airflow space whose width is delimited between said pair of inward protrusions, said airflow space having a widened lower end that coincides with bottom ends of said inward protrusions, and from which said airflow space tapers upwardly to a lesser width than said widened lower end. 
     According to yet another aspect of the invention, there is provided a protective shield for shielding facial and cranial regions of a user&#39;s head, said protective shield comprising a singular unitary piece of transparent material comprising an upper cranial portion arranged to overlie a top of the user&#39;s head, at least at a frontal scalp thereof, and a lower facial portion arranged to hang downwardly from the cranial portion over the facial region of the user&#39;s head, and in a cross-sectional measuring plane that is either a midplane that bisects the cranial and facial regions, or another plane that lies parallel to said midplane, a slope of the lower facial portion toward the bottom end of the dome or shell and a slope of the upper cranial portion toward the top end of the of the dome or shell are of divergent relationship to one another over an entirety of each of said upper cranial and lower facial portions. 
     According to yet another aspect of the invention, there is provided a protective shield for shielding facial and cranial regions of a user&#39;s head, said protective shield comprising a singular unitary piece of transparent material comprising an upper cranial portion arranged to overlie a top of the user&#39;s head, at least at a frontal scalp thereof, a lower facial portion arranged to hang downwardly from the cranial portion over the facial region of the user&#39;s head, said single unitary piece of see through material stiffening ridges formed therein at opposing lateral sides thereof in matching orientations extending rearwardly away from the facial region toward. 
     According to a further aspect of the invention, there is provided a protective shield for worn use on a user&#39;s head to protect facial and cranial regions thereof, said protective shield comprising:
         a piece of transparent material comprising an upper cranial portion arranged to overlie a top of the user&#39;s head, at least at a frontal scalp thereof, and a lower facial portion arranged to hang downwardly from the cranial portion over the facial region of the user&#39;s head;   wherein said upper cranial portion has an airflow channel formed therein, said airflow channel having opposing inlet and outlet ends situated respectively distally and proximally, with the outlet end being open to an interior space of the protective shield at or near the facial region thereof so that airflow fed through the inlet end of the airflow channel is directed into an air space between the shield and the facial region of the user&#39;s head.       

     According to another aspect of the invention, there is provided a protective shield for worn use on a user&#39;s head to protect at least a facial region thereof, said protective shield comprising:
         a shield piece sized to span at least said facial region in both superior-inferior and lateral directions;   at a region of said shield piece arranged to reside at generally equal elevation to a forehead of the user&#39;s head when said shield piece is donned in a worn position, and at an exterior of said piece of said shield piece that faces outward from the user&#39;s head in said worn position, an uncovered external support surface arranged to jut anteriorly outward from the forehead of the user in said worn position to accommodate mounting of one or more accessories atop said external support surface at said exterior of the shield piece.       

     According to yet another aspect of the invention, there is provided a protective shield for worn use on a user&#39;s head to protect at least a facial region thereof, said protective shield comprising:
         a piece of transparent material sized to span at least said facial region in both superior-inferior and lateral directions;   an out-turned flange projecting from a boundary edge of the piece of transparent material around at least a partial perimeter thereof; and   a flexible connector clip configured to clip to said shield at said out-turned flange and to support a bib or shroud thereon.       

     According to yet another aspect of the invention, there is provided a protective shield for shielding facial and cranial regions of a user&#39;s head, said protective shield comprising a singular unitary piece of transparent material comprising an upper cranial portion arranged to overlie a top of the user&#39;s head, at least at a frontal scalp thereof, a lower facial portion arranged to hang downwardly from the cranial portion over the facial region of the user&#39;s head, and one or more support protrusions that are integrally formed in, or attached to, said cranial portion and jut downwardly from an underside thereof relative to surrounding surface areas of said underside of the cranial portion for resting of said support protrusions against the top of the user&#39;s head so as to support said surrounding surface areas in elevated relation over the top of the user&#39;s head to enable airflow therebetween. 
     According to yet another aspect of the invention, there is provided a one-piece adjustable length headband for support of a protective shield on a users head, said headband comprising a singular unitary strip of foam material having al length dimension in which said strip of foam material is elongated relative to width and thickness dimensions thereof that are orthogonal to both one another and to said length dimension, said strip of foam material having opposing first and second ends between which said length dimension is measured, said strip of foam material having a barbed tail region spanning a partial length of the length dimension from the first end toward the second end, and a widened end region that resides adjacent the second end and is of greater measure in the width dimension than said barbed tail region, said strip of foam material being flexibly bendable in said length dimension to bring the first and second ends toward one another to form a closed loop, said barbed tail region being barbed on opposing sides thereof, and said the widened end region having at least one receiver opening therein through which the first end is insertable to engage the barbed tail through said receiver opening, whereupon the barbed sides of the barbed tail region resist pulling of the first end back through said receiver opening, thereby securing the headband in said closed loop, which is adjustable in size by pulling more of the barbed tail onward through said receiver opening. 
     According to yet another aspect of the invention, there is provided a two-piece adjustable length headband for support of a protective shield on a users head, said headband comprising a first strip of foam material having a first pair of opposing ends separated from one another by a length dimension of said first strip of foam material, and a second strip of foam material having a second pair of opposing ends separated from one another by a length dimension of said second strip of foam material, one of two widthwise faces of the first strip having a respective piece of hook or loop fastener thereon adjacent each of the first pair of opposing ends, and one of two widthwise faces of the second strip having a respective piece of loop or hook fastener thereon adjacent each of the second pair of opposing ends that is matable with one of the hook or loop fasteners on the first strip, whereby the first and second strips are connectable face-to-face in end-overlapping fashion to form a closed loop, and at least one of the pieces of fastener is elongated in the length dimension of the respective strip of foam material to enable coupling together of the two strips in varying degrees of overlap to thereby adjustably size said headband. 
     According to yet another aspect of the invention, there is provided a method of using, in combination, a protective shield for covering at least a facial region of a user&#39;s head, and a headband for worn support of said protective shield on said user&#39;s head, wherein said protective shield, at an elevation configured to reside at approximately forehead level on the user&#39;s head when worn, has a pair of inward protrusions jutting from surrounding inner surface areas of said protective shield at laterally spaced positions from one another so as to span toward and brace against a forehead of the user&#39;s head at laterally spaced positions thereacross when worn, and said headband comprises a length of foam coupled to terminal ends of said pair of inward protrusions for foam-padded abutment of the pair of inward protrusions against the forehead when the headband and protective shield are worn on the user&#39;s head, and the method comprises cutting out a section of said foam between said pair of inward protrusions to enable airflow through said cut out section of the headband when worn. 
     According to yet another aspect of the invention, there is provided a protective shield for shielding facial and cranial regions of a user&#39;s head, said protective shield comprising a singular unitary piece of transparent material comprising an upper cranial portion arranged to overlie a top of the user&#39;s head, at least at a frontal scalp thereof, a lower facial portion arranged to hang downwardly from the cranial portion over the facial region of the user&#39;s head, and at a transitional region that joins said lower facial and upper cranial portions, at approximately forehead level when said protective shield is worn, at least one inward protrusion jutting inwardly from the transitional region relative to surrounding inner surface areas thereof, wherein, in a cross-sectional measuring plane that is parallel to a midplane that bisects the cranial and facial regions, at least a partial region of the lower facial portion has a linear slope, and at least a partial surface of a distal end each inward protrusion has a relative slope of obliquely oriented and downwardly convergent relationship to said linear slope of the lower facial portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the invention will now be described in conjunction with the accompanying drawings in which: 
         FIG.  1    is a perspective view of a head and face shield and cooperating support frame according to a first embodiment of the present invention, shown in an assembled state for use. 
         FIG.  2    is another perspective view of the shield and support frame of  FIG.  1   , but shown in a disassembled state to illustrate the removability of the head and face shield from said support frame. 
         FIG.  3    is a perspective view of the shield and support frame of  FIG.  1    during use, as viewed from an anterior/inferior (front/bottom) perspective. 
         FIG.  4    is another perspective view of the shield and support frame of  FIG.  3   , but from a lateral/superior (side/top) perspective. 
         FIG.  5    illustrates manufacture of the shield by vacuum forming thereof over a suitably shaped form. 
         FIG.  6    illustrates the formed shield of  FIG.  5    after removal thereof from said form. 
         FIGS.  7 A through  7 E  illustrate attachment of an optional front bib to the head and face shield of the preceding figures. 
         FIG.  8    illustrates attachment of an optional full-circumference shroud to the head and face shield to provide more comprehensive coverage that the front bib of  FIG.  7   . 
         FIGS.  9 A,  9 B and  9 C  are side, front and top views of a second embodiment of the head and face shield. 
         FIGS.  10 A,  10 B and  10 C  are perspective, front and rear views of a third embodiment of the head and face shield, and  FIG.  10 D  is a cross-sectional view thereof as taken lone line D-D of  FIG.  10 C . 
         FIGS.  11 A and  11 B  are exploded and assembled views illustrating installation of airflow channel components on the head and face shield of  FIG.  10   , and  FIG.  11 C  illustrates connection of the finished airflow channel to a source of forced supply air. 
         FIG.  11 D  illustrates the shield of  FIG.  11 C  in use with an attached shroud equipped with a pass-through port via which an air supply conduit is routed between the airway channel of the shield and the source of forced supply air. 
         FIGS.  12 A through  12 E  are front perspective, top-front perspective, side elevational, front elevational and rear perspective views of a variant of the third embodiment shield of  FIGS.  10  and  11   , and of which  FIG.  12 C  illustrates optional use of a top ledge of a bumped-out lower facial portion the shield to support a headlight or other accessory. 
         FIG.  13 A  shows the cross-sectioned shield of  FIGS.  10 D and  11 C , but equipped with a variant of the airflow channel components of  FIG.  11   . 
         FIG.  13 B  is an exploded perspective view of the variant airflow channel components of  FIG.  13 A ; 
         FIG.  13 C  is a partial closeup view of one of the variant airflow channel components of  FIG.  13 B . 
         FIG.  14 A  is a rear perspective view of the shield of  FIG.  12 E  with a flexible attachment clip installed on a flanged boundary edge around a rear opening of the shield. 
         FIGS.  14 B and  14 C  are fragmentary perspective and cross-sectional views of the flexible attachment clip of  FIG.  14 A , illustrating one possible profile thereof, with  FIGS.  14 D and  14 E  being matching views showing a slight variation in said profile. 
         FIGS.  15 A,  15 B and  15 C  are front perspective, side elevation and top-front perspective views of a final fourth embodiment of the head and face shield. 
         FIGS.  15 D and  15 E  show cross-sectional profiles of the shield of  FIG.  15 C  as cross-sectioned along lines D-D and E-E thereof, respectively. 
         FIG.  15 F  is a rear elevational view of the shield of  FIGS.  15 A through  15 E . 
         FIG.  16    illustrates the cross-sectioned shield of  FIG.  15 E  in a worn position on a user&#39;s head. 
         FIG.  17 A  is a top plan view of an adjustable one-piece foam headband of the present invention, laid out flat before curling thereof into a closed loop wearable around a user&#39;s head. 
         FIG.  17 B  is a top plan view of the adjustable one-piece foam headband once curled into a closed loop and secured in this closed state using a barbed tail of the headband. 
         FIG.  17 C  is a rear perspective view of the adjustable one-piece foam headband installed on one of the shields, with the headband in an open state ready for placement around a user&#39;s head. 
         FIG.  17 D  is another rear perspective view of the headband and shield of  FIG.  17 C , but with the headband secured in the closed state using the barbed tail of the headband. 
         FIG.  18 A  illustrates an adjustable two-piece foam headband of the present invention, prior to assembly and installation thereof on a shield. 
         FIG.  18 B  is a rear perspective view of the two-piece foam headband of  FIG.  18 A  once installed on a shield and assembled into a closed state suitable to span around a user&#39;s head. 
         FIG.  18 C  is a rear perspective view of the headband and shield of  FIG.  18 B  after optional cut-out of a central section of a front piece of the originally two-piece headband to enable improved airflow within the interior of the shield. 
     
    
    
     DETAILED DESCRIPTION 
     The figures of the illustrated embodiments show a face and head shield  10  composed of a singular unitary piece of transparent polymeric material formed into a three-dimensional non-spherical dome or shell that bounds three out of four sides of a hollow interior space within this dome or shell. At a fourth side of the dome or shell (referred to herein as a rear side), a boundary edge of the dome or shell delimits an opening through which a user&#39;s face is received into the interior space of the dome or shell in order to don the face and head shield in a working position. Once donned in such position, the shield protects both the entire facial region of the user&#39;s head, and a substantial cranial region thereof, from physical contact with potential hazards, for example droplet or aerosol carried contagions emitted by a coughing, sneezing or otherwise contagion-emitting patient under the medical care of the user. The same face shield may of course also be used for other protective applications. 
     In the first and second embodiments example, the boundary edge of the dome or shell resides in a singular flat plane, for example as would be seen if the dome or shell were placed boundary edge down atop a flat tabletop. This plane is used as a reference plane governing directions in which height and width dimensions H, W of the shield are measured orthogonally of one another. A third depth dimension D of the shield is measured in a third direction residing normal to this reference plane, and thus orthogonal to the height and width dimensions. The depth of the shield&#39;s interior space thus refers to measurement made perpendicularly from the plane of the shield&#39;s open rear side to an inner surface of the shield that resides oppositely of, and faces toward, said open rear side of the shield. The height and width of the shield are at their greatest in the aforementioned reference plane at the open rear side of the dome or shell. The height of the opening exceeds the width thereof, whereby the opening of the shield has an oblong shape having an elongated primary dimension and a shorter secondary dimension. As used herein, the top and bottom ends of the shield  12 ,  14  are those which are spaced apart by the longer primary dimension, while lateral sides  16 ,  18  of the shield are spaced apart by the smaller secondary dimension. 
     A rounded apex  20  of the shield&#39;s dome-like or shell-like shape, i.e. the area thereof at which the depth dimension D is at its greatest, resides nearer to the top end  12  of the shield  10  than to the opposing bottom end  14  thereof. From the rounded profile of the apex  20 , the depth of the shield tapers toward the bottom end  14  of the shield, initially in a generally linear fashion for a majority of the distance from the apex  20  to the bottom end  14 , before curving downward more aggressively just before the bottom end  14  in order to impart a rounded shape, rather than a sharp point, to the shield&#39;s bottom end. Likewise, the top end  12  of the shield is also slightly rounded in side-view profile, though at a relatively steep slope from the nearby apex  20 . The depth of the shield is also curved in its end-view profile, in which both the apex  20  and the depth-tapered lower portion therebelow have a subtle curvature over a central majority of the shield&#39;s width, before the depth drops off more aggressively near the two lateral sides  16 ,  18 . The relatively flat, but subtly curved central region of the shield&#39;s width spans across the user&#39;s face in the worn position of the shield, from which the more sharply curved side-adjacent regions of the shield will then turn posteriorly (rearwardly) of the user&#39;s face to cover at least the cheeks and temples of the user, and possibly also an entirety or partial fraction of the user&#39;s ears. 
     The forgoing shape of the shield  10  is symmetric in the width direction, i.e. 
     symmetric across a longitudinal midplane running in the height direction in orthogonal relation to the reference plane. On the other hand, the shield is asymmetric in the height direction, i.e. lacking symmetry across any transverse plane running in the width direction in orthogonal relation to the reference plane. By having a three-dimensional form that is of profiled shape in both end view (i.e. as viewed from either top or bottom end  12 ,  14 ) and side view (i.e. as viewed from either lateral side  16 ,  18 ), the shield is able to more comprehensively protect the user&#39;s head relative to the aforementioned conventional shields. 
     This improved protective coverage of can be seen in  FIGS.  3  and  4   , where the shield is shown in a worn position on the user&#39;s head, from which it can be seen that the elongated primary dimension (height H) of the shield&#39;s rear opening is large enough to accommodate a chin-to-crown measurement of the user&#39;s head in an superior-inferior (top to bottom) anatomical direction, and the shorter secondary dimension (width W) of the shield&#39;s rear opening accommodates a narrower width measurement of the user&#39;s head in a lateral anatomical direction (side to side). A substantial portion of the user&#39;s head, including the entire face thereof, is thus safely protected within the confines of the dome-like or shell-like structure of the shield  10 . 
     In the first illustrated embodiment, the shield  10  is supported on the user&#39;s head by a headband style support frame  30  that is worn circumferentially around the user&#39;s head at forehead level. It will be appreciated that other known styles of support frame may alternatively be employed, for example using an eyewear-style support frame that is borne on the user&#39;s ears and bridge of the nose. In the headband example of the first illustrated embodiment, a front segment  32  of the headband that spans across the user&#39;s forehead features a set of one of more coupling elements  34 A thereof, of which there are two in the illustrated example. Each coupling element  34 A is shown carried at a forwardly protruding mounting area  36  of the front segment  32  that resides adjacent a respective lateral end of the front segment. Each mounting area  36  juts forwardly from a remainder of the segment  32  that fits in generally flush conforming fashion against the user&#39;s forehead. The protruding mounting area(s) are used to set the shield in anteriorly (forwardly) spaced relation to the user&#39;s face when worn, as shown in the figures, to allow airflow between the user&#39;s face and the shield. In the illustrated example, each coupling element  34 A is a piece of hook or loop fastener. 
     A matching set of corresponding coupling elements  34 B are provided on the shield at the inner surface thereof, and at an elevation at or near the apex  20 , thus closer to the top end  12  of the shield than to the bottom end  14  thereof. In the illustrated example with two coupling elements per set, the spacing between the support frame&#39;s coupling elements  34 A matches that between the shield&#39;s corresponding coupling elements  34 B, of which the latter are situated at opposite ends of the shield&#39;s central region so as to reside near, but inward from, the lateral sides  14 ,  16  of the shield. Accordingly, elements  34 B align with the support frame&#39;s coupling elements  34 A that are worn at or near opposite ends of the user&#39;s forehead, thus residing near, but inward from, the user&#39;s temples. In the illustrated example, each of the shield&#39;s coupling elements  34 B is a piece of hook or loop fastener matable with the respective hook or loop fastener  34 A of the support frame  30 . The illustrated embodiment thus represents a scenario in which the shield is removably attachable to the support frame  30 , whereby the support frame may be worn on an ongoing basis, and repeatedly re-used, while the shield is instead intermittently swapped out for a replacement shield after each use (e.g. after each patient, in medical applications). Such replacement may be performed on a single-use disposable basis, where the worn shield is destroyed after use, rather than sterilized and re-used. It will be appreciated that releasable couplers other than hook and loop fasteners may be employed. In other embodiments, couplers capable of repeated attachment and detachment need not necessarily be used, for example in instances where the head frame is also treated as a one-time-use disposable product that is discarded together with the used shield. 
     As shown in  FIGS.  3  and  4   , when the shield is worn, the reference plane containing the open rear side of the shield  10  lies at an oblique incline relative to the anatomical planes of the user&#39;s body. This oblique plane cuts through the user&#39;s head in a posterior-anterior (back to front) and superior-inferior (top to bottom) direction from a location situated superior to (above) the crown of the user&#39;s head, to a location situated inferior to (below) the user&#39;s chin and anterior to (in front of) the user&#39;s neck. With the open rear side of the shield  10  in this oblique plane, the apex  20  of the shield resides anteriorly of the user&#39;s forehead, from which the depth-tapered lower portion of the shield hangs downwardly over the user&#39;s face. The portion of the shield spanning from the forehead-level apex  20  to the bottom end  14  of the shield&#39;s rear opening is thus referred to herein as the lower facial portion  44 , since it cover&#39;s the facial areas of the wearer, while the portion of the shield spanning from the forehead-level apex  20  to the top end  12  of the shield&#39;s rear opening is referred to as the upper cranial portion  46 , since it spans posteriorly over the user&#39;s cranium. In this worn position of the shield, the entire face of the user&#39;s head thus resides within the protected interior space of the shield, as does a substantial cranial region of the user&#39;s head, including at least the forehead, temples, and frontal scalp, and preferably also including the mid-scalp, and optimally also at least part of the crown of the user&#39;s head. The coverage may also include all or parts of the user&#39;s ears. So unlike conventional shields that employ a profiled shape only in the horizontal width direction to curve around to the sides of the face, the novel dome-like or shell-like shape of the inventive shield also curves upwardly over the forehead and spans rearwardly over the scalp. The shield thus avoids susceptibility to falling droplets or aerosol particles from above, and also protects against accumulation of such contaminants in the user&#39;s hair, which can present a risk for later infection. 
     As shown in  FIGS.  5  and  6   , the shield can be easily and affordably manufactured by application of a thermal forming or vacuum forming process applied to a form that has been fabricated according to the intended size and shape of the shield, though other manufacturing techniques may alternatively be employed.  FIG.  5    shows the platform P of a vacuum former atop which such a form F has been placed, over which a sheet of transparent plastic is placeable for heating and vacuum forming over the form F to impart the shield&#39;s three-dimensional dome or shell shape to the heated plastic.  FIG.  6    shows the vacuum formed plastic once cooled and removed from the form, at which point an outer peripheral margin M of the plastic sheet projects outwardly from around the boundary edge of the dome or shell&#39;s opening, before this margin M is trimmed off, or trimmed down, to leave behind the final shape of the finished shield. As shown in the embodiments of  FIGS.  12 ,  14   , for even further comprehensive coverage of the user&#39;s head and neck, the shield may optionally include an out-turned flange  112  at the boundary edge around the rear opening of the shield, whether spanning an entirety or partial fraction of the opening&#39;s circumference. By way of this flange, an additional flexible bib or shroud may optionally be attached to cover any exposed parts of the user&#39;s neck, shoulders, upper chest, and/or back of the head that are not covered by the shield and whatever garment is worn on the user&#39;s upper torso. However, it will also be appreciated that particular inclusion of a flange is not be essential to such optional attachment of a bib or shroud at the perimeter of the shield&#39;s rear opening, as such accessory may instead be adhered directly to the domed surface of the shield, rather than a supplementary flange projecting outwardly therefrom around the rear opening. 
       FIG.  7    illustrates such optional attachment of a front bib  38  to the shield over only a lower portion of the rear opening&#39;s circumference, whereby this front bib hangs anteriorly of the user&#39;s neck and upper chest to provide additional protection thereto, which otherwise may be left unprotected above the neckline of the user&#39;s upper torso garment. As an alternative to the  FIG.  7    bib that spans only a partial circumference of the rear opening of the shield,  FIG.  8    illustrates a larger shroud  38 ′ that spans the entire circumference of the shield&#39;s rear opening, so as to provide fully comprehensive coverage of the back of the user&#39;s head, along with the front, rear and sides of the user&#39;s neck, and also the shoulders and upper chest. 
     In addition to the front bib and shroud,  FIGS.  7  and  8    also illustrate a two-piece assembly of the headband style support frame  30 ′, where the front segment  32  of the headband is composed of a foam piece, and a remainder of the headband is composed of a flexible strap  39  of preferably elastic material that is resiliently stretchable in a longitudinal direction of the strap. The foam piece of the front segment  32  has a foam base strip that abuts generally flush against the user&#39;s forehead, and a pair of smaller foam blocks attached to a front side of the base strip to define the protruding mounting areas  36  so that the shield stands off from the user&#39;s face in the worn position to maintain the air space between the user&#39;s face and the shield. Longitudinally opposing ends of the strap  39  are attached to the two opposing ends of the foam base strip of the front segment piece  32  to collectively form the overall headband  30 ′. 
       FIG.  9    illustrates a second embodiment of the head and face shield  10 ′ that can be used to omit the need for a full-circumference headband  30 ,  30 ′ with protruding mounting features  36  on its front segment  32 . In this embodiment, the shield  10 ′ features a pair of inward protrusions  40 A,  40 B formed as seamlessly integral features of the dome or shell. These protrusions project inwardly from the inner surface of the dome or shell at the central region thereof, and at an elevation of that region at or near where the apex  20  and the tapered lower portion of the dome or shell join together. This way, the protrusions  40 A,  40 B reside at an elevation generally equal to the user&#39;s forehead in the worn position of the shield  10 ′. As an integral part of the dome or shell, the protrusions  40 A,  40 B at the inner surface of the shield  10 ′ each coincide with a respective matching depression  42 A,  42 B in the opposing outer surface of the shield that faces away from the user&#39;s face in the shield&#39;s worn position. The two protrusions  40 A,  40 B are spaced apart from one another, in the same cross-wise direction in which the width W of the rear opening is measured, by a suitable distance d such that these protrusions are placed adjacent opposite ends of the user&#39;s forehead, but inward from the user&#39;s temples. In one example, this distance d between the protrusions  40 A,  40 B measured between five and six inches, inclusive. 
     The protruding distance of the two protrusions  40 A,  40 B measured from immediately surrounding areas of the shield&#39;s inner surface, or the corresponding recessed depth of the depressions  42 A,  42 B measured from immediately surrounding areas of the shield&#39;s outer surface, may be between 1 and 2 inches, and more particularly between 1.25 and 1.75 inches in some embodiments, for example measuring 1.5 inches in one particular non-limiting example. A protrusion axis A on which each protrusion  40 A,  40 B juts into the interior space of the shield may be at a slightly oblique downward angle relative to the slope at which an upper portion  46  of the shield spans between the top end  12  of the shield and the rounded apex  20 . In the worn position of the shield, where the upper portion  46  thereof spans posteriorly from the top of the forehead over the scalp in a generally horizontal orientation, the protrusion axes A are thus angled at a slightly downward slope toward the user&#39;s forehead, though at a lesser downward slope than the angle of the shield&#39;s depth dimension D, which is perpendicular to the plane of the shield&#39;s rear opening. 
     For optimal comfort and/or gripping effect, a pad  48  of foam or other cushioning, grippy or sweat-absorbent material of distinct composition from that of the polymeric shield may be adhered to the terminal end of each protrusion  40 A,  40 B inside the interior space of the shield&#39;s dome or shell shape. In the worn position of the shield  10 ′, these terminal ends of the inward protrusions  40 A,  40 B abut against the user&#39;s forehead, whether directly, or indirectly through the optional pads  48 . The protrusions thus serve as stand-offs for the purpose of maintaining the shield  10  in anteriorly (forwardly) spaced relation from the user&#39;s face in order to create an open air space therebetween for the comfort of the user. Incorporating these stand-offs directly into the shield itself simplifies the manufacture of the overall apparatus by which the shield is supported on the wearer, as the front headband segment  32  of the earlier embodiment can be omitted altogether, having been replaced by integrally formed features of the shield itself. As shown in  FIGS.  9 A and  9 C , the same flexible, preferably elastic strap  39  previously used with the foam-piece front segment  32  of the earlier headband embodiment is instead coupled directly to the shield  10 ′ itself at the lateral sides  16 ,  18  thereof near the perimeter of the rear opening, and at matching or similar elevation to the protrusions  40 A,  40 B. 
     For the purpose of such connection between the shield and the strap  39 , the coupling elements  34 B used in the earlier embodiment to attach the central region of the shield&#39;s inner surface to the front segment of the two-piece headband  30 ′ may instead be relocated to the lateral sides  16 ,  18  of the shield for coupling with corresponding coupling elements on the flexible elastic strap  50  at or near the longitudinally opposing ends thereof. However, instead of the hook and loop fastener elements, any other coupling means capable of enabling attachment between the shield  10 ′ and the strap  39  may alternatively be used via cooperating features on these two components. In one alternative example, the ends of the straps may be fed through small slits in the sides of the shield  10 ′, so that the shield is frictionally held on the strap. Or a pair of holes may be provided in the sides of the shield for snap fit mating with male coupler features on the strap  39 . 
     It will be appreciated that the same integral incorporation of stand-off protrusions into the shield itself may be used on shields of more conventional shape, and not just on the novel dome or shell-like shape of the inventive shield whose inner user-facing side is concavely shaped in both of the orthogonal height and width dimensions of the shield. It will also be appreciated that while the illustrated example employs two small protrusions  40 A,  40 B at laterally spaced locations across the inside of the shield, another embodiment could alternatively a singular wider protrusion that spans more of the shield&#39;s width to achieve sufficient contact area with the forehead to also maintain a consistent and uniform air space between the shield and the user&#39;s face. It will also be appreciated that in the illustrated vacuum formed example, the inward protrusions on the inner side of the shield are coexistent with matching recessed depressions at the outer side of the shield, it will be appreciated that these need not be case in the instance of other manufacturing technics (plastic molding, 3D printing, etc.), where protrusions one side need necessary coincide with depressions on the other. 
     A third embodiment of the head and face shield  10 ″ is shown in  FIGS.  10  and  11   . The shield  10 ″ once again features a dome-like or shell-like shape having a singular open side at the rear thereof through which the user&#39;s head is received into the interior space of the shield when donned, and once again features two inward protrusions  40 A′,  40 B′ jutting from the inner surface of the shield at forehead level at or near the apex  20 , though in this example these protrusions and the matching depression  42 A′,  42 B′ in the opposing outer surface of the shield are larger than in the earlier embodiment of  FIG.  9   , thus increasing the surface area of the terminal end of each protrusion. 
     In this embodiment, the shield may be supported by a full-circumference headband that spans around the wearer&#39;s entire head, with the front segment of the headband being adhesively bonded (e.g. with double sided tape) or otherwise fastened (e.g. via hook and loop fastener) to the terminal ends of the protrusions  40 A′,  40 B′. To guide proper alignment between the headband and the shield  10 ″, the illustrated example of the shield features a vertical alignment marker  43 A lying upright on each side  16 ,  18  of the shield just outside the respective depression  42 A′,  42 B′ and a horizontal alignment marker  43 B lying laterally across the terminal end of each protrusion  40 A′,  40 B′. In the illustrated embodiment, each marker  43 A,  43 B is an integrally formed narrow groove recessed in the exterior of the shield, thus coinciding with a protruding narrow rib on the interior of the shield. 
     The upper cranial portion  46  of the shield  10 ″ differs from that of the earlier embodiments in that instead of a smooth and continuous curvature in its side-to-side width profile (as viewed from the front or rear of the shield), its side-to-side profile instead has a corrugated central region. Here, two troughs  52 A,  52 B are recessed into the exterior of the shield on opposing sides of a singular airflow channel  54  of parallel relation to the two neighbouring troughs  52 A,  52 B. The troughs  52 A,  52 B and airflow channel  54  run longitudinally of the cranial portion  46  of the shield from the top end  12  of the shield&#39;s rear opening toward, but stopping short of, the apex  20  of the shield. A floor  56  of each trough defines a narrow strip-like seat for resting atop the wearer&#39;s scalp. A ceiling  58  of the airflow channel  54  is of elevated relation to the trough floors  56 , as are the neighbouring areas  60  of the topside of the cranial portion  46  that reside outward of the two troughs  52 A,  52 B. Accordingly, when the trough floors  56  are seated atop the wearer&#39;s scalp, the channel ceiling  58  and neighbouring areas  60  are stood off from the wearer&#39;s scalp in spaced relation thereover. The troughs  52 A,  52 B and the airflow channel  54  are seamlessly integral parts of the preferably vacuum-formed (though optionally molded, or 3D-printed) shape of the shield itself. 
     The end of the airflow channel  54  that intersects the rear opening of the shield at the top end  12  thereof, and thus residing distally of the shield&#39;s lower facial portion  44 , is referred to an as inlet end  54 A of the channel  54 , as it is this end through which airflow in induced through the airflow channel  54  during use of the shield. An inlet fitting  62  of materially distinct and separate construction from the shield itself is installed in the airflow channel  54  at the inlet end thereof, for example being adhesively bonded to the transparent polymeric material of the shield at the ceiling  58  and/or sidewalls of the airflow channel  54  by one or more pieces of double sided tape  64  ( FIG.  11 A ), though other suitable adhesives compatible with the shield material may alternatively be employed. The inlet fitting  62  has a cross-sectional shape of matching outer profile to the airflow channel  54  so as to fully occupy and close off the inlet end thereof, except for an internal through-bore  62 A of the fitting through which air is admissible to the airflow channel  54  from an outside source, as described in more detail below. 
     A channel cover  64  is also defined separately of the shield itself, at least in the illustrated embodiment where the shield  10 ″ is vacuum formed. The channel cover  64  may be of the same material of the shield, or of distinct material composition therefrom. In the illustrated embodiment, the channel cover  64  is also adhesively bonded to the polymeric material of the shield, but at the undersides of the trough floors  56 , for example using two elongated strips of double sided tape  66  each running along a respective perimeter of the channel cover  64 . The channel cover  64  has an elongated strip-like shape spanning a nearly full length of the airflow channel  54 , starting from the inlet end  54 A or inlet fitting  62  thereof, but stopping short of an opposing outlet end  54 B thereof ( FIG.  11 C ). This outlet end  54 B resides near the apex  20  of the shield, and thus proximally of the lower facial portion  44  of the shield that is joined to the channel-equipped upper cranial portion by said apex  20 . The outlet end  54 B of the airflow channel  54  is left uncovered by the channel cover  64 , which otherwise closes off the bottom of the airflow channel over the full length thereof between the inlet and outlet ends  54 A,  54 B, or at least over a substantially full length thereof from the inlet fitting  62  to the outlet end  54 B if the channel cover does not span fully across the underside of the inlet fitting  62  right to the terminus of the channel&#39;s inlet end  54 A. With the cover  64  installed, the originally open-bottomed airway channel  54  is now an enclosed channel bound on all four sides thereof. 
     The purpose of the airflow channel is illustrated in  FIG.  11 C , where an air supply conduit  68 , typically comprised of one of more sections of flexible hose, has an output end thereof coupled to the inlet fitting  62  of the finished airflow channel  54 . An opposing supply end of the air supply conduit  68  is coupled to a forced air source  69 , such as a portable, battery-operated fan carried somewhere on the user&#39;s person. Forced air from the fan  69  is routed through the conduit  68  into the airflow channel  54  of the finished shield  10 ″ via the installed inlet fitting  62  thereof. The air flows longitudinally through the airflow channel  54  to the outlet end  54 B thereof, where the air is blown downwardly along in the inner surface of the shield apex  20  to the lower facial portion  44  of the shield, thus feeding into the space between the wearer&#39;s face and the lower facial portion  44  of the shield. Such airflow is useful to prevent or limit condensation buildup/fogging of the shield, and to help cool the user&#39;s skin. Alternatively, the fan may be accompanied a heater to blow warm air for use of the shield in cold environments. 
       FIG.  11 D  shows the shield  10 ″ of  FIG.  10 C  in combination with a shroud  38 ″ attached around the full circumference of the shield&#39;s rear opening. The shroud  38 ″ in this case is equipped with a conduit port  70  by which the air supply conduit  68  can be routed from the inlet fitting  62  of the shield&#39;s airflow channel  54  to the forced air source  69 . In the illustrated example, the port  70  is a pass-through port having a flexible gasket  70 A that seals externally around a flexible hose section of the air supply conduit  68 . Alternatively, the port  70  may be a connection port to which two different sections of a multi-section air supply conduit may connected inside and outside the shroud to make respective connections to the forced air source  69  and the channel-equipped shield  10 ″. Either way, the channel-equipped shield  10 ″ can be connected to a portable forced air source  69  worn on the user&#39;s person somewhere beneath the user&#39;s shroud, but without sacrificing the effective germ barrier provided by the protective shield  10 ″ and attached shroud  38 ″. 
       FIG.  12    shows a variant  10 ′″ of the head and face shield of  FIG.  10   . The variant shield  10 ′″ once again features integrally formed inward protrusions and matching external depressions  42 A′,  42 B′ at a forehead-level elevation on the shield, and once again also features the externally recessed troughs  52 A,  52 B and central airflow channel  54  in the upper cranial portion  46  of the shield. As also illustrated in the  FIG.  10    version, the two external depressions  42 A′,  42 B′ are separated from one another by an upright central brow ridge  80  that embodies the apex of the shield, and whose externally convex shape forms the gradually curved transition from the upper cranial portion  46  of the shield to the lower facial portion  44  of the shield. The overall area that resides at forehead level of the wearer and is occupied by the internal protrusions, coincident external depressions, and the upright brow ridge  80  therebetween, is therefore referred to herein as a transitional region, since it joins together the downwardly hanging facial portion of the shield that covers the wearer&#39;s face and the rearwardly extending cranial portion that overlies the top of the wearer&#39;s head. 
     The variant of  FIG.  12    differs from the  FIG.  10    shield in that the lower facial portion  44 ′, instead of being a smoothly continuous extension of the brow ridge  80 , is bumped forwardly outward therefrom, whereby the lower facial portion  44 ′ of this variant  10 ′″ is spaced further from the plane of the shield&#39;s open rear than in the  FIG.  10    shield. The variant shield  10 ′″ of  FIG.  12    thus possesses a greater depth at the lower facial portion  44 ′ than in the earlier  FIG.  10    shield. In the worn position of the shield, the lower facial portion  44 ′ thus resides further forward (anteriorly) of the user&#39;s face than the earlier  FIG.  10    shield, which leaves more space between the user&#39;s face and the shield at elevations below the forehead-level depressions  42 A′,  42 B′. This modified shape and increased depth of the shield at the lower facial portion  44 ′ thereof better accommodates wearing of facially protruding equipment (magnification loupes, surgical/dental headlight, etc.) behind the shield. For example, this variant of the shield may be particularly beneficial to dental and surgical practitioners who often require such equipment, typically worn on an eyewear frame. A light-equipped and/or loupe-equipped eyewear frame could thus be worn under the shield of  FIG.  12   . 
     The bumped-out position of the lower facial portion  44 ′ relative to the overlying transitional apex or brow ridge  80  of the shield creates a broad external ledge  84  that spans across an entirety, or substantial entirety, of the width of the shield. This external ledge  84  resides at an elevation that is shared by the bottom walls of the two inward protrusions found on the interior of the shield. The topsides of these bottom walls of the inward protrusions define bottom floors  86  of the two matching depressions  42 A,  42 B in the exterior of the shield. The external ledge  84  is thus composed of these floors  86  of the two depressions, plus a shallower joining strip  88  that spans across the front of the brow ridge  80  and joins together the two depression floors  86 . The external ledge  84  juts forwardly from the two depressions  42 A′,  42 B′ and the central brow ridge  80 , and thus in the worn position of the shield, juts anteriorly outward from the wearer&#39;s face at a lower area of the forehead just over the user&#39;s eyes (e.g. at approximately eyebrow level). While the increased shield depth crated by the bumped-out shape of the lower facial portion  44 ′ allows loupes or a headlight to be worn under the shield, as described above, the external ledge  84  also creates an exposed external support surface that is uncovered by any other features lying overhead thereof, and on which loupes, a headlight or other accessories may optionally be mounted externally to the shield itself, instead of being worn beneath the shield. 
     This is schematically illustrated in  FIG.  12 C , where a surgical or dental headlight  90  is mountable in secured fashion atop the external ledge  84 . In the illustrated example, securing the headlight accessory  90  is attained by co-operable mating of a first piece of hook or loop fastener material  90  that is adhered or adherable to the underside of a support base of the headlight  90 , and a corresponding second piece of loop or hook fastener material  92  that is adhered or adherable on top of the external ledge  84  of the shield. Other fasteners, e.g. 
     double-sided adhesive tape, may alternatively be employed for such mounting of a component to the external ledge  84 , provided that the bonding or coupling strength thereof is sufficient to hold the accessory. 
     While the variant in  FIG.  12    features a broad external ledge that spans an entire or substantially entire width of the shield, thus enabling fastened connection to the external ledge  84  at the center joining strip  88  thereof for optimal central placement of a headlight or other typically-centered accessory, it will be appreciated that the floors  86  of the two external depressions  42 A′,  42 B′ in the earlier shield of  FIG.  10    may similarly be employed as support surfaces to which one or more accessories may be mounted externally to the shield. This may be a singular accessory, with a U-shaped or suitably shaped base capable of placement atop the two depression floors  86  in embracing relation about the front of the brow ridge  80 , or two separate accessories, each mounted to the floor  86  of a respective one of the two depressions  42 A′,  42 B′. 
       FIGS.  13 A through  13 C  illustrate a variant of the airflow channel componentry shown earlier in  FIGS.  11 A through  11 D . In the variant of  FIG.  13   , the air inlet fitting  62 ′ for receiving the output end of the air supply conduit  68  is not adhesively bonded to the shield as describe previously. Instead, the inlet fitting  62 ′ is clipped to the shield over the boundary edge of the shield&#39;s rear opening using a connector clip  94  that is attached to a topside of the inlet fitting  62 ′. The clip  94  is attached to the inlet fitting  62 ′ at or near a rear end  62 B thereof that remains outside the airflow channel  54  of the shield when the inlet fitting  62 ′ has been clipped thereto. Though the illustrated example shows the entirety of the inlet fitting  62 ′ residing outside the airflow channel  54  at the inlet end thereof, it will be appreciated that at least part of the inlet fitting  62 ′ may reside inside airflow channel  54  and conform to the cross-sectional shape thereof, as described earlier with reference to  FIG.  11   . 
     Another difference in the  FIG.  13    variant is that the channel cover  64 ′ of this variant is attached to the inlet fitting  62 ′, as is therefore at least partially supported thereby, rather than being separately attached to the shield independently of the inlet fitting. Accordingly, the inlet fitting  62 ′ and channel cover  64 ′ can be quickly and conveniently attached to the shield through a singular clipped connection. That being said, additional adhesion of the channel cover  64 ′ to the shield may also be employed to best ensure that it is securely held in its intended position closing off the bottom of the airflow channel  54 . The channel cover  64 ′ is cantilevered from the inlet fitting  62 ′ at a front end  62 C thereof that is opposite to the rear end  62 B at which the output end of the air supply conduit  68  is connectable. Another difference in this variant is that the channel cover  64 ′ has a two-piece construction, rather than the one-piece construction shown in  FIG.  11   . Of the two pieces in the  FIG.  13    variant, one piece is a stationary cover component  96 , and the other piece is a movable adjustment component  98 . 
     The stationary cover component  96  is an elongated component that serves the same purpose as the one-piece channel cover  64  of  FIG.  11   , i.e. to form a floor or bottom wall of the shield&#39;s airflow channel  54  when installed on the shield. However, in the  FIG.  13    variant, the stationary cover component  96  has a series of vent openings  100 A therein that are spaced apart from one another along the elongated length dimension of the piece, whereby these vent openings  100 A are longitudinally distributed along the floor or bottom wall of the airflow channel  54  when the channel cover  64 ′ is installed on the shield. The movable adjustment component  98  is also an elongated component having a matching series of vent openings  100 B therein that are spaced apart from one another along the elongated length dimension of the piece. The quantity of vent openings in the two components  96 ,  98  are equal, as is the spacing between the vent openings in each component. The movable adjustment component  98  is slidably mated with the stationary cover component so as to be slidable back and forth thereon in the longitudinal/lengthwise direction thereof, as schematically shown by arrow  102  in  FIG.  13 A . The movable adjustment component  98  is thereby movable relative to the stationary cover component  96  to control the degree to which the vent openings  100 A of the stationary cover component are covered or open. 
     In a fully open position of the movable adjustment component  98 , all of the vent openings  100 A in the stationary cover component  96  are fully aligned with the matching vent openings  100 B in the movable adjustment component  98 , whereby the crown and/or scalp of the user&#39;s head are exposed to the airflow through the airflow channel  54 . This can be used help cool the user, or alternatively to warm the user if the shield is being worn in a cold environment and the fan  69  is accompanied by a heater to increase the temperature of the force airflow through the channel  54 . In a fully closed position of the movable adjustment component  98 , each of the vent openings  100 A in the stationary cover component  96  is unaligned with the matching vent opening  100 B in the movable adjustment component  98 . Instead, the vent openings  100 A of the stationary cover component  96  are fully covered by solid areas of the movable adjustment component  98 , i.e. closed areas that are materially intact between the vent openings  100 B thereof. The movable adjustment component  98  may also be moved into intermediate positions in which the vent openings  100 A of the stationary cover component  96  partially overlap with the vent openings  100 B of the movable adjustment component  98 , thereby achieving a partially open state of the two-piece channel cover  64 ′. 
     In the illustrated embodiment, both channel cover components  96 ,  98  are channel-shaped, thus having a pair of upright sidewalls  104 A,  104 B with a central bottom wall  106 A,  106 B spanning therebetween. The vent openings  100 A,  100 B of each component  96 ,  98  reside in the bottom wall  106 A,  106 B thereof, and the movable adjustment component  98  fits externally over the stationary cover component  96  at the underside thereof. Accordingly, the bottom wall  106 B of the movable adjustment component  98  underlies the bottom wall  106 A of the stationary cover component  98 , and the sidewalls  104 B of the movable adjustment component  98  neighbour the sidewalls  104 A of the stationary cover component  96  at the exterior sides thereof. In the installed position of the airflow channel cover  64 ′, the sidewalls  104 A,  104 B of both channel cover components  96 ,  98  reside inside the airflow channel  54  of the shield, and run along the interior of the two sidewalls of the airflow channel  54 . At the front end  62 C of the inlet fitting  62 ′, the interior through-bore  62 A thereof opens into the space between the two sidewalls  104 A of the stationary cover component  96 , as shown in  FIG.  13 C . 
     To maintain the slidably coupled relationship between the two components  96 ,  98 , mating longitudinal ribs and slots may be provided on the interior of the movable adjustment component&#39;s sidewalls  104 B and the exterior of the stationary cover components sidewalls  104 A. It will be appreciated that the movable adjustment component  98  need not necessarily be a channel shaped component residing externally and beneath a slightly narrower channel-shaped stationary cover component  96 . For example, the movable adjustment component  98  may instead ride atop the bottom wall  106 A of the stationary cover component in the space between the sidewalls  104 A thereof, provided that some part of the movable component  98  is accessible from outside the stationary cover component  96  to enable manipulation of the movable component&#39;s position along the stationary component. 
     The clip  94  of the inlet fitting  62 ′ is shown as an integrally attached clip, e.g. part of a plastic molded or 3D printed inlet fitting, though other means of attachment between the clip  94  and the body of the inlet fitting  62 ′ may alternatively be employed. The clip  94  has an elongated arm spanning forwardly from its attachment to the body of the inlet fitting  62 ′, and reaching past the front end  62 C thereof in overhanging relation thereto. The clip arm has a terminal end tab  108  at its free end, a bottom tip  108 A of which represents a lowermost point of the clip  94  in a normal default position thereof. Over at least a partial length of the overhanding portion of the clip arm that spans from the front end  62 C of the inlet fitting  62 ′ to the terminal end tab  108 , a series of tooth-like serrations  110  are provided on the underside of the clip arm. In a default position of the clip  94 , the bottom tip  108 A of the terminal end tab  108  resides at a lower elevation than a reference plane occupied by the top ends of the stationary sidewalls  104 A of the air channel cover  64 ′. To install the inlet fitting  62 ′ and attached airflow channel cover  64 ′, the clip  94  is temporarily flexed upwardly from its default position, and the boundary edge of the shield&#39;s rear opening, and more specifically the portion of this boundary edge denoting the inlet end of the airflow channel  54 , is slipped between the temporarily opened space between the reference plane and lifted clip. Once the inlet end of the airflow channel abuts the front end  62 A of the inlet fitting, the clip  94  is released from its raised position, whereupon it will resiliently flex back downwardly toward its default position. This return of the clip  94  biases the bottom tip  108 A of the end tab  108  down against the ceiling of the airflow channel  54 , and likewise forces the serrations  110  down against the boundary edge of the airflow channel&#39;s inlet end, thus clamping the inlet fitting  62 ′ and attached channel cover  64 ′ in place in operable relation to the airflow channel. It will be appreciated that the particular design of the clip  94  and the particular area of the shield engaged thereby at or near the inlet end of the airflow channel  54  may vary from this particular example. 
     With reference to  FIG.  12 E , the rear perspective view of the shield  10 ′″ shows the inclusion of the out-turned flange  112 , which in the illustrated example spans around the entirety of the boundary edge around the shield&#39;s rear opening. In such embodiments with the airflow channel  54 , it be seen that the out-turned flange may protrude further outward from the rear opening at areas immediately neighbouring the airflow channel  54  on either side thereof. 
     In the illustrated example, the protruding depth of the flange  112  increases gradually over these channel-neighbouring areas in a centrally inward direction toward the airflow channel  54 . As a result, this variable-depth section of the flange  112 A forms a triangular gusset that serves to reinforce the shape of the airflow channel at the inlet end thereof. 
     Turning from  FIG.  12 E  to  FIGS.  14 A through  14 E , illustrated therein is a flexible attachment clip  114  having an extruded profile that is generally J-shaped in profile, as best shown in the isolated views of the flexible attachment clip  114  in  FIGS.  14 B- 14 E . This J-shaped profile includes a lower overbent hooking portion  116  denoting the curved bottom end of the J-shape, and a stem  118  standing upright from the hooking portion  116  to the define the top end of the J-shape. An originating bottom span  116 A of the overbent hooking portions  116  juts outwardly to one side of the stem  118  from a bottom base end thereof. A returning top span  116 B of the overbent hooking portion  116  is bends backward over the originating bottom span  116 A, thus reaching back toward the stem  118 . The returning top span  116  stops short of the stem  118  so as to leave a small gap space  120  between the stem  118  at a terminal end  116 C of the returning top span  116 B.  FIGS.  14 B and  14 C  illustrate one version of the J-shaped profile, where after the 180-degree curve at the hooking portion&#39;s distal bend  116 D furthest from the stem  118 , the remainder of the returning portion  116 B is generally linear in its reach back toward the stem, and lies generally parallel to the similarly linear originating bottom span  116 A.  FIGS.  14 D and  14 E  illustrate an alternate variant of the J-shaped profile, where the returning upper span  116 B is curved throughout, and thus curves downwardly toward the originating bottom span  116 A during its inward return toward the stem  118 , rather than running parallel to the originating bottom span  116 A. 
     The overbent hooking portion  116  is resiliently flexible, which allows the returning upper span  116 B to be temporarily flexed away from the originating lower span  116 A such that the out-turned flange  112  of the shield  10 ′″ can be inserted between the two spans  116 A,  116 B of the overbent hooking portion  16  via the small gap  120  left between the stem  118  and the terminal end  116 C of the overbent hooking portion  116 . The returning upper span  116 B will snap back into its default position closely adjacent the originating bottom span  116 A, thus biasing itself against the front side of the shield&#39;s out-turned flange  112 , thereby holding the flexible connector clip  114  on the shield  10 ′″. In this installed position of the connector clip  114  on the shield  10 ′″, the stem  118  of the connector clip&#39;s J-shaped profile reaches into the interior space of the shield  10 ′″ through the rear opening thereof, and lines the interior surface of the shield along a perimeter strip thereof around the rear opening of the shield, as shown in  FIG.  14 A . 
     The flexible connector clip, for example composed of a flexible polymeric material, is flexible in its elongated extrusion direction, allowing it to conform to the interior contours of the shield at this interior perimeter strip around the rear opening of the shield. In the illustrated example, the extruded length of the flexible connector clip  114  spans a majority of the perimeter distance around the rear opening, preferably spanning all perimeter areas thereof, except for the inlet end of the airflow channel and the neighbouring areas occupied by the gusset-shaped portions  112 A of the out-turned flange  112 . In embodiments lacking the airflow channel  54 , the flexible connector clip  114  may span the entire perimeter of the shield&#39;s rear opening. 
     In either case, the flexible connector clip may be used to attach a shroud to the shield. For such purposes, an exposed outer side  118 A of stem  118  (the side opposite the overbent hooking portion  116 ) is equipped with a deposit of hook or loop fastener material  122 , whether a continuous strip thereof spanning the full extruded length of the flexible connector clip, or discrete pieces of fastener material attached at spaced apart locations therealong. The shroud is equipped with a mating deposit of loop or hook fastener material around the head opening of the shroud. Accordingly, fastening together of hook and loop material on the shroud and the flexible connector clip  114  is operable to secure the shroud to the shield. Inside the shield  10 ′″, additional hook or loop fastener material may be applied across the bottom of the airflow channel cover  64 ,  64 ′, and on the neighbouring internal areas of the shield on either side of the airflow channel, in order to also mate with the loop or hook fastener material on the shroud, thereby achieving fastened connection of the shroud around the entire rear opening of the shield. Double sided tape or snap fasteners may alternatively be used in place of the hook and loop fastener to similarly enable convenient quick assembly by a customer or end-user from initially separate components. Alternatively, the shroud and the flexible connector clip  114  may instead be combined into a singular unit by a manufacturer or supplier, for example where the shroud is pre-sewn, pre-bonded with suitable adhesive, or even heat sealed to the stem of the flexible connector clip  114 . A shorter flexible clip occupying only a lower half of the shield&#39;s perimeter edge may be similarly used to attach a front bib to the shield, instead of a full-circumference shroud. 
     Rather than rely solely on the gripping action of the overbent hooking portion  116  to hold the connector clip  114  on the shield  10 ′″, an additional deposit of hook or loop fastener material  124  may also be applied to the opposing inner side  118 B of the stem  118  (i.e. the side facing the overbent hooking portion  116 ), again whether as a continuous strip or discrete pieces, for mating with mating deposit of loop or hook fastener applied to the interior surface of the shield  10 ′″ at the perimeter strip thereof neighbouring the rear opening. Alternatively, rather than hook and loop fastener, double sided tape may be used to adhesively bond the inner side  118 B of the stem  118  of the flexible connector clip  114  to the opening-adjacent perimeter strip of the shield&#39;s interior. In yet another alternative, depending on the polymeric materials used for the flexible connector clip  114  and the shield, it may be possible to heat seal or sew these two components together, for example at the manufacturer or supplier level, instead of relying on customer or end-user assembly with hook and loop fastener or double-sided tape. 
       FIGS.  15 A through  15 C  illustrate a fourth embodiment of the shield  10 ″″ that, like the second and third embodiments, once again features the inward protrusions  40 A′,  20 B′ and matching external depressions  42 A′,  42 B′ in the shield&#39;s transitional region at forehead level, and the airflow channel  54  and neighbouring troughs  52 ,  52 B in the cranial portion  46  of the shield, and, as shown, may include the outer rim  112  from the third embodiment for optional use of the flexible attachment clip  114 . The fourth embodiment differs however in different relative angles between particular features of the shield, and in the further inclusion of a pair of supportive downward protrusions  130 A,  130 B on the underside of the cranial portion, each of which corresponds with a matching recessed depression  132 A,  132 B in the topside of the cranial portion. 
     Each recessed depression  132 A,  132 B is an elongated channel-shaped depression residing in an anterior region of the cranial portion that resides nearest to the facial portion  44  of the shield. Each channel shaped depression  132 A,  132 B and coincident downward protrusion  130 A,  130 B lies longitudinally of the cranial portion  46  of the shield in parallel relation to the airflow channel  54 , and is therefore of elongated shape in the front-to-back or anterior-posterior direction in which the cranial potion  46  spans from its connection to the facial portion  44 . The illustrated example features two channel-shaped depression  132 A,  132  and two coincident downward protrusion  130 A,  130 B, which are symmetrically disposed on opposite sides of the centrally located airflow channel  54  that resides a bisecting midplane that cuts symmetrically and vertically through the facial and cranial portions  44 ,  46  of the shield (as shown by line D-D of  FIG.  15 C ). In the illustrated example, a front end of each channel-shaped depression  132 A,  132  intersects with the top end of the respective forehead level depression  42 A′,  42 B′ on the respective side of the midplane at the transitional region of the shield. 
     The downward protrusions  130 A,  130 B each protrude downwardly surrounding areas of the underside of the cranial portion  46 , to an even lower elevation than the floors of the troughs  52 A,  52 B. The bottom of each downward protrusion  130 A,  130 B thus denotes a lowermost surface of the cranial portion, the purpose of which is best seen in  FIG.  16   , where the shield has been vertically cross-sectioned in a plane that is parallel to the midplane, but offset therefrom so as to cut centrally through one of the downward protrusions and its coincident topside depression. Here the bottom of this cross-sectioned protrusion  130 B can be seen to rest on the top of the user&#39;s head at the frontal scalp and/or mid-scalp thereof. As a result, other than this contact between the bottom of each downward protrusion with the top of the user&#39;s head, the entirety of the cranial portion  46  of the shield is elevated off of the top of the user&#39;s head, to enable airflow between the user&#39;s head and the cranial portion  46  of the shield for better ventilation and cooling. As an alternative to integrally formed depressions/protrusions on the cranial portion of the shield, a small block or bar of foam or other material may alternative be attached to the underside of the cranial portion of the shield, for example by double sided tape or hook and loop fastener, for the same purpose of maintaining clearance space between the top of the user&#39;s head and the cranial portion of the shield for airflow purposes, as illustrated by inclusion of such a foam block in  FIGS.  1  and  2   . 
     To also increase the available space for airflow at the top of the user&#39;s head for comfortable wear, the fourth embodiment differs from the earlier embodiments in the relative angle between the cranial portion  46  and the facial portion  44 , as best shown in the cross-sectional profile of  FIG.  15 D , where shield has been vertically bisected at its midplane. The facial region  44  has a linear profile in this cross-sectional plane over a substantial majority thereof, starting from its top end where it hangs down from the curved brow ridge  80  of the shield&#39;s transitional region. In this embodiment, the angle of divergence A 1  between the linear slopes of the facial and cranial portions is greater than 90-degrees, preferably at least 95-degrees, and approximately 100-degrees in one exemplary scenario. In the earlier embodiments, the relative angle between the linear slope profiles of the facial and cranial portions was a right angle of 90-degrees. In the present embodiment with the greater angle of divergence A 1 , the clearance space between the top of the user&#39;s head and the overlying cranial portion of the shield is greater, and increases toward the back of the user&#39;s head, allowing plenty of room for ventilation and user comfort. In the illustrated example, the facial region  44  only deviates from this linear profile at a curved lower chin region  134  that connects the linear majority of the facial portion  44  to the terminal bottom end  14  of the opening&#39;s boundary edge. In the illustrated example, the cranial portion  46  is linearly profiled over its entire span from the top end of the brow ridge  80  to the top end of the opening&#39;s boundary edge. In this example, the divergence angle A 1  is therefore uniform over an entirety of cranial portion  46  and a substantial majority, and near entirety, of the facial portion  44 . Regardless of the degree of uniformity in the chosen divergence angle, at no point along either of the facial portion nor the cranial portion does the slope of the cranial portion toward the rear end thereof (i.e. toward the top end of the shield&#39;s rear opening) ever have a divergent relationship to the slope of the facial portion toward the bottom end thereof (i.e. toward the bottom end of the shield&#39;s rear opening). 
     Another unique angular relationship between features of the fourth embodiment is the angular relationship found between the linear majority of the facial portion  44  and a headband attachment surface found the terminal end of each inward protrusion  40 A,  40 B at the forehead level transition region, as measured in cross-sectional planes that are parallel to the bisecting midplane of the shield, but that are offset therefrom so as to cut vertically through the terminal end of either inward protrusions  40 A,  40 B. This is best shown in  FIG.  15 E , in which the shield has been cross-sectioned through inward protrusion  40 B. In this example, the distal end of inwardly protrusion  40 B has a top half  136 A that lies generally parallel to the linear majority of the facial portion  44  of the shield, but also a distinctly oriented bottom half  136 B that serves as the headband attachment surface to which the front segment of a headband is attachable by suitable coupling elements, such as double sided tape applied to the headband or to headband attachment surface, or matably co-operable pieces of hook and loop fastener respectively applied to each thereof. This headband attachment surface  136 B is not parallel to the linear majority of the shield&#39;s facial portion  44 , and instead is obliquely angled at a small angle thereto in downwardly convergent relationship therewith. In the second and third embodiments, the distal end of each inward protrusion  40 A,  40 B is parallel to the linear majority of the facial portion  44  in cross-sectional planes that cut through the inward protrusions in parallel relation to the midplane. As a result, in those earlier embodiments, attachment of the front segment of a headband to the distal ends of the inward protrusions would place the linear majority of the facial portion  44  in parallel relationship to the front of the headband. So presuming the front of the headband is vertically oriented in a worn position of the user&#39;s head, the linear majority of the facial region would likewise reside in a vertical orientation in the worn position of the shield. In testing, applicant found that such design tended to produce a glare in the sight line of the wearer. 
     Referring to  FIG.  16   , where the non-parallel headband attachment surface  136 B at the terminal end of the inward protrusion  40 B is shown in a generally vertical orientation, as would be supported by the generally vertical front of a worn headband (not shown), the result of the downwardly convergent relationship between the headband attachment surface  136 B and the majority of the facial portion  44  is that the facial portion  44  is tilted in a downwardly rearward fashion angling toward the chest of the user. Testing found that this tilting of the worn position of the shield was effective to move the aforementioned glare out of the wearer&#39;s normal sight line. In prototyping, the tilt angle A 2  between the headband attachment surface  136 B and the linearly sloped major surface of the facial region was selected as 5-degrees, though this angle may varied, for example between 2-degrees and 10-degrees, or more particularly between 3-degrees and 8-degrees. As also shown by  FIG.  16   , the relative tilt angle A 2  between the headband attachment surface  136 B and the linearly sloped major surface of the facial region has compounding effect with the relative divergence angle A 2  between the cranial and facial portions in terms of the resulting angular tilt of the cranial portion  46  relative to the top of the wearer&#39;s head, whereby tilt angle A 2  serves to further increase the available clearance space for airflow between the top of the user&#39;s head and the cranial portion of the shield. So, if headband attachment surface is oriented vertically in the worn position, the angle of inclination of the cranial portion  46  relative to horizontal, in degrees, would be A1+A2−90. It will be appreciated in practice however the front of the headband, in practice, would likely not have a truly vertical orientation, and instead have a slight upwardly rearward (posterior) slant in the worn position, owing to a natural slope of the forehead, and so the illustrated position of  FIG.  16    with the vertical orientation of headband attachment surface  136 B likely represents an exaggeration of the actual tilt that would be seen in the worn position of the shield, but is nonetheless useful to illustrate the rearwardly inclined slope of the cranial portion, and downwardly inward tilt of the facial portion. 
     Another change in relative orientation of features in the fourth embodiment is in the relative orientation of the inner sidewalls  138  of the two forehead-level depressions  42 A,  42 B and coincident inward protrusions  40 A,  40 B at the transitional region of the shield, which also double as sidewalls of the upright brow ridge  80  that separate the two forehead-level depressions  42 A,  42 B. When the shield is worn, air can flow upwardly or downwardly over the wearer&#39;s forehead through the inside of the brow ridge  80  between the two external depressions  42 A,  42 B, i.e. through the open airflow space  140  ( FIG.  15 F ) left between the two internal protrusions  40 A,  40 B. To help with exhaust of warm air and carbon dioxide from the facial area, bottom halves  138 A of the sidewalls  138  are in non-parallel tilted relation to one another in an upwardly convergent and downwardly divergent fashion. As a result, the airflow space between the two inward protrusions  40 A is wider at a lower end  140  thereof that coincides with the bottom ends of the inward protrusions, i.e. the floors of the external depressions  42 A,  42 B, that it is at a narrower mid-region situated further up this airflow space. Top halves  138 B of the sidewalls  138  are also tilted relative to one another, but in opposing fashion to the lower halves, thus being upwardly divergent and downwardly convergent to one another. From its wider bottom end, the airflow space initially tapers to a narrower width to the mid-region of the airflow space, and then widens again toward an open, unobstructed top end of the airflow space, which resides coincident with the top ends of the inward protrusions  40 A,  40 B. Accordingly, the airflow space is configured with a constricted mid-region between two ends of greater with than said mid-region, with the intent of providing a chimney or venturi like effect for more effective drawing of heated/exhaled air upwardly out of the user&#39;s facial area for escape through the open clearance space between the cranial portion of the shield and the top of the user&#39;s head. Another differentiating feature of the fourth embodiment shield  10 ″″ is the inclusion of a respective stiffening ridge  142  integrally formed in each of the lateral sides of the shield in symmetrically matching positions each running longitudinally rearward from the floor of the respective forehead-level depression  42 A,  42 B in a coincident plane therewith to the boundary edge of the shield&#39;s rear opening. The headband attachment surface  136 B stands upright from this plane, such that when the front segment of a headband is attached this surface  136 B of the shield, the headband will run rearwardly from this attachment surface with a bottom edge of the headband in generally parallel relation to the stiffening ridge  142 . The stiffening ridges thereby help retain the form and stability of the shield when worn. 
       FIG.  17    shows a one-piece adjustable foam headband  200  of the present invention, which is just one example of a type of headband that may be attached to any of the forgoing shields at the terminals ends of the forehead-level protrusions  40 A,  40 B, whether or not the attachment surfaces thereof to which the headband is attached is parallel or not to the facial portion  44  of the shield. The headband  200  is composed of a singular unitary strip of foam material having a length dimension LS in which said strip of foam material is elongated relative to the other two of its three orthogonal dimension, namely its width WS and its thickness TS. Of these three dimensions, the thickness TS is the smallest, the length LS is the greatest, and the width WS in intermediate of the two, and many times lesser than the length LS. The strip has two faces F 1 , F 2  that that lie opposite of one another and between which the thickness TS is measured. The strip has first and second ends E 1 , E 2  lying oppositely of one another, and between which the length dimension LS is measured. A fractional portion of the strip&#39;s length spanning from the first end E 1  toward the second end E 2  is configured as a barbed tail  202  that has matching sets of barbs  204  arranged in series along the length of the strip on the two sides of the strip that lie opposite one another across the width WS of the strip. Another fractional portion of the strip&#39;s length is a widened end region that resides adjacent the second end E 2 , and that has a greater width than the barbed tail. As shown, this widened end region  204  may constitute a majority of the strip, thus spanning a substantially full length from end E 2  to the barbed tail, though preferably with a tapered transition rather than a squared shoulder where the two meet. The strip of foam is flexible and bendable in said longitudinal dimension, such that the first and second ends can be brought together to impart a curvature to the strip, and form the strip into a closed loop. The widened end region has one or more receiver openings therein, for example a pair of receiver slots  206  spaced apart in the length dimension. Each receiver opening has a width that is slightly less than the tip-to-tip width of the barbed tail at any pair of aligned barbs on its opposing sides. 
     The compressibility of the foam allows this tip-to-tip width of the barbed tail to be temporarily reduced, whereby the second end E 2  of the strip and any number of the barb pairs can be forced through each of the receiver slots  206 , whereafter the tip-to-tip width of the barbs forced through the slots  206  will return to its default width. At their full width, the barbs resist pulling of the barbed tail back through the slots. As shown in  FIG.  17 B , insertion of the barbed tail through one slot from one face of the strip to the other in a first direction, and subsequent passage of the barbed tail through the next slot in the reverse direction, is operable to secure the strip in a closed loop state. With the strip curled into such a loop, preferably the barbed tail is inserted inwardly through the first slot  206 A nearest to the end E 2  from the outer face of the strip that faces outwardly from the closed loop shape, and then fed back outwardly through the second slot  206 B further from the end E 2  and back to the outside the loop. To tighten the headband around one&#39;s head, the wearer can then simply grab the exposed first end E 1  of the barbed tail outside the loop, and pull on it, to cinch the headband tighter. 
     To secure the headband  200  to the headband attachment surfaces  136 B at the forehead level protrusions  40 A,  40 B of a shield, coupling elements  208  may be preinstalled on the outer face of the headband  200  at a mid-length, preferably full-width, area of the foam strip  210  that resides beyond the inner end of the barbed tail and will form the front section of the headband once installed on the shield, and/or installed on the headband attachment surfaces  136 B of the shield. The illustrated example employs two pieces of double-sided tape  208  as the coupling elements, which are pre-attached to the foam strip of the headband at a lengthwise spacing from one another that matches the known distance between a shield&#39;s headband attachment surfaces. Each piece of tape includes a respective peel-away cover that is removed to reveal the tape come time for assembly of the headband onto a shield. In other examples, such double-sided tape may instead be applied to the headband attachment surfaces of the shield. In another example, hook fastener material may be applied to a first one of either the headband or the shield, and loop fastener material applied to the second one of either the headband or shield for cooperative mating of the hook and loop fastener materials when the time comes to secure the headband and shield together.  FIGS.  17 C and  17 C  show the one-piece, pull-tight adjustable headband installed in attached relation to the headband attachment surfaces of a shield. 
       FIG.  18 A through  18 C  illustrate another headband  300  of the present invention, also constituted entirely of foam except for coupling elements used to connect different component, and also capable of adjusting the size of the closed-loop formed by the headband around the user&#39;s head, but employing a two-piece construction rather than the one-piece construction of  FIG.  17   . This headband  300  features a first strip  300 A of foam material having a first pair of opposing ends E 1 , E 2  again separated from one another by a respective length dimension of that strip, and a second strip of foam material  300 B having a second pair of opposing ends D 3 , E 4  likewise separated from one another by a respective length dimension of that strip. Once again, the length dimension of each strip is its greatest dimension, followed by its width, and finally its thickness, and each strip once again has two opposing faces, each of which spans the length and width dimensions of the strip, and between the two of which the thickness dimension is measured. Like the foam-strip headband of  FIG.  17   , preferably the thickness dimension is uniform throughout each strip. On one of its two faces, the first strip  300 A has a respective piece of hook or loop fastener  302 A,  302 B thereon adjacent each of the first pair of opposing ends E 1 , E 2 . One of the two faces of the second strip  300 B has a respective piece of loop or hook fastener thereon  304 A,  304 B adjacent each of the second pair of opposing ends E 3 , E 4 . The loop or hook fastener material  304 A,  304 B used on the second strip  300 B is of a matable type the hook or loop fastener material  302 A,  302 B used on the first strip  300 A. For example, if hook fastener is used on the first strip, then loop fastener is used on the second strip, or vice versa. Accordingly, the first and second strips are connectable face-to-face in end-overlapping fashion with one another to form a closed loop. 
     At least one of the pieces of fastener  302 A,  302 B,  304 A,  304 B is elongated in the length dimension of the respective strip of foam material to enable coupling together of the two strips in varying degrees of overlap to thereby adjustably size said headband. In the illustrated example, the two fastener pieces  304 A,  304 B on the second strip  300 B are both elongated in the length dimension of that strip. The first strip has two coupling elements  308  installed a mid-region of its length at lengthwise spacing from one another that that matches the known distance between a shield&#39;s headband attachment surfaces, whereby the first strip is attachable to a shield at the headband mounting surfaces thereof to form a front section of the overall headband. Once again, each piece of tape  308  includes a respective peel-away cover that is removed to reveal the tape come time for assembly of the headband onto a shield. In other examples, such double-sided tape may instead be applied to the headband attachment surfaces of the shield. As described for the  FIG.  17    embodiment, hook and loop fastener may alternatively be used as coupling elements for attaching the headband to the shield. In the illustrated embodiment, the first strip  300 A is longer than the second strip  300 B, and may be sufficiently long to ensure that when its attached to the headband attachment surfaces of the shield, the ends E 1 , E 2  of the first strip will reach out from the interior space of the shield through the rear opening, thereby placing fastener pieces  302 A,  302 B outside the shield for easy access. The two ends E 3 , E 4  of the second strip  300 B are respectively attachable to these exposed ends E 1 , E 2  of the first strip, in a user-selectable amount of overlap to control the overall size of the closed headband loop co-operably formed by the two connected strips  300 A,  300 B. 
       FIG.  18 C  shows how, after attachment of the first strip  300 A to the headband attachment surfaces at the terminal ends of forehead-level protrusions  40 A,  40 B, a central section of that strip  300 A that spans between the two spaced apart protrusions  40 A,  40 B may be cut out, thus dividing the strip  300 A into two separate smaller strips with a gap therebetween. This resulting gap in the front section of the headband leave the airflow space  140  between the two protrusions  40 A,  40 B fully open at the rear side thereof that faces the user&#39;s forehead to maximize the overall available area for airflow between the shield and the user&#39;s forehead. The air can now flow through the combined airflow space  140  and headband gap G, rather than only through the shield&#39;s original airflow space  140  in front of the installed headband. The same cutting of a central section of the headband to improve overall airflow accommodation can likewise be performed on the installed headband of  FIG.  17   , or any other style of strap likewise attached to the forehead-level protrusions  40 A,  40 B of the shields described herein. 
     Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.