Patent Publication Number: US-2020289777-A1

Title: Headgear for breathing mask

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
     Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference and made a part of the present disclosure. 
    
    
     BACKGROUND 
     Field 
     The present invention generally relates to headgear of breathing masks. More particularly, certain aspects of the present invention relate to headgear used with breathing masks that seal under the nose and around the mouth. 
     Description of the Related Art 
     Breathing masks come in many different configurations. To secure the breathing masks to the user, headgear can be attached to the masks. While different styles of headgear are available, the headgear and the breathing masks ideally cooperate to provide a desired interface assembly. 
     SUMMARY 
     In some configurations, masks can be provided that seal around a mouth of a user and on an underside of a nose of the user. Such a mask can provide pressurized air flow to both the nose and the mouth of the user. In some configurations, the mask may omit a forehead support, which is different from many of the nasal masks and many of the oral-nasal masks available in the market. 
     With such masks, the headgear has to overcome one or more of a number of challenges. For instance, the nasal sealing surface should be secured up against the lower surface of the user&#39;s nose. Securing the nasal sealing surface against the nose helps achieve an effective seal without applying excessive force to the nose. To achieve this, the headgear can provide a force to the mask that is at least partially perpendicular to the underside of the nose. 
     In some configurations, the lack of a forehead support means that the mask may be prone to rocking on the face. In such configurations, the headgear can hold the seal against the face evenly in such a manner that the likelihood is reduced of significant rocking of the top away from the nose or movement of the bottom of the mask away from the chin. 
     An aspect involves an interface assembly including a mask and a headgear. The mask includes a seal that surrounds and delivers a flow of breathing gas to a mouth of a user. The headgear secures the mask to the face of the user. The headgear includes relatively rigid portions that contact the cheeks of the user and support the mask relative to the face of the user. The relatively rigid portions have sufficient rigidity to maintain a position of the mask and limit compression of the seal in response to tightening of the headgear. 
     In some configurations, a cheek pad positioned on at least a skin-contacting side of each of the relatively rigid portions. The cheek pad can be contoured. The cheek pad can surround the relatively rigid portion. 
     In some configurations, the headgear further comprises an upper arm or strap extending rearwardly from each of the relatively rigid portions toward a location generally above the user&#39;s ear. 
     In some configurations, the headgear includes a rear halo portion surrounding a parietal region of the user&#39;s head and coupled to the upper arms or straps. A portion of the rear halo portion, the upper arms or straps, and the mask can cooperate to form a front halo portion. 
     In some configurations, the headgear comprises a crown strap, which forms a part of each of the front halo portion and the rear halo portion, and a rear strap, which forms a part of the rear halo portion. 
     In some configurations, at least portions of the upper arm, the crown strap and the rear strap are constructed from a relatively rigid material or a relatively non-stretch material. 
     In some configurations, the headgear includes a pair of rigid sections, each rigid section comprising an upper arm, a portion of the crown strap and a portion of the rear strap, wherein each of the crown strap and the rear strap comprises adjustment arrangements that connect the rigid sections to one another and permit adjustment of the front halo portion and the rear halo portion. The adjustment arrangements can comprise flexible straps. 
     In some configurations, each of the rigid sections is covered by a soft material padding. The soft material padding can be overmolded onto the rigid sections. 
     In some configurations, the mask is supported relative to the headgear by a rotational coupling. The mask can be secured in a rotational position relative to the headgear. The mask can be secured in the rotational position by a lock or detent mechanism incorporated into the rotational coupling. In some configurations, the mask is secured in the rotational position by a strap of the headgear. 
     In some configurations, at least one quick-release mechanism permits separation of two portions of the interface assembly to open or increase a circumference of the interface assembly. The quick-release mechanism can include a tether between the two portions of the interface assembly. The tether can be elastic. In some configurations, the quick-release mechanism comprises a clip that connects the headgear to the mask. The clip can define at least two spaced engagement points with the mask. In some configurations, a magnetic coupling guides the clip into position relative to the mask. The quick-release mechanism can include a clip that connects the headgear to the mask, and the tether can be hidden between the clip and the mask when the clip is secured to the mask. In some configurations, the quick-release mechanism comprises a release buckle. 
     In some configurations, a position of the seal is adjustable relative to a frame or support structure of the mask to which the relatively rigid portions are connected. A dial adjuster can be provided that adjusts the position of the seal. 
     An aspect involves an interface assembly including a mask and a headgear. The mask includes a seal that surrounds and delivers a flow of breathing gas to a mouth of a user. The headgear secures the mask to the user&#39;s face. A closed loop adjustment mechanism couples a first portion of the interface assembly to a second portion of the interface assembly and is movable between a contracted orientation and an elongated orientation to vary an overall circumference of the interface assembly while maintaining a closed loop. In the contracted orientation, the mask is supported against the face of the user and, in the elongated orientation, the interface assembly can be applied to or removed from the head of the user. At least a portion of the closed loop adjustment mechanism is located on the mask. 
     In some configurations, the closed loop adjustment mechanism comprises a loop that forms a portion of the circumference of the interface assembly, wherein the loop can be secured to the mask at first and second spaced locations to define a first section length, and wherein the loop can be disconnected from the second location to define a second section length that is greater than the first section length to increase the circumference of the interface assembly. In some configurations, the second location can be a retention cleat that the loop can be looped around. In some configurations, the second location can be an opening or bar that is engaged by a clip connected to the loop. The first location can be a friction guide through which the loop passes, wherein the friction guide frictionally engages the loop to maintain a desired relative position between the loop and the mask in response to normal operational forces. 
     In some configurations, the closed loop adjustment mechanism comprises a clip that connects the headgear to the mask. The clip can define at least two spaced engagement points with the mask. In some configurations, a magnetic coupling that guides the clip into position relative to the mask. The closed loop adjustment mechanism can include a tether between the clip and the mask. In some configurations, the tether is elastic. The closed loop adjustment can include a clip on each side of the mask and the tether can extend between the two clips. In some configurations, the tether is hidden between the clip and the mask when the clip is secured to the mask. 
     In some configurations, the closed loop adjustment mechanism comprises a folding clasp having multiple segments movable between an open position and a closed position. In some configurations, at least two segments of the folding clasp are nested in the closed position of the folding clasp. In some configurations, one of the segments defines a generally U-shape and a second one of the segments is positioned within a central space of the U-shaped segment in a closed position of the folding clasp. In some configurations, one of the segments is carried by the mask and a second one of the segments is carried by the headgear. A locking adjuster can be provided between the second one of the segments and the headgear to permit adjustment of a relative position of the folding clasp and the headgear. In some configurations, the folding clasp locks in the closed position. 
     An aspect involves an interface assembly including a mask and a headgear. The mask includes a seal that surrounds and delivers a flow of breathing gas to a mouth of a user. The headgear secures the mask to the user&#39;s face and includes at least one adjustment loop. A sliding buckle receives a portion of the headgear within a tortuous pathway and is coupled to a portion of the adjustment loop, wherein movement of the sliding buckle along the portion of the headgear alters a size of the adjustment loop to alter an overall size of the headgear. 
     In some configurations, a pull tab is coupled to the sliding buckle to facilitate movement of the sliding buckle. In some configurations, a coupler secures the pull tab relative to the sliding buckle when not in use. The coupler can be a magnetic coupler. 
     In some configurations, the pull tab is slidably mounted to the sliding buckle such that the pull tab can move relative to the sliding buckle in a direction of movement of the sliding buckle. 
     In some configurations, at least one clip that couples the headgear to the mask. The clip can be tethered to the mask. 
     In some configurations, clip defines at least two spaced engagement points with the mask. 
     An aspect involves an interface assembly including a mask and a headgear. The mask includes a seal that surrounds and delivers a flow of breathing gas to a mouth of a user. The headgear secures the mask to the user&#39;s face. The headgear is constructed from at least two flat portions of material that are connected along sew lines to form a seam, wherein the sew lines of the portions of material do not have the same shape, such that, when connected, tension and/or compression is introduced into the material to provide the headgear with a contoured shape. 
     In some configurations, the sew lines are defined by edges of the portions of material. 
     In some configurations, the connection between the portions extends in a vertical direction along a rear portion of the headgear. 
     An aspect involves an interface assembly including a mask and a headgear. The mask includes a seal that surrounds and delivers a flow of breathing gas to a mouth of a user. The headgear secures the mask to the face of the user. The headgear includes a rear halo portion surrounding a parietal region of the user&#39;s head and the headgear cooperates with the mask to form a front halo portion surrounding a frontal region of the user&#39;s head. The headgear includes a relatively stretchable portion and a relatively non-stretchable portion, wherein the relatively non-stretchable portion surrounds at least one of the front halo portion and the rear halo portion. 
     In some configurations, the relatively non-stretchable portion surrounds each of the front halo portion and the rear halo portion. 
     In some configurations, one or both of the front halo portion and the rear halo portion are adjustable in circumference. 
     In some configurations, a break-fit assembly permits the headgear to move between a normal configuration and an enlarged configuration. The break-fit assembly can include a separation between a first portion of the headgear and a second portion of the headgear, wherein the first and second portions are held together in the normal configuration and are moved apart in the enlarged configuration. The first and second portions can be held together by a magnetic closure. 
     In some configurations, the first and second portions comprise first and second flaps, respectively. In some configurations, the first and second flaps are joined by a pleat. 
     In some configurations, the front halo portion connects to each side of the mask at a first location, wherein the headgear further comprises straps on each side of the headgear that each connect to a respective side of the mask at a second location spaced from the first location. The first and second locations can be upper and lower locations, respectively. 
     In some configurations, strengthening features are formed into or otherwise secured to the relatively stretchable portion of the headgear. 
     An aspect involves an interface assembly including a mask and a headgear. The mask includes a seal that surrounds and delivers a flow of breathing gas to a mouth of a user, the mask comprising a support structure having an elongated slot. The headgear secures the mask to the face of the user, wherein the headgear comprises an end portion that passes through the elongated slot of the mask and is folded to form a loop, the loop having a fold that supports the mask, wherein the end portion can be adjusted in an upward or downward direction to adjust an angle of the mask relative to the headgear. 
     In some configurations, the end portion defines a tapered shape. 
     In some configurations, the end portion can be coupled to the headgear to secure the mask in a desired angular position. 
     In some configurations, the elongated slot is linear in shape. 
     In another aspect, the invention involves the headgear of any of the above-described interface assemblies configured for use with any of the above-described interfaces or any other compatible interface. 
     In a further aspect, the invention consists in components as herein described with reference to any one or more of the drawings. 
     The term “comprising” as used in this specification and claims means “consisting at least in part of”. When interpreting each statement in this specification and claims that includes the term “comprising”, features other than that or those prefaced by the term may also be present. Related terms such as “comprise” and “comprises” are to be interpreted in the same manner. 
     This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application and/or statements of invention, individually or collectively, and any or all combinations of any two or more said parts, elements features or statements of invention, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth. 
     The invention consists in the foregoing and also envisages constructions of which the following gives examples only. 
     In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art. 
     Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects and advantages of the present disclosure are described with reference to the drawings of preferred embodiments, which embodiments are intended to illustrate and not to limit the disclosure. 
         FIG. 1  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 2  is a front view of the interface assembly of  FIG. 1 . 
         FIG. 3  is a rear view of the interface assembly of  FIG. 1 . 
         FIGS. 4A-4F  illustrate various possible cross-sections of a headgear of the interface assembly of  FIG. 1 . 
         FIGS. 5A and 5B  illustrate a break-fit arrangement of the interface assembly of  FIG. 1 . 
         FIG. 6  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 7  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 8  is a front view of the interface assembly of  FIG. 7 . 
         FIG. 9  is a rear view of the interface assembly of  FIG. 7 . 
         FIGS. 10A-10E  are side views of several interface assemblies, each having an interface, such as a mask, and a headgear. 
         FIGS. 11A-11C  are side views of several interface assemblies, each having an interface, such as a mask, and a headgear. 
         FIGS. 12A-12I  are side views of several interface assemblies, each having an interface, such as a mask, and a headgear. 
         FIG. 13  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 14  is a front view of the interface assembly of  FIG. 13 . 
         FIG. 15  is a rear view of the interface assembly of  FIG. 13 . 
         FIG. 16  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 17  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 18  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 19  is an exploded view of the rotational adjuster of the interface assembly of  FIG. 18 . 
         FIG. 20  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 21  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 22A  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 22B  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 23  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 24  is a front view of the interface assembly of  FIG. 23 . 
         FIG. 25  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 26  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 27  is a cross-sectional view of a first portion of the headgear of the interface assembly of  FIG. 26 . 
         FIGS. 28A-28C  illustrate several possible cross-sections of a second portion of the headgear of the interface assembly of  FIG. 26 . 
         FIG. 29  is a side view of an interface assembly having an interface, such as a mask, and a headgear. The interface assembly has a rotational coupling between the mask and the headgear. 
         FIG. 30  is an exploded view of the rotational coupling of the interface assembly of  FIG. 29 . 
         FIG. 31  is a side view of an interface assembly having an interface, such as a mask, and a headgear. The headgear includes a cheek pad. 
         FIG. 32  is a perspective view of a cheek pad portion of the headgear of the interface assembly of  FIG. 31 . 
         FIG. 33  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 34  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 35  is a side view of an interface assembly having an interface, such as a mask, and a headgear. The interface assembly includes quick-release mechanisms between the headgear and the mask. 
         FIG. 36  is a side view of an alternative quick-release mechanism. 
         FIG. 37  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 38  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 39  is a rear view of the interface assembly of  FIG. 38 . 
         FIG. 40  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 41  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 42  is a front view of the interface assembly of  FIG. 41 . 
         FIG. 43  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 44  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 45  is a front view of the interface assembly of  FIG. 44 . 
         FIG. 46  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 47  is a side view of an interface assembly having an interface, such as a mask, and a headgear. The headgear includes a low profile adjustment mechanism. 
         FIG. 48  is an enlarged view of the low profile adjustment mechanism of  FIG. 47 . 
         FIG. 49  is a side view of an interface assembly having an interface, such as a mask, and a headgear. 
         FIG. 50  is a perspective view of an interface assembly having an interface, such as a mask, and a headgear. The interface assembly includes a quick-release mechanism between the mask and the headgear. 
         FIG. 51  is a perspective view of an interface assembly having an alternative quick-release mechanism. 
         FIG. 52  is a perspective view of an interface assembly having another alternative quick-release mechanism. 
         FIG. 53  is a perspective view of an interface assembly having yet another alternative quick-release mechanism. 
         FIG. 54  is a perspective view of an interface assembly having still another alternative quick-release mechanism. 
         FIG. 55  is a perspective view of an interface assembly having another alternative quick-release mechanism including a clip. 
         FIG. 56  is a perspective view of the mask of the interface assembly of  FIG. 55 . 
         FIG. 57  is a perspective view of an interior surface of the clip of the quick-release mechanism of the interface assembly of  FIG. 55 . 
         FIG. 58  is an exploded perspective view of an interface assembly having a quick-release mechanism. 
         FIG. 58  is a perspective view of an interface assembly having a quick-release mechanism, which includes an elasticated tether that couples the clip to a remainder of the mask. 
         FIG. 59  is a perspective view of an interface assembly having an alternative quick-release mechanism with an elasticated tether. 
         FIG. 60  is a perspective view of an interface assembly having another alternative quick-release mechanism with an elasticated tether. 
         FIG. 61  is a perspective view of the interface assembly of  FIG. 60  with the quick-release mechanism in a disconnected state. 
         FIG. 62  is a side view of an interface assembly having an interface, such as a mask, and a headgear. The interface assembly includes a folding clasp quick-release mechanism between the mask and the headgear. 
         FIG. 63  is a top view of the folding clasp quick-release mechanism of  FIG. 62  in a closed state. 
         FIG. 64  is a top view of the folding clasp quick-release mechanism of  FIG. 62  in an open state. 
         FIG. 65  is a perspective view of an interface assembly with an alternative folding clasp quick-release mechanism connecting the headgear and the mask. The folding clasp quick-release mechanism is shown in a closed state. 
         FIG. 66  is a perspective view of the interface assembly of  FIG. 65  with the folding clasp quick-release mechanism in an open state. 
         FIG. 67  is a cross-sectional view of the folding clasp quick-release mechanism of  FIG. 65 . 
         FIG. 68  is an enlarged view of a headgear strap adjustment assembly of the interface assembly of  FIG. 65 . 
         FIG. 69  is a side view of an interface assembly having an interface, such as a mask, and a headgear. A sliding buckle adjustment mechanism permits adjustment of the headgear. 
         FIG. 70  is a cross-sectional view of the sliding buckle adjustment mechanism of  FIG. 69 . 
         FIG. 71  is a perspective view of the sliding buckle adjustment mechanism of  FIG. 69 . 
         FIG. 72  is a cross-sectional view of an alternative sliding buckle adjustment mechanism having a slidable pull tab. 
         FIG. 73  illustrates portions of a contoured headgear prior to joining. 
         FIG. 74  illustrates the portions of  FIG. 73  joined to create a contoured headgear. 
         FIG. 75  is a front perspective view of an interface assembly having an interface, such as a mask, and a headgear. The headgear includes at least one relatively rigid section. 
         FIG. 76  is a side view of the interface assembly of  FIG. 75 . 
         FIG. 77  is a rear perspective view of the interface assembly of  FIG. 75 . 
         FIG. 78  is top view of an adjustment mechanism within a crown strap portion of the headgear of  FIG. 75 . 
         FIG. 79  is a rear view of an adjustment mechanism within a rear strap portion of the headgear of  FIG. 75 . 
         FIG. 80  is a perspective view of an alternative adjustment mechanism of  FIGS. 78 and 79  having a break-fit arrangement with a tether to couple portions of the adjustment mechanism. 
         FIG. 81  is a top view of the interface assembly of  FIGS. 75-79  illustrating a difference between an untightened headgear (left side) and a tightened headgear (right side). 
         FIG. 82  is a front view illustrating a location of contact of a rigid portion of the headgear of the interface assembly of  FIGS. 75-79  on a user&#39;s face. 
         FIG. 83  is a top view illustrating the location of contact of  FIG. 82 . 
         FIG. 84  is a side view illustrating a location of an axis of rotation of the mask of the interface assembly of  FIGS. 75-79 . 
         FIG. 85  is a side view of a mask of the interface assembly of  FIGS. 75-79  illustrating a range of rotational adjustment of the mask. 
         FIGS. 86A-86G  are cross-sectional views of a portion of the headgear of  FIGS. 75-79  illustrating several possible shapes of a rigid portion and a pad. 
         FIG. 87  is a side view of the headgear of  FIGS. 75-79  illustrating a front halo portion and a rear halo portion. 
         FIGS. 88A-88F  illustrate alternative headgear arrangements relative to  FIG. 87  each having a front halo portion and a rear halo portion. 
         FIGS. 89A-89F  illustrate several possible locations for break-fit assemblies within a headgear, such as the headgear of  FIGS. 75-79 . 
         FIG. 90  is a side view of a headgear for an interface assembly illustrating optional locations for relatively rigid and relatively non-rigid portions of the headgear. 
         FIG. 91  is a side view of an interface assembly having an interface, such as a mask, and a headgear. The interface assembly includes a rotational coupling between the mask and the headgear. 
         FIG. 92  is a perspective view of an interface assembly having an interface, such as a mask, and a headgear. The interface assembly includes an adjustment arrangement for a position of the mask. 
         FIG. 93  is a perspective view of an interface assembly having an interface, such as a mask, and a headgear. The interface assembly includes a cheek pad in the headgear and a quick-release mechanism between the mask and the headgear. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1-3 , an interface assembly  100  is illustrated. The interface assembly  100  can have any suitable configuration. The illustrated interface assembly  100  includes an interface portion, or interface  102 , and a headgear portion, or headgear  104 . The illustrated interface  102  is a nasal-oral mask but, in some configurations, certain features, aspects and advantages of the disclosed embodiments can be used with any type of interface, including but not limited to full face masks, nasal masks, nasal pillows, oral masks and cannulas. Accordingly, the interface  102  is also referred to herein as a “mask” for convenience. The use of the term “mask” is intended to cover interfaces generally, and can be replaced with the term “interface” unless indicated otherwise, either explicitly or by the context of the disclosure. Examples of nasal-oral masks are provided in PCT Patent Publication No. WO2013/066195, the entirety of which is incorporated by reference herein. 
     The illustrated mask  102  generally comprises a support structure, such as a frame  106 , which supports a seal  108 . The mask  102  (e.g., the frame  106  and/or the seal  108 ) can be connected to a supply conduit (not shown), which in some configurations can be connected to the frame by an elbow. The supply conduit can be used to supply breathing gases to a user through the seal  108 . The seal  108  or a combination of the seal  108  and the frame  106  can define a chamber that receives the breathing gases from the supply conduit. 
     As described above, in some configurations, the mask  102  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  102  can provide pressurized air flow to both the nose and the mouth of the user. With such masks  102 , the headgear  104  preferably secures the nasal sealing surface up against the lower surface of the user&#39;s nose. Securing the nasal sealing surface against the nose helps achieve an effective seal without applying excessive force to the nose. As the air pressure within the chamber of the mask  102  increases, the force applied by the headgear  104  attempts to restrain the mask  102  from lifting from the face. As a result of the mask  102  being sealed against the underside of the user&#39;s nose, the force applied to the mask  102  as a result of the air pressure has a downwardly-directed component. However, in general, the largest component of the force is directed away from the user&#39;s face. To address the forces acting on the mask as a result of the air pressure, the headgear  104  preferably provides a force to the mask  102  that has at least a small upwardly-directed component. In some configurations, the headgear  104  can provide a force to the mask  102  that is directed generally or substantially perpendicular to the underside of the user&#39;s nose. 
     Preferably, the mask  102  comprises mounting locations or mounting points  110 . The mounting points  110  can be formed on at least one of the frame  106 , the seal  108 , the conduit and the elbow. Any suitable mounting points  110  can be used to facilitate connection between the mask  102  and the headgear  104 , which will be described below. Often, the mounting points  110  are located on a relatively rigid portion of the mask  102 , such as the frame  106  or another support structure for the seal  108 . Therefore, references to the frame  106 , in the context of the headgear  104  being coupled at the mounting points  110  on the frame  106 , can refer to any support structure of the mask  102  to which the headgear  104  is coupled, such as a seal housing, for example. 
     In some configurations, the mounting points  110  facilitate easy connection and disconnection of the headgear  104  and the mask  102 . In some configurations, the headgear  104  and the mask  102  can be joined together such that the headgear  104  is not generally removable from one or more component of the mask  102 . In some configurations, the headgear  104  and the mask  102  can be integrally formed. In some configurations, two mounting points  110  are provided on each side of the mask  102  and are spaced from one another in a vertical direction or height direction of the mask  102 . 
     In some configurations, the headgear  104  can comprise a front halo portion  112  and a rear halo portion  114 . Preferably, the headgear  104  comprises at least the rear halo portion  114 . The front halo portion  112  can be configured to generally encircle the frontal region or upper half of the face of the user and resist rearward and downward directed forces. The rear halo portion  114  can be configured to generally encircle the parietal region of the head and resist forward and downward directed forces. In some configurations, the rear halo portion  114 , when coupled to the mask  102 , can resist a substantial portion or an entirety of the magnitude and/or direction of forces applied to the mask  102  during use. Thus, in some configurations, the rear halo portion  114  can be utilized without the front halo portion  112 . However, the front halo portion  112  can assist in inhibiting or preventing rotation of the interface assembly  100  on the user&#39;s head. The front halo portion  112  can also resist downward forces to support the weight of the mask  102  and other generally downward forces, such as hose pull forces, for example. Thus, in many applications, the use of a front halo portion  112  can be desirable. In some configurations, the front halo structure  112  and the rear halo structure  114  are generally adjacent to each other. In some such configurations, the front halo structure  112  and the rear halo structure  114  can share a common crown strap  116 . 
     In some configurations, under-ear straps or ear straps  118  can extend from lower portions of the rear halo portion  114  on each side of the headgear  104 . As shown in the illustrated configurations, lower or forward strap portions  120  of the front halo structure  112  can be attached to the upper section of the mask  102  at mounting points  110  on each side of the mask  102 . The forward strap portions  120  of the front halo structure  112  can be angled such that the force applied by the forward strap portions  120  will have an upwardly-directed component. As described above, in some configurations, the force can be approximately or largely perpendicular to the underside of the user&#39;s nose. Such an arrangement can assist in creating a seal between the mask  102  and the underside of the user&#39;s nose. The attachment location and the angle will help to address both of the challenges mention above. 
     The ear straps  118  can be attached to the lower portion of the mask  102  at mounting points  110  on each side of the mask  102 . By attaching the ear straps  118  to the lower portion of the mask  102 , forces applied by the ear straps  118  can cooperate with forces applied by the forward strap portions  120  of the front halo portion  112  to influence an angular position of the mask  102 , as described below. The forward strap portions  120  of the front halo portion  112  can be referred to as “upper straps” relative to the ear straps  118 , which are the relative “lower straps” and can be referred to as such herein. The balancing of forces can reduce the likelihood of mask rocking. 
     With reference to  FIG. 1 , the mask  102  can be viewed as having an upper point P 1  and a lower point P 2  at which the mask  102  contacts the user&#39;s face. The upper point P 1  can be generally or substantially at an intersection between the underside of the user&#39;s nose and upper lip. The lower point P 2  can be located on the user&#39;s chin. Adjustment of the forward strap portions  120  tends to rotate the mask  102  about the lower point P 2 . Adjustment of the ear straps  118  tends to rotate the mask  102  about the upper point P 1 . Thus, the existence of both of the straps  118 ,  120  tends to inhibit or prevent undesired rotation about either point P 1 , P 2  when the headgear  104  is properly adjusted. 
     The headgear  104  can apply a force Fl to the mask  102  through the upper straps  120  and a force F 2  to the mask  102  through the lower straps  118 . The force F 1  can be at least be oriented upward relative to horizontal or relative to a line that is perpendicular to a line passing through the points P 1  and P 2  (or a line defined by upper and lower points on the mask seal  108 ). The force F 2  can be generally rearward, horizontal or along a line that is perpendicular to a line passing through the points P 1  and P 2  (or a line defined by upper and lower points on the mask seal  108 ). The force F 1  can be between about 0 degrees and about 90 degrees. However, because the force applied to the headgear  104  by the mask  102  as a result of air pressure is primarily away from the user&#39;s face, preferably, a horizontal component FH of the force F 1  is at least as large as or larger than a vertical component FV of the force F 1 . Thus, the angle of the force F 1  can be about 45 degrees or less. However, if a greater vertical component FV is desired, such as to increase sealing force on the underside of the user&#39;s nose, the angle of the force F 1  can be adjusted. 
     In some configurations, one or more of the upper straps  120  and the lower straps  118  used to attach to the mask  102  may be adjustable in length. In some configurations, both of the upper straps  120  and the lower straps  118  can be adjustable in length. However, in the illustrated arrangement, the length of the upper straps  120  is fixed and the overall circumference of the front halo portion  112  is adjusted by the central adjustment feature  122 , which also adjusts the circumference of the rear halo portion  114 . The lower straps  118  are adjustable to permit a rotational position of the mask  102  (relative to the upper mounting points  110  of the upper straps  120 ) to be adjusted. 
     In some configurations, the crown strap  116  can have a central adjustment feature  122 . The central adjustment feature  122  can allow the size of the headgear  104  to be modified. The central adjustment feature  122  can have any suitable configuration. In some configurations, the central adjustment feature  122  can include a buckle component and portions of the crown strap  116  can pass through the buckle and double over another portion of the crown strap  116 . In some configurations, the central adjustment feature  122  can be as simple as providing a hook and loop connection between two portions the crown strap  116 . 
     The headgear  104  can be formed of any suitable materials. In some configurations, at least a portion of the headgear  104  will be made of a material with some stretch. In some configurations, the headgear  104  is formed of a stretchable material, such as Breath-o-prene®, for example but without limitation. Breath-o-prene® is a heat laminated material made of polyurethane foam with an outer layer of nylon and spandex. In some configurations, the headgear  104  may be thermoformed to provide structure and support. 
     The headgear  104  also may comprise non-stretch sections  124 . In some configurations, the non-stretch sections  124  can extend around the perimeters of one or both of the halo portions  112 ,  114 . In the illustrated arrangement, non-stretch sections  124  extend around an entire perimeter of the front halo portion  112  (with the exception of the mask  102 ) and an entire perimeter of the rear halo portion  114 . In some configurations, non-stretch sections can also be incorporated in the lower strap  118 . The non-stretch sections  124  can reduce the likelihood of the front halo portion  112  and/or rear halo portion  114  stretching over the head relative to a similar arrangement of stretchable material. Stretching of the rear halo portion  114  can cause the mask  102  to move away from or slip off the face. Stretching of the front halo portion  112  can allow rotation of the headgear  104  on the user&#39;s head. As used herein, the term “non-stretch” in the context of the non-stretch sections  124  refers to sections that are less stretchable than the stretchable or other portions of the headgear  104 . In some configurations, the non-stretch sections  124  can resist substantial stretching or elongation in response to normal or expected forces applied to the mask  102  or headgear  104  to retain the halo portion(s)  112 ,  114  in place on the user&#39;s head, but may still be somewhat stretchable. The non-stretch sections  124  can reduce the likelihood of the upper sealing surface of the seal  108  being pulled away from the nose. In some configurations, the non-stretch sections  124  may be included in other regions of the headgear  104 . Stretchable material can refer to materials typically used in headgear assemblies or can refer to materials that exhibit greater stretch than materials typically used in headgear assemblies. 
       FIGS. 4A-4F  illustrates some possible strap cross-sections but any suitable strap configuration or combination of configurations can be used. In  FIGS. 4A-4F , the hashed regions  124  can represent a material that is largely or relatively non-stretch or semi-rigid. The non-hashed regions  126  can represent a softer and/or more stretch/less rigid/more elastic material, such as Breath-o-prene®, for example. In the illustrations shown in  FIGS. 4A-4F , it is intended that the lower edge of each cross-section represents the surface that would be in contact with the patient&#39;s head. In most configurations, at least part of the surface that comes into contact with the patients head can be formed from or of a softer material. 
     In  FIG. 4A , the strap cross-section includes a non-stretch region  124  at at least one lateral edge and, preferably, at each lateral edge of the strap. A stretch region  126  extends between the laterally-spaced non-stretch regions  124 . In  FIG. 4B , the strap cross-section includes a central non-stretch region  124  with stretch regions  126  on each side of the non-stretch region  124 . In  FIG. 4C , the strap cross-section includes a plurality of spaced non-stretch regions  124  alternating with stretch regions  126 . In the illustrated arrangement, the stretch regions  126  are positioned on each lateral edge and in the center with non-stretch regions  124  between the center and edge stretch regions  126 . In  FIG. 4D , a non-stretch region  124  extends in a width direction of the strap cross-section. In the illustrated arrangement, the regions are layered with a stretch region  126  on at least one side and, preferably, on each side of the non-stretch region  124 . In  FIG. 4E , a non-stretch region  124  and a stretch region  126  extend in a width direction of the strap and each occupies one-half of the strap thickness. In the illustrated arrangement, the stretch region  126  is positioned closest to the user&#39;s head. In  FIG. 4F , the entire strap cross-section is a stretch region  126 . 
     With reference to  FIGS. 1, 5A and 5B , in some configurations, the headgear  104  can include a so-called break-fit assembly  130 , which can be utilized to move the headgear  104  between a fitted or operating condition, in which the headgear  104  holds the mask  102  in contact with the user&#39;s face, and a fitment or removal condition, in which application or removal of the headgear  104  is facilitated. Preferably, the operating condition is a properly adjusted condition for an individual user and the break-fit assembly  130  permits quick and easy transition between the operating condition and the fitment/removal condition. That is, in contrast to designs that readjustment with each application of the interface assembly  100 , the break-fit assembly  130  allows the headgear  104  to remain in a properly adjusted state, but be enlarged or opened to a certain extent to facilitate application or removal. Preferably, adjustment features separate from the break-fit assembly  130  are provided to permit adjustment of the headgear  104  to fit an individual user. Break-fit assemblies could be provided in other locations of the headgear  104 , such as any strap portion of the headgear  104  or any of the other locations disclosed herein, such as in connection with  FIG. 89 , for example and without limitation. 
     The break-fit assembly  130  can resist elongation/expansion under some conditions and permits elongation/expansion under other conditions. For example, the break-fit assembly  130  can be automatic, in which elongation/expansion of the headgear  104  is resisted or prevented until a predetermined or desired yield force is exceeded, at which point the headgear can elongate/expand. In some configurations, the break-fit assembly  130  can be manually operated to move the headgear  104  between the operating condition and the fitment/removal condition. 
     The illustrated break-fit assembly  130  comprises a separation  132  between a first flap  134  and a second flap  136  of material. As illustrated in  FIGS. 5A and 5B , the first flap  134  and the second flap  136  can be joined or their respective edges brought close to one another to define a fitted or operating condition or the flaps  134 ,  136  can be separated to define a fitment/removal condition. Optionally, a retention mechanism, fastener or closure  138 , such as a magnetic closure, can be utilized to secure the flaps  134 ,  136  in a fitted or operation condition. In some configurations, the flaps  134 ,  136  can be connected to one another by material extending between the edges defining the separation  132 , such as by a pleat. Other suitable arrangements to facilitate fitment of the headgear  102  and/or interface assembly  100  can also be used. For example, the break-fit assembly can include any of those described in U.S. Provisional Patent Application No. 61/681,024, filed on Aug. 8, 2012, for example but without limitation, which is hereby incorporated by reference in its entirety. 
     With reference to  FIG. 6 , another interface assembly  600  is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  600  includes an interface  602  and a headgear  604 . The illustrated interface  602  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  604 . The illustrated mask  602  generally comprises a frame  606  that supports a seal  608 . The mask  602  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  602  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  602  can provide pressurized air flow to both the nose and the mouth of the user. The headgear  604  can be coupled to the mask  602  at one or more mounting locations or mounting points  610 , as described below. Unless indicated otherwise, features of the interface assembly  600  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     In some configurations, the headgear  604  can comprise a generally non-stretch/semi-rigid halo shaped portion  614  (referred to herein as the “halo portion”). In some such configurations, the halo portion  614  can generally encircle the parietal region of a user&#39;s head. In some such configurations, the headgear  604  can have a mounting portion in the form of rigid hook-shaped extensions or hook portions  612  that extend forward from the halo portion  614  on each side of the user&#39;s face. Preferably, the hook portions  612  sit over and in front of the user&#39;s ears and provide a mounting location for coupling the mask  602  to the halo portion  614 . 
     Preferably, the headgear  604  comprises two or more straps that couple the mask  602  to the halo portion  614 . In the illustrated configuration, a first or lower strap  618  and a second or upper strap  620  are provided on each side of the headgear  604  to connect the mask  602  to the halo portion  614  and permit rotational adjustment of the mask  602 . The illustrated straps  618 ,  620  indirectly couple the mask  602  to the halo portion  614 . The straps  618 ,  620  are coupled directly to the hook portions  612 , which transfer force from the straps  618 ,  620  to the halo portion  614 . In some configurations, the one or more of the straps  618 ,  620  can have an adjustable length or an adjustable effective length. In the illustrated arrangement, the actual length of each strap  618  and  620  is fixed; however, the positioning of the straps  618 ,  620  on the hook portions  612  can be varied to adjust a length of each of the straps  618 ,  620  that extends forward from the hook portions  612 . The straps  618 ,  620  can be secured to hook portions  612  and mask  602  by any suitable arrangement, such as cooperating hook-and-loop fastener portions  640 . A substantial portion of the hook portions  612  can be covered by the hook-and-loop fastener portions  640  to provide a substantial amount of length adjustment of the straps  618 ,  620 . In some configurations, an entirety or substantial entirety of an inward-facing surface of the straps  618 ,  620  can comprise hook-and-loop fastener portions  640 . 
     In some configurations, the halo portion  614  is generally semi-rigid. In some such configurations, the semi-rigid halo portion  614  can help the headgear  604  remain open to facilitate the application or fitment process. In some such configurations, the semi-rigid halo portion  614  can reduce the likelihood of the headgear  604  (especially the halo portion  614 ) collapsing as a result of its own weight. In some such configurations, the semi-rigid nature of the halo portion  614  makes fitting easy while not being so rigid that the halo portion  614  is uncomfortable to wear. 
     In some configurations, the hook portions  612  of the headgear  604  can be more rigid than the halo portion  614 . In some configurations, the hook portions  612  are rigid enough to reduce the likelihood of bending above the ear in response to normal or expected forces during use. Undesired movement of the mask  602  can result from substantial bending of the hook portions  612 . 
     In some configurations, an initial extension  642  of the hook portions  612  from the halo portion  614  may be substantially perpendicular. In some configurations, the substantially perpendicular extension  642  can help apply a desired force angle to the mask  602 . In some such configurations, the desired force angle helps to seal the mask  602  along the bottom of the user&#39;s nose. 
     The upper strap  620  can be attached to the hook portions  612  at an angle. In some such configurations, the angle can be approximately perpendicular to the underside of the user&#39;s nose. The lower strap  618  can be attached to the bottom of the mask  602 . In some such configurations, the lower strap  618  can reduce the likelihood of the mask  602  lifting upwards away from the user&#39;s chin. In some configurations, one or more of the lower and upper straps  618 ,  620  can be formed of or from a material such as Breath-o-prene®, for example but without limitation. The straps  618 ,  620  can be formed of or from a material that provides flexibility for easy adjustment and to minimize excessive force being applied to the user&#39;s face. Preferably, the straps  618 ,  620  at least substantially limit extension along an axial direction of the straps  618 ,  620  in response to normal or expected forces in use to maintain the mask  602  in position on the user&#39;s face. As used herein, an “axial” direction can be a direction aligned with a geometric axis of the strap (or other component) in a lengthwise direction or a direction along which the relevant force is applied. An axis of a strap or other component can be non-linear (e.g., curved). In some instances, such as in connection with straps or components having a complex shape, an “axial” direction may not be aligned with a geometric axis, but may be defined by end or connection points of the strap or may be generally aligned with a resistance force provided by the strap or other component. 
     With reference to  FIGS. 7-9 , another interface assembly  700  is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  700  is substantially similar to the interface assembly  600  in that the interface assembly  700  includes a mask  702  and a headgear  704 . The illustrated mask  702  is a nasal-oral mask, but could be any other type of interface. The headgear  704  includes a halo portion  714  and a pair of hook portions  712  on each side of the headgear  704 . A lower strap  718  and an upper strap  720  connect the mask  702  to the hook portions  712  on each side of the headgear  704 . Unlike the interface assembly  600 , the straps  718 ,  720  of the interface assembly  700  preferably are adjustable in length by varying a portion of the strap  718 ,  720  that is doubled over on itself. In the illustrated arrangement, mounting points  710  of the mask  702  include a ring, bar or similar structure that permits the strap  718 ,  720  to be connected to the mask  702  in a loop, with a free end of the strap  718 ,  720  doubled back on itself and secured, such as with a hook-and-loop fastener. In other respects, the interface assembly  700  can be the same as or substantially similar to the interface assembly  600 , including any of the features described with respect thereto, or can be of any other suitable arrangement. 
     With reference to  FIGS. 10A-10E , several variations of interface assemblies  1000  are shown, each of which can be substantially similar to the interface assemblies  600  and  700  and to one another. Accordingly, the same reference numbers are utilized throughout  FIGS. 10A-10E  for the same or corresponding components or features. Each interface assembly  1000  includes a mask  1002  and a headgear  1004 . Each headgear  1004  also includes at least a rear halo portion  1014  or a similar effective arrangement. Preferably, each headgear  1004  also includes a front halo portion  1012  or similar effective arrangement. As described previously, the mask  1002  can cooperate with the headgear  1004  to form a portion of the front halo portion  1012 . A lower strap  1018  and an upper strap  1020  are provided on each side of the headgear  1004  to connect the mask  1002  to the headgear  1004 . Preferably, the upper strap  1020  applies a force to the mask  1002  in a direction that facilitates or assists in sealing the mask  1002  against a bottom surface of the user&#39;s nose and the lower strap  1018  facilitates or assists in rotational adjustment of the mask  1002 . A crown strap  1016 , a rear strap  1050  and/or a rigid backbone  1060 , among other portions of the interface assemblies  1000 , can be adjustable to fit an individual user. In some configurations, multiple sizes of headgear  1004  can be provided. The unique features and arrangements of the interface assemblies  1000  will now be described. 
     The interface assembly  1000  of  FIG. 10A  includes a relatively wide rear strap portion  1050  that rests at least partially on the occipital bone and spreads the load over a larger area of the user&#39;s head as compared to a thin strap. The lower strap  1018  passes below the user&#39;s ear and connects to the rear portion  1050 . The upper strap  1020  passes above the user&#39;s ear and connects to a forward extension  1052  of the rear portion  1050  at a junction with the crown strap  1016 . The crown strap  1016  and rear portion  1050  cooperate to form a halo portion  1014 . The entire headgear  1004  can be constructed of a flexible material, such as Breath-o-prene®, for example. 
     The interface assembly of  FIG. 10B  includes a rigid backbone portion  1060 , which extends along the back of the user&#39;s head near the base of the skull and up and over the ears on each side. The rigid backbone  1060  can be more rigid than other portions of the headgear  1004  and can be formed from a semi-rigid or rigid material. Preferably, the ends of the rigid backbone  1060  extend forward of the user&#39;s ears. In the interface assembly  1000  of  FIG. 10B , the ends of the rigid backbone  1060  extend downwardly in front of the user&#39;s ears to form a shape similar to the hook portions  612  or  712 . The upper strap  1020  and lower strap  1018  can extend between the mask  1002  and the ends of the rigid backbone  1060 . A crown strap  1016  can pass over the crown of the user&#39;s head and connect to each side of the rigid backbone  1060 . The crown strap  1016  and rear portion of the rigid backbone  1060  cooperate to form a halo portion  1014 . Preferably, at least the end portions of the rigid backbone  1060  are constructed from a relatively rigid material, similar to the hook portions  612  or  712 , to resist bending. In some configurations, the entire rigid backbone  1060  can be constructed from a relatively rigid material. The lower, upper and crown straps  1018 ,  1020  and  1016  can be constructed from a softer, less rigid, more flexible or more stretchable material. 
     The interface assembly  1000  of  FIG. 10C  includes rigid ear loop portions  1070  on each side, which extend in an arcuate manner behind the user&#39;s ear from below to above the ear. A halo portion  1014  can couple the ear loop portions  1070  to one another. The upper straps  1020  extend from respective upper ends of the ear loop portions  1070  and the lower straps  1018  extend from respective lower ends of the ear loop portions  1070 . Preferably, at least the ear loop portions  1070  are constructed from a relatively rigid material. The other portions can be constructed from a softer, less rigid, more flexible or more stretchable material. 
     The interface assembly  1000  of  FIG. 10D  includes rigid ear loops  1070  that completely encircle the user&#39;s ears. A crown strap  1016  passes over the crown of the user&#39;s head and connects the ear loops  1070  and a rear strap  1050  passes across the rear of the user&#39;s head and also connects the ear loops  1070 . Each of the crown strap  1016  and the rear strap  1050  extend in a generally radial direction from the ear loop  1070  and are oriented generally perpendicular to one another. The crown strap  1016 , rear strap  1050  and portions of the ear loops  1070  between the crown strap  1016  and the rear strap  1050  cooperate to define a halo portion  1014 . As described above, preferably, the crown strap  1016  and rear strap  1050  are capable of adjustment such that the ear loops  1070  can be properly positioned relative to the user&#39;s ears. Preferably, at least the ear loop portions  1070  are constructed from a relatively rigid material. The other portions can be constructed from a softer, less rigid, more flexible or more stretchable material. 
     The interface assembly  1000  of  FIG. 10E  includes a rigid backbone portion  1060  similar to the headgear  1004  of  FIG. 10B ; however, the ends of the rigid backbone  1060  in  FIG. 10E  do not extend downwardly in front of the user&#39;s ear, or at least to any significant extent or as compared to the rigid backbone  1060  of  FIG. 10B . The lower straps  1018  extend from the rigid backbone  1060 , below the user&#39;s ears, and connect to the mask  1002 . The upper straps  1020  extend from the ends of the rigid backbone from a location above the user&#39;s ear and connect to the mask  1002  at a location above the lower straps  1018 . The upper straps  1020  can be of a thin construction, such as a line or cable-type construction, to minimize height and interference with vision, while providing suitable tensile properties. Preferably, at least the rigid backbone  1060  is constructed from a relatively rigid material. The other portions can be constructed from a softer, less rigid, more flexible or more stretchable material. In other respects, the interface assemblies  1000  can be the same as or substantially similar to the interface assemblies  600  or  700 , including any of the features described with respect thereto, or can be of any other suitable arrangement. Features of the various interface assemblies  600 ,  700 ,  1000  can be combined with one another as desired, such as to the extent that the features are not mutually exclusive. 
       FIGS. 11A-11C  illustrate several variations of interface assemblies  1000 , each of which can be substantially similar to the interface assemblies  1000  of  FIGS. 10A-10E . Accordingly, the same reference numbers are utilized throughout  FIGS. 11A-11C  for the same or corresponding components or features. The interface assembly  1000  of  FIG. 11A  preferably is identical to the interface assembly  1000  of  FIG. 10A . The interface assemblies  1000  of  FIGS. 11B and 11C  are described with respect the differences relative to the interface assembly  1000  of  FIG. 11A . The interface assembly  1000  of  FIG. 11B  includes a relatively more rigid or semi-rigid portion  1080  positioned within the rear portion  1050 . Preferably, the semi-rigid portion  1080  extends along a lower edge of the rear portion  1050 , such as along an entirety or at least a substantial entirety of the rear portion  1050 . The semi-rigid portion  1080  can reduce pressure on the back of the user&#39;s neck and/or reduce or prevent slipping of the headgear  1004  on the user as a result of the increased rigidity at least relative to the interface assembly  1000  of  FIG. 11A . 
     The interface assembly  1000  of  FIG. 11C  includes a relatively more rigid or semi-rigid connector  1090  that couples the upper strap  1020 , the crown strap  1016  and an upper portion of the rear strap or rear portion  1050 . The semi-rigid connector  1090  can reduce or prevent rotation of the crown strap  1016  by stabilizing or fixing the relative positions of the crown strap  1016 , the upper strap  1020  and the upper portion of the rear strap or rear portion  1050 . In other respects, the interface assemblies  1000  can be the same as or substantially similar to the interface assemblies  600  or  700 , or the interfaces  1000  of  FIGS. 10A-10E , including any of the features described with respect thereto, or can be of any other suitable arrangement. Features of the various interface assemblies  600 ,  700 ,  1000  can be combined with one another as desired, such as to the extent that the features are not mutually exclusive. 
       FIGS. 12A-12I  illustrate several variations of interface assemblies  1000 , each of which can be substantially similar to the interface assemblies  1000  of  FIGS. 10A-10E or 11A-11C . Accordingly, the same reference numbers are utilized throughout FIGS.  12 A- 12 I for the same or corresponding components or features. The interface assembly  1000  of  FIG. 12A  preferably is substantially similar to the interface assembly  1000  of  FIG. 10E , except the illustrated upper straps  1020  are wider or have a greater height dimension in the orientation as worn. The upper straps  1020  of the interface assemblies  1000  of  FIGS. 12B-12I  can be of a thin construction, such as a line or cable-type construction, similar to the interface assembly  1000  of  FIG. 10E . The interface assemblies  1000  of  FIGS. 12B-12I  are described with respect the differences relative to the interface assembly  1000  of  FIG. 12A . 
     In the interface assembly  1000  of  FIG. 12B , the rear section of the rigid backbone  1060  sits lower on the user&#39;s head compared to the interface assembly  1000  of  FIG. 12A . Preferably, the rear portion of the rigid backbone  1060  sits at or near a junction between the skull and the neck muscles of the user. In some configurations, the rear portion can sit on the neck muscles of the user. In addition, the lower straps  1018  can be straight and arranged in a generally horizontal manner from the rear portion of the rigid backbone  1060  to the mask  1002 . 
     In the interface assembly  1000  of  FIG. 12C , the rear portion of the rigid backbone  1060  is higher than the interface assembly  1000  of  FIG. 12A  and, preferably, sits on the occipital bone of the user. Such an arrangement reduces the likelihood of the headgear  1004  rotating on the user&#39;s head. The rigid backbone  1060  can extend downwardly from the rear portion and partially around the ear of the user in a manner similar to the ear loops  1070  of  FIG. 10C . The crown strap  1016  and the rear portion of the rigid backbone  1060  can be oriented approximately perpendicular to one another. 
     In the interface assembly  1000  of  FIG. 12D , the rigid backbone  1060  includes ear portions similar to the ear loops  1070  of  FIGS. 10C and 12C . However, preferably, the rear portion of the rigid backbone  1060  passes across the top of the head, such as across the parietal bone. In some configurations, the rear portion of the rigid backbone  1060  passes across an intermediate portion of the parietal bone and can be positioned generally between the crown strap  1016  and the rear portion of the rigid backbone  1060  of the headgear  1004  of  FIG. 12C . Accordingly, the crown strap  1016  can be omitted in the headgear  1004  of  FIG. 12D . 
     The interface assembly  1000  of  FIG. 12E  is similar to the interface assembly  1000  of  FIG. 12D  except that the rigid backbone  1060  includes full ear loops similar to the ear loops  1070  of  FIG. 10D . The lower straps  1018  can extend from a lower portion of the ear loops of the rigid backbone  1060  to a lower portion of the mask  1002 . In the illustrated arrangement, the lower straps  1018  extend from a position above a lowermost portion of the ear loop. However, in other arrangements, the lower straps  1018  could extend from a lowermost portion of the ear loops and/or could be generally horizontal. 
     In the interface assembly  1000  of  FIG. 12F , the lower strap  1018  includes additional material at least in the rear portion to increase the height of the strap  1018  and the overall height of the combination of the strap  1018  and the rear portion of the rigid backbone  1060 . A lower edge of the rear portion of the strap  1018  can be positioned at or near a junction between the skull and the neck muscles of the user. In some configurations, the lower edge can be on the neck muscles of the user. In some configurations, the entire rear portion can be defined by the rigid backbone  1060 . 
     Relative to the interface assembly  1000  of  FIG. 12F , the interface assembly  1000  of  FIG. 12G  includes relatively rigid extensions  1062  provided on lateral sides of the rear portion of the rigid backbone  1060 . Preferably, the extensions  1062  extend downwardly and/or forwardly from the rear portion of the rigid backbone  1060  and provide an anchor point or support for the lower straps  1018 . Such an arrangement can guide the lower straps  1018  and, in some configurations, permit the lower straps  1018  to have a generally horizontal orientation. 
     In the interface assembly  1000  of  FIG. 12H , the rigid backbone  1060  is shaped substantially similar to the rigid backbone  1060  of  FIG. 12A . Preferably, the rear portion of the rigid backbone  1060  extends across a lower portion of the bottom of the user&#39;s skull, such as across the occipital bone and, in some configurations, above the user&#39;s neck muscles. The lower straps  1018  preferably extend in a generally horizontal manner and can connect at a higher point on the mask  1002  relative to the interface assembly  1000  of  FIG. 12 . In some configurations, the lower straps  1018  are still vertically-spaced from the upper straps  1020  at the mask  1002 . The lower straps  1018  can include a downwardly-curved or U-shaped section that defines a cut-out or space to accommodate the user&#39;s ears. 
     In the interface assembly  1000  of  FIG. 12I , the rigid backbone  1060  defines a halo portion  1014  including a rear portion and a portion equivalent to the crown strap. The entire halo portion  1014  can be constructed from a relatively rigid material, such as a semi-rigid or rigid material, or certain portions can be constructed from a relatively rigid material (e.g., the hook portions) and other portions can be constructed from a relatively less rigid material (e.g., the upper crown portion). 
       FIGS. 13-15  illustrate an interface assembly  1300  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  1300  includes an interface  1302  and a headgear  1304 . The illustrated interface  1302  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  1304 . The illustrated mask  1302  generally comprises a frame  1306  that supports a seal  1308 . The mask  1302  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  1302  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  1302  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  1304  can be coupled to the mask  1302  at one or more mounting locations or mounting points  1310 , as described below. The headgear  1304  can include a crown strap  1316  that extends across the top of the user&#39;s head. Preferably, a lower strap  1318  and an upper strap  1320  are provided on each side of the headgear  1304  to connect the mask  1302  to the rear halo portion  1314  or a rear portion of the headgear  1304 . Preferably, the headgear  1304  can also define a front halo portion  1312 . Unless indicated otherwise, features of the interface assembly  1300  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The headgear  1304  can incorporate one or more support portions or support members  1330  that can engage the head of the user to help secure the headgear  1304  in place, guide portions of the headgear  1304  in a desired path, or improve user comfort or user experience. In some configurations, the support members  1330  can contact an anatomical feature of the user&#39;s head. In the illustrated configuration, the upper straps  1320  include cheek supports  1330  that contact the cheeks of the user. In particular, the cheek supports  1330  can contact the cheeks at or near a location of the zygomatic and/or maxilla bones of the user. The cheek supports  1330  can be utilized to guide the upper straps  1320  into a non-linear path. The cheek supports  1330  can allow the upper straps  1320  to extend from the mask  1302  initially in a generally lateral direction and then upwardly to a connection point with the halo portion  1314  or a junction between the crown strap  1316  and a rear strap portion  1350  of the headgear  1304 . The non-linear path can position the upper straps  1320  further from the user&#39;s eyes for improved vision and/or comfort. 
     In some configurations, the cheek supports  1330  can be relatively rigid and can anchor against the user&#39;s cheeks to reduce compression of the seal  1308  of the mask  1002  in response to tightening of the headgear  1304 . That is, the cheek supports  1330  inhibit the retention force of the headgear  1304  from being fully transferred to the seal  1308 . The cheek supports  1330  can be provided with a soft covering or skin-contact material for comfort and/or to increase grip on the user&#39;s skin to assist with redirection of the upper straps  1320 . In some configurations, the cheek supports  1330  can be a portion of the mask frame  1306 . In some configurations, the cheek supports  1330  can be a separate member that is coupled to the mask frame  1306 . The cheek supports  1330  can have an upwardly curved shape (in the illustrated orientation) to be positioned out of or further away from the user&#39;s line of sight for a less intrusive experience when worn. 
       FIG. 16  illustrates an interface assembly  1600  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  1600  includes an interface  1602  and a headgear  1604 . The illustrated interface  1602  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  1604 . The illustrated mask  1602  generally comprises a frame  1606  that supports a seal  1608 . The mask  1602  can be connected to a supply conduit  1609 , which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  1602  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  1602  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  1604  can be coupled to the mask  1602  at one or more mounting locations or mounting points  1610 . Preferably, a lower strap  1618  and an upper strap  1620  are provided on each side of the headgear  1604  to connect the mask  1602  to a rear portion of the headgear  1604 . Unless indicated otherwise, features of the interface assembly  1600  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The illustrated headgear  1604  is of a pocket-like arrangement that receives and cups the back of the user&#39;s head. In the illustrated configuration, the headgear  1604  is of a skeleton or web-like configuration that includes interior open spaces within the headgear  1604 . In some configurations, an outer perimeter  1614  of the headgear  1604  generally defines a rear halo portion. Interior strap portions  1622  extend between different points of the perimeter  1614  in generally vertical and/or generally horizontal directions and can help maintain the shape of the outer perimeter  1614 . The upper strap  1620  and the rear portion of the headgear  1604  can cooperate to define a front halo portion  1612 . 
     The headgear  1604  can include one or more relatively rigid portions  1624 , which can be more rigid than other portions of the headgear  1604  and can be semi-rigid or rigid. The rigid portions  1624  can define mounting locations between the rear portion of the headgear  1604  and one or both of the lower strap  1618  and the upper strap  1620 . In some configurations, the rigid portions  1624  can be located behind each ear of the user and can be curved to generally follow the shape of the ear. The rigid portions  1624  can provide anchor points for the lower strap  1618  and upper strap  1620  below and above the ear, respectively. The rigid portions  1624  can transfer the load of the straps  1618 ,  1620  to a larger portion of the rear portion of the headgear  1604  and help maintain the shape of the outer perimeter  1614  of the headgear  1604  in response to forces applied by the straps  1618 ,  1620 . The interior straps  1614  and portions of the outer perimeter  1614  other than the rigid portions  1624  can be constructed from a flexible, less rigid material, such as a textile material, for example. Such an arrangement can provide even load distribution over a significant area of the user&#39;s head without excessive heat retention. 
     The lower strap  1618  and upper strap  1620  can be constructed from an elastic material to have some amount of stretch. The stretch inherent in the straps  1618 ,  1620  can be selected to provide an appropriate mounting force for the mask  1602 . However, the straps  1618 ,  1620  could, in addition or in the alternative, be capable of length adjustment. In some configurations, a portion  1626  of the mask  1602  to which the straps  1618 ,  1620  are coupled can be removable to loosen the straps and facilitate fitment or removal of the interface assembly  1610 . For example, the removable portion  1626  can have a snap-fit arrangement with a remainder of the mask  1602 . The removable portion  1626  can be selectively disengaged from the remainder of the mask  1602 . The removable portion  1626  can be completely separated from the remainder of the mask  1602  such that the interface assembly  1600  defines an open loop or the removable portion  1626  can remain tethered to the remainder of the mask  1602  to create an increased-circumference to facilitate fitment or removal of the interface assembly  1600 . A push button release  1628  can be provided to facilitate disengagement of the removable portion  1626 . The removable portion  1626  can be coupled to the remainder of the mask  1602  by any suitable coupling arrangement, including those disclosed herein, for example but without limitation. A removable portion  1626  can be provided on each side of the mask  1602 , if desired. 
       FIG. 17  illustrates an interface assembly  1700  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  1700  includes an interface  1702  and a headgear  1704 . The illustrated interface  1702  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  1704 . The illustrated mask  1702  generally comprises a frame  1706  that supports a seal  1708 . The mask  1702  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  1702  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  1702  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  1704  can be coupled to the mask  1702  at one or more mounting locations or mounting points  1710 . Preferably, the mask  1702  is capable of rotational adjustment relative to the headgear  1704  to permit angular adjustment of the mask  1702  to fit different facial geometries. Unlike the prior interfaces that rely on a pair of straps to permit angular adjustment of the mask, the interface assembly  1700  utilizes relative rotational movement between the mask  1702  and the headgear  1704 , as described below. Unless indicated otherwise, features of the interface assembly  1700  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The headgear  1704  can comprise a single side arm or side strap  1720  on each side of the interface assembly  1700 . The side strap  1720  can be relatively rigid such that it substantially retains its shape in response to normal or expected forces in use. The side strap  1720  can extend from the mask  1702  to a location above the user&#39;s ear. In some configurations, the side strap  1720  can be curved along its length. The side strap  1720  can connect to the mask  1702  at a mounting point  1710  that is located in a generally intermediate vertical position of the mask  1702 , as illustrated. However, in other configurations, the mounting point  1710  can be located elsewhere, such as generally at a pivot point of the mask  1702  at a junction between the underside of the user&#39;s nose and the user&#39;s upper lip (see, for example,  FIGS. 1 and 84 ). The side strap  1720  can curve upwardly in a direction from front to rear to be positioned at a desirable location on the user&#39;s face, which can be away from the user&#39;s eyes. In some configurations, the side strap  1720  can include padding that rests against the user&#39;s skin, such as a cheek pad  1730  on an inside surface of the side strap  1720 . In other configurations, a greater portion or a substantial entirety of the side strap  1720  can be provided with padding. As described above, the mask  1702  can be rotatable relative to the side strap  1720  and, preferably, can be secured in a desired rotational position. 
     The headgear  1704  can include a crown strap  1716 . In some configurations, the crown strap  1716  can be integrated or formed as a single piece with the side straps  1720 . For example, the crown strap  1716  can be constructed from a less rigid material, such as a semi-rigid material, and can be removably or permanently coupled to the side straps  1720 . The crown strap  1716  can be a member that is overmolded onto the side straps  1720 . Each side strap  1720  can include an extension or mounting portion  1724  that provides a mechanical interface for the overmolded crown strap  1716 . In some configurations, the crown strap  1716  can be formed from a thermoplastic elastomer or silicone material, for example. 
     The headgear  1704  can also include a rear strap  1750  that extends along the back of the user&#39;s head between rear portions of the side straps  1720 . The rear strap  1750  can be relatively less rigid than the side straps  1720 . In some configurations, the rear strap  1750  is a flexible and/or somewhat stretchable material, such as a textile material. The rear strap  1750  can have one or more adjustment portions  1752 , such as an adjustment portion  1752  on each end of the rear strap  1750 . The adjustment portion  1752  can be an adjustable loop that is passed through an opening or slot  1754  of the side strap  1720 . The loop can be secured to the rear strap  1750  by a suitable connector  1756 , such as a hook-and-loop fastener, for example. In some configurations, one or more additional adjustment points can be provided, such as an adjustment feature  1722  within the crown strap  1716 , which permits a length of the crown strap  1716  to be adjusted. In the illustrated configurations, three adjustment points are provided, thereby permitting adjustment of a circumference of a front halo portion  1712  (via the adjustment feature  1722 ) and a circumference of a rear halo portion  1714  (via the adjustment feature  1722  and the adjustment portions  1752 ). 
       FIG. 18  illustrates an interface assembly  1700  preferably that is substantially similar to the interface assembly  1700  of  FIG. 17 . Accordingly, the same reference numbers are utilized for the same or corresponding components or features. The interface assembly  1700  of  FIG. 18  is described with respect the differences relative to the interface assembly  1700  of  FIG. 17 . Unless indicated otherwise, features of the interface assembly  1700  or portions thereof can be the same as or similar to other interfaces or portions thereof of the interface assembly  1700  of  FIG. 17 , other interface assemblies described herein, or can be of another suitable arrangement. 
     The side strap  1720  of the interface assembly  1700  of  FIG. 18  can have a rearward end positioned at or near a forward, upper portion of the user&#39;s ear. The side strap  1720  and the rear strap  1750  can connect to a base of the crown strap  1716 , which can be a separate component from the side strap  120  and/or rear strap  1750 . The rearward end of the side strap  1720  can include a hook  1760  that engages a loop  1762  of the crown strap  1716 . The loop  1762  can be a portion of the crown strap  1716  material that is folded over onto itself and sewn in place. Other suitable arrangements can also be used, such as a ring member coupled to the crown strap  1716 , for example. The adjustment portion  1752  of the rear strap  1750  can be a sliding buckle adjuster, for example. 
       FIG. 19  illustrates a rotational adjustment arrangement or rotational adjuster  1900  that can provide rotational adjustment between two components of an interface assembly, such as between the mask and the headgear. The rotational adjuster  1900  can be utilized in the interface assemblies  1700  of  FIGS. 17 and 18 , for example, as well as other interface assemblies, including those disclosed herein. For convenience, the rotational adjuster  1900  is described in the context of the interface assemblies  1700 . 
     Preferably, the rotational adjuster  1900  includes a first portion  1902  that is capable of engagement with a second portion  1904  in a plurality of rotational positions in order to adjust the fit to different facial geometries. In the illustrated arrangement, the first portion  1902  is a male portion and the second portion  1904  is a female portion. The first portion  1902  is formed by, carried by or otherwise coupled to the headgear  1704  (e.g., the side strap  1720 ) and the second portion  1904  is formed by, carried by or otherwise coupled to the mask  1702 . However, this arrangement could be reversed. The illustrated first portion  1902  is an axle and the illustrated second portion  1904  is a sleeve or hub. The axle  1902  is received within the sleeve  1904  in one of a plurality of optional rotational positions. The axle  1902  and the sleeve  1904  can comprise cooperating interference or detent surfaces  1906 , which permit rotational adjustment between a plurality of relative rotational positions. The detent surfaces  1906  can be of any suitable arrangement, such as protrusions and recesses, for example. 
     In some configurations, the axle  1902  comprises two or more flexible or deflectable tabs  1908  to permit the axle  1902  to be assembled into engagement with the sleeve  1904 . Preferably, the tabs  1908  are stiff enough to inhibit undesired rotational movement of the mask  1702  in response to normal or expected forces in use. A rim or flange  1910  can be provided at a free end of the axle  1902  to secure the axle  1902  within the sleeve  1904  in an axial direction. However, other rotational adjustment arrangements can be used with the interface assembly  1700  or any other interface assembly disclosed herein. Any suitable arrangement for providing rotational adjustment between two components can be used. In some configurations, the rotational adjustment arrangement can be fixed in the desired rotational position instead of relying on another fixing component, such as another mask strap, for example. For example, a nut-and-bolt arrangement, ratchet-type arrangement or other types of detent arrangements could be used, among other suitable arrangements. 
       FIG. 20  illustrates an interface assembly  2000  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  2000  includes an interface  2002  and a headgear  2004 . The illustrated interface  2002  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  2004 . The illustrated mask  2002  generally comprises a frame  2006  that supports a seal  2008 . The mask  2002  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  2002  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  2002  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  2004  can be coupled to the mask  2002  at one or more mounting locations or mounting points  2010 . Preferably, a lower strap  2018  and an upper strap  2020  are provided on each side of the headgear  2004  to connect the mask  2002  to a rear portion of the headgear  2004 . Unless indicated otherwise, features of the interface assembly  2000  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     In the illustrated arrangement, forward ends of the lower strap  2018  and the upper strap  2020  can join one another and be coupled to the mask  2002  at a single mounting location or mounting point  2010  on each side of the mask  2002 . The rear strap portion  2050  can have bifurcated end portions, each having an upper end portion  2052  and a lower end portion  2054 . The upper end portion  2052  can connect to the upper strap  2020  and, in some configurations, with a crown strap  2016 . The lower end portion  2054  can connect to the lower strap  2018 . In some configurations, the lower strap  2018 , upper strap  2020 , crown strap  2016  and rear strap portion  2050  can be constructed as a single piece or single structure of any suitable material, such as a relatively flexible material. The crown strap  2016  can include an adjustment feature  2022  to permit adjustment of a front halo portion  2012  and a rear halo portion  2014  and/or other adjustment mechanisms for the headgear  2004  can be provided. 
     An adjustment strap  2060  can be provided on each side of the interface assembly  2000  to couple the mask  2002  to a main portion of the headgear  2004 . The adjustment strap  2060  can engage a buckle  2062 , which can be connected to the main portion of the headgear  2004  (e.g., the combined forward ends of the straps  2018 ,  2020 ) by any suitable arrangement, including a loop  2064  of material, for example. The adjustment strap  2060  can be movable within the buckle to adjust an effective length of the strap  2060  and thereby adjust a position of the mask  2002  relative to the headgear  2004 . To tighten the strap  2060 , a user can pull on a free end  2066  of the strap  2060 . Such an arrangement can be quieter to adjust and/or easier to fine tune the adjustment compared to a hook-and-loop fastener adjustment, for example. 
     The mask  2002  can include an elongate slot  2070  near an edge of the mask frame  2006  such that the mask frame  2006  defines an elongate bar  2072 . The strap  2060  can be secured to the bar  2062  to couple the strap  2060  to the mask  2002 . In some configurations, the slot  2070  and/or bar  2072  define a length (or height in the illustrated orientation) that is greater than a width (or height in the illustrated orientation) of the strap  2060  such that the strap  2060  is movable within the slot  2070  or along the bar  2072 . Preferably, the slot  2070  and/or bar  2072  are arcuate or curved in shape such that moving the mask  2002  relative to the strap  2060  changes an angle or rotational position of the mask  2002  relative to the headgear  2004  and the user. In use, the user can position the mask  2002  and headgear  2004  and then tighten the strap(s)  2060  to secure the mask  2002  in place. The strap(s)  2060  can automatically settle into a desired location within the slot  2070  or along the bar  2072 . The user could also manually adjust an angle or rotational position of the mask  2002  relative to the strap(s)  2060  and/or headgear  2004  after the interface assembly  2000  has been fitted. 
       FIG. 21  illustrates an interface assembly  2100  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  2100  includes an interface  2102  and a headgear  2104 . The illustrated interface  2102  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  2104 . The illustrated mask  2102  generally comprises a frame  2106  that supports a seal  2108 . The mask  2102  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  2102  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  2102  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  2104  can be coupled to the mask  2102  at one or more mounting locations or mounting points  2110 . Preferably, a lower strap  2118  and an upper strap  2120  are provided on each side of the headgear  2104  to connect the mask  2102  to a rear portion of the headgear  2104 . Unless indicated otherwise, features of the interface assembly  2100  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     In the illustrated arrangement, the mask  2102  includes an elongate, rearwardly-extending rigid arm  2160  on each side of the mask  2102  that is coupled to a respective one of the upper straps  2120  of the headgear  2104 . In some configurations, the rigid arm  2160  can be a portion of the mask frame  2106 . In some configurations, the rigid arm  2160  can be a separate member that is coupled to the mask frame  2006 . The rigid arm  2160  can have an upwardly curved shape (in the illustrated orientation) to be positioned out of or further away from the user&#39;s line of sight for a less intrusive experience when worn. In some configurations, the rigid arm  2160  can include padding, such as a cheek pad  2130  that contacts the skin of the user for comfort and/or grip on the skin. 
     The rigid arm  2160  can be coupled to the upper strap  2120  by any suitable arrangement. In some configurations, the rigid arm  2160  includes an opening  2162  through which the upper strap  2120  can be passed and doubled over on itself to form a loop. The loop of the upper strap  2120  can be secured by a connector  2156 , such as a hook-and-loop fastener, for example. In some configurations, the opening  2162  of the rigid arm  2160  is defined by a hook  2164 , which defines an entry into the opening  2162  to facilitate quick separation of the upper strap  2120  from the rigid arm  2160 . 
     The lower strap  2118  can be coupled to the mask  2102  by any suitable arrangement, such as passed through an opening  2170  in the mask  2102  and doubled over on itself to form a loop. The loop of the lower strap  2118  can be secured by a connector  2172 , such as a hook-and-loop fastener, for example. As in other interface assemblies described herein, the upper strap  2120  and lower strap  2118  can be adjusted to place the mask  2102  in a desirable rotational position. In some configurations, the crown strap  2116  can include an adjustment feature  2122 . Other suitable arrangements can also be used to permit adjustment of the headgear  2104  (e.g., the front halo portion  2112  and/or rear halo portion  2114 ), including one or more of the lower strap  2118 , upper strap  2120  and crown strap  2116 , for example and without limitation. 
       FIGS. 22A and 22B  illustrate interface assemblies  2200  that are arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assemblies  2200  include an interface  2202  and a headgear  2204 . The illustrated interface  2202  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  2204 . The illustrated mask  2202  generally comprises a frame  2206  that supports a seal  2208 . The mask  2202  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  2202  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  2202  can provide pressurized air flow to both the nose and the mouth of the user. The frame  2206  can comprise rigid, upwardly-extending paddle portions  2206   a  positioned on each side of the nose portion of the seal  2208  to resist expansion of the nose portion of the seal  2208  in response to pressurized air within the mask  2202 . 
     The headgear  2204  can be coupled to the mask  2202  at one or more mounting locations or mounting points  2210 . Preferably, a lower strap  2218  and an upper strap  2220  are provided on each side of the headgear  2204  to connect the mask  2202  to a rear portion of the headgear  2204 . Unless indicated otherwise, features of the interface assemblies  2200  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. In particular, the interface assemblies  2200  are similar to the interface assembly  2100  of  FIG. 21  and, for the sake of convenience, will be described in the context of the differences relative to that interface assembly  2100 . 
     In the illustrated arrangement of  FIG. 22A , the upper strap  2220  is coupled to the mask  2202  at a mounting point  2210  that is located at or near the seal  2208  of the mask  2202 . In particular, the mounting point  2210  of the upper strap  2220  preferably is located between a forward edge and a rearward edge of the seal  2208  when viewed from the side. In some configurations, the mounting point  2210  is located at or near the upper end of the seal  2208  and/or at or near the user&#39;s nose. Such an arrangement can provide a suitable force vector to facilitate the creation of a seal between the mask seal  2208  and the underside of the user&#39;s nose. The upper strap  2220  can be coupled to the mask  2202  by any suitable arrangement, such as passed through an opening  2262  in the mask  2202  and doubled over on itself to form a loop. The loop of the upper strap  2220  can be secured by a connector  2256 , such as a hook-and-loop fastener, for example. 
     The lower strap  2218  can be coupled to the mask  2202  at a mounting point  2210  that is located toward a bottom portion of the seal  2208 , such as at or near the user&#39;s mount or chin. In a fore-aft direction, the mounting point  2210  can be generally aligned with the mounting point  2210  of the upper strap  2220 . The lower strap  2218  can be coupled to the mask  2202  by any suitable arrangement, such as passed through an opening  2270  in the mask  2202  and doubled over on itself to form a loop. The loop of the lower strap  2218  can be secured by a connector  2272 , such as a hook-and-loop fastener, for example. 
     As in other interface assemblies described herein, the upper strap  2220  and lower strap  2218  can be adjusted to place the mask  2202  in a desirable rotational position. The substantial vertical separation between the mounting points  2210  of the upper strap  2220  and the lower strap  2218  permits fine control of the angular adjustment of the mask  2202 . 
     In some configurations, a crown strap  2216  of the headgear  2204  can include an adjustment feature  2222 . Other suitable arrangements can also be used to permit adjustment of the headgear  2204  (e.g., the front halo portion  2212  and/or rear halo portion  2214 ), including one or more of the lower strap  2218 , upper strap  2220  and crown strap  2216 , for example and without limitation. 
     The interface assembly  2200  of  FIG. 22B  provides quick-release couplings  2280  between the mask  2202  and the headgear  2204 . In particular, each strap  2218 ,  2220  is coupled to the mask by a clip  2282 , which preferably includes a hook-shaped end portion or other suitable arrangement to engage the respective openings  2262 ,  2270  of the mask  2202 . The straps  2218 ,  2220  can be adjusted relative to the clips  2282 . In addition, the headgear  2204  includes separate upper and lower portions. The upper strap  2220  is coupled to the upper portion of the headgear  2204 , which preferably includes the crown strap  2216  and a first or upper rear head strap  2290 . The upper strap  2220 , the crown strap  2216  and the upper rear head strap  2290  cooperate to form the front halo portion  2212  and the rear halo portion  2214 . The upper rear head strap  2290  can extend around the back of the user&#39;s head at, near or above a level of an upper portion of the user&#39;s ears, such as on or near a transition between the parietal bone and the occipital bone. The lower strap  2218  is coupled to a second or lower rear head strap  2292 , which can extend around the back of the user&#39;s head at, near or blow a level of a lower portion of the user&#39;s ears. In some configurations, the lower rear head strap  2292  sits on the user&#39;s occipital bone and/or on the user&#39;s upper neck muscles. A rear portion of the lower rear head strap  2292  can be enlarged in a vertical direction to spread the load on the user&#39;s neck and/or head area. The provision of separate straps  2290 ,  2292  can facilitate fitting and removal. 
       FIGS. 23 and 24  illustrate an interface assembly  2300  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  2300  includes an interface  2302  and a headgear  2304 . The illustrated interface  2302  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  2304 . The illustrated mask  2302  generally comprises a frame  2306  that supports a seal  2308 . The mask  2302  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  2302  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  2302  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  2304  can be coupled to the mask  2302  at one or more mounting locations or mounting points  2310 . Preferably, a strap  2315  including a lower strap portion  2318  and an upper strap portion  2320  is provided on one or both sides of the headgear  2304  to connect the mask  2302  to a rear portion of the headgear  2304 . In some configurations, the strap  2315  can be substantially non-stretchable. The strap  2315  can be constructed from a thin textile webbing. Unless indicated otherwise, features of the interface assembly  2300  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     In the illustrated configuration, each strap  2315  on each side of the interface assembly  2300  is a single strap comprising an upper strap portion  2320  and a lower strap portion  2318 . One or both of the upper strap portion  2320  and the lower strap portion  2318  can be adjustably secured to the headgear  2304 . In the illustrated arrangement, the upper strap portion  2320  is fixedly secured to the headgear  2304  and the lower strap portion  2318  is adjustably secured to the headgear  2304 . However, this arrangement could be reversed. The lower strap portion  2318  can be coupled to the headgear  2304  by a suitable adjustment mechanism, such as a buckle  2340 , for example and without limitation. 
     The strap  2315  can include an intermediate strap portion  2350  that engages the mask  2302  at the mounting points  2310 . The mask  2302  can include a pair of spaced-apart mounting points  2310  on the same side of the mask  2302 . In some configurations, the mounting points  2310  comprise an upper mounting point and a lower mounting point. One of the upper and lower mounting points  2310  can permit the intermediate strap portion  2350  to be conveniently disengaged from the mounting point  2310  to provide slack in the strap  2315 , which can facilitate fitment or removal of the interface assembly  2300 . If such straps  2315  are provided on each side of the interface assembly  2300 , the amount of slack provided can be doubled. 
     In the illustrated arrangement, the mask  2302  comprises a retention structure  2360 , such as a cleat or a block, around which the intermediate strap portion  2350  can be passed and retained and which defines a mounting point  2310 . However, other suitable structures or arrangements could also be used. Preferably, the mask  2302  also comprises a guide  2362  for the intermediate strap portion  2350  that defines another mounting point  2310 . The guide  2362  can be an opening or slot that preferably frictionally engages the intermediate strap portion  2350  to inhibit or prevent movement in response to normal or expected forces on the strap  2315  during use to retain the mask  2302  in a desired orientation (e.g., angular orientation) relative to the headgear  2304 . However, preferably, the guide  2362  allows movement of the strap  2315  when desired to permit adjustment of the mask  2302  relative to the headgear  2304 . In the illustrated arrangement, the guide  2362  defines an upper mounting point  2310  and the retention structure  2360  defines a lower mounting point  2310 . However, this arrangement could be reversed or the mounting points  2310  could be otherwise spaced. 
     The headgear  2304  preferably comprises a front halo portion  2312  and a rear halo portion  2314 . The headgear  2304  preferably also comprises a rear strap portion  2370  that is coupled to the rear halo portion  2314 . Adjustment of the rear halo portion  2314  can be provided by, for example, an adjustment feature  2322 . The lower strap portion  2318  can be coupled to the rear strap portion  2370  and the upper strap portion  2320  can be coupled to the rear strap portion  2370  such that the upper strap portion  2320  is passes above an ear of the user and the lower strap portion  2318  passes below the ear of the user. 
     In use, the intermediate strap portion  2350  can be disengaged from the retention structure  2360  to introduce slack into the strap  2315  as illustrated by the dashed lines of  FIG. 24 . The interface assembly  2300  can be fitted to the user with the mask  2302  placed over the user&#39;s mouth and against the underside of the user&#39;s nose. The headgear  2304  can be placed on the back of the user&#39;s head. Then, the intermediate strap portion  2350  can be engaged with the retention structure  2360  to take up the slack in the strap  2315 . If necessary or desired, the rotational position of the mask  2302  relative to the headgear  2304  can be adjusted by moving the intermediate strap portion  2350  through the guide  2362 . Preferably, the guide  2362  then holds the intermediate strap portion  2350  in place to maintain the desired rotational position of the mask  2302 . In some cases, such as if the interface assembly  2300  has been previously fitted, the rotational position of the mask  2302  may already be set. To remove the interface assembly  2300 , the process is reversed and the intermediate strap portion  2350  is disengaged from the retention structure  2360  to provide slack in the strap  2315 . As discussed, such a strap  2315  can be provided on one or both sides of the interface assembly  2300 . Even if two such straps  2315  are provided, disengagement of one strap  2315  may provide sufficient slack to permit removal of the interface assembly  2300 . 
       FIG. 25  illustrates an interface assembly  2500  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  2500  includes an interface  2502  and a headgear  2504 . The illustrated interface  2502  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  2504 . The illustrated mask  2502  generally comprises a frame  2506  that supports a seal  2508 . The mask  2502  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  2502  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  2502  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  2504  can be coupled to the mask  2502  at one or more mounting locations or mounting points  2510 . Preferably, a strap  2515  that includes a lower strap portion  2518  and an upper strap portion  2520  is provided on each side of the headgear  2504  to connect the mask  2502  to a rear portion of the headgear  2504 . Unless indicated otherwise, features of the interface assembly  2500  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. In particular, the interface assembly  2500  is similar to the interface assembly  2300  of  FIGS. 23 and 24  and, for the sake of convenience, will be described in the context of the differences relative to that interface assembly  2300 . 
     The headgear  2504  preferably comprises a front halo portion  2512 , a rear halo portion  2514  and a rear strap portion  2570  that is coupled to the rear halo portion  2314 . Adjustment of the rear halo portion  2514  can be provided by, for example, an adjustment feature  2522 . The upper strap portion  2320  can be coupled to rear halo portion  2514  of the headgear  2504 . 
     An intermediate strap portion  2550  of the strap  2515  extends from a friction guide  2562  of the mask  2502  to the rear strap portion  2570  of the headgear  2504 . Preferably, a low friction guide or ring  2540  is coupled to the rear strap portion  2570  of the headgear  2504 . The strap  2515  passes through an opening of the low friction guide  2540  and a lower strap portion  2518  of the strap  2515  extends toward a lower end of the mask  2502 . Preferably, the lower strap portion  2518  is connected to the mask  2502  by a clip  2360 . The clip  2360  can releasably engage the mask  2502 , such as with a hook and bar arrangement, for example. The clip  2360  can include a buckle portion  2564  through which the lower strap portion  2518  can be passed. The lower strap portion  2518  can be adjusted relative to the buckle portion  2564  to permit an effective length of the lower strap portion  2518  to be adjusted. 
     Similar to the interface assembly  2300 , the strap  2515  can be adjusted relative to the friction guide  2562  to adjust an effective length of the upper strap portion  2520 . The lower strap portion  2518  can be adjusted relative to the clip  2360  to adjust an angular or rotational position of the mask  2502 . Adjustment of the lower strap portion  2518  can also adjust the tension of the strap  2515  when the interface assembly  2500  is fitted to a user. 
     To fit or remove the interface assembly  2500 , the clip  2560  can be disengaged from the mask  2502 , which can free the lower portion of the mask  2502 . With the clip  2360  disengaged, the low friction guide  2540  also permits an effective length of the intermediate strap portion  2550  to be increased to thereby increase a distance between the rear strap portion  2570  and the mask  2502 , which may permit the interface assembly  2500  to be fitted or removed from the user. In necessary or desired, the strap  2515  can also be adjusted relative to the friction guide  2562  to increase an effective length of the upper strap portion  2520  to facilitate fitment of removal of the interface assembly  2500 . 
       FIGS. 26-28  illustrate an interface assembly  2600  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  2600  includes an interface  2602  and a headgear  2604 . The illustrated interface  2602  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  2604 . The illustrated mask  2602  generally comprises a frame  2606  that supports a seal  2608 . The mask  2602  can be connected to a supply conduit  2609 , which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  2602  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  2602  can provide pressurized air flow to both the nose and the mouth of the user. The headgear  2604  can be coupled to the mask  2602  at one or more mounting locations or mounting points  2610 . Unless indicated otherwise, features of the interface assembly  2600  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     In the illustrated arrangement, a lower strap  2618  and an upper arm  2620  are provided on each side of the headgear  2604  to connect the mask  2602  to a rear portion of the headgear  2604 . Preferably, similar to the interface assembly  600  of  FIG. 6 , the headgear  2604  of the interface assembly  2600  includes a hook portion  2615  extending downwardly in front of the user&#39;s ear that supports the lower strap  2618 . The upper arm  2620  and the hook portion  2615  can be an integral or single-piece construction. In some configurations, a gusset  2630  or other support structure can be provided between the upper arm  2620  and the hook portion  2615 . 
     The headgear  2604  can also include a crown strap  2616  portion and a rear strap  2650  portion. The upper arm  2620  and crown strap  2616  can cooperate to form a front halo portion  2612  and the rear strap  2650  can cooperate to form a rear halo portion  2614 . Some or all of the upper arm  2620 , hook portion  2615 , crown strap  2616  and rear strap  2650  portions of the headgear  2604  can be an integrated or single-piece construction. In some configurations, some or all of the upper arm  2620 , hook portion  2615 , crown strap  2616  and rear strap  2650  portions of the headgear  2604  can comprise a relatively rigid frame  2640  that can be partially or completely covered by a softer and/or less rigid material exterior or cover  2642 . Any materials suitable for the rigid frame  2640  and soft cover  2642  can be used. For example and without limitation, the rigid frame  2640  can be constructed from polycarbonate, nylon, ABS, polypropylene or other materials having similar mechanical properties, especially with respect to rigidity. The soft cover  2642 , for example and without limitation, can be constructed from silicone, thermoplastic elastomer, thermoplastic polyurethane, other materials with similar mechanical properties, cloth-type materials (cloth covered foam), rubber/foam materials or other suitable soft materials. In some configurations, an adjustment mechanism, stretchable component or less rigid portion can be provided within the crown strap  2616  and/or rear strap  2650  to facilitate size adjustment or fitting. Thus, the headgear  2604  could be constructed from multiple sections or portions (e.g., two halves), each of which could comprise an integrated or single-piece construction of some or all of the upper arm  2620 , hook portion  2615 , crown strap  2616  or rear strap  2650 . 
     Preferably, a coupler  2644  allows for rotational or pivotal movement of the mask  2602  relative to the upper arm  2620 . Any suitable arrangement of the coupler  2644  to achieve rotational or pivotal movement of the mask  2602  can be used. For example, the mask  2602  can be coupled to the upper arm  2620  by a flexible shaft or cable or by a pivotal joint. In addition, preferably, the lower strap  2618  is capable of length adjustment, such as by any of the adjustment arrangements disclosed herein or any other suitable arrangement. Accordingly, rotational adjustment and fixation of the mask  2602  can be achieved. The coupler  2644  can allow the mask to freely rotate with fixation provided by the lower strap  2618 . In other configurations, other rotational adjustment arrangements could be used that allow adjustment and fixation of the mask  2602 , such as the arrangement disclosed in connection with  FIG. 19 , for example and without limitation. 
     In some configurations, one or more portions of the headgear  2604  can comprise a padded portion  2646 . For example, a junction between the upper arm  2620 /hook portion  2615 , the crown strap  2616  and the rear strap  2650 , which can be located generally above the user&#39;s ear, can comprise a padded portion  2646 . Any suitable type of padding can be used. For example, with reference to  FIG. 27 , a padding material  2648 , such as a gel or other highly compressible material can be utilized, such as between the rigid frame  2640  and soft cover  2642 . A bottom surface of the section of the headgear  2604  in  FIG. 27  represents a surface that would contact the user&#39;s head. 
       FIGS. 28A-28C  illustrate possible constructions for other (e.g., non-padded) portions of the headgear  2604 . For example, portions of some or all of the upper arm  2620 , hook portion  2615 , crown strap  2616  or rear strap  2650  could be constructed in a manner similar to any of the arrangements of  FIGS. 28A-28C . A bottom surface of the section of the headgear  2604  in  FIGS. 28A-28C  represents a surface that would contact the user&#39;s head. The arrangement of  FIG. 28A  comprises a variable thickness cover  2642 . For example, the thickness is greater in a center portion of the cross-section compared to the edge portions, which results in a non-linear surface adjacent the user&#39;s head and/or facing away from the user&#39;s head.  FIG. 28B  illustrates an arrangement with consistent thickness of the cover  2642  and the overall cross-section of the portion of the headgear  2604 .  FIG. 28C  illustrates a version in which the cover  2642  does not cover an entirety of the rigid frame  2640 . For example, a center portion of the rigid frame  2640  is left exposed and the cover  2642  is provided on each edge portion of the rigid frame  2640 . Any suitable manner of coupling the cover  2642  and/or padding  2648  to the rigid frame  2640  can be utilized, such as overmolding, for example. Arrangements to provide mechanical interlocking of the rigid frame  2640  and the cover  2642  and/or padding  2648  can be utilized for increased durability. 
       FIG. 29  illustrates an interface assembly  2900  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  2900  includes an interface  2902  and a headgear  2904 . The illustrated interface  2902  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  2904 . The illustrated mask  2902  generally comprises a frame  2906  that supports a seal  2908 . The mask  2902  can be connected to a supply conduit  2909 , which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  2902  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  2902  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  2904  can be coupled to the mask  2902  at one or more mounting locations or mounting points  2910 . Preferably, a lower strap portion  2918  and an upper arm  2920  are provided on each side of the headgear  2904  to connect the mask  2902  to a rear portion of the headgear  2904 . Unless indicated otherwise, features of the interface assembly  2900  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. In particular, the interface assembly  2900  is similar to the interface assembly  2600  of  FIGS. 26-28  and, for the sake of convenience, will be described in the context of the differences relative to that interface assembly  2600 . 
     The headgear  2904  utilizes a rear strap  2950  portion that couples to the hook portion  2915  at a lower end thereof, such that the rear strap  2950  extends below the user&#39;s ear toward the hook portion  2915 . Thus, a crown strap  2916 , the hook portion  2915  and the rear strap  2950  of the headgear  2904  cooperate to form a generally U-shaped or C-shaped profile. One or more supports, such as elasticated or semi-rigid straps  2930 , can provide support between different portions of the headgear  2904 . For example, one or more (e.g., a pair) of straps  2930  can extend between the crown strap  2916  and the rear strap  2950  to support the “ends” of the U-shaped or C-shaped profile and inhibit those portions from moving apart from one another. In some configurations, the straps  2930  cross one another. 
     In the illustrated configuration, an upper portion of the mask  2902  is rotationally or pivotally coupled to the upper arm  2920  by a rotational coupling  2944 . The lower strap  2918  can permit adjustment of a rotational position of the mask  2902 . For example, a length of the lower strap  2918  could be adjustable. In some configurations, the lower strap  2918  can be constructed from an elasticated material that automatically adjusts a rotational position of the mask  2902 . 
       FIG. 30  illustrates one possible construction of the rotational coupling  2944 . In some configurations, one of the mask  2902  and the headgear  2904  supports a shaft or axle  2946  and the other of the mask  2902  and the headgear  2904  supports a hub  2948 . The hub  2948  is rotatable about the axle  2946  to permit rotational adjustment of the mask  2902  relative to the headgear  2904 . In the illustrated arrangement, the axle  2946  is carried by the mask  2902  and the hub  2948  is carried by the headgear  2904 . However, this arrangement could be reversed. If desired, a detent assembly could be utilized to maintain a desired rotational position of the mask  2902 . In some configurations, the lower strap  2918  is utilized to maintain a desired rotational position of the mask  2902 . 
       FIGS. 31 and 32  illustrate an interface assembly  3100  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  3100  includes an interface  3102  and a headgear  3104 . The illustrated interface  3102  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  3104 . The illustrated mask  3102  generally comprises a frame  3106  that supports a seal  3108 . The mask  3102  can be connected to a supply conduit  3109 , which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  3102  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  3102  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  3104  can be coupled to the mask  3102  at one or more mounting locations or mounting points  3110 . Preferably, a lower strap portion  3118  and an upper strap portion  3120  are provided on each side of the headgear  3104  to connect the mask  3102  to a rear portion of the headgear  3104 . Unless indicated otherwise, features of the interface assembly  3100  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. In particular, the interface assembly  3100  is similar to the interface assembly  1300  of  FIGS. 13-15  and, for the sake of convenience, will be described in the context of the differences relative to that interface assembly  1300 . 
     The upper strap portion  3120  of the headgear  3104  incorporates a cheek pad  3130 , which preferably is constructed from a relatively or highly compressible material for user comfort.  FIG. 32  is an enlarged view of the cheek pad  3130  and upper strap portion  3120  of the opposite side of the headgear  3104  from that shown in  FIG. 31 . As illustrated, the cheek pad  3130  can have a contoured shape, with a wider portion being positioned closer toward the mask  3102  or centerline of the user&#39;s head than the narrower portion. For example, the cheek pad  3130  could have a generally teardrop shape, among other possible tapered or non-tapered shapes. The cheek pad  3130  can be secured to the upper strap  3120  by any suitable arrangement, such as by overmolding, for example. In some configurations, the cheek pad  3130  can include an interior passage and the cheek pad  3130  can be slid onto the upper strap  3120 . If desired, the cheek pad  3130  can be rigid to provide a hard stop in response to tightening of the headgear  3104  to at least partially isolate compression of the mask seal  3108  from tightening forces applied to the headgear  3104 , such as described in connection with  FIGS. 13-15 and 75-79 , for example. 
     The headgear  3104  can include various features configured to influence the flexibility, strength or rigidity. For example, if the headgear  3104  is constructed primarily from a flexible material, the features can alter the inherent or base properties (e.g., flexibility, strength or rigidity) of the material of the headgear  3104 . In some configurations, the features can comprise one or more types of strips or ribs  3132  formed into or applied to the headgear  3104  in a manner to provide desirable properties to the headgear  3104 . For example, elongate ribs  3132  can be provided on one or more of the upper strap  3120 , a crown strap  3116  or a rear strap  3150  of the headgear  3104 . Each or any one of the elongate ribs  3132  can define an end portion that diverges or splits, such as an end nearest a convergence of the upper strap  3120 , crown strap  3116  or rear strap  3150 . For example, the ribs  3132  of the upper strap  3120 , crown strap  3116  or rear strap  3150  can increase the tensile or bending strength of the straps. 
     A rear portion of the bottom strap  3118  near a junction between a rearward end of the bottom strap  3118  and the rear strap  3150  can comprise a rib or ribs  3132 . For example, a series of ribs  3132  can be vertically-stacked or stacked in a width direction of the strap  3118 . The ribs  3132  can follow a curvature (e.g., an upward curvature) of the rear portion of the rear strap  3150 . The ribs  3132  of the rear strap  3150  can increase the bending strength of the rear strap  3150  and can help the curved rearward portion of the rear strap  3150  maintain its shape in response to loading. 
     The lower strap  3118  can include a series of ribs  3132  spaced from one another in a lengthwise direction of the strap  3132 . In the illustrated arrangement, the ribs  3132  are or comprise chevrons. Such an arrangement can inhibit folding of the strap  3118  along a lengthwise axis and/or can increase bending strength, but can maintain the inherent axial properties (e.g., tensile strength or flexibility in an axial direction). 
     The ribs  3132  can be of any suitable arrangement. For example, the ribs  3132  could be formed into the material of the headgear  3104  (e.g., thermoformed). The ribs  3132  could protrude outwardly from an adjacent or base surface of the headgear  3104  or could extend inwardly from an adjacent or base surface of the headgear  3104 . In some configurations, the ribs  3132  could be additional structures that are attached (e.g., adhesive, RF welding, ultrasonic welding, thermoforming, stitching, chemical bonding, mechanical bonding or otherwise adhered) to the base headgear  3104  structure. The features of the headgear  3104  can be applied to any of the other headgear arrangements described herein. 
       FIG. 33  illustrates an interface assembly  3300  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  3300  includes an interface  3302  and a headgear  3304 . The illustrated interface  3302  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  3304 . The illustrated mask  3302  generally comprises a frame  3306  that supports a seal  3308 . The mask  3302  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  3302  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  3302  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  3304  can be coupled to the mask  3302  at one or more mounting locations or mounting points  3310 . Preferably, a lower strap portion  3318  and an upper strap portion  3320  are provided on each side of the headgear  3304  to connect the mask  3302  to a rear portion of the headgear  3304 . Unless indicated otherwise, features of the interface assembly  3300  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The headgear  3304  can comprise a rigid portion or portions and a less rigid portion or portions. In the illustrated arrangement, the upper arm  3320  is constructed from a relatively rigid or rigid material. Other portions of the headgear  3304  can be constructed from a relatively less rigid material, such as flexible material. For example, a crown strap  3316  can be coupled to the rigid upper arm  3320  and can be constructed from a less rigid material. In some configurations, the headgear  3304  can include a rear strap  3350  that is coupled to the rigid upper arm  3320  and can be constructed from a less rigid material. In the illustrated arrangement, the less rigid portions (e.g., the crown strap  3316 , the rear strap  3350  or the lower arm  3318 ) of the headgear  3304  can be coupled to the rigid upper arm  3320  such that forces applied to the less rigid portions are substantially or primarily axial. That is, preferably, the forces applied to the less rigid portion are generally aligned with a lengthwise direction of the portions, in a direction aligned with a geometric axis of the portions or otherwise aligned with a direction in which the portions are configured to resist elongation. In some configurations, an axial direction can include a direction passing through end points or end portions of a strap or other component or a direction along which forces are applied to the strap or other component. In some cases, the axial direction may not coincide with the shape of the strap or other component, but may define a virtual axis. 
       FIG. 34  illustrates an interface assembly  3400  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  3400  includes an interface  3402  and a headgear  3404 . The illustrated interface  3402  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  3404 . The illustrated mask  3402  generally comprises a frame  3406  that supports a seal  3408 . The mask  3402  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  3402  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  3402  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  3404  can be coupled to the mask  3402  at one or more mounting locations or mounting points  3410 . Preferably, a strap portion  3420  is provided on each side of the headgear  3404  to connect the mask  3402  to a rear portion of the headgear  3404 . In the illustrated arrangement, the strap portion  3420  is positioned in a manner similar to the upper straps/arms in other arrangements disclosed herein and the lower strap can be omitted. Thus, the strap  3420  on each side can be the only connection between the mask  3402  and a rear portion of the headgear  3404 . The strap  3420  can be oriented generally perpendicular with respect to a halo portion  3414  of the headgear  3404 , which can be defined by a combination of a crown strap portion  3416  and a rear strap portion  3450 . Preferably, the crown strap portion  3416  and the rear strap portion  3450  are aligned with one another such that the halo portion  3414  is generally flat or planar. The strap  3420  can extend upwardly from the mask  3402  and above the user&#39;s ear to the halo portion  3414  and can be generally straight or only slightly curved in comparison to many upper strap portions disclosed herein. 
     The halo portion  3414  can have a forward portion  3414 a and a rearward portion  3414   b.  The strap  3420  can be coupled to the rearward portion  3414   b  and gussets  3460  can extend between the strap  3420  and the forward portion  3414   a  of the halo portion  3414  on one or both sides of the strap  3420 . The strap  3420  and the halo portion  3414  can be constructed from a relatively rigid material or a relatively less-rigid material or any combination thereof. In some configurations, the strap  3420  can be constructed from a relatively rigid material and the halo portion  3414  can be constructed from a relatively less rigid material. Otherwise, features of the interface assembly  3400  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
       FIG. 35  illustrates a portion of an interface assembly  3500  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  3500  includes an interface  3502  and a headgear  3504 . The illustrated interface  3502  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  3504 . The illustrated mask  3502  generally comprises a frame  3506  that supports a seal  3508 . The mask  3502  can be connected to a supply conduit  3509 , which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  3502  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  3502  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  3504  can be coupled to the mask  3502  at one or more mounting locations or mounting points  3510 . Preferably, a lower strap portion  3518  and an upper strap portion  3520  are provided on each side of the headgear  3504  to connect the mask  3502  to a rear portion of the headgear  3504 . Unless indicated otherwise, features of the interface assembly  3500  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The lower strap  3518  and the upper strap  3520  can be coupled to the mask  3502  by quick-release mechanisms, such as snap-locks or clips (e.g., hook-and-bar arrangement)  3530 . The lower strap  3518  and upper strap  3520  can be rotatable relative to the clips  3530  to permit angular adjustment of the straps  3518 ,  3520 . For example, the ends of the straps  3518 ,  3520  can carry pins  3532  that engage openings of the clips  3530 . The portions of the mask  3502  that receive the clips  3530  can define one or more elongate protrusions  3534 , surfaces of which extend outwardly beyond adjacent surfaces of the mask  3402 . In some configurations, a surface between the portions of the mask  3502  that receive the clips  3530  is recessed such that a pair of protrusions  3534  is provided. Such an arrangement can provide tactile indications of the proper locations for engaging the clips  3530  with the mask in addition to providing a unique appearance. 
       FIG. 36  illustrates an arrangement in which the clips  3530  are coupled to one another such that both clips  3530  and both straps  3518 ,  3520  can be coupled to the mask  3502  in a single action. For example, a bridge or strut portion  3540  can extend in a vertical direction between the clips  3530 , which could be angled relative to one another. The clips  3530  and strut  3540  can be formed from a single piece of material, if desired. In addition, in the arrangement of  FIG. 36 , the pins  3532  are carried by the clips  3530  and corresponding openings are provided in the ends of the straps  3518 ,  3520 . 
       FIG. 37  illustrates an interface assembly  3700  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  3700  includes an interface  3702  and a headgear  3704 . The illustrated interface  3702  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  3704 . The illustrated mask  3702  generally comprises a frame  3706  that supports a seal  3708 . The mask  3702  can be connected to a supply conduit  3709 , which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  3702  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  3702  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  3704  can be coupled to the mask  3702  at one or more mounting locations or mounting points  3710 . Preferably, a lower strap portion  3718  and an upper strap portion  3720  are provided on each side of the headgear  3704  and connect to the mask  3702  by any suitable arrangement, such as by a quick-release mechanism (e.g., snap-lock or clips). In the illustrated arrangement, the straps  3718 ,  3720  extend from one side of the mask  3702  to the other and central portions of the straps  3718 ,  3720  form a rear portion of the headgear  3704 . In addition, the lower strap  3718  connects to the mask  3702  at an upper mounting point  3710  and the upper strap  3720  connects to the mask  3702  at a lower mounting point  3710  such that the straps  3718 ,  3720  cross one another rearwardly of the mask  3702 , preferably between the mask  3702  and the user&#39;s ear. The straps  3718 ,  3720  can be coupled to one another at the location in which they cross, if desired. The straps  3718 ,  3720  can be constructed of a flexible material, which may be elasticated, and can included enlarged width rear portions  3718   a ,  3720   a  to spread load for user comfort. In other arrangements, the straps  3718 ,  3720  could connect to a separate rear portion of a headgear  3704 . Unless indicated otherwise, features of the interface assembly  3700  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
       FIGS. 38 and 39  illustrate an interface assembly  3800  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  3800  includes an interface  3802  and a headgear  3804 . The illustrated interface  3802  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  3804 . The illustrated mask  3802  generally comprises a frame  3806  that supports a seal  3808 . The mask  3802  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  3802  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  3802  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  3804  can be coupled to the mask  3802  at one or more mounting locations or mounting points  3810  by any suitable coupling, such as a quick-release mechanism, for example. Preferably, a strap portion  3820  is provided on each side of the headgear  3804  to connect the mask  3802  to a rear portion of the headgear  3804 . In the illustrated arrangement, the headgear  3804  includes a single strap portion  3820  that is coupled to the mask  3802  at a single, vertically-elongated mounting point  3810  on each side of the interface assembly  3800 . The strap portion  3820  can pass directly over the user&#39;s ear and, in some configurations, is wide enough to cover most, substantially all or the user&#39;s entire ear. The strap  3820  can extend all the way from one side of the mask  3802  to the other side and a central portion of the strap  3820  can define a rear strap portion  3850 , which can include a vent  3852  to reduce heat build-up under the strap portion  3850 . The vent  3852  can be constructed of a mesh or other breathable material and can extend along a substantial entirety of a length of the rear strap portion  3850 . The vent  3852  can also extend along a substantial portion of the height of the rear strap portion  3850  such that the vent  3852  occupies a substantial portion of an overall area of the rear strap portion  3850 , such as at least about 50, 60, 70 or 80% of an overall area. Preferably, the vent  3852  is of a sufficient size to significantly reduce heat build-up under the rear strap portion  3850  relative to a similarly sized strap without a vent. In some configurations, the vent  3852  is sized to maximize vented area while not compromising the structure of the strap portion  3850  or creating pressure points on the user&#39;s head. 
     The headgear  3804  can include a top strap  3860  that can extend upwardly from a center of the mask  3802  over top of the user&#39;s head and connect to the rear strap portion  3850 . The top strap  3860  can extend along the user&#39;s nose, between the eyes and can bifurcate into two strap portions  3860   a,    3860   b  to form a triangulated arrangement with the rear strap portion  3850  and form a halo portion  3814 . The top strap  3860  can apply an upwardly-directed force to the mask  3802  to assist in creating a seal against the underside of the user&#39;s nose. In some configurations, a length of the top strap  3860  is adjustable to allow for adjustment of a position of and/or upward force applied to the mask  3802 . In other respects, features of the interface assembly  3800  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
       FIG. 40  illustrates an interface assembly  4000  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  4000  includes an interface  4002  and a headgear  4004 . The illustrated interface  4002  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  4004 . The illustrated mask  4002  generally comprises a frame  4006  that supports a seal  4008 . The mask  4002  can be connected to a supply conduit  4009 , which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  4002  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  4002  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  4004  can be coupled to the mask  4002  at one or more mounting locations or mounting points  4010  by any suitable coupling arrangement. In the illustrated arrangement, the headgear  4004  includes a single strap portion  4020  that is coupled to the mask  4002  at a single, vertically-elongated mounting point  4010  on each side of the interface assembly  4000 . The strap  4020  can extend all the way from one side of the mask  4002  to the other side. Preferably, the strap  4020  is bifurcated rearwardly of the mask  4002  to define an upper strap  4020   a  and a lower strap  4020   b  that pass above and below the user&#39;s ear, respectively. Central portions of the upper strap  4020   a  and the lower strap  4020   b  can be enlarged in a width or vertical direction to spread a load applied to the user&#39;s head over a relatively large area for comfort. 
     Each side of the mask  4002  can include an elongate slot  4030  through which the strap  4020  can pass. End portions  4040  of the strap  4020  can fold over to form a loop and can be secured to a portion of the strap  4020  rearward of the mask  4002  by a suitable fastener, such as a hook-and-loop fastener, for example. The end portions  4040  of the strap  4020  can include a finger tab  4032 , which can provide a finger grip area to facilitate assembly and adjustment of the strap  4020  relative to the mask  4002 . The slot  4030  can be generally or substantially straight and, in some configurations, can be generally or substantially aligned with a rearward surface of the mask  4002  (e.g., rearward surface of the frame  4006  and/or seal  4008 ). An overall size or circumference of the interface assembly  4000  can be adjusted by altering a length of the end portions  4040  of the strap  4020  that are pulled through the slot  4030  to vary a size of the loop. Angular adjustment of the mask  4002  can be accomplished by moving the end portions  4040  in a generally vertical direction to alter a vertical orientation of a forward end or fold  4042  of the end portions  4040  of the strap  4020 . That is, the end portion  4040  can be moved or angled upwardly to pull in the bottom of the mask  4002  relative to the top of the mask  4002 . Conversely, the end portion  4040  can be moved or angled downwardly to pull in the top of the mask  4002  relative to the bottom of the mask  4002 . Thus, preferably, the straps  4020  increase in height (in the illustrated orientation or in a width direction of the strap  4020 , itself) in a direction from each of the end portions  4040  toward the center of the strap  4020  to provide surface area of the strap  4020  for upward and downward adjustment of the end portions  4040  of the strap  4020 . In other respects, features of the interface assembly  4000  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
       FIGS. 41 and 42  illustrate an interface assembly  4000  that is similar in many respects to the interface assembly  4000  of  FIG. 40 . Therefore, the same reference numbers are used to refer to the same or corresponding components or features. In addition, the interface assembly  4000  of  FIGS. 41 and 42  is described in the context of the differences relative to the interface assembly  4000  of  FIG. 40 . Features of the interface assembly  4000  or portions thereof not specifically described can be assumed to be the same as or similar to features of the interface assembly  4000  of  FIG. 40 , other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     In the arrangement of  FIGS. 41 and 42 , the upper strap  4020   a  and the lower strap  4020   b  can be positioned closer to one another than in the arrangement of  FIG. 40 . For example, the upper strap  4020   a  can be positioned lower on the user&#39;s head (e.g., at or near an upper edge of the occipital bone) and can pass just above the user&#39;s ear. The lower strap  4020   b  can be positioned higher on the user&#39;s head, such as above the user&#39;s neck muscled and/or on the occipital bone. In addition, the upper strap  4020   a  and the lower strap  4020   b  can be connected by one or more vertical connecting portions  4050 . For example, on each side of the interface assembly  4000 , a first vertical connecting portion  4050  can be positioned behind the user&#39;s ear and a second vertical connecting portion  4050  can be positioned further rearward of the first vertical connecting portion  4050 . The vertical connecting portions  4050  can secure the upper strap  4020   a  and the lower strap  4020   b  in desired positioned relative to one another and inhibit or prevent migration of the straps  4020   a,    4020   b  apart from one another. 
       FIG. 43  illustrates an interface assembly  4000  that is similar in many respects to the interface assemblies  4000  of  FIGS. 40-42 . Therefore, the same reference numbers are used to refer to the same or corresponding components or features. In addition, the interface assembly  4000  of  FIG. 43  is described in the context of the differences relative to the interface assemblies  4000  of  FIGS. 40-42 . Features of the interface assembly  4000  or portions thereof not specifically described can be assumed to be the same as or similar to features of the interface assembly  4000  of  FIGS. 40-42 , other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The positioning of the upper strap  4020   a  and the lower strap  4020   b  of the headgear  4004  of  FIG. 43  relative to the user&#39;s head can be similar to the straps in the headgear  4004  of  FIG. 40 . However, preferably, one or more connecting straps  4050  are provided that extend between and connect the upper strap  4020   a  and the lower strap  4020   b , similar to the headgear  4004  of  FIGS. 41 and 42 . 
     In addition, the strap  4020  can be connected to the mask  4002  in a different manner. For example, the upper strap  4020   a  and the lower strap  4020   b  can be coupled to the mask  4002  at separate mounting points  4010 . In some configurations, the straps  4020   a ,  4020   b  can be coupled to the mask  4002  by connectors having some amount of elasticity. In some configurations, the elasticity is relatively low. For example, the connectors can be silicone tension straps  4060 . Such silicon tension straps  4060  can provide for rotational adjustment and tensioning of the mask  4002  against the user&#39;s face. However, other adjusters for the mask  4002  and/or headgear  4004  could also be provided. In addition, other materials with properties (e.g., elasticity, flexibility) similar to silicone could also be used. 
       FIGS. 44 and 45  illustrate an interface assembly  3800  that is similar in many respects to the interface assembly  3800  of  FIGS. 38 and 39 . Therefore, the same reference numbers are used to refer to the same or corresponding components or features. In addition, the interface assembly  3800  of  FIGS. 44 and 45  is described in the context of the differences relative to the interface assembly  3800  of  FIGS. 38 and 39 . Features of the interface assembly  3800  or portions thereof not specifically described can be assumed to be the same as or similar to features of the interface assembly  3800  of  FIGS. 38 and 39 , other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     Unlike the strap portion  3820  of the headgear  3804  of  FIGS. 38 and 39 , the strap portion  3820  of  FIGS. 44 and 45  preferably does not cover the user&#39;s ear. Rather, the strap portion  3820  preferably passes below the user&#39;s ear. The rear portion  3850  of the strap  3820  can be smaller in height (or width of the strap  3820 , itself) compared to the rear portion  3850  of  FIGS. 38 and 30 . In some configurations, the strap  3820  is coupled to the mask  3802  by a rotatable coupling, such as those described in connection with  FIGS. 35 and 36  or elsewhere herein. 
     In addition, the mask  3802  can include support portions, such as paddles  3870  that support the upper portion of the seal  3808 . For example, the paddles  3870  can be a portion of or can be connected to the mask frame  3806  and can be positioned on lateral sides of the upper portion of the seal  3808  to provide support to the seal  3808  and maintain the seal  3808  in contact with the user&#39;s nose when the seal  3808  is pressurized. In some configurations, the paddles  3870  are constructed from silicone, or a similar material. In addition,  FIG. 45  illustrates the supply conduit  3809 . 
       FIG. 46  illustrates an interface assembly  4600  that is similar in many respects to the interface assembly  3500  of  FIGS. 35 and 36  and the interface assembly  4000  of  FIG. 43 . The interface assembly  4600  is described primarily in the context of the differences relative to the interface assemblies  3500  and  4000 . Features of the interface assembly  3500  or portions thereof not specifically described can be assumed to be the same as or similar to features of the interface assemblies  3500  or  4000 , other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The interface assembly  4600  utilizes an interface or mask  4602  that is substantially similar to the mask  3502  of  FIG. 35  and a headgear  4604  that is substantially similar to the headgear  4004  of  FIG. 43 . In particular, the mask  4602  preferably includes a frame  4606  and a seal  4608 . A supply conduit  4609  delivers breathing gases to a user. As described above, in some configurations, the mask  4602  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  4602  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  4604  can be coupled to the mask  4602  at one or more mounting locations or mounting points  4610  by any suitable coupling arrangement. For example, the headgear can comprise a strap  4620  having an upper strap portion  4620   a  and a lower strap portion  4620   b  coupled to each side of the mask  4602  at separate mounting points  4610 . A connecting strap portion  4650  couples the upper strap portion  4620   a  and the lower strap portion  4620   b.  The connecting strap portion  4650  can be provided on each side of the headgear  4604  behind the user&#39;s ear. 
     One or both of the upper strap  4620   a  and the lower strap  4620   b  can be coupled to the mask  4602  by any suitable arrangement. In some configurations, the straps  4620   a ,  4620   b  are coupled to the mask  4602  by quick-release mechanisms, such as snap-locks or clips (e.g., hook-and-bar arrangement)  4630 . In some configurations, the straps  4620   a ,  4620   b  can be rotatable relative to the clips  4630  to permit angular adjustment of the straps  4620   a,    4620   b.  The portions of the mask  4602  that receive the clips  4630  can define one or more elongate protrusions  4634 , surfaces of which extend outwardly beyond adjacent surfaces of the mask  4602 . In some configurations, a surface between the portions of the mask  4602  that receive the clips  4630  or straps  4620   a ,  4620   b  is recessed such that a pair of protrusions  4634  is provided. Such an arrangement can provide tactile indications of the proper locations for engaging the clips  4630  with the mask in addition to providing a unique appearance. Unless indicated otherwise, features of the interface assembly  4600  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
       FIG. 47  illustrates an interface assembly  4000  that is similar in many respects to the interface assembly  4000  of  FIG. 40  and the interface assembly  4000  of  FIGS. 41 and 42 . Therefore, the same reference numbers are used to refer to the same or corresponding components or features. In addition, the interface assembly  4000  of  FIG. 47  is described in the context of the differences relative to the interface assemblies  4000  of  FIGS. 40-42 . Features of the interface assembly  4000  or portions thereof not specifically described can be assumed to be the same as or similar to features of the interface assemblies  4000  of  FIGS. 40-42 , other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     In the arrangement of  FIG. 47 , the upper strap  4020   a  and the lower strap  4020   b  can be positioned relative to one another in a manner similar to the arrangement of  FIGS. 44 and 42 . In addition, the upper strap  4020   a  and the lower strap  4020   b  are similarly connected by one or more vertical connecting portions  4050 . In the illustrated arrangement, a vertical connecting portion  4050  can be positioned behind the user&#39;s ear on each side of the interface assembly  4000 . A crown strap  4016  can extend over the top of the user&#39;s head from one side of the upper strap  4020   a  to the other side of the upper strap  4020 a. In some configurations, the crown strap  4016  can be aligned with the connecting portions  4050 . 
     The headgear  4004  can be constructed as a composite structure of a relatively rigid material and a relatively less rigid material. For example, a flexible material, such as a textile material, can be utilized to construct a base  4060  of the headgear. A semi-rigid or rigid material can be applied to the base  4060  to form a support structure  4062 . One example of a semi-rigid material is polypropylene sheet material having a thickness of about 0.5 millimeters, for example. The support structure  4062  can be bonded to an outer surface of the base  4060 , such as with an adhesive, RF welding, ultrasonic welding, thermoforming, stitching, chemical bonding, mechanical bonding or any other suitable method. In the illustrated arrangement, the base  4060  has a greater width than the support structure  4062 . The support structure  4062  can be provided on some portions or a substantial entirety of the headgear  4004 . For example, preferably, the support structure  4062  extends along at least a substantial length of the upper strap  4020   a , lower strap  4020   b,  the crown strap  4016  and the connecting straps  4050 . In some configurations, the support structure can be constructed from a single piece of material. 
       FIG. 48  illustrates a low-profile adjustment arrangement  4800  that can be used to adjust a length of a headgear strap, such as any of the straps of the headgear  4004  of  FIG. 47 . In one arrangement, the low-profile adjustment arrangement  4800  is utilized in the crown strap  4016  of the headgear  4004  of  FIG. 47 . In the illustrated arrangement, the crown strap  4016  is split along its length into a first crown strap portion  4016   a  and a second crown strap portion  4016   b.  The first crown strap portion  4016   a  comprises a first component  4802  of a fastener, such as a hook-and-loop fastener, and the second crown strap portion  4016   b  comprises a second component  4804  of the fastener. The first component  4802  can be selectively engaged at a desired position with the second component  4804  to adjust a length of the crown strap  4016 . 
     In some configurations, the first component  4802  is carried by or secured to one of the base  4060  and the support structure  4062  of the crown strap  4016  and the second component  4804  is carried by or secured to the other of the base  4060  and the support structure  4062  of the crown strap  4016 . Such an arrangement takes advantage of the dual layer construction of the crown strap  4016  to provide adjustment without doubling the thickness of the crown strap  4016 . In some configurations, an end of at least one of the first crown strap portion  4016   a  and the second crown strap portion  4016   b  comprises a loop  4810  that surrounds the other of the first crown strap portion  4016   a  and the second crown strap portion  4016   b  to facilitate maintaining axial alignment of the first crown strap portion  4016   a  and the second crown strap portion  4016   b.    
       FIG. 49  illustrates an interface assembly  4900  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  4900  includes an interface  4902  and a headgear  4904 . The illustrated interface  4902  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  4904 . The illustrated mask  4902  generally comprises a frame  4906  that supports a seal  4908 . The mask  4902  can be connected to a supply conduit  4909 , which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  4902  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  4902  can provide pressurized air flow to both the nose and the mouth of the user. The mask frame  4906  can include or carry support structures  4970  for providing lateral support to an upper portion of the mask seal  4908 . The support structures  4970  can be the same as or similar to the paddles  3870  of  FIGS. 44 and 45 . 
     The headgear  4904  can be coupled to the mask  4902  at one or more mounting locations or mounting points  4910 . In some configurations, the mask  4902  can be rotatably coupled to the headgear  4904  by a rotational coupling  4944 , which can be substantially similar to the rotational couplings of  FIG. 29, 35 or 36 , for example. In addition, the headgear  4904  can include a lower strap or lower arm  4918  on each side of the interface assembly  4900  that pass below the user&#39;s ears and can omit upper straps. Thus, in some configurations, the lower arms  4918  are the only connections between the mask  4902  and the headgear  4904 . The headgear  4904  can include a rear portion  4914 , which can be a rear halo portion or can be of a similar arrangement. In some configurations, the rear portion  4914  is not annular in shape. The rear portion  4914  can comprise a cradle structure that extends in a vertical direction along the back of the user&#39;s head and, in some configurations, from a location at or near a lower end of the user&#39;s head to a location at or near a crown of the user&#39;s head. The cradle structure of the rear portion  4914  can be curved in a vertical and/or horizontal direction to generally conform to the shape of the user&#39;s head. 
     The lower arm  4918  can comprise an adjustment arrangement  4960  that permits a distance between the mask  4902  and the rear portion  4914  of the headgear  4904  to be adjusted. In the illustrated interface  4900 , the adjustment arrangement  4960  comprises a sliding arrangement. In particular, the adjustment arrangement  4960  comprises a first arm portion  4962  that is fixed for movement with the rear portion  4914  in at least a fore-aft direction and a second arm portion  4964  that is fixed for movement with the mask  4902  in at least a fore-aft direction. In some configurations, the second arm portion  4964  can be integral or unitary with a portion of the mask  4902  (e.g., the mask frame  4906 ). 
     The first arm portion  4962  and the second arm portion  4964  are slidably or telescopically engaged with one another, for example by one or more loops  4966  coupled to one of the first arm portion  4962  and the second arm portion  4964 , which surround the other of the first arm portion  4962  and the second arm portion  4964 . Thus, movement of the second arm portion  4964  relative to the first arm portion  4962  can adjust a retention force applied to the mask  4902 . Preferably, the adjustment arrangement  4960  secures the arm portions  4962 ,  4964  and, thus, the mask  4902  and headgear  4904  in a desired position once adjusted. For example, the loops  4966  can frictionally engage the arm portion  4962  or  4964 . In other configurations, a lock arrangement can be provided to secure the arm portions  4962  or  4964  in a desired position. Other suitable arrangements could also be used. In other respects, features of the interface assembly  4900  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
       FIG. 50  illustrates an interface assembly  5000  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. Unless indicated otherwise, features of the interface assembly  5000  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. The illustrated interface assembly  5000  includes an interface  5002  and a headgear  5004 . The illustrated interface  5002  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  5004 . The illustrated mask  5002  generally comprises a frame  5006  that supports a seal  5008 . The mask  5002  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. 
     As described above, in some configurations, the mask  5002  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  5002  can provide pressurized air flow to both the nose and the mouth of the user. The mask  5002  can include supports or paddles  5070  that extend upwardly from the mask frame  5006  along the sides of the nose portion of the seal  5008  to provide lateral support to the nose portions of the mask seal  5008 . The supports  5070  can be permanently or removably coupled to the mask  5002 . In the illustrated configuration, the supports  5070  are removably coupled to the mask frame  5006  and can be provided in several sizes or shapes to allow a user to fine tune the amount of support provided to the sides of the nose portion of the seal  5008 . 
     The headgear  5004  can be coupled to the mask  5002  at one or more mounting locations or mounting points  5010 . Preferably, a lower strap portion  5018  and an upper strap portion  5020  are provided on each side of the headgear  5004  to connect the mask  5002  to a rear portion of the headgear  5004 . In the illustrated arrangement, the lower strap  5018  and the upper strap  5020  on at least one side of the mask  5002  are coupled to the mask  5002  by a single clip  5030 , which can be the same as or similar to the arrangement described in connection with  FIGS. 35 and 36 . In some configurations, a clip  5030  is provided on only one side of the mask  5002 . The straps  5018 ,  5020  can be permanently coupled to the mask  5002  on the other side or coupled in a manner that is not as convenient to connect and remove as the clip  5030  (e.g., coupled via an adjustment mechanism). 
     The clip  5030  and the mask frame  5006  can be configured in a complementary manner to facilitate location of the proper position of the clip  5030  for engagement with the mask  5002  and/or to inhibit undesired disengagement of the clip  5030  from the mask  5002 . For example, the mask frame  5006  can comprise one or more edges  5032  that cooperate to define a recess for receiving the clip  5030 . In the illustrated arrangement, the edges  5032  define a rearwardly-opening recess and the clip  5030  passes through the rearward opening  5034 . In some configurations, the clip  5030  is configured to occupy an entirety or a substantial entirety of the recess defined by the edges  5032 . Thus, an outwardly-facing surface  5036  of the clip  5030  can be flush with an outwardly-facing surface  5038  of adjacent portions of the mask frame  5006 , at least at locations in which the clip  5030  and the mask frame  5006  meet. With such an arrangement, the edges  5032  of the recess inhibit the clip  5030  from moving in a direction (e.g., forwardly) that would permit undesired or unintentional disengagement of the clip  5030  from the mask  5002 . However, a user could intentionally move the clip  5030 , for example, in a lateral direction away from the mask frame  5006  and out of engagement with the mask  5002 . 
     As illustrated by the arrows in  FIG. 50 , the clip  5030  can be brought adjacent to the mask frame  5002  and, preferably, at least slightly forward of the recess defined by the edges  5032 . The edges  5032  can provide tactile feedback to the user to facilitate identification of the proper location for the clip  5030 . The clip  5030  can be moved or allowed to move rearwardly and into engagement with the recess defined by the edges  5032 . In some configurations, a forward end of the clip  5030  can be first engaged with the recess and then a rear portion of the clip  5030  can be moved inwardly into engagement with the recess. In some such configurations, a rear portion  5040  of the clip  5030  can abut against a rear edge  5042  of the mask frame  5006  to inhibit undesired forward movement and/or undesired or unintentional disengagement of the clip  5030  from the mask frame  5006 . 
     In some configurations, the clip  5030  defines one or more finger access or finger grip portions  5050 , which can provide a convenient location for the user to grasp the clip  5030 . In some configurations, the finger grip portion  5050  provides tactile feedback to the user to facilitate non-visual location of the clip  5030 . In the illustrated arrangement, a finger grip portion  5050  is provided between and at a forward end of a space  5052  defined by rearward protruding portions  5054  of the clip  5030 . Finger grip portions  5050  are also provided on upper and lower edges of the clip  5030 . Any combination or all of the illustrated locations can be used. The protruding portions  5054  can be generally aligned with a length or axial direction of the straps  5018 ,  5020 . 
       FIGS. 51-57  illustrate interface assemblies  5000  that are similar in many respects to the interface assembly  5000  of  FIG. 50 . Therefore, the same reference numbers are used to refer to the same or corresponding components or features. In addition, the interface assemblies  5000  of  FIG. 51-57  are described in the context of the differences relative to the interface assembly  5000  of  FIG. 50  and/or the differences relative to each other. Features of the interface assemblies  5000  or portions thereof not specifically described can be assumed to be the same as or similar to features of the interface assembly  5000  of  FIG. 50 , other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The interface assembly  5000  of  FIG. 51  places the finger grip portion  5050  on a forward portion of the clip  5030 . In particular, the finger grip portion  5050  is defined by a raised or outwardly offset portion on a forward edge of the clip  5030 . The finger grip portion  5050  can be generally centered in a vertical direction of the clip  5030 . The mask frame  5006  can define a recessed portion  5060  that is positioned adjacent the finger grip portion  5050  and facilitates the user accessing the inward-facing surface of the finger grip portion  5050 . In the interface assembly  5000  of  FIG. 52 , the finger grip portion  5050  is not raised relative to a surrounding portion of the clip  5030 . Instead, the recessed portion  5060  of the mask frame  5006  can be configured (e.g., enlarged relative to the portion  5060  of  FIG. 51 ) to facilitate access to the finger grip portion  5050 . 
     The interface assembly  5000  of  FIG. 53  is similar to  FIG. 52  in that the finger grip portion  5050  is not raised or outwardly offset relative to surrounding portions of the clip  5030 . However, the recessed portion  5060  of the mask frame  5006  can extend along a substantial portion or a substantial entirety of a front edge of the clip  5030 . In some configurations, the recessed portion  5060  has a length that is a substantial portion of the overall height of the mask frame  5006 , such as at least about one-half or at least about two-thirds of a height of the mask frame  5006 . 
     The interface assembly  5000  of  FIG. 54  incorporates a lock arrangement  5070  to secure the clip  5030  to the mask frame  5006 . The lock arrangement  5070  can be in addition to or in alternative to other engagement features of the clip  5030  (e.g., hook-and-bar arrangement). The lock arrangement  5070  can comprise a snap-lock feature, such as a resilient locking clip  5072 , for example and without limitation. The resilient locking clip  5072  can be placed on either the mask frame  5006  or the clip  5030  and can be located in a manner similar to the finger grip portions  5050  or recessed portions  5060  described herein. When placed on the clip  5030 , the resilient locking clip  5072  can also function as a finger grip portion  5050 . 
     The interface assembly  5000  of  FIGS. 55-56  is similar to the assemblies  5000  of  FIGS. 52 and 53 . In particular, the finger grip portion  5050  of the clip  5030  of  FIGS. 55-56  is not raised or outwardly offset relative to adjacent portions of the clip  5030  and the recessed portion  5060  of the mask frame  5006  is configured to facilitate access to the finger grip portion  5050 . The recessed portion  5060  is a relatively discrete structure with a relatively sharp transition from surrounding surfaces of the clip  5030  similar to the portion  5060  of  FIG. 52 , but extends along a greater vertical distance similar to the portion  5060  of  FIG. 53 . 
       FIG. 56  illustrates an example of interference or interlocking features  5080  of the mask frame  5006  and the clip  5030 . In the illustrated arrangement, the mask frame  5006  comprises at least one opening and, preferably, a pair of openings  5082   a,    5082   b . The forward opening  5082   a  is completely surrounded by the mask frame  5006 , while the rear opening  5082   b  is only partially surrounded by the mask frame  5006 . The clip  5030  comprises at least one engagement member or engagement block and, preferably, a pair of engagement blocks  5084   a,    5084   b  configured to engage a respective one of the openings  5082   a,    5082   b.  The openings  5082   a,    5082   b  and engagement blocks  5084   a ,  5084   b  are axially-spaced (e.g., generally aligned with a direction of a force vector acting on the clip  5030 ) to inhibit rotation of the clip  5030  relative to the mask frame  5006 . In the illustrated arrangement, the openings  5082   a,    5082   b  and engagement blocks  5084   a ,  5084   b  are aligned in a vertical direction; however, the openings  5082   a ,  5082   b  and engagement blocks  5084   a ,  5084   b  could be offset in the vertical direction. In some configurations, the clip  5030  defines a recess  5086  that is shaped complementary to and receives an overlapping portion of the mask frame  5006  when the clip  5030  is engaged with the mask frame  5006 . 
     When engaged with the mask frame  5006 , the clip  5030  exerts a generally rearward force on the mask frame  5006  via engagement of the openings  5082   a ,  5082   b  and engagement blocks  5084   a ,  5084   b.  As a result of the laterally-curved shape of the mask frame  5006  and/or the complete perimeter engagement of the engagement block  5084   a  with the surfaces of the mask frame  5006  defining the opening  5082   a , the force acting on the clip  5030  (which can be generated by the headgear) tends to pull the engagement block  5084   b  into engagement with the opening  5082   b  thereby enhancing engagement of the clip  5030  with the mask frame  5006 . 
       FIG. 57  illustrates another example of an interlocking feature  5080  between a mask frame  5006  and a clip  5030 . The illustrated arrangement comprises a hook-and-bar type interaction between the clip  5030  and the frame  5006 . Preferably, the clip  5030  includes a hook  5090  that engages an engagement surface or bar  5092  of the mask frame  5006 . In some configurations, this arrangement could be reversed. The mask frame  5006  includes an opening  5094  that accommodates the hook  5090  of the clip  5030  when the clip  5030  is engaged with the mask  5002 . In some configurations, a surface that defines a portion of the opening  5094  also defines the bar  5092 . The bar  5092  can be any structure or portion of a structure configured to interact with the hook  5090  and retain the clip  5030  to the mask  5002 . To couple the clip  5030  to the mask  5002 , a portion of the hook  5090  can be passed through the opening  5094  to engage the hook  5090  with the bar  5092  and the body of the clip  5030  can be rotated into a resting position adjacent or against the mask  5002  (e.g., mask frame  5006 ). To remove the clip  5030 , this process can be reversed. 
       FIGS. 50-57  (among others herein) disclose interface assemblies  5000  that permit a circumferential loop of the interface assembly  5000  to be opened to facilitate application and removal of the interface assembly  5000 . In such configurations, the headgear  5004  can be completely separated from the mask  5002  at at least one location to define an open loop. While such an open loop configuration can facilitate application or removal of the interface assembly  5000 , it has been discovered by the present inventors that it can sometimes be difficult or annoying for a user to locate the loose clip  5030  or other portion of the headgear  5004  for attachment to the mask  5002 . Even if only one clip  5030  is disengaged from the mask  5002 , depending on the configuration of the headgear  5004 , the loose clip  5030  could move a significant distance from the mask  5002 , such as fall behind the head of the user, for example. If clips  5030  on both sides of the mask  5002  are disengaged, complete separation of the headgear  5004  from the mask  5002  can occur. Accordingly, in some applications or uses, it can be desirable to tether the clip  5030  to the mask  5002  to facilitate location of the clip  5030 , especially when visual location is difficult or not possible. The interface assemblies  5800  of  FIGS. 58-61  are closed loop configurations, which move between an expanded orientation, which facilitates application or removal of the interface assembly  5800 , and a contracted orientation. Preferably, the interface assemblies  5800  are elasticated closed loop configurations, in which an elasticated tethering arrangement maintains a closed loop, but permits expansion or enlargement of the circumference of the interface assembly  5800  to facilitate application or removal. 
     The interface assemblies  5800  of  FIGS. 58-61  generally include an interface  5802  and a headgear  5804 . The illustrated interface  5802  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  5804 . The illustrated mask  5802  generally comprises a frame  5806  that supports a seal  5808 . The mask  5802  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  5802  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  5802  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  5804  can be coupled to the mask  5802  at one or more mounting locations or mounting points by any suitable arrangement, including the clips  5830  that are the same as or similar to the clips  5030  of  FIGS. 50-57 , for example and without limitation. In some configurations, a lower strap  5818  and an upper strap  5820  are provided on each side of the headgear  5804  to connect the mask  5802  to a rear portion of the headgear  5804 . Unless indicated otherwise, features of the interface assembly  5800  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The interface assembly  5800  of  FIG. 58  includes an elasticated tether  5840  that couples the clip  5830  to the mask  5802 . The illustrated elastic tether  5840  is a cable or cord-like member that is coupled between the clip  5830  and the mask  5802  in a triangulated manner. In particular, a center portion of the elastic tether  5840  is coupled to the mask  5802  and end portions of the elastic tether  5840  are coupled to the clip  5830 . Preferably, the elastic tether  5840  is configured to not only retain the clip  5830  near the mask  5802  when the clip  5830  is disengaged from the mask  5802 , but also tends to locate the clip  5830  properly relative to the mask  5802 . For example, a tension on the upper and lower or the two end portions of the elastic tether  5840  can be generally even when the clip  5830  is properly located relative to the mask  5802 . Thus, the elastic tether  5840  tends to pull the clip  5830  into the proper position for engagement with the mask  5802 . 
     The interface assembly  5800  of  FIG. 59  includes an elasticated tether  5840  in the form of a wide elastic strap. The elastic strap  5840  can extend from one side of the mask  5802  to the other. Each end of the elastic strap  5840  can connect to a clip  5830 . An intermediate portion of the elastic strap  5840  can be secured to the mask  5802 . For example, the mask frame  5802  can comprise a loop portion  5842  that forms a passage through which the elastic strap  5840  can pass. In some configurations, the elastic strap  5840  is loosely received in the passage and is movable relative to the mask  5802 . The clips  5830  can prevent the elastic strap  5840  from being disengaged from the mask  5802 . 
     In the interface assemblies  5800  of  FIGS. 58 and 59 , the elastic tethers  5840  are exposed. In some applications or uses, it may be desirable for the elastic tether  5840  to be covered or concealed, at least when the clip  5830  is engaged with the mask  5802 . The interface assembly  5800  of  FIGS. 60 and 61  conceals the elastic tether  5840  when the clip  5830  is engaged with the mask  5802 . In the illustrated configuration, the elastic tether  5840  includes at least one and preferably a pair of elastic elements. The elastic elements can be in the form of elastic straps  5840 , which can be spaced vertically from one another and extend generally in a fore-aft direction. In some configurations, the elastic straps  5840  can be generally or substantially aligned with a respective one of the lower strap  5818  and the upper strap  5820  of the headgear  5804 . 
     The clip  5830  can capture the elastic straps  5840  between the clip  5830  and the mask frame  5806  when the clip  5830  is engaged with the mask  5802 . In the illustrated arrangement, a first end of each elastic strap  5840  is secured to a rearward end portion of the mask frame  5806  and a second end of each elastic strap  5840  is secured to a forward end of the clip  5830 . Such an arrangement permits the elastic straps  5840  to lay relatively flat between the mask frame  5806  and the clip  5830  and also maximizes the growth in the circumference of the interface assembly  5800  permitted by the elastic straps  5840 . The mask frame  5806  and/or the clip  5830  can include recesses  5844  that receive and at least partially accommodate a thickness of the elastic straps  5840  when the clip  5830  is engaged with the mask  5802 . 
     As described above, the elastic tethers  5840  can be configured to help guide the clip  5830  to a proper location for engagement with the mask  5802 . However, in the configuration of  FIGS. 60 and 61 , the elastic straps  5840  may not pull the clip  5830  all the way to the proper position for engagement with the mask  5802 . That is, the clip  5830  can be moved away from the engagement location by a distance generally equivalent to an un-stretched length of the elastic straps  5840 . In such a configuration, or if desirable in any other configuration, the interface assembly  5800  can include additional features to assist in location of the clip  5830  relative to the mask  5802 . For example, one or more magnets  5846  can be provided on the mask  5802 , the clip  5830  or both to facilitate location of the clip  5830  relative to the mask  5802 . A single magnet arrangement can be used, but the other component typically will have a magnetically attractive material. In the illustrated arrangement, a magnet  5846  is provided at the forward ends of the recesses  5844  on the mask  5802  and clip  5830  (magnets  5846  not shown on the clip  5830 ). In addition,  FIG. 61  illustrates an opening  5848 , which can be engaged by a suitable structure of the clip  5830 , such as a hook or block (not shown). 
       FIGS. 62-64  illustrates an interface assembly  6200  that is of an elongating closed loop configuration, which permits the interface assembly  6200  to move between an expanded orientation and a contracted orientation. The interface assembly  6200  is similar to the interface assemblies  5800  of  FIGS. 58-61  in that the circumference can be enlarged to facilitate application or removal; however, preferably, the interface assembly  6200  provides the ability to enlarge the circumference via a non-elasticated folding clasp  6240  in contrast to the elasticated arrangements of  FIGS. 58-61 . 
     The illustrated interface assembly  6200  includes an interface  6202  and a headgear  6204 . The illustrated interface  6202  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  6204 . The illustrated mask  6202  generally comprises a frame  6206  that supports a seal  6208 . The mask  6202  can be connected to a supply conduit  6209 , which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  6202  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  6202  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  6204  can be coupled to the mask  6202  at one or more mounting locations or mounting points  6210 . Preferably, a lower strap portion  6218  and an upper strap portion  6220  are provided on one or both sides of the headgear  6204  to connect the mask  6202  to a rear portion of the headgear  6204 . In some configurations, the headgear  6204  can provide for adjustment in addition to the folding clasp  6240  or other elongation arrangement. With such an arrangement, the headgear  6204  can be adjusted to an appropriate or desired adjustment position separately from the action of the folding clasp  6240 , such that the folding clasp  6204  can be used solely to facilitate application and, once properly adjusted, the headgear  6204  should not require readjustment with each application of the interface assembly  6200 . Any suitable adjustment mechanism for the headgear  6204  can be provided, such as folding over the straps  6218 ,  6220  on one or both sides of the interface assembly  6200  after engagement with the mask  6202  to create adjustment loops  6222  that can be secured by any suitable fastener, such as a hook-and-loop fastener, for example. 
     The folding clasp  6240  can include multiple sections or segments that are foldable relative to one another between a contracted (e.g., stacked or folded) orientation and an expanded (e.g., unfolded) orientation. In the illustrated arrangement, a first segment  6242  is defined or carried by the mask  6202 , such as by the mask frame  6206 . A second segment  6244  is defined by or carried by a member (e.g., a clip) coupled to the headgear  6204  (e.g., one or both of the straps  6218 ,  6220 ). In some configurations, an third or intermediate segment  6246  is pivotally connected to the first segment  6242  at a first end and to the second segment  6244  at a second end. The pivot axes between the segments  6242 ,  6244 ,  6246  preferably are aligned with one another and oriented perpendicular to a circumferential direction of the headgear  6204 /interface assembly  6200 . Such an arrangement maintains the segments  6242 ,  6244 ,  6246  in the proper plane relative to one another and, in the illustrated arrangement, maintains the forward portion of the headgear  6204  in horizontal alignment with the mask  6202  to facilitate non-visual location of the second segment  6244  of the folding clasp  6240  in the unfolded orientation. 
     As illustrated in  FIGS. 63 and 64 , respectively, in the contracted orientation the segments  6242 ,  6244 ,  6246  are stacked relative to one another to have an increased overall thickness and reduced length and in the expanded orientation the segments  6242 ,  6244 ,  6246  are unstacked and positioned end-to-end to reduce the overall thickness and increase the length. Folding clasps  6240  can be provided on one or both sides of the interface assembly  6200 . Preferably, when contracted or folded, the folding clasp  6240  is located on the mask  6202  or forward of a rearward edge of the mask  6202 . Such an arrangement avoids contact between the folding clasp  6240  and the user for increased comfort. In some configurations, the a locking mechanism (e.g., snap-fit arrangement) can be provided to lock or retain the folding clasp  6240  in the closed position or contracted orientation and inhibit or prevent unintentional opening of the folding clasp  6240 . A finger grip portion  6250  and corresponding recessed portion  6260  can be provided on the clip  6230  and mask frame  6206 , respectively, to facilitate opening of the folding clasp  6240 . Unless indicated otherwise, features of the interface assembly  6200  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
       FIGS. 65-68  illustrate an interface assembly  6200  that is similar in many respects to the interface assembly  6200  of  FIGS. 62-64 . Therefore, the same reference numbers are used to refer to the same or corresponding components or features. In addition, the interface assembly  6200  of  FIGS. 65-68  is described in the context of the differences relative to the interface assembly  6200  of  FIGS. 62-64 . Features of the interface assembly  6200  or portions thereof not specifically described can be assumed to be the same as or similar to features of the interface assembly  6200  of  FIGS. 62-64 , other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The folding clasp  6240  of  FIGS. 65-68  is more space efficient in at least some respects compared to the folding clasp  6240  of  FIGS. 62-64 . In particular, the folding clasp  6240  of  FIGS. 65-68  has an overall thickness that is substantially equal to a thickness of two of the segments  6242 ,  6244 ,  6246  in a closed or folded configuration, as illustrated in  FIG. 67 . Any one or all of the segments  6242 ,  6244 ,  6246  can define a height that is less than a height of the second segment  6244 . In some configurations, the height of the first segment  6242  can be substantially equal to or less than a distance between the lower strap  6218  and the upper strap  6220  at a location where the straps  6218 ,  6220  meet the mask  6202 . The height of the second segment  6244  can be substantially equal to or greater than a distance between a lower edge of the lower strap  6218  and an upper edge of the upper strap  6220  at a location where the straps  6218 ,  6220  meet the mask  6202 . The second segment  6244  can have a generally U-shaped profile with a base  6270  and a pair of arms  6272 . The arms  6272  can define a space  6270  therebetween, which can have a distance between the arms  6272  that is at least as great as a height of the first segment  6242 . The intermediate segment  6246  can be connected at one end to a rearward end of the first segment  6242  and at a second end to a base  6270  of the second segment  6244 . The intermediate segment  6246  can be received within the space  6270  and can overlap at least a portion of the first segment  6242  in a folded orientation of the folding clasp  6240 . 
     The folding clasp  6240  can comprise a locking mechanism, such as a resilient latch  6280 , which engages a surface surrounding an opening  6282  to secure the folding clasp  6240  in the closed position or folded orientation. In the illustrated arrangement, the opening is defined by the mask frame  6206  or first segment  6242  and the latch  6280  is carried by the second segment  6244 . 
     Rearward or free ends of the arms  6272  of the U-shaped second segment  6244  can connect to the straps  6218 ,  6220  of the headgear  6204 . The straps  6218 ,  6220  can be adjustable relative to the mask  6202  and/or folding clasp  6240 . For example, the straps  6218 ,  6220  can be folded to define adjustment loops  6222 . The adjustment loops  6222  can be secured by a locking mechanism, such as a locking lever  6284 . The locking lever  6284  can include an engagement portion  6286  that engages the loops  6222  of the strap  6218 ,  6220  to selectively secure the strap  6218 ,  6220  in place. 
       FIGS. 69-71  illustrates an interface assembly  6900  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  6900  includes an alternative arrangement for providing adjustability and/or closed-loop elongation functionality. In particular, the interface assembly  6900  incorporates one or more sliding buckle arrangements  6940  that permits adjustment of a circumference of the interface assembly  6900 . Sliding buckle arrangements  6940  can be provided on one or both sides of the interface assembly  6900 . 
     Similar to other interface assemblies disclosed herein, the interface assembly  6900  includes an interface  6902  and a headgear  6904 . The illustrated interface  6902  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  6904 . The illustrated mask  6902  generally comprises a frame  6906  that supports a seal  6908 . The mask  6902  can be connected to a supply conduit  6909 , which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  6902  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  6902  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  6904  can be coupled to the mask  6902  at one or more mounting locations or mounting points  6910  by any suitable arrangement, such as any of those disclosed herein. Preferably, a lower strap portion  6918  and an upper strap portion  6920  are provided on each side of the headgear  6904  to connect the mask  6902  to a rear portion of the headgear  6904 . In the illustrated configuration, a sliding buckle arrangement  6940  is provided within each of the lower strap  6918  and the upper strap  6920  to permit length adjustment of the straps  6918 ,  6920 . Sliding buckle arrangements  6940  can be provided on one or both sides of the headgear  6904 .  FIGS. 70 and 71  illustrate a sliding buckle arrangement  6940  within one of the straps  6918 ,  6920 ; however, other sliding buckle arrangements  6940  can be of the same or a similar construction. 
     The illustrated sliding buckle arrangement  6940  includes a buckle  6942  having multiple posts  6944 , which create a tortuous path for the strap  6918 ,  6920 . The strap  6918 ,  6920  can be engaged (directly or indirectly) with the mask  6902  and folded over onto itself to create an adjustment loop  6946 . An end of the adjustment loop  6946  is coupled to the buckle  6942  such that movement of the buckle  6942  along the strap  6918 ,  6920  varies the size of the adjustment loop  6946 , or the length of the overlap of the strap  6918 ,  6920 , to adjust an effective length of the strap  6918 ,  6920 . The buckle  6942  can be moved in either direction along the strap  6918 ,  6920  to permit lengthening or shortening of the strap  6918 ,  6920 . 
     The buckle  6942  can include a finger grip tab or pull tab  6950  to facilitate movement of the buckle  6942 . The pull tab  6950  can include a coupler  6952  to allow the pull tab  6950  to be secured to the buckle  6942  and/or strap  6918 ,  6920  when not in use. The illustrated coupler  6952  is a magnetic coupler; however, other suitable couplers could be used, including snaps, clips or hook-and-loop fastener, for example and without limitation. The pull tab  6950  can be generally centrally-located along a length of the buckle  6942 , such as rotatably supported by a post  6954 .  FIG. 72  illustrates a sliding pull tab  6950  in which the post  6954  is slidably supported within a slot  6956 , which permits the pull tab  6950  and post  6954  to move toward an end of the buckle  6942  in the direction of travel or intended travel of the buckle  6942 . 
     The sliding buckle arrangement  6940  can be utilized for closed-loop elongation or can be used for headgear  6904  adjustment and other opening arrangements can be provided, such as a clip  6930  that is removable from the mask  6902 . The clip  6930  can be completely separable from the mask  6902  (i.e., open loop) or can be tethered to the mask  6902  (i.e., closed loop). Unless indicated otherwise, features of the interface assembly  6900  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The elongating closed-loop arrangements described herein (such as in  FIGS. 58-72 , for example) preferably provide sufficient elongation in an open state to permit removal and/or application of the associated interface assembly. As described, elongating arrangements can be provided on one or both sides of the interface assembly. If provided on only one side, preferably, the single elongating arrangement provides sufficient elongation in an open state to permit removal and/or application of the associated interface assembly. If provided on both sides, each elongating arrangement can provide sufficient elongation in an open state to permit removal and/or application of the associated interface assembly so that a user can elect to use one side or the other. In some configurations, however, each elongating arrangement can provide a portion of the total elongation, which preferably is sufficient to permit removal and/or application of the associated interface assembly; however, the elongation of either one of the arrangements may not be sufficient on its own to permit removal and/or application of the associated interface assembly. In some configurations, the total elongation between a closed state and an open state is at least 100 millimeters. In elastic configurations, the elongation with the elastic element(s) in an unstretched state can be less than 100 millimeters, but can increase to at least 100 millimeters upon stretching of the elastic element(s). For example, in some configurations, the initial elongation can be about 30 millimeters with the elastic element(s) unstretched and the elastic element(s) can stretch to provide at least 100 millimeters of total elongation. In some configurations, the initial elongation (without stretching) can be about one-third to about one-half of the total elongation (with stretching). 
       FIGS. 73 and 74  illustrate a contoured headgear arrangement  7300  in component parts ( FIG. 73 ) and as assembled ( FIG. 74 ). Many of the headgear assemblies disclosed herein can be constructed in whole or in part of a flexible material, such as a fabric or textile material, for example. Such flexible materials often are in the form of a flat sheet, which can result in a semi-cylindrical shape or curvature about only one axis (a vertical axis) when formed into a headgear assembly. In some configurations, the disclosed headgear arrangements, including but not limited to the headgear arrangement  7300 , are curved about at least two axes (a vertical axis and one or more horizontal axes). Such an arrangement allows the headgear arrangement  7300  to better conform to the user&#39;s head shape and, preferably, spread loads relatively evenly within an area of the headgear arrangement  7300  to reduce pressure points, such as line loads along the edges, for example. Such contoured headgear arrangements  7300  can also tend to hold their shape when not fitted to a user, such as resisting gravitational forces and tangling, for example. Such partially or fully self-supporting constructions can make the headgear arrangements  7300  and associated interface assemblies easier to fit to a user. 
     In the illustrated arrangement, two or more components  7302  are assembled together by a suitable process (e.g., sewing, bonding, welding, etc.) to form a portion or an entirety of a headgear arrangement  7300 . In some configurations, the components  7302  are in the form of flat patterns of textile material. The shape of the patterns  7302  can be adjusted to create desired tension or compression in the material when the components  7302  are assembled. By adjusting the outline shape of the flat pattern  7302 , the assembled headgear arrangement  7300  can be made to fit more ergonomically to the user&#39;s head shape. Such an arrangement can spread the loading more evenly over the user&#39;s head. 
     In the illustrated configuration, a shape of edges  7304  that create a vertical (e.g., rear) seam of the headgear arrangement  7300  are selected to provide a desired final shape once assembled. For example, the patterns  7302  can be mirror images of one another and can include cut-outs  7306  that together form an opening in the headgear arrangement  7300  to accommodate, for example, a user&#39;s hair arranged in a ponytail. An upper portion  7310  of the patterns  7302  above the cut-out  7306  can have a curved edge  7304  that curves outwardly in a direction from a bottom to a top of the edge  7312 . A lower portion  7320  of the patterns  7302  below the cut-out  7306  can have a curved edge  7304  that curves inwardly from a bottom to a top of the edge  7304 . Overall, the edges  7304  can cooperate to define a generally hourglass shape, as illustrated in  FIG. 73 . As illustrated in  FIG. 74 , such an arrangement, when assembled, can result in an upper strap portion  7310  that curves inwardly from bottom to top and a lower strap portion  7320  that has a concave curvature. The lower strap portion  7320  can also generally move inwardly from top to bottom. Such an arrangement can conform to the shape of the user&#39;s head, for example, the rear of the head. The lower strap portion  7320  can conform to the portion of the head formed by the occipital bone and/or the upper neck. The upper strap portion  7310  can be positioned higher, such as on a portion of the head formed by the parietal bone or a junction between the parietal bone and the occipital bone. Although illustrated as edges  7304 , portions of material can be connected along sew lines or attachment lines that are not edges of material, but one or more of the sew lines or attachment lines can be located in an intermediate portion of material. 
       FIGS. 75-79  illustrates an interface assembly  7500  that is arranged and configured in accordance with certain features, aspects and advantages of the present disclosure. The illustrated interface assembly  7500  includes an interface  7502  and a headgear  7504 . The illustrated interface  7502  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  7504 . The illustrated mask  7502  generally comprises a frame  7506  that supports a seal  7508 . The mask  7502  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  7502  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  7502  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  7504  can be coupled to the mask  7502  at one or more mounting locations or mounting points  7510 . Preferably, at least a portion of the headgear  7504  comprises or is constructed from a relatively rigid material, such as a semi-rigid or rigid material. As described herein, preferably, the relatively rigid material resists substantial deformation in response to blow-off forces and, preferably, in response to hose pull forces and/or other expected external forces. For example and without limitation, the relatively rigid material can be polycarbonate, nylon, ABS, polypropylene or other materials having similar mechanical properties, especially with respect to rigidity. In some configurations, at least a portion of the headgear  7504  that contacts the user&#39;s face is relatively rigid. As described further below, the relatively rigid portion(s)  7570  that contact the user&#39;s face can be positioned on or near the user&#39;s cheeks, such as a portion corresponding to the zygomatic and/or maxilla bones. In some configurations, the relatively rigid portions  7570  that contact the user&#39;s face are positioned adjacent each side of an upper portion of the mask  7502 , such as generally rearward of the corresponding (e.g., upper) mounting points  7510 . Such an arrangement can permit the headgear  7504  to anchor onto or be supported on the user&#39;s face at the portions  7570  so that tightening of the headgear  7504  tends to cause an increase in the pressure applied to the user&#39;s face by the headgear  7504 , with substantial compression of the mask seal  7508  avoided or limited. Rather, compression of the mask seal  7508  can be at least primarily controlled by the geometry of the interface assembly  7500  (and/or a seal adjustment mechanism, such as the arrangement described in connection with  FIG. 92 ) instead of the force applied to the mask  7502  by the headgear  7504 . That is, the headgear  7504  can be configured to support the mask  7502  at a desired location relative to the user&#39;s face and the contact of the rigid portions  7570  of the headgear  7504  with the user&#39;s face can avoid or limit substantial compression of the seal  7508  in response to tightening of the headgear  7504 . In other words, the rigid portions  7570  of the headgear  7504  may fix the distance between the user&#39;s cheeks and the seal housing or frame  7506 , thereby inhibiting or preventing possible over-compression of the seal  7508  as a result of tightening of the headgear  7504 . Preferably, forces created by tightening of the headgear  7504  are resisted at least in part by the relatively rigid portion(s)  7570  and not entirely by the mask seal  7508 . In some configurations, the relatively rigid portion(s)  7570  provide significantly greater resistance to tightening forces than the mask seal  7508 . 
     In some configurations, a lower strap portion  7518  and an upper arm portion  7520  are provided on each side of the headgear  7504  to connect the mask  7502  to a rear portion of the headgear  7504 . The lower strap  7518  and upper arm  7520  can connect to the mask  7502  at respective lower and upper mounting locations  7510 . In some configurations, the rigid portions  7570  can be defined by, secured to or otherwise carried by the upper arm  7520 . The rigid portion  7570  of the upper arm  7520  can comprise support arms  7572  that extend away from the user&#39;s face and define the mounting points  7510  between the headgear  7504  and the mask  7502 . 
     The headgear  7504  can also comprise a crown strap portion  7516  and a rear strap portion  7550 . The crown strap  7516  extends from respective rearward ends of the upper arms  7520  across the top of the user&#39;s head. The rear strap portion  7550  extends from rearward ends of the upper arms  7520  around the back of the user&#39;s head. The upper arm  7520 , crown strap  7516  and rear strap  7550  can converge at a location generally above an ear of the user. 
     In some configurations, at least the upper arms  7520  comprise or are constructed from a relatively rigid material. In some configurations, at least portions of one or both of the crown strap  7516  and the rear strap  7550  comprise or are constructed from a relatively rigid material. In the illustrated arrangement, at least portions of both of the crown strap  7516  and the rear strap  7550  comprise or are constructed from a relatively rigid material. The upper arms  7520  and crown strap  7516  (along with the mask  7502 ) can define a front halo portion  7512 . The rear strap  7550  and the crown strap  7516  can define a rear halo portion  7514 . Preferably, the lower straps are constructed from a less rigid material, such as a flexible material. 
     The headgear  7504  can provide for adjustment to allow the headgear  7504  to be adjusted to fit an individual user. For example, one or more adjustment mechanisms  7540  can be provided to within portions of the headgear  7504 , such as one or both of the crown strap  7516  and the rear strap  7550 . In the illustrated configuration, each of the crown strap  7516  and the rear strap  7550  comprise an adjustment mechanism  7540 , which permits a length of the straps  7516 ,  7550  to be adjusted. Thus, adjustment of a circumference of each of the front halo portion  7512  and the rear halo portion  7514  is permitted. The adjustment mechanism  7540  can comprise a flexible strap section  7542  within the straps  7516 ,  7550 . Each flexible strap section  7542  can comprise a portion that doubles over onto itself to form an adjustment loop  7544 . The adjustment loop  7544  can be secured by any suitable fastener, such as a hook-and-loop fastener, for example. 
     In the illustrated configuration, the headgear  7504  includes two relatively rigid sections  7546 , each including one of the upper arms  7520 , a portion of the crown strap  7516  and a portion of the rear strap  7550 . The rigid sections  7546  can be substantial mirror images of one another and can be shaped to conform to the shape of a user&#39;s head. Thus, the rigid sections  7546  can comprise curved shapes at any or all of forward, rearward and upper end portions and can be less curved in a central portion, which can be positioned generally on the side of the user&#39;s head. Such shaping can provide feedback to the user for proper placement of the headgear  7504  on the head and/or can reduce or eliminate pressure points when the headgear  7504  is slept on. 
     In some configurations, portions or a substantial entirety of the rigid sections  7546  can be partially or completely covered by a pad  7590 . The pad  7590  can be constructed of any suitable material for increasing comfort for the user. The pad  7590 , for example and without limitation, can be constructed from silicone, thermoplastic elastomer, thermoplastic polyurethane, other materials with similar mechanical properties, cloth-type materials (cloth covered foam), rubber/foam materials or other suitable soft materials. In some applications, it may be desirable for the pad  7590  to provide increased friction with the user&#39;s skin. As described above, one suitable material for a pad  7590  is silicone, which may be overmolded or otherwise applied onto the rigid sections  7546 . If desired, the silicone or other material used for the pad  7590  can be mechanically interfaced with the rigid sections  7546 , such as by including openings or depressions in the rigid sections  7546  that are filled with the pad  7590  material to interlock the pad  7590  with the rigid section  7546 . In some configurations, the pad  7590  is provided only on a skin-contacting side of a portion or a substantial entirety of the rigid sections  7546 . However, in the illustrated arrangement, the pad  7590  completely surrounds the rigid sections  7546 . 
     Ends of the crown strap  7516  and rear strap  7550  of each rigid section  7546  can comprise one or more connectors, such as one or more loops  7548 , which can provide for coupling of the flexible strap sections  7542  to the rigid sections  7546 . The ends of the rear strap  7550  include two loops  7548 . One loop  7548  allows coupling of the flexible strap section  7542  to the rigid section  7546  and the second loop  7548  allows coupling of the lower strap  7518  to the rigid section  7546 . The loops  7548  can be oriented to direct the flexible strap sections  7542  in a desired direction. The loops  7548  of the crown strap  7516  and the loop of the rear strap  7550  for the flexible strap section  7542  can be oriented with the slot of the loop  7548  generally perpendicular to an axial direction of the strap  7516 ,  7550 . 
     In some configurations, the mask  7502  is coupled to the upper strap  7520  by a rotational coupling  7560 , which can be the same as or similar to any of the rotational couplings disclosed herein, such as the rotational coupling  1900  of  FIG. 19 , the rotational coupling  2944  of  FIGS. 29 and 30  or the rotational couplings of  FIGS. 35 and 36 , for example and without limitation. Other suitable rotational couplings could also be used. The rotational coupling  7560  defines a pivot axis of the mask  7502 . In some configurations, the lower strap  7518  can be used to secure the mask  7502  in a desired rotational position. In other configurations, the mask  7502  can be secured in a desired rotational position by another suitable mechanism, such as the detent rotational coupling  1900  of  FIG. 19  or a separate lock, and the lower strap  7518  could be omitted. Unless indicated otherwise, features of the interface assembly  7500  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
       FIG. 80  illustrates the flexible strap section  7542  of the rear strap  7550  with a break-fit arrangement  8000  incorporated therein to permit quick transition of the rear strap  7550  between an elongated orientation and a tightened orientation. As described herein, such an arrangement can permit the rear strap  7550  to be adjusted to a desired length with the break-fit arrangement  8000  connected or in the tightened orientation. The break-fit arrangement  8000  can be disconnected or moved to the elongated orientation to permit removal or donning of the interface assembly  7500 . Once donned, the break-fit arrangement  8000  can be connected to move the rear strap  7550  to the tightened orientation, which preferably results in a proper fit without requiring adjustment of the rear strap  7550  with each application of the interface assembly  7500 . A break-fit arrangement  8000  can be provided in any of the flexible strap sections  7542  or within any other portion of the headgear  7504  or interface assembly  7500 . 
     The illustrated break-fit arrangement  8000  includes a snap buckle or release buckle  8002  interposed within the rear strap  7550 . The buckle  8002  can be positioned at one end of the flexible strap section  7542  or can be within the flexible strap section  7542 . Preferably, a leash or tether  5804  can be provided to couple the portions of the rear strap  7550  that are separated by the break-fit arrangement  8000  to facilitate location of the separated portions of the rear strap  7550  even when the portions are not visible to the user. The tether  8004  preferably has a length that is sufficient to permit the headgear  7504 /interface assembly  7500  to be applied to the user&#39;s head. In some configurations, the tether  8004  can be constructed from an elastic material, which permits elongation of the tether  8004  for application of the interface assembly  7500  and then moves the portions of the rear strap  7550  closer together to facilitate connection of the break-fit arrangement  8000 . Other suitable break-fit arrangements could also be utilized, such as any of those described herein, for example and without limitation. 
       FIGS. 81-83  illustrate an interface assembly having relatively rigid support portions which support the interface assembly relative to the user&#39;s head to provide at least some isolation of the interface from forces applied to tighten the headgear. Such an interface assembly may be the same as or substantially similar to the interface assembly  7500  and is described in that context using the same reference numbers.  FIG. 81  is a top view of a portion of the user&#39;s face with the interface assembly  7500  applied. The left side of  FIG. 81  (from the perspective of the viewer) illustrates the interface assembly  7500  in a less tensioned or less tightened state and the right side of  FIG. 81  illustrates the interface assembly  7500  in a more tensioned or more tightened state relative to the left side to illustrate the result of an application of tensioning or tightening force to the interface assembly  7500 . 
     With respect to the left side of  FIG. 81 , in a less tightened state, the rigid portion  7570  of the upper arm  7520  can lightly contact the user&#39;s face or, in some cases, may not contact the user&#39;s face. For example, under some conditions, the mask seal  7508  can hold the rigid portion  7570  away from the user&#39;s face. Preferably, at least a portion of the mask seal  7508  extends rearwardly of the forward-most edge of the rigid portion  7570  or a projection of the rigid portion  7570  to ensure that the seal  7508  contacts the user&#39;s face. The support arm  7572  holds the mask  7502  at a desired location relative to the headgear  7504  and/or the user&#39;s face. 
     The right side of  FIG. 81  illustrates the result of a tightening force being applied to the interface assembly  7500  or headgear  7504 , which is illustrated by the arrows in  FIG. 81 . The tightening force tends to pull the mask  7502  towards the user&#39;s face. However, unlike many interface assemblies, the rigid portion  7570  of the illustrated interface assembly  7500  contacts the user&#39;s face to limit rearward movement of the mask  7502  and, thus, limit compression of the mask seal  7508 . As illustrated, the pad  7590  (if provided) can be compressed as a result of applied tightening force, but the underlying rigid portion  7570  can inhibit or prevent further rearward movement once the pad  7590  is compressed. 
     With reference to  FIGS. 82 and 83 , preferably, the rigid portions  7570  contact a portion of the user&#39;s head that can provide resistance to rearward movement of the mask  7502 . In some configurations, the rigid portions  7570  contact a forward-facing portion of the user&#39;s head or face. In the illustrated arrangement, the rigid portions  7570  contact the user&#39;s cheeks.  FIGS. 82 and 83  are front and top views, respectively, of a user&#39;s face illustrating one desired contact area  8200  for the rigid portions  7570 , which preferably encompasses the location indicated by the dot  8202 . The area  8200  can be located on the user&#39;s zygomatic and/or maxilla bone. The dot  8202  can be located on either one of the zygomatic or maxilla bone, but in at least some configurations is located on the maxilla. Placing the rigid portions  7570  close to the user&#39;s nose may be advantageous to maximize resistance to rearward movement of the rigid portions  7570  and, thus, the mask  7502 . However, as is apparent from  FIGS. 81-83 , the shape and/or size of the mask  7502  may limit the available locations for the rigid portions  7570 . Therefore, in some configurations, the rigid portions  7570  are located as close to the user&#39;s nose as possible in view of the size and shape of the particular mask  7502  or other interface that is used or with which the headgear  7504  is intended for use. 
     As described above, in some configurations, the mask  7502  can be rotatably supported by the headgear  7504 . Preferably, the arms  7572  of the headgear  7504  are configured to position a pivot axis of the mask  7502  at a desired location relative to the user&#39;s face and/or the rigid portions  7570  of the headgear  7504 . With reference to  FIGS. 84 and 85 , in some configurations, the pivot axis  8400  of the mask  7502  is located below the user&#39;s nose. Preferably, the pivot axis  8400  is located below the user&#39;s nose and above the user&#39;s upper lip. In some configurations, the pivot axis  8400  can be positioned generally at a junction between the underside of the user&#39;s nose and the user&#39;s upper lip area. In practice, location of the pivot axis  8400  may vary from the preferred location due to differences in facial geometry within the overall user population. However, the location of the pivot axis  8400  will be sufficiently close to the preferred location such that the mask seal  7508  will seal against the underside of the user&#39;s nose. As described above, and illustrated in  FIG. 85 , the mask  7502  can rotate about the pivot axis  8400  to adjust to the user&#39;s facial geometry (e.g., chin shape) and to properly seal against the user&#39;s face. The mask  7502  can be secured in the desired rotational position relative to the pivot axis  8400  by any suitable arrangement, such as the bottom strap  7518 , for example and without limitation. 
       FIGS. 86 a -86 g    illustrate several possible cross-sectional arrangements for the rigid sections  7546  and/or rigid portions  7570  of the headgear  7504  in configurations having a pad  7590 , with the bottom surface being the skin contact surface. In  FIG. 86 a   , the rigid section  7547 /rigid portion  7570  is generally oval in cross-sectional shape. The pad  7590  completely surrounds the rigid section  7547 /rigid portion  7570  and defines a generally or substantially flat skin contact surface. A surface opposite the skin contact surface has a convex curved shape as a result of the pad  7590  extending over the rigid section  7547 /rigid portion  7570 . The pad  7590  includes lateral side portions (relative to the orientation in  FIG. 86 a   ) extending outward from the rigid section  7547 /rigid portion  7570 . The arrangement of  FIG. 86 b    is substantially similar to the arrangement of  FIG. 86 a   , except the rigid section  7547 /rigid portion  7570  is rectangular or square in cross-sectional shape in  FIG. 86   b.    
       FIG. 86 c    illustrates an arrangement having a generally oval rigid section  7547 /rigid portion  7570  covered by a generally oval pad  7590 . The pad  7590  can have lateral side portions than are thicker than the portions above and below the rigid section  7547 /rigid portion  7570 .  FIG. 86 d    illustrates an arrangement having a generally oval rigid section  7547 /rigid portion  7570  and a pad  7590  that defines a generally flat skin contacting surface. One lateral end of the pad  7590  can be curved and generally match the shape of the rigid section  7547 /rigid portion  7570  and the other lateral end of the pad  7590  can have a tapered shape. 
       FIGS. 86 e -86 g    illustrate arrangements having a generally flat strap or flat rectangular shaped rigid section  7547 /rigid portion  7570 . In  FIG. 86 e   , the pad  7590  covers each end of the rigid section  7547 /rigid portion  7570  and leaves a center portion of the rigid section  7547 /rigid portion  7570  uncovered. In  FIG. 86 f   , the pad  7590  covers both ends and a skin contact side of the rigid section  7547 /rigid portion  7570 , with a center portion of the side opposite the skin contact side of the rigid section  7547 /rigid portion  7570  uncovered. In  FIG. 86 g   , the pad  7590  does not cover the skin contact surface. However, preferably, the pad  7590  covers all other surfaces of the rigid section  7547 /rigid portion  7570 . Such arrangements are merely examples. Other suitable arrangements can also be used. 
       FIG. 87  is a side view of a user with the rigid section  7547  of the headgear  7504  positioned on the user. As described herein, many of the interface assemblies generally define one or both of a front halo portion and a rear halo portion. The headgear  7504  defines both a front halo portion  7512  and a rear halo portion  7514 , each of which define a generally halo shape. As illustrated in  FIG. 87 , the halo shape of the halo portions  7512 ,  7514  does not necessarily coincide with the physical structure of the headgear  7504  throughout the entire circumference of the halo shape. However, the physical structure of the headgear  7504  alone or in combination with the mask  7502  or other interface preferably defines a closed loop for each halo portion  7512 ,  7514 . Many different physical shapes to accomplish the halo portions  7512 ,  7514  are possible. 
       FIGS. 88 a   - 88 f illustrate approximate shapes of a headgear that can form both a front halo portion  8812  and a rear halo portion  8814 . The headgear can include additional structures, as well, such as lower mask straps, for example. In  FIG. 88 a   , the front halo portion  8812  and the rear halo portion  8814  meet at the top of the user&#39;s head. In some configurations, an ear strap portion  8816  can extend over the user&#39;s ear between the front halo portion  8812  and the rear halo portion  8814 . In  FIG. 88 b   , the rear halo portion  8814  is a generally continuous circular shape. The front halo portion  8812  curves over the user&#39;s ear to intersect with the rear halo portion  8814 , in a manner similar to the ear strap portion  8816  of  FIG. 88 a   . However, the upper part of the rear halo portion  8814  above the intersection with the lower front halo portion  8812  also defines an upper part of the front halo portion  8812 . 
     In  FIG. 88 c   , the headgear has a front strap portion  8820 , a rear strap portion  8850  and a crown strap portion  8816 . The crown strap  8816  passes directly over the top of the user&#39;s head from ear to ear. The crown strap  8816  forms a portion of each of the front halo portion  8812  and the rear halo portion  8814  in combination with the front strap  8820  and the rear strap  8850 , respectively. In  FIG. 88 d   , each of the front halo portion  8812  and the rear halo portion  8814  is substantially circular in shape. The front halo portion  8812  and the rear halo portion  8814  cross over one another at a location generally above the user&#39;s ear such that an upper portion of the front halo portion  8812  is rearward of an upper portion of the rear halo portion  8814 . 
     In  FIG. 88 e   , the front halo portion  8812  is substantially circular and the rear strap  8850  extends from one side of the front halo portion  8812  to the other passing over the user&#39;s ears and around the back of the head. The rear strap  8850  and the upper part of the front halo portion  8812  form the rear halo portion  8814 . In  FIG. 88 f   , the rear halo portion  8814  is substantially circular and the front straps  8820  curved from a side of the rear halo portion  8814  passing above the user&#39;s ears and toward the underside of the nose. The upper part of the rear halo portion  8814  and the front straps  8820  cooperate to form the front halo portion  8812  (along with the mask or other interface). The headgear of  FIG. 88 f    is substantially similar to the headgear of  FIG. 88 d    with the upper part of the front halo portion  8812  removed. The shapes of  FIGS. 88 a -88 f    are merely examples of possible headgear having front halo portions  8812  and rear halo portions  8814 . Other shapes are also possible. 
     As described herein, the various interface assemblies can include break-fit assemblies that permit the interface assembly to be conveniently enlarged to facilitate application and removal. Preferably, the break-fit assemblies permit application and removal of the interface assemblies without readjustment upon each application.  FIGS. 89 a -89 f    illustrate various possible locations for the break-fit assemblies within the headgear.  FIGS. 89 a  and 89 b    illustrate a break-fit assembly  8900  within a rear halo portion, such as a rear strap  8950  of the headgear, which extends around the back of the user&#39;s head.  FIG. 89 a    illustrates the break-fit assembly  8900  in a connected state and  FIG. 89 b    illustrates the break-fit assembly  8900  in a disconnected state. Optionally, the portions  8902 ,  8904  of the break-fit assembly  8900  can be coupled by a tether  8910  that limits separation of the portions  8902 ,  8904  and can facilitate non-visual location of the portions  8902 ,  8904  for reconnection. In some configurations, the tether  8910  is elasticated. 
       FIGS. 89 c  and 89 d    illustrate a break-fit assembly  8900  in a front halo portion, such as an upper strap  8920  of the headgear.  FIG. 89 c    illustrates the break-fit assembly  8900  in a connected state and  FIG. 89 d    illustrates the break-fit assembly  8900  in a disconnected state. The portions  8902 ,  8904  of the break-fit assembly  8900  can optionally be coupled by a tether  8910 , which can be elasticated in some configurations. 
       FIGS. 89 e  and 89 f    illustrate a break-fit assembly  8900  between a front halo portion  8912  and a rear halo portion  8914  of the headgear. For example, the break-fit assembly  8900  can be positioned at an intersection of a rear strap portion  8950 , an upper strap portion  8920  and a crown strap portion  8916 . The break-fit assembly  8900  can permit at least limited separation of the front halo portion  8912  and the rear halo portion  8914  to facilitate application or removal of the headgear. In some configurations, the front halo portion  8912  and the rear halo portion  8914  do not completely separate and, therefore, a tether is not provided. However, if desired, a tether could be provided whether or not the front halo portion  8912  and the rear halo portion  8914  completely separate. 
     With reference to  FIG. 90 , a headgear  9004  is illustrated that is similar to other headgear arrangements disclosed herein. The headgear  9004  has a front or upper strap or arm portion  9020 , a crown strap portion  9016  and a rear strap portion  9050 . Although not illustrated, the headgear  9004  could include additional structural portions, such as a lower strap portion, for example. Similar to the headgear  7504  of the interface assembly  7500 , preferably at least a portion of the headgear  9004  is relatively rigid, such as rigid or semi-rigid. In the illustrated arrangement, at least the upper arm  9020  is relatively rigid. Preferably, a rearward portion of the upper arm  9020  that is divided and forms initial portions of the crown strap  9016  and the rear strap  9050  is also relatively rigid and can be of a unitary construction with the remainder of the upper arm  9020 . As illustrated, the upper arm  9020  is curved. Preferably, the upper arm  9020  is sufficiently rigid to inhibit substantial deformation of the curved shape at least in response to blow-off forces. 
     Preferably, at least the initial curved portions  9052  of the rear strap  9050  rearward of the user&#39;s ears (end portions of the rear strap  9050  indicated with dashed lines) are constructed from at least a semi-rigid material to resist deformation of the curved shape at least in response to blow-off forces. In some configurations, the portions  9052  are constructed from a rigid material, which can be the same material as the upper arm  9020 . The portions  9052  can be unitarily formed with the upper arms  9020 . The remaining portions  9016   a,    9050   a  of the crown strap  9016  and the rear strap  9050 , respectively, can be constructed from a relatively rigid material or a non-rigid material. As illustrated, the portions  9016   a  and  9050   a  are subject to primarily axial forces. Accordingly, flexible or non-rigid materials can be used if desired, such as for comfort reasons. 
       FIG. 91  illustrates an interface assembly  9100  comprising an interface  9102  and a headgear  9104 . The interface  9102  (shown schematically) can be any suitable interface  9102 , such as a nasal-oral mask that can seal around a mouth of a user and on an underside of a nose of the user, for example. The mask  9102  can be similar to any of the interfaces/masks disclosed herein. However, other types of interfaces can be used with the disclosed headgear  9104 . The illustrated headgear  9104  is coupled to the mask  9102  at a mounting location or mounting point  9110  on each side of the mask  9102 . Preferably, the mask  9102  is coupled to the headgear  9104  by a rotational coupling  9144 , which can be of any suitable arrangement, such as any of the rotational couplings herein. Preferably, the rotational coupling  9144  can be locked in a desired rotational position. For example, the rotational coupling  9144  can include a detent arrangement, such as the arrangement described with respect to  FIG. 19 , for example. The rotational coupling  9144  could be manually locked in the desired rotational position. Other suitable arrangements could also be used. 
     Preferably, the rotational coupling  9144  can be secured in place without a lower strap portion. However, if desired, the headgear  9104  can include a lower strap portion. The illustrated headgear  9104  includes an upper strap portion  9120  on each side of the headgear  9104  to connect the mask  9102  to a rear portion of the headgear  9104 . The headgear  9104  can also include a crown strap  9116  and a rear strap  9150 . Unless indicated otherwise, features of the interface assembly  9100  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
       FIG. 92  illustrates an interface assembly  7500  that is similar in many respects to the interface assembly  7500  of  FIGS. 75-79 . Therefore, the same reference numbers are used to refer to the same or corresponding components or features. In addition, the interface assembly  7500  of  FIG. 92  is described in the context of the differences relative to the interface assembly  7500  of  FIGS. 75-79 . Features of the interface assembly  7500  or portions thereof not specifically described can be assumed to be the same as or similar to features of the interface assembly  7500  of  FIGS. 75-79 , other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The illustrated interface assembly  7500  includes an interface  7502  and a headgear  7504 . The illustrated interface  7502  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  7504 . The illustrated mask  7502  generally comprises a frame  7506  that supports a seal  7508 . The mask  7502  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  7502  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  7502  can provide pressurized air flow to both the nose and the mouth of the user. 
     As described herein, the headgear  7504  preferably supports the mask  7502  at a desired location relative to the headgear  7504  and the mask  7502  is at least partially isolated from tightening of the headgear  7504 . That is, tightening of the headgear  7504  does not substantially alter a position of the mask  7502  relative to the user&#39;s face. Thus, in the illustrated arrangement, the mask  7502  includes a seal adjustment arrangement  9200 , which permits a position of the seal  7508  to be adjusted relative to the frame  7506 . Such an arrangement permits the position of the seal  7508  to be micro-adjusted to accommodate variations in facial geometry. Preferably, rotational adjustment of the mask  7502  is also permitted. 
     The illustrated seal adjustment arrangement  9200  includes a threaded tube  9202  that is coupled to the mask seal  7508 . The tube  9202  can be coupled to the supply conduit and can deliver breathing gases from the supply conduit to the interior of the seal  7508 . A dial  9204  can be supported by the mask frame  7502  and can include internal threads that mate with the threads of the tube  9202 . Rotation of the dial  9204  can cause translation or linear movement of the seal  7508  toward and away from the mask frame  7506 . Other suitable adjustment mechanisms can also be used. Examples of similar adjustment arrangements are disclosed in PCT Publication No. WO2004/052,438, the entirety of which is incorporated by reference herein. 
       FIG. 93  illustrates an interface assembly  7500  that is similar in many respects to the interface assembly  7500  of  FIGS. 75-79 . Therefore, the same reference numbers are used to refer to the same or corresponding components or features. In addition, the interface assembly  7500  of  FIG. 93  is described in the context of the differences relative to the interface assembly  7500  of  FIGS. 75-79 . Features of the interface assembly  7500  or portions thereof not specifically described can be assumed to be the same as or similar to features of the interface assembly  7500  of  FIGS. 75-79 , other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The illustrated interface assembly  7500  includes an interface  7502  and a headgear  7504 . The illustrated interface  7502  is a nasal-oral mask but, as described herein, other types of interfaces can be used with the disclosed headgear  7504 . The illustrated mask  7502  generally comprises a frame  7506  that supports a seal  7508 . The mask  7502  can be connected to a supply conduit (not shown), which can be used to supply breathing gases to a user. As described above, in some configurations, the mask  7502  can seal around a mouth of a user and on an underside of a nose of the user. Such a mask  7502  can provide pressurized air flow to both the nose and the mouth of the user. 
     The headgear  7504  can be coupled to the mask  7502  at one or more mounting locations or mounting points  7510 . Preferably, a lower strap portion  7518  and an upper arm portion  7520  are provided on each side of the headgear  7504  to connect the mask  7502  to a rear portion of the headgear  7504 . The mask  7502  can be rotatably supported relative to the upper arm  7520  with the lower strap  7518  fixing a rotational position of the mask  7502 . Unless indicated otherwise, features of the interface assembly  7500  or portions thereof can be the same as or similar to other interfaces or portions thereof described herein, or can be of another suitable arrangement. 
     The illustrated interface assembly  7500  includes an enlarged and/or contoured relatively rigid or cheek-contacting portion  7570 . Such an arrangement can increase the ability of the headgear  7504  to anchor on the face of the user and at least partially isolate the mask  7502  from the adjustment of the headgear  7504 . Such an arrangement can also spread the load applied to the user&#39;s face over a larger area for improved comfort. In some configurations, the portion  7570  is formed by the pad  7590  that covers the underlying rigid section  7546 . 
     To facilitate application and removal of the interface assembly  7500 , a quick-release mechanism  9300  can be provided to move the interface assembly  7500  to an enlarged circumference or open state. The quick-release mechanism  9300  can be of any suitable arrangement, such as any of the arrangements of  FIGS. 50-72  or any others disclosed herein, for example and without limitation. In the illustrated arrangement, the quick-release mechanism  9300  comprises a clip  9302  that can be disconnected from the remainder of the mask  7502 . In some configurations, the clip  9302  can be tethered or otherwise coupled to the remainder of the mask  7502  in the disconnected state to facilitate reconnection of the clip  9302 . 
     Although the present invention has been described in terms of a certain embodiments, other embodiments apparent to those of ordinary skill in the art also are within the scope of this invention. Thus, various changes and modifications may be made without departing from the spirit and scope of the invention. For instance, various components may be repositioned as desired. Moreover, not all of the features, aspects and advantages are necessarily required to practice the present invention. 
     In addition, some portions of one assembly could be used with other portions of other assemblies to provide further assemblies not explicitly shown herein. For example, straps or portions of straps of one assembly may be used with a halo or the like from another assembly. Any of the various quick-release arrangements can be utilized with any of the headgear assemblies disclosed herein. Any of the rotational connections between the interface and the headgear can be used with any of the headgear assemblies disclosed herein. Any break-fit assemblies can be incorporated into any of the interface assemblies disclosed herein. In general, any feature from interface assembly can be incorporated into any other interface assembly to the extent possible or apparent to those skilled in the art. Such further variations should be considered expressly contained herein. Accordingly, the scope of the present invention is intended to be defined only by the claims that follow.