GB2616279A

GB2616279A - A mask

Info

Publication number: GB2616279A
Application number: GB2202889.8A
Authority: GB
Inventors: Hugh Moffat Joshua; Barber Ann
Original assignee: Globus Shetland Ltd
Current assignee: Globus Shetland Ltd
Priority date: 2022-03-02
Filing date: 2022-03-02
Publication date: 2023-09-06
Also published as: GB202202889D0

Abstract

A respirator mask 100 comprises an orinasal body portion 102 comprising filtering material for capturing potentially harmful gas or vapour particles and a transparent window element 118 extending across and closing a window aperture 120 provided in the body portion for viewing oral features of the wearer through the mask. The window aperture is defined by a plurality of substantially linear edge portions 130, 132, 134, 136, 140, 142, 144, 146,148, 150 (Figure 2) and comprises opposed upper corner regions each spaced from a rear edge 111 of the body portion by at least 25% of a depth of the body portion from a front edge 108 thereof to the rear edge, and from a respective one of opposed side edges 109 of the body portion by at least 20% of a width of the body portion between the opposed side edges. Each upper corner region may further comprise inner and outer substantially linear corner portions, defining an inner corner angle of less than 180 degrees with respect to each other.

Description

A MASK

The present invention relates to a mask and in particular, but not exclusively, to a non-valved respirator mask including a transparent window for viewing the mouth of 5 a wearer.

Conventional non-valved respirator masks, often referred to as maintenance-free masks or filtering face masks, typically include two or more panels of air filtering material and are worn over the mouth and nose of a wearer to prevent potentially harmful particles entering the wearer's respiratory tract and to protect others from being exposed to pathogens exhaled by the wearer. They are often foldable when not in use along at least one horizontal or vertical fold line depending on the number of panels. However, the ability of the wearer to efficiently communicate with another person, and vice versa, by speech and expression is significantly compromised when one or both parties are wearing such a mask for personal protection purposes. For example, the ability of a healthcare professional, such as a speech therapist, to deliver therapy is dependent on being able to see the mouth, lips, tongue and tonsils of the patient, and to demonstrate actions to the patient with their own such oral features.

Completely transparent masks and faceguards are known and providing a transparent window in a maintenance-free respirator mask is also known. However, existing maintenance-free respirator masks including a window in an attempt to improve communication when wearing the mask undesirably sacrifice the amount of air filtering material surrounding the window which in turn compromises the filtering and protective performance of the mask, whilst also increasing breathing resistance and discomfort for the wearer.

It is an aim of certain embodiments of the present invention to provide a maintenance-free respirator mask having an orinasal portion of air filtering material and a window disposed therein for viewing a wearer's mouth without unduly compromising the filtering and protective performance of the mask.

It is an aim of certain embodiments of the present invention to provide a maintenance-free respirator mask having an orinasal portion of air filtering material and a window disposed in an upper portion of the orinasal portion, wherein an area of the filtering material is at least 80% of the total area of the orinasal portion.

It is an aim of certain embodiments of the present invention to provide a maintenance-free respirator mask having an orinasal portion of air filtering material and a window aperture disposed in an upper portion of the orinasal portion, wherein the window aperture is defined by a plurality of linear portions including opposed upper corner regions formed by substantially linear portions which are angled with respect to each other and distanced from a respective upper corner region of the body portion to provide additional filtering material between the upper corner regions of the window aperture and the upper corner regions of the body portion.

According to a first aspect of the present invention there is provided a maintenance-free respirator mask comprising: an orinasal body portion comprising filtering material for capturing potentially harmful gas or vapour particles responsive to a wearer of the mask inhaling or exhaling; and a transparent window element extending across and closing a window aperture provided in the body portion for viewing oral features of the wearer through the mask, wherein the window aperture is defined by a plurality of substantially linear edge portions and comprises opposed upper corner regions each spaced from a rear edge of the body portion by at least 25% of a depth of the body portion from a front edge thereof to the rear edge, and from a respective one of opposed side edges of the body portion by at least 20% of a width of the body portion between the opposed side edges.

Optionally, each substantially linear side edge portion of the window aperture is 30 oriented by 20-30 degrees with respect to the respective side edge of the body portion.

Optionally, an area of the window aperture is 15-25%, and optionally 19%, of a total surface area of the filtering material.

Optionally, each upper corner region comprises an inner substantially linear corner portion and an outer substantially linear corner portion defining an inner corner angle of less than 180 degrees with respect to each other.

Optionally, the inner corner angle is from 120 to 160 degrees and optionally 145 degrees.

Optionally, each outer linear corner portion of the respective corner region of the window aperture defines an angle with a respective one of the linear side portions of from 100 to 125 degrees and optionally 113 degrees.

Optionally, a substantially linear lower edge portion of the window aperture defines an angle of from 100 to 125 degrees, and optionally 107 degrees, with respect to each substantially linear side edge portion of the window aperture.

Optionally, an upper region of the window aperture comprises a substantially U-shaped channel region substantially disposed on a central axis of the body portion and located between the opposed upper corner regions of the window aperture.

Optionally, the channel region is sized to accommodate the nose of a wearer in use.

Optionally, the channel region is defined by a pair of opposed, upwardly diverging and linear channel side portions and a linear base portion extending therebetween.

Optionally, each channel side portion defines an angle with the channel base portion of from 100 to 150 degrees and optionally 120 degrees.

Optionally, the body portion comprises an upper panel joined to a lower panel and 30 the window aperture is disposed in the upper panel.

Optionally, the upper and lower panels are joined along side edge regions thereof and a front fold line defines the front edge of the body portion.

Optionally, the panels are joined by welding.

Optionally, a peripheral edge region of the window element is attached to the filtering material surrounding the window aperture by welding.

Optionally, the mask comprises at least one strap coupled at each end region thereof to a respective rear corner region of the body portion.

Optionally, each end region of the at least one strap is attached to a lug extending from a respective one of the corner regions.

According to a second aspect of the present invention there is provided a method of manufacturing a maintenance-free respirator mask, comprising: providing a window aperture in an orinasal body portion comprising filtering material for capturing potentially harmful gas or vapour particles responsive to a wearer of the mask inhaling or exhaling; and locating a transparent window element across the window aperture to close the same and allow oral features of the wearer to be viewed in use through the mask, wherein the window aperture is defined by a plurality of substantially linear edge portions and comprises opposed upper corner regions each spaced from a rear edge of the body portion by at least 25% of a depth of the body portion from a front edge thereof to the rear edge, and from a respective one of opposed side edges of the body portion by at least 20% of a width of the body portion between the opposed side edges.

Optionally, each substantially linear side edge portion of the window aperture is oriented by 20-30 degrees with respect to the respective side edge of the body portion.

Optionally, each upper corner region of the window aperture comprises an inner substantially linear corner portion and an outer substantially linear corner portion defining an inner corner angle of less than 180 degrees with respect to each other.

Optionally, the method comprises welding a peripheral edge region of the window element to the filtering material surrounding the window aperture.

Optionally, the method comprises: folding a length of said filtering material to define upper and lower panels of the orinasal body portion and a front fold line therebetween to define the front edge of the body portion; and joining the upper and lower panels together along side edge regions thereof.

Description of the Drawings

Certain embodiments of the present invention will now be described with reference 25 to the accompanying drawings in which: Figure 1 illustrates an isometric front view of a maintenance-free respirator mask according to certain embodiments of the present invention; Figure 2 illustrates a front view of the mask of Figure 1; Figure 3 illustrates a side view of the mask of Figures 1 and 2; Figures 4a and 4b illustrate example angles of the window aperture edge portions; and Figure 5 illustrates a web of filtering material including a window aperture therein for making a mask according to certain embodiments of the present invention.

Detailed Description

As illustrated in Figure 1, a maintenance-free respirator mask 100 according to certain embodiments of the present invention includes an orinasal body portion 102 having an upper portion or panel 104 joined to a lower portion or panel 106. The mask body is formed from a single piece of filtering material which is folded approximately midway along its length to form the upper and lower panels 104,106 and a front fold line 108 therebetween defining a front boundary limit of each panel.

The panels 104,106 are joined together along their opposed side regions which defines opposed side boundary limits 109 of each panel.

The panels are joined together by ultrasonic welding along the side regions, and aptly by two lines of spot welding extending along each side region. Aptly, each spot weld is 1x1 mm square and each spaced apart by around 1mm. Alternatively, the panels may be adhered or stitched together, or the like, along their side regions. Further alternatively, the panels may be separate pieces of filtering material joined along their front and side edge regions by welding, adhering or the like.

The upper and lower panels 104,106 each have a rear edge 111 defining a rear boundary limit to each panel which is shaped to at least closely, if not sealingly, engage with the wearer's face and under their chin respectively, i.e. to receive and accommodate the nose and mouth of the wearer in an interior region of the orinasal body portion 102.

An outwardly extending tab 110 is provided at each rear corner region of the orinasal body portion 102 for attaching a respective end region of a pair of elastic straps 112,114 to the body portion. One strap 112 is for securing the mask to the backside of the wearer's head and the other strap 114 is for securing the mask to the wearer's neck. The elasticity and resilience of the strap material, e.g. a rubber, urges the rear edges of the panels against the wearer's face and under their chin to securely retain the mask in place over the wearer's mouth and nose when in use. Each tab 110 is aptly formed by welding or adhering corresponding tab portions together each extending outwardly from a respective one of the upper and lower panels. Aptly, the respective end regions of the straps may be sandwiched between the corresponding tab portions before the same are welded or adhered together to securely attach the straps to the mask body. Alternatively, the strap end regions may be stapled, adhered, or the like to the tabs or the mask body itself.

The panels of the illustrated mask are in an open 'ready to use' configuration but may be urged substantially together along the front fold line and side join lines into a closed and substantially flat configuration for storage etc. when not in use. The tabs of the mask when in the open configuration may be gripped by a user and pulled apart in opposed directions to urge the panels towards each other and into the closed configuration. Welding, such as 1x1 mm square spot welds, used to attach the tab portions together and fix the corresponding strap end regions therebetween may desirably provide a textured region to one or both surfaces of each tab to aid a user when gripping and pulling the tabs apart to close the mask and/or when fitting the mask to their face.

The upper panel 104 of the mask also includes a nose clip (not shown) made from a substantially malleable strip or wire of metal, such as aluminium or the like, which can be plastically conformed to the shape of the wearer's nose by the wearer to ensure the rear edge of the upper panel engages at least closely to the wearer's face and particularly the contours of the wearer's nose. The nose clip may be disposed on the outer surface or inner surface of the upper panel or located therebetween such as between layers of the filtering material or in a pocket welded closed to secure the nose clip therein. Additionally, or alternatively, a foam strip or the like may be provided on the inner surface proximal to the rear edge region of the upper panel for engagement with the wearer's nose and to improve comfort and grip.

The mask 100 further includes a window 118 in the upper panel 104. The window comprises a substantially transparent sheet of plastics material, such as cast polypropylene (CPP) or vinyl, which is configured to prevent condensation or fog build-up in use, such as by including an anti-fog layer or coating on the inside surface thereof. The sheet of transparent material overlaps the edge of a correspondingly shaped window aperture 120 in the upper panel to thereby close the aperture and is welded in place, such as by 1x1 mm square spot welds, to fix the overlapping peripheral edge region of the transparent sheet material to the filtering material surrounding the aperture. The overlapping peripheral edge region is aptly around lOmm wide. The transparent sheet material extending across and closing the window aperture to form the window may be located on the inner or outer surface of the upper panel or located between layers of the filtering material. Aptly, around three lines of spot welds are used to fix the transparent sheet material in or to the upper panel.

As illustrated in Figure 2, the window aperture 120 provided in the upper panel, and in turn which defines the transparent window area of the mask, is configured to maximise the viewing area of the wearer's mouth, lips, tongue and tonsils, whilst retaining a maximum surface area of filtering material for efficient filtration and in turn protection to the wearer or others. The aperture 120 is defined by an upper region 122, a lower region 124 and opposed side regions 126,128 extending therebetween.

The upper region 122 of the window aperture in the illustrated embodiment is defined by seven distinct and substantially linear portions; a first pair of linear portions 130,132 angled with respect to each other to define a first upper corner region of the aperture, a second pair of linear portions 134,136 angled with respect to each other to define a second upper corner region of the aperture opposed to the first upper corner region, and a central channel region 138 defined by a pair of opposed, upwardly diverging and linear channel side portions 140,142 and a linear base portion 144 extending therebetween.

Aptly, as illustrated in Figures 4a and 4b, the adjacent substantially linear portions (130,132 and 134,136) defining each upper corner region of the window aperture define an inner angle ci therebetween of around 145 degrees. Aptly, each of the inner substantially linear portions 132,136 of the upper corner regions defines an inner angle 13 with the respective channel side portion 140,142 of around 117 degrees. Aptly, each channel side portion of the channel region defines an outer angle y (outboard of the window edge and inside the channel profile) with the substantially linear channel base portion of around 122 degrees. Aptly, each of the outer substantially linear portions 130,134 of the upper corner regions defines an inner angle 6 of around 113 degrees with a substantially linear side portion 146,148 defining the respective side region 126,128 of the window aperture 120. The lower region 124 defining the aperture 120 comprises a substantially linear lower portion 150 extending between lower ends of the opposed substantially linear side portions 146,148. The substantially linear side portions 146,148 each define an inner angle E with respect to the linear lower portion 150 of around 107 degrees.

The upper panel 104 may have a lower edge length of around 90 mm and a side edge length from the lower edge to the respective tab 110 of around 80 mm. The inner angle between the lower edge and each side edge of the upper panel is around 130 degrees. Aptly, the distance 'a' as referenced in Figures 1 and 5 is around 44 mm which is measured substantially midway along and perpendicularly from the channel base portion 144 to the rear edge 111 of the upper panel 104. Aptly, the distance 'b' which is measured substantially perpendicularly from the upper edge of the window aperture to the rear edge of the upper panel is around 33 mm. Aptly, the distance 'c' which is measured substantially midway along and perpendicularly from the side edge of the window aperture to the side edge of the upper panel is around 27 mm from the side edge of the upper panel 104. Aptly, the distance 'd' is around 11 mm which is measured substantially midway along and perpendicularly from the lower edge of the window aperture to the lower edge of the upper panel 104/front fold line of the mask.

As illustrated in Figure 5, the lower edge of the aperture is aptly substantially parallel with the lower edge of the upper panel, i.e. the front fold line of the mask. Aptly, the inner substantially linear portions 132,136 of the upper corner regions of the aperture are substantially parallel with the upper/rear edge of the upper panel. Aptly, each substantially linear side portion of the aperture defines an angle 0 of around 24.5 degrees with the respective side edge of the upper panel.

The word 'substantially' has been specifically used to describe the substantially linear edge portions defining the window aperture because one or more of these edges may be slightly curved whilst appearing substantially linear. For example, the lower edge portion 150 of the aperture may have a radius of curvature of around 1140 mm which would appear substantially linear to a user. Likewise, each outer portion 130,134 of each upper corner region of the aperture may have a radius of curvature of around 95 mm which again would appear substantially linear to a user in view of its relatively short length. Each inner portion 132,136 of each upper corner region of the aperture may have a radius of curvature of around 1175 mm. The channel base portion may have a radius of curvature of around 290 mm and each channel side portion may have a radius of curvature of around 72 mm. Each side portion of the aperture may have a radius of curvature of around 326 mm.

Furthermore, adjacent substantially linear portions of the aperture may be directed connected together to form a relatively 'tight' and well-defined angled and linear corner therebetween or they may be connected by a relatively small radiused corner region. For example, based on the dimensions above for the window aperture of a mask according to one possible embodiment of the presently claimed invention, a corner region between the channel base portion and each channel side portion may have a radius of around 8.5 mm. A corner region between each channel side portion and a respective one of the inner portions 132,136 of each upper corner region may have a radius of around 5 mm. A corner region between each of the inner and outer portions of the upper corner regions of the aperture may have a radius of around 10 mm. A corner region between each outer portion 130,134 of each upper corner region and each side portion may have a radius of around 6 mm, and a corner region between each side portion and the lower edge portion may also have a radius of around 6 mm.

An alternative embodiment of the window aperture may include upper corner regions each defined by a single substantially curved corner portion following a similar outwardly curved profile as, for example, the two linear portions (130,132 or 134,136) of the corner regions in the illustrated embodiment. The upper region of the window aperture would then be defined by five distinct portions defining the corner regions and the channel region in between.

Figure 5 illustrates the flat web of filtering material prior to being folded along the front fold line 108 and spot welded to join the upper and lower panels, and corresponding tab portions thereof, together. As shown, the window aperture 120 is defined by substantially linear edge portions wherein adjacent ones of the substantially linear edge portions are connected together by slightly radiused corner regions.

According to certain embodiments of the present invention, each of the upper corner regions of the window aperture is substantially spaced from the rear edge and side edges of the mask body to thereby provide additional filtering material which is otherwise lost in conventional maintenance-free 'window' masks.

Aptly, the uppermost point of each corner region is spaced from the rear edge of the mask body portion by around 25 -40 mm, aptly around 30 -35 mm, and preferably around 33 mm, as referenced by dimension e' in Figure 5. This is at least around 25%, aptly around 26-42%, and preferably around 35%, of the depth of the upper panel measured from the front edge to the rear edge, i.e. along a substantially vertical plane when referring to Figure 5.

Aptly, the outermost point of each corner region is spaced from the corresponding side edge of the mask body portion by around 40 -50 mm, and preferably around 45 mm, as referenced by dimension 'f' in Figure 5. This is at least around 20%, aptly around 24-26%, and preferably around 25%, of the width of the upper panel measured from one side edge to the other side edge of the upper panel, i.e. along a substantially horizontal plane when referring to Figure 5 which intersects both outermost points of the opposed corner regions. Aptly, the outermost point of each corner region is substantially on the same vertical plane as the corresponding end of the lower edge of the upper panel, as illustrated in Figure 5.

Aptly, each side portion of the window aperture is angled by around 20 -30 degrees, and preferably around 25 degrees, with respect to the respective side edge of the mask body portion to provide the desired spaced of each upper corner region of the window aperture from the side edges and rear edge of the mask body. Aptly, each side portion of the window aperture is spaced at its midpoint from the respective side edge of the mask body by around 25 -30 mm and preferably around 27 mm.

By providing a window aperture according to certain embodiments of the present invention, the most efficient display of a wearer's oral features is achieved, whilst retaining as much filtering material as possible for optimal filtering and personal protection. The U-shaped central channel region 138 which extends into the window area (compared to if the channel region was not present) provides filtering material in an area where visibility of the wearer's oral features is not needed. The U-shaped profile also moves the welded edge region fixing the window to the filtering material in this area downwardly and away from a wearer's nose which could otherwise cause irritation and discomfort to the wearer. Aptly, the area of the aperture 120, i.e. the area of the transparent window for viewing the wearer's oral features through, is around 15-25%, and preferably around 19%, of the total surface area of the orinasal body portion 102, i.e. of a combined surface area of the upper and lower panels. This arrangement has been found by the applicant to provide an optimal window for a third party to view the wearer's oral features, i.e. mouth, lips, tongue and tonsils, from all angles through the mask, whilst providing an increased amount of filtering material compared to conventional maintenance-free masks including a window which maximises protection to the wearer and/or third parties, minimises breathing resistance and improves comfort and user experience for the wearer.

Aptly, the orinasal portion 102 may comprise a plurality of layers including an inner layer, an outer layer and at least one filtering layer located therebetween for capturing particles, such as gas or vapour particles, passing through the filtering material responsive to the wearer inhaling and/or exhaling. A stiffening layer may also be provided to add stiffness to at least a portion of the orinasal body portion.

Aptly, the inner layer is 30 gsm spunbond polypropylene, the outer layer is 50 gsm spunbond polypropylene, and aptly two filtering layers of 25 gsm meltblown polypropylene are provided between the inner and outer layers. Aptly, the clear window is a sheet of 100 micron CPP.

Certain embodiments of the present invention therefore provide a maintenance-free respirator mask having an orinasal portion of air filtering material and a window disposed therein for viewing a wearer's mouth whilst not compromising the filtering and protective performance of the mask. The maintenance-free respirator mask has an orinasal portion of air filtering material and a window disposed in an upper portion thereof, wherein an area of the filtering material is at least 80% of the total area of the orinasal portion to thereby maximise protection to the wearer and/or third parties, minimise breathing resistance and improve comfort for the wearer. The substantially linear-sided window aperture also allows for easier and quicker manufacturing, particularly when welding the window to the filtering material.

Claims

Claims 1. A maintenance-free respirator mask comprising: an orinasal body portion comprising filtering material for capturing potentially harmful gas or vapour particles responsive to a wearer of the mask inhaling or exhaling; and a transparent window element extending across and closing a window aperture provided in the body portion for viewing oral features of the wearer through the mask, wherein the window aperture is defined by a plurality of substantially linear edge portions and comprises opposed upper corner regions each spaced from a rear edge of the body portion by at least 25% of a depth of the body portion from a front edge thereof to the rear edge, and from a respective one of opposed side edges of the body portion by at least 20% of a width of the body portion between the opposed side edges. 2. 3. 4. 5. 6.
The mask according to claim 1, wherein each substantially linear side edge portion of the window aperture is oriented by 20-30 degrees with respect to the respective side edge of the body portion.
The mask according to claim 1 or 2, wherein an area of the window aperture is 15-25%, and optionally 19%, of a total surface area of the filtering material.
The mask according to any preceding claim, wherein each upper corner region comprises an inner substantially linear corner portion and an outer substantially linear corner portion defining an inner corner angle of less than 180 degrees with respect to each other.
The mask according to claim 4, wherein the inner corner angle is from 120 to 160 degrees and optionally 145 degrees.
The mask according to any of claim 4 or 5, wherein each outer linear corner portion of the respective corner region of the window aperture defines an angle with a respective one of the linear side portions of from 100 to 125 degrees and optionally 113 degrees.
7. The mask according to any preceding claim, wherein a substantially linear lower edge portion of the window aperture defines an angle of from 100 to 125 degrees, and optionally 107 degrees, with respect to each substantially linear side edge portion of the window aperture.
8. The mask according to any preceding claim, wherein an upper region of the window aperture comprises a substantially U-shaped channel region substantially disposed on a central axis of the body portion and located between the opposed upper corner regions of the window aperture.
9. The mask according to claim 8, wherein the channel region is sized to accommodate the nose of a wearer in use.
10. The mask according to claim 8 or 9, wherein the channel region is defined by a pair of opposed, upwardly diverging and linear channel side portions and a linear base portion extending therebetween.
11. The mask according to claim 10, wherein each channel side portion defines an angle with the channel base portion of from 100 to 150 degrees and optionally 120 degrees.
12. The mask according to any preceding claim, wherein the body portion comprises an upper panel joined to a lower panel and the window aperture is disposed in the upper panel.
13. The mask according to claim 12, wherein the upper and lower panels are joined along side edge regions thereof and a front fold line defines the front edge of the body portion.
14. The mask according to claim 13, wherein the panels are joined by welding.
15. The mask according to any preceding claim, wherein a peripheral edge region of the window element is attached to the filtering material surrounding the window aperture by welding.
16. The mask according to any preceding claim, comprising at least one strap coupled at each end region thereof to a respective rear corner region of the body portion.
17. The mask according to claim 16, wherein each end region of the at least one strap is attached to a lug extending from a respective one of the corner regions.
18. A method of manufacturing a maintenance-free respirator mask, comprising: providing a window aperture in an orinasal body portion comprising filtering material for capturing potentially harmful gas or vapour particles responsive to a wearer of the mask inhaling or exhaling; and locating a transparent window element across the window aperture to close the same and allow oral features of the wearer to be viewed in use through the mask, wherein the window aperture is defined by a plurality of substantially linear edge portions and comprises opposed upper corner regions each spaced from a rear edge of the body portion by at least 25% of a depth of the body portion from a front edge thereof to the rear edge, and from a respective one of opposed side edges of the body portion by at least 20% of a width of the body portion between the opposed side edges.
19. The method according to claim 18, wherein each substantially linear side edge portion of the window aperture is oriented by 20-30 degrees with respect to the respective side edge of the body portion.
20. The method according to claim 18 or 19, wherein an area of the window aperture is 15-25%, and optionally 19%, of a total surface area of the filtering material.
21. The method according to claim 20, wherein each upper corner region of the window aperture comprises an inner substantially linear corner portion and an outer substantially linear corner portion defining an inner corner angle of less than 180 degrees with respect to each other.The method according to claim 21, wherein each outer linear corner portion of the respective corner region of the window aperture defines an angle with a respective one of the linear side portions of from 100 to 125 degrees and optionally 113 degrees.The method according to any of claims 18 to 22, wherein an upper region of the window aperture comprises a substantially U-shaped channel region substantially disposed on a central axis of the body portion and located between the opposed upper corner regions of the window aperture.The method according to any of claims 18 to 23, comprising welding a peripheral edge region of the window element to the filtering material surrounding the window aperture.The method according to any of claims 18 to 24, comprising: folding a length of said filtering material to define upper and lower panels of the orinasal body portion and a front fold line therebetween to define the front edge of the body portion; and joining the upper and lower panels together along side edge regions thereof. 22. 23. 24. 25.