CA1311662C

CA1311662C - Face mask

Info

Publication number: CA1311662C
Application number: CA000594734A
Authority: CA
Inventors: Amad Tayebi
Original assignee: Better Breathing Inc
Current assignee: Better Breathing Inc
Priority date: 1989-03-23
Filing date: 1989-03-23
Publication date: 1992-12-22
Anticipated expiration: 2009-12-22

Abstract

ABSTRACT

A face mask is disclosed that can be reusable or disposable, and which filters particulate matter and noxious and poisonous gasses from breathed air. The mask has a mask shell that is thermoformed of cross-linked, cross-cell foam sheet that is impermeable to air while having good shape retention and elasticity. The mask shell is perforated with multiple holes in its central area to permit inhaled air to pass through the otherwise impermeable shell. This mask shell is stiff enough to support filter liners made of, for example, an activated charcoal impregnated fibrous sheet that covers the holes and is retained to the inside and/or the outside of the mask shell by a retainer which is easily removed to replace the filter liner(s).
Alternatively, the filter liner(s) may be bonded to the inside and/or the outside of the mask shell to make a disposable mask. A
one-way valve is mounted through the wall of the mask shell to exhaust exhaled air. Alternatively, a retainer is not used. In lieu thereof a mounting piece is fastened to the exterior and/or the interior of the mask. The mounting piece(s) have a large opening that surrounds the holes through which inhaled air passes. Filter liners having adhesive strips around their periphery are fastened thereby to the mounting pieces, and may be removed for replacement of the filter strips.

Description

1 3 ~ 2 Face MaQk -Field of the Inventlon The preQent in~ention relates to face masks that cover the noqe and mouth while filtering breathed air and, in particular, face ma~ks having a molded or thermoformed, non-porou or porous shells, and filter cartridges or one or more liner~ or layer~ of fibrou~ or other filter material that may be impregnated with a sub~tance to remove noxiou~ or other material including gasss~
from the breathed air.

Background of the Invention Examination of the prior art yields a variety of face maQks or respirators for treatment of breathed air. Generally, the masks of the prior art may be categorized into one of two cla~es, namely; di3posable or single-use re~piratorQ and replaceable cartridge respiratorq.

In general, diqposable masks of the prior art are made of a permeable fibrous media formed into a cup shape to fit the contour of the face of the wearer. In Qome ma~ks the fibrou~
media i8 formed to fit the face of the wearer and, simultaneously, achieves a seal against the flow of toxic du~ts and mists into the breathed air chamber. In other ma~ks a nose clip i~ attached to the face ma!Qk and is u~ilized to achieve a Qeal around the nose area.

In the majority of disposable fibrou~ media ma~ks of the prior art, b~eathed air treatment and filtration i~ achieved by air flow through most of the area of the face maQk. Although this 1~

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`~' ~ '- ' ~L 3 ~ 2 iq relatively coqtly, since a large amount of filtration media i~
used to fabricate the entire mask ~hell in addition to the exces~ive between ~hell cut-out wa3te, it iq advantageous Qince it results in a relatively lower pres3ure drop acros3 the filtration media for the 3ame breathed air volume flow rate.
Those maQkq still have a limited capacity and lack the ability to carry a sufficient charge of air treatment 3ubstance~ for the absorption of toxic gaq~es, fume~, vapor3, etcatera in order to provide the wearer with protection in harmful environment3. Thus, ~uch disposable face maqks cannot meet standards or requirements for governmental approval in such applications. For example, it i~ difficult to impregnate the di~po~able face mask fibrous media with a sufficient charge of activated charcoal granuleq (approximately 100 gramq) to pass government requirement~
for paint spray, organic vapor, acid ga~ or pesticide applications. This i3 due to the limited capacity of the fibrou media for encapsulating or for being loaded or impregnated with toxic gas treatment media. In certain inqtances, even when a relatively thicker fibrous shell i~ uced~ the amount of charcoal encapsulated in the mask 3hell is in~ufficient for meeting the National In~titute for Occupational Safety and Health (NIOSH) requirements for certification or approval for paint spray applications. In such cases the re~ulting mask, lacking NIOSH
approval, is usually referred to as a nuisance mask.
In many cases, however, where the ~iltration media is impregnated with air treatment 3ubstances or i loaded with additional fibrou~ media, the face ma~k is relatively thicker and a good face-ma~k ~it and 3eal are much harder to achieve. In theYe cases a nose clip and/or wide, low extensibility heavy duty straps are used in order to apply a high force to pull the mask against the face of the wearer. AQ a re~ult, the air seal i~ obtained by deforming the wearer' 9 face to conform to the perimet~r of the ~: ' ... . . . .. .. .

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, ~ 3 ~ 2 mask, rather than deforming the ma~k to conform to the face of the wearer. Needle~s to say, ~uch a mask i~ not comfortable to wear.

Therefore, a limiting factor in making single use respirators that m~et NIOSH requirements iq that it is very difficult to produce a fibrou~ media mask carrying a weight of approximately 100 grams of activated charcoal granules while maintaining the total mas~ of the mask within bearable limit3.
Examination of prior art ma~k~ ~howq that the formation of the majority of di~po~able ma3ks involve~ heating, Qtretching and/or compre~ive compaction of the filtration media. Such processing factor~ may adver3ely influence the effectivene~ of the filtration media with regard to it3 filtration efficiency and pressure drop. The examination also qhows that, in the majority of di~po~able masks, the area of contact with the face of the wearer i~ of a fibrou~ nature and thus cannot pro~ide an airtight seal similar to an ela3tomeric material seal as required by ~0 regulatory agencies for certain application against toxic gasses and vapor~.

In the manufacture of re3pirators designed for single use or for a finite period u3e, a significant portion of the overall product cost i3 the coQt of the filtration media. A~ the cost of media (including cut out waqte) increase3, the competitiveness of the overall product in the marketplace suffera significantly.
This i3 typically true in all face mask~ targeted to the particulate filtration applications, including toxic du~ts and mist~. In the majority of such masks the area of filtration media ~ Ln the final product is equal to the area of the mask hell.

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:- . . , , ~,, ~3~62 In the prior art, numerouq products and patentq are directed toward~ obtaining an effective air-tight seal between the perimeter of the mask qhell and the face o~ a wearer. In certain in~tance~ a polymeric bead, rim, flap, or their combination~ are added at the perimeter of the fibrou~ ghell face mask. Except for use of a thin rim of impermeable clo~ed cell ela~tomeric m~terial or foam around the perimeter of the face mask in the zone in contact with the face of the wearer, examination of prior art maQks and patents haQ ~hown no sugge~tion or use of impermeable polymeric foam material~ in the ba3ic shell compriqing the body of face masks.

On the other hand, replaceable cartridge masks of the prior art are generally comprised of an elastomeric face piece designed to fit the face of the wearer and achieve an air-tight seal with the face of the wearer. The ela~tomeric face piece i~ usually fitted w.ith at least one opening to receive a detachably attached cartridge for treatment of the breathed air. The ela~tomeric face piece is al~o usually fitted with a one-way exhalation valve.
In order to achieve and maintain an air-tight qeal around the perimeter of a cartridge , the mask ~hell ic stiffened either through ribbing or through the u~e of increased material thicknes~, particularly around the cartridge receiving opening.
Hence, the face ma~k is generally made of a heavy con~truction and thus feel~ heavy on the face of the wearer. As an example, a replaceable cartridge mask of the prior art was weighed and yielded tha following data. The ~otal weight of tha ba~ic face mask ~hell with mounting straps and two replaceable activatsd charcoal granule filters i3 327 grams. The weight of the two filter cartridge~ is 183 gram~. The ratio of the weight of the ma~k functional components (filters) to the total ma3k weight, R = 1~2/327 = 0.56.

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, From a maqk wearer's comfort Qtandpoint, whils a mask is performing itQ intended function, it may be concluded that it iQ
desirable to maintain the ratio R aq high aq possible, particularly for ma~k3 requiring relatively heavy functional component~ (filter~). In such case~, as R approache~ it~ limit value of 1, the wearer's discomfort i9 minimized.

Generally ~peaking, however, NIOSH approved maskQ which utilize detachably attached, replaceable cartridgeQ are costly since a ~izable initial capital inve3tment ha~ to be made for the durable face maqk ~hell. Other indirect coqts include the C08t of periodic Qhell cleaning, ~aniti2ation, testing for cuts, crack~, leakage, etcetera and ~torage. In certain work places individuals using ~uch durable face masks prefer or require that no other co-worker may use the same face maQk qhell at any other time.
Thiq i~ usually done for the pravention of trancmittal of communicable diseases through breathing contaminated air or through skin or ~aliva contact with a contaminated maQk shell. In this casa certain face mask shellq are numbered and deqignated for u3e only by certain individualq.

Additionally, in certain application~, for example in asbe~tos fiber contaminated environments, the qubsequent shaking off o~ the mask ~hell after use contaminates the clean environment. In ~uch ca3es it is de~irable to dispose of the entire ma~k ~hell and air filtering cartridge~ after each use.
Such di posal is costly since a major expense is incurred in the cost of the mask ~hell. On the o~her hand, recently adopted government regulations diQallowed approval of conventional disposable face masks for use in aqbesto3 fiber contaminated environments.

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~311~ 2 A1QO~ most durable ma3k~, particularly approved oneQ, require a high force to pull them againQt the face of a wearer in order to achieve an effective ~eal with the face of the wearer. When such ma~k~ are made of a heavy duty conQtruction the need al o ariseQ for head-top band in order to prevent the ma~k from falling off the face of the wearer and to maintain a complete Qeal with the face of the wearer. Such head-top band i~ usually branched off the above-the-ear band and iQ placed on top of the head of the wearer of the maQk. Such a head-top band 0 iQ particularly unde~irable when the wearer'~ head top i9 bald at the location of the head-top band.

As may be concluded from the above, there iQ a need in the art ~or an inexpen~ive, flexible shell that i~ light weight, single-user (~ingle or repeated use) face ma3k which ~it~ around and achieveQ a complete air tight ~eal with the face of the wearer. Such a mask qhould have a fit and ~eal that ara comparable to the fit and ~eal obtained with presently available elastomeric face pieces, while feeling light and thuQ relatively more comfortable, and being able to carry a charge of air treatment or filtration media and/or devices qufficient to perform the de~ired protection against qpecific environmental hazards.

The need~ of the prior art are met by the face mask taught and claimed herein. The novel ma~k bridges the gap between unapproved disposabla maqks and expen3ive, approved replaceable cartridge re3piratOrQ. Thi~ m~sk features a reduced coqt of filtration media through the use of a relatively ~maller portion o~ such madia~ becau~e the media doeQ not have to und~rgo adverse proces~ing conditions ~uch as heating, stretching and/or compre~sive compaction.

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, , ~311 ~ ~62 Summary of the Invention The above need~ of the prior art are met by the present novel face mask which can be non-di~posable or diqposable, which filters particulate matter, noxiou~ and poiqonous gasses from inhaled air, which is of relatively light weight, which is soft and flexible and formQ a good 3eal to a wearers face around the no~e and mouth without the need for tight ela~tic ~traps, which does not deform the face of the wearer to accompli~h a good seal, which iq comfortable to wear for extended periods of time, and which is relatively inexpen~ive. Such a face mask i~ a viable alternative to prior art rubber shell maQk~ so that each worker may have their own reuqable mask or may di~po~e of a mask after a qingle use.
The primary embodiment of the novel ma~k has an outer shall that is thermoformed of croqs-linked, closedcell foam shoet. The foam shell iq impermeable to air while being soft and flexible, and having good ~hape retention and elasticity. The center area of the shell is perforated with multiple holes to permit inhaled air to paq~ through the otherwise air impermeable ~hell and through the filter linar(s) po3itioned inside or out~ide the ma~k over the holeq. Thi3 mask shall is ~tiff enough to support a variety of filtar liner~, either singly or in combination, ranging from a simple fibrouq filter liner for filtering du~t or mi~t, to an activated charcoal impregnated fibrous qheet liner for filtering noxiou~ and poisonous ga~eq and other dangerous material~. The filter~ may be removable retained to the in~ide or to the outside of the shell over the holes by a force fit retainer or by clip~ that are both easily remsved to replace the filter liner. The remo~able filter liners may also be attached to the inside or outside of the shell by qelf adhe~ive Ytrips around the periphery of the filter liner. The filter liner~ may al~o be thermobonded or otherwise permanently bonded to the inside or ' 1 3 ~ 2 out~ide of the mask over the hole3 to make a disposable verqion of the ma~k. When filter liners are attached to both the inside and to the outside of the qhell over the holes, the outer liner ~erveQ aq a pxe-filter, and the inner liner qer~es aq a post-filter.

A one-way exhaust valve may be mounted through the wall of the foam mask shell to vent exhaled air. The exhaust valve i9 located in a poqition where it does not in~erfere with the filter liner(s).

In an alternative embodim~nt o~ the invention the basic ~hell may be ~ormed o two parts. The periphery of the shell which contact~ the face of the wearer and makes an air tigh~ seal thereto, and to which straps would attach, would be formed of the air impermeable foam material. Attached to the shell periphery by thermobonding, adhesives or other methods is a piece of air permeable foam that eliminates the need for the holes in the primary embodiment o the invention. The ~ilter are Qtill attached tc ths inside and/or the outside of the mask over the air permeable foam material. The *ilters are attached permanently for a disposable maqk, and are remo~able as previou~ly mentioned for a reusable ma3k.
In still another embodiment of the invention the closed cell foam material from which the mask shell i thermoformed is made up of a layared mat~rial. The outermost layer that i on the side ma~k shell that contactG the face may be of a material that permits mor~ com~oxtable wearing of th~ ma~k, or that ia be~t to reduce chafing or hxpoallergenic ef~ect~. The other layer~ may be chosen for ~hape retention, aasthetics, or for many other reasonq.

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~L 3 ~ 2 In another embodiment of the invention one or more filter layers are not attached to the in3ide and/or the outqide of the foam ~hell but, rather, one or more filter cartridgeq are attached through the wall of the qhell. The cartridge~ may be detachably faQtened to collar~ that mount through and are faqtened to the foam shell.

In yet another alternative embodiment of the invention the maqk ~hell may not be formed of cloqed cell foam, but may compri~e a qhell that i~ fabricated by thermoforming a ~heet of commercially available, synthetic fiber, nonwoven, filter material. The shell ~o formed may be cup-~haped. During forming a piece of a fibrous ~heet material impregnated with activated charcoal or other filtration subqtance i3 thermobonded or otherwise fa~tened to the in~ide of the ma~k but not overlapping the edge of the mask. In thiq manner the filter material forming the ba~ic ma~k ~hell al~o doe~ pro~filtering, and the filter liner affixed to the inside of the ~hell i~ the po~t-filter.

De~cri~tion of the Draw nq The pre~ent invention will be batter understood upon reading the following d~tailed description in conjunction with the drawing in which:

FIGUR~ a *ront view of a mask having only on~ filter which i~ mountod on the inside of the ma~k, ~howing a plurality of holes through which inhaled air pa~seq, ~howing the exhaled air exhaus~ valv~, and the ela3tic ~qtrap~ that hold the mask to the face of a wearer;

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:'' ' ~3~62 FIGURE 2 is a qide cross-sectional view of a mask having a filter attached to the front of the magk, showing the exhaled air exhaust valve, and the elastic traps that hold the mask to the face of a wearer;

FIGURE 3 i~ a qide crosR-sectional view of the mask~ that have inside and/or external filters 3howing the orientation of the in3ide mounted filter media, a filter retainer, and an exhaust valve;
FIGURE 4 is an iqometric ~ectional view of a snap in plastic retainer used for holding a filter media liner in~ide a mask that has only a filter mounted internally;

FIGURE 4A i3 a cro~q ~ectional view of the mask shell showing the ~nap-in retainer of Figure 4 in position inside the mask shell;

FIGURE 5 show~ a filter retainer arrangement used with a mask that ha~ both an external pre-filter and an internal post-filter;

FIGURE 6 i~ a view of a filter liner showing different layer~ thereof;

FIGURE 7 is a cro~s-sectional view of a foam ~hell ma~k having only on~ filter which i9 replaceably mounted on the outside of the ma~k by means of a 3elf adhesive ~trip;
FIGUR~ 8 i3 a cros~-sectional view of a foam shell mask that utilizes one or more filter cartridge detachably fastened to collar~ that mount through and are fa~tened to the foam shell in lieu of filter linerQ; and . .

~ 3 ~ 2 FIGURE 9 Yhows a croqs-~ectional view of a fibrou~ 3hell mask in which a po~t-filter liner i5 bonded during manufacture.

Detailed De~cri~tion In accordance with the pre~ent invention it iQ advantageouq to u~e an imperm~able polymeric foam as the haQic ~ace mask qhell. U~e of quch foam, having a ~igni~icantly lower den~ity re~ults in a generally lower weight ma~k, a~ well as a highly de~irabla higher filter media weight to total mask weight ratio R. Such a high ratio i3 not only desirable from a comfort ~tandpoint, but al~o from a coqt and overall weight qavings, particularly for military ga~ ma~ks.
For the pUrpO9e of deqcri~ing t~e pre~ent invention an impermeable polymeric foam shall be defined a~ a medium which i3 impermeable to the flow of gasses and liquids and having a mass denqity lower than the product of the standard mas3 den~ity of water (62.4 lbm/ft3) and the qpecific gravity of the qolid consistency of the polymer or combination of polymers from which the mask shell medium i~ made. For example, an impermeable polyethylene foam ~hall have a denqity lower than 62.4 lbm/ft3 X
0.91 = 56.784 lbm/ft3 and, likewise, a nylon 66 foam shell have a den~ity lower than 62.4 lbm/ft3xl.14=71.136 lbm/ft3, and 30 on.
In accordance with the above definition, an initially permeable fibrou~ ~heet or open c911 foam sheet coated or ~ealad on one or both sides in order to be impermeable to the flow o~ ~luid~ may be defined as an impermeable foam. Other material~ that may alternatively be u~ed to ma~e the subject mask ~hell are combination~ or laminates of polymeric sheet~ or film~, fibrou~
wQbs, fabrics, open c811 foams and/or cIosed cell foam9.

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' 1 311~62 Due to the lower den~ity of the foam it i~ po~qible to form thick, yet light face ma~k shellR. Thiq iQ particularly desirable ~ince a thicker ~hell offer~ a greater overall ~tiffnesq that enable~ the ma~k ~hell to retain its Qhape while being able to carry a large maQQ of filtration or air treatment media without ~acrificing on the ea~e of Qurface deformability of the Qhell.
Thiq i9 a feature that i9 eY~ential for an effective face fit and Qeal. ~ an example, a 1~8 inch thicknes~ lightly croqq-linked closed cell, polyethylene foam, made by Voltek, with a den~ity of 2 lbm/ft3 was formed into a cup Qhape shell-like face mask o~ the type di~clo~ed in U.S. Patsnt 4,641,645. The formed foam shell, weighing about three grams, was attached to two exten~ibl~ light duty 1/4 inch width braided ela~tic 3traps weighing about two gram3 (commonly med for light weight face mask~. This basic qhell was able to carry a load of 150 grams exterior to it~ qurface and, altornatively, interior to its sur~acs without collapsing, falling off the woarer' Q face, or lo~ing the air tight seal between its perimeter and the face o~ the wearer. The re~ulting ma~k had an R ratio 150/(150+2+3) = O.97 and wa~ more comfortablo to wear for a longer period of time than the generally heavier approved mask3. Further, it did not require a head-top ~trap as do the majority of approved masks. Generally, an activated charcoal granule charge and other media weighing a total of approximately one-hundred grams are sufficient for providing the ma~k wearer with protection against a variety of toxic ga3sq~, vapors, etcetera, in accordance ~ith NIOSE requirements.

It i9 worth noting from an economicY ~tandpoint and from a wear~r' 9 co~ort viewpoint, that it i~ more desirable to uq~
narrower and lighter, more exten~ible bands to hold a mask to the face. Th~ all poa~ible with the pre~ent invention.

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. -1 3 ~ 2 In comparison to a continuou~ uniform pha~e polymericmaterial, a polymeric foam ~hell i~ ea~ier to cut and perforate.
Thus, it i~ possible to obtain a ~hell with a good face seal while utilizing ea~ier and lower capital equipment fabrication techniqueq quch a~ thermoforming. The cutting and/or perf orating proceqq may be performed on ~ormed foam maqk ~hellq obtain~d by thermoforming, injection molding, rotational molding, blow molding or any other ~abrication technique. Although it is equally functional to u~e a plurality of perforation~ or a single large cutout, it i~ preferable to u~e a plurality of perforations. Thi~ iq particularly advantageou~ for minimi~ation of un~upported filtration media outwardly bulging or inwardly retracting during exhalation and inhalation and for obtaining better ~hape retention and support of load interior and/or exterior of the mask ~hell, a well as additional points within the filtration area for anchoring the media without blocking of air passage. Such anchoring poink~ help maintain the ~hape of the filtration media even when the interior of the mask i~ highly humid or when ~uch media is wetted by such high humidity. The feature of shape retention and resistance to collapsing in the wet condition i~ I highly desirable and in certain ca~q iQ
required ~or certain applications.

The u~e of foam for th~ inn~r and/or outer surfaces oP the ~hall al90 provid~s a ~lexible ~urfaca. Such flexibility of the inn~r and/or outer ~urface o~fer~ the additional I advantage o~
providing a conformable ~urface for obtaining a complete seal between a replaceable cartridge, or ~edia liner and the 3hell of the ma~k.
In accordance with the pre~ent invention, impermeable laminate~ compri~ing at least one layer of polymeric foam material may be u~ed ~or ~abrication of the ma~k shell. U~e of quch laminate~ make~ it pos~ible to obtain combinations of ,~S.i~ 13 -,~ .

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13~1662 color~, qoftne~q and/or high tack of the qide of the mask Qhell in contact with the face of the wearer, and firmnegq of the outer qhell ~hile maintaining the low weight of the entire ma~k qhell and Food and Drug Admini~tration (FDA) approved and unapproved materials. Such laminates algo make it posgible to reduce the overall material and/or fabrication co~tq and enhance the elastic recovery from deformation, strength and mechanical propertieq of the ma~k ~hell, particularly at the fixation or threading pointq or the ~trap hole~.
The foam denqity may be as low aq 4 oz/ft3. Experiment~
conducted on lightly cro~q-linked polyethylene foam mask ~hells with a variety of den~itie~ yielded a preferred (although not nece~arily optimum) den~qi~y of 4 lb/*t3. The u~e of ela#tomeric polymeric foam make~ it possible to qimultaneou~ly obtain a desired combination of wearer'q comfort, product competitivones~
in the market place, and mask functional feature~ not possible with any of the prior art masks. For example: (1) clinging to the ~kin of the wearer'q ~ace at the perimeter of contact of the ma~k with the ~ace of the wearer, thug ensuring an air-tight seal as ef~ective a3 that obtained from conventional uniform solid phase ela~tomeric or rubber face piece~; (2) softness of contact force between the wearer's face and the ma~k shell, since the ease of deformity of the foam re3ult~ in ~preading of the ~orce o~
applied pull onto the mask shell over a larger qurface area of the ~earer' 9 face, thereby eliminating the harYh or exces~iv0 loading points on the wearer's face which u~ually cause rednes~
on the wearar' 8 face after even a ~hort duration of wearing the mask; (3) lightnes~ of shell yielding improved wearer's comfort and increa~e of the ratio R of weight o~ the filter media to the total weight of the ma~k. Increa3ing thi~ ratio also reduces the overall ma~erial co~t of the mask and enhances its competitivenesq in the marketplace. It al30 makes it equally attractive, ~rom a product cogting ~tandpoint, to use ~uch ~oam .
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~L 3 ~ 2 ma~k Qhell3 for nuiqance maqk3 (unapproved) and NIOSH approved applications. The lightn2s~ of the Rhell makeq it po~sible to u~e narro~er, llghter, more readily extensible bands for holding the mask ~hell onto the fa~e of the wearer without exce~3ive force and preferably without a head-top hand; (4) obtaining a ~tiff, yet light ma~k qhell able to carry a mass of filtration and/or air treatment media qufficient to meet NIOSH approval for certain application~; and (5) enhancing the shape retention and reco~ery from deformation by using ela3tomaric material foam~ 3uch aq polyurethane or lightly cro~-linked polyethylene, and 3ati~fying NIOSH requirementq for ela~tomeric face pieca~ for certain applications, and other desirable feature3 aq de~cribed in this application.

The mask of the present invention features a face piece covering mouth and noqe of a wearer and generally conforming to the contour of the face of the wearer in the zone of contact between the face of t~e wearer and the face piece. In addition, the mask ha~ a rear portion bead of impermeable material, preferably clo~ed cell polymeric foam or generally impermeable polymeric foam. The rear portion ha~ a circumferential zone ~hich is in contact wi~h the face of the wearer. This zone i~
impermeable to air and i~ made o~ ~lexible, ~oft, high-tack, generally elaskomeric material in order to provide an air-tight and complete ~eal ~etween th~ fac~ of the wearsr and the entir~
circumferential zone. For lower fabrication costs the circum~erential zone m~y be an integral part of the rear poxtion.
~t may al~o be an added segment attached to the side of the rear portion facing the wearer'~ face.
There i9 also a front portion made of impermeable material preferably closed cell polymeric foam or generally imp~rmeable polymeric foam. For lower fabrication costs the front portion and the rear portion may be integral part3 of one continuou~

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~ 3 ~ 2 impermeable 3hell formed of polymeric cloqed cell ~oam or generally impermeable polymeric foam, light impermeable polymeric material or laminate~ of foam~ and/or other polymeric materials.
The front portion may alqo be attached to the rear portion in a manner that provides a complete and continuouq air tight Qeal in the zone joining the front portion to the rear portion.

The front portion haq at least one circumferential zone on itq interior qurface ~acing the face of the wearer and/or on its exterior surface. The front portion i~ made permeable to the pasqage of air, ga~qe3, particulate~, vapor~, e~cetera by having a single large cutout area or preferably a plurality of smaller cutout area~, hole~ or perforations ~urrounded by the circumferential zone(~).
At lea~t one air permeable treatment medium, ~uch a~ a liner, plurality of linerq or replaceable or permanently attached cartridqe i8 attached to the interior and/or the exterior of the front portion in an air-tight manner ~long the circumferential zone, thereby creating a treated air chamber enclo~ed between the interior qurface of the air treatment medium, the interior ~urface of the front portion, the interior ~urface of the rear portion and the face o~ the wearer.

For the ca~e where more than ona air permeable treatment medium are used, the fir~t medium may be attached to the exterior o~ the front portion and would thereby act a~ a pre-treatment or initial pre-filtration medium. Such is the ca~e ~or application~
~uch a~ paint spray mask~ and the like.

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- - . .. ~-The air permeable treatment medium may be attached to ths outer portion qingularly or in combinations, in one location or in a plural.ity o~ location~, mechanically, frictionally, by a tight fit, by a snap fit, adhesively or coheQively (i.e. by intPrfacial melting or fu~ion and cosolidification), permanently or detachably.

The outer portion may be ~haped to accommodate a permeable liner, a cartridge or a plurality of cartridge~ and/or liner~ for treatment of breathed air in one location or in a plurality of locations. The liner~ or cartridges may treat the breathed air in Qerie~ or in parallel. Further, the outer portion may be bellow~
shaped in order to accommodate-cartridges of various thicknesses.

In Figure 1 iq ~hown a front view of a face ma~k 10 which has only an internal filter liner. The mask comprise3 an outer shell 11 which is thermoformed from a ~inglelayer sheet of cross-linked, Glosed-cell foam that is impermeable to air. Many foam materials may be used but in the embodiment of the invention disclosed herein three-sixteenth~ inch thick foam available ~rom Voltek, a division of United Foam Corporation, is utilized. Thi~
foam material is soft but i9 thick enough that the thermo~oxmod 3hell ha~ good ela~tic propertie~ yet is stiff enough that it has good shape retention and can support a ~ilter liner and retainer therein behind holes 12 as shown in Figure 3. The holes 12 through the csntral portion of the ma~k shell 11 may be punched through the foam sheet prior to thermoforming of ma~k ~hell 11, or may be punched after ~hell 11 i3 formed. Holes 12 are preferably one-quarter inch diameter and tha qpacing bet~een the holes is preferably one half the diameter o~ the hole~, but one skilled in the art may ~ary the diameter and spacing of the hole~.

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~ 3 ~ 2 Ma~k ~hell 11 al~o ha~ two elastic straps 13 and 14 attached thereto on rim 15. Straps 13 and 14 go behind the head of a wearer of maqk 10 when the maqk i3 worn and hold ma~k 10 comfortably to the wearerrq face without deforming the face while maintaining an airtight qeal between the rim 15 of maqk shell 11 and the face of a wearer. The qtrap~ 13 and 14 are Qtapled to rim 15 in the preferred embodiment of the invention, but may al~o be ~ewn, thermobonded or adhesively attached thereto in a manner well known in the art. Although ~trap3 13 and 14 are shown as single pieces of elaQtic material, in an alternative e~bodiment of the invention ~traps 13 and 14 may be made adju table in a manner well ~nown in the art.

In Figure 1 is alQo ~hown a one-way exhaust valve 16 of a type known and used extengively in the face ma~k art. Valve 16 i~
mounted in a hole or a suitably ~haped cavity (Figures 2 and 3) through the lower portion of mask ~hell 11 qo as not to interfere with a filter liner ~no~ shown) inside of ma~k 10 behind all of holes 12. Valve 16 permits a waarer o~ the mask to inhale through the filter liner but on exhalation valve 16 opens to vent exhalad air.

Although not qpecifically shown in Figure 1, but qhown in Figure 3, there iQ a filter liner 17 mounted in the in erior of mask qhell 11 behind all of holes 12 to filter inhaled air pa~sing through hole~ 12. As described in detail further in this specification internal filter liner 17 may al~o ba retained in~ide of mask shell 11 by a sn~p-in retainer (not 3hown) which iq shown in ~igure~ 3 and 4 to produce a rausable mask ~0. With a reusable ~ace ma~k th~ filters may be periodically chang~d to continue the uqe in the same anvironment, or changed to a new type of filter for use in a new environment. Hewever, the snap-in retainer may be di~pensed with and filter liner 17 may be perma~ently fastened inside of mask shell 11 by thermobonding or ~,..

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, ' ~ 3~1~62 adhe3ives in a manner well known in the art to produce a di~po~able face maqk that i~ used only once and then diQcarded.

When wearing face ma3k 10 qhown in Figure 1, mask shell 11 iq flexible enough and i~ shaped 80 that it easily conform~ to the contour~ of a wearer'q face around the nose and mouth and deformation of the wearer's face i9 not required to achieve a good ~eal. In addition, rim 15 iq ~oft enough that it fitq very comfortably to the face of the wearer, generally with leQs force than prior art di po~able mask~ that are ~tiff becau~e of how they are fabricated. Accordingly, face ma3k 10 may be comfortably worn for long periodq of time.

In Figure 2 iq shown a side cros~-sectional view of a face mask 10 with an external filter liner 18 mounted thereon. This mask al~o compri~es an outer shell 11 which i9 thermoformed from a single-layer ~heet of cro~s-linked, closed-cell foam that i9 impermeable to air, and exhaust valve 16. Mas~ 10 al90 has holes 12 through the front of foam ma~k ~hell 11. In a di~posabls version of mask 10 external filter liner 18 i3 fa~tened over holeq 12 by thermobonding or by adhesiveq to create a dispo3able ma~k. However, external filter liner 18 may al~o be removably attached to the out~ide of ma~k shell 11 by a rstainer arrangement ~uch as ~hown and described hereinafter with 2S reference to Figure 5 to create a reu~able face mask. With a reusable face mask the filters may be periodically changed to continue th~ u~e in the same environment, or changed to a new type of filt~r for U89 in a new environment.

In Figure 3 i9 shown a side cro3s sectional view of face mask 10. One-way exhau~t valve 16 is ~een mounted through the wall of the lower portion of mask shell 11 where it does not interfsre with fi}ter liner 17. Filter liner ~7 may be permanently ~a3t~ned inside of mask shell 11 over holeY 12 by thermobonding or by .

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~3~6~2 adhe~ive~ for a di~po3able mask, or filter liner 17 may be detachably fastened inqide of maqk ~hell 11 over holes 12 by a ~nap-in retainer 19 ag qhown to create a reuqable ma~k. Further detail~ of retainer 19 are ghown in Figure 4 , and further detail~ of how retainer 19 holdq replaceable liner 17 inside of ma~k qhell ll by being held in a molded receaq around the inner wall of the qhell 11 ars ~hown in Figure 4-a. The conqtruction of an exemplary multilayer filter liner 17 i~ shown in Figure 6.
Basically, internal filter liner 17 i8 prefabricated with one or more than one layer and then is stamped out in flat rectangular or other shape piece~. In a multilayer ver ion of filter liner 17 there iq a fir3t layer (not shown) of a fibrous material impregnated with activated charcoal. There i~ al~o a ~econd layer (not ~hown) that is attached to the activated charcoal layer. The qecond layer i8 preferably a net layer for appearance purpose~.
Filter liner 17 fits in the middle of the inside of mask ~hell ll covering all of holeq 12. Due to the flexibility of liner 17 it readily conform~ to the inside of tha central portion of mask shell 11.
In Figure 4 is shown an isometric sectional view of 3nap-in retainer 19. Retainer 19 i9 molded of a flexible thermoplaatic material that can bend a~ it i9 inserted unto the interior of mask ~hell 11 and is held in a groove therein a~ 3hown in detail in ~'igure 4a. The pla~tic Prom ~hich retainer 19 i molded i9 also tough, and coupled with the thickne~s of the retainer it does not break ~a3ily. The outer edge3 20 ~nap into the aforementioned groo~e around the interior of ma~k shell 11 to retain filt~r liner 17 inside ma3k shell 11. On a~embly into ~face ma~k 10 retainer 19 al~o deform3 to match the contour of the inside of ma~k shell ll. There are alqo rib~ 21 that help hold int~rnal filter liner 17 against the inner qurface of mask shell 11 over hole I2. Rib~ 21 have much ~pace between them 90 they do not materially impede the flow of inhaled air pa~sing through :

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~3~6~2 filter liner 17 to the inqide of ma~k 10. It should be appreciated that there may be many deqigns of retainer 19 that will work with the maqk. When it i~ deqired to replace ~ilter liner 17, retainer 19 i~ gra~ped near one edge and pulled, removing the retainer from the inQide o~ mask ~hell 11. The ~pent *ilter iq then removed and replaced with a new filter liner 17, and retainer 19 iq then rein~talled.

In Figure 4-a i~ a cro~3 qectional view of ma~k shell 11 that ~howQ groove 22 that i~ formed around the inside of ~hell 11 during thermoforming. Retainer 19 i~ shown in it3 Qnapped-in po~ition with its outer edgeQ 20 in a force fit engagement in groove 22. It can be ~e~n that on in~ertion retainer 19 deforms to hold filter 17 inQide of ma~k 3hell 11 up again~t holes 12. This force fit engagement maintain~ a good qeal 90 that no inhaled air pasqe~ around filter liner 17.

While the description o~ Figureq 1 through 3 ha~ been for mask~ in which the filter liner 17 may be remo~ed and be replaced, the retaining means 19 may be eliminated and filtar liner 17 may be thermo~onded or adheqively bonded to the inside and/or the outside of mask shell 11. This make~ a di~po~able faco ma~k 10 that is replaced after a ~ingle u3a.

The interior view of mask 10 ~hown in Figure 3 is for a version of the ma~k wherein there i~ only th~ interior ~ilter liner 17. With thi~ ver~ion Qnap-in retainer 19 is u~ed. When a verqion o~ ma3k 10 has both an interior filter liner 17 ~Figurs 1) and an exterior ~ilter liner 18 ~Figure 2)-, diff~rent filter retainer mean~ may be utilized. Thi~ dif~erent retainer mean~ is retainer means 23 ~hown in Figure 5. Retainer means 23 jointly holds both interior filter liner 17 and external filter liner 18 at the ~ame time. ~etainer 23 compri e~ pieces 24 ~hrough 27 that are molded out of a thermopla~tic, or are made out of metal.

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~31~6~2 Piece 24 i9 a rectangular, or other suitable 3hape, frame havinga number of central area holeq or rib pieceq alike 3nap-in retainer 19 and that qerve the ~ame purpoqe, and having a number of protruqions 25 around itQ edge as Rhown. Piece 26 iq another rectangular, or other 3uitable qhape, frame having the qame dimen~ions aQ frame 24 and may also have holes or rib element3 but having number of hole~ 27 therethrough inQtead of protrusions 25. The holes 27 are located around the edge of frame piece 26 in exact regiqtration with protrusion~ 25 around the edge of frame piece 24. In manufacture ma~k ~hell 11 ha3 a number of hole~ 28 made therethrough that are equal in number to the number of protruqionq 25 and are of the ~ame diameter as holes 27. Th0se extra holes 28 through mask shell 11 ~urround hole~ 12 through which inhaled air pasQes. The outer dimen~ions of the edge~ of filter liners 17 and 18 are such that they just fit within protrusions 25. Alternatively, filter liners 17 and 18 may have the same outer edge dimen~ions a~ frame piece3 24 and 26. When thi~ i9 the case there are a number of holes (not shown) through filter liner~ 17 and 18 around their edge3. The diameter of the~e holes is the Qame a~ holes 27 and they are in the 9ame po~ition~.

On assembly o~ filter retainer 23 to mask shell ll with filter linars that have no holes through them, external filter liner 18 i~ laid on the rib3 of frame pigCe 24 between protrusions 25. The protrusions 25 ars th~n in~erted from the front of ma~k 10 through the corre~ponding holes around the holes 12 to tha inRide of mask qhell 11. Frame piece 26 is then placed in the in~ids of mask shsll ll ~o that the portion~ of protrusions 25 extending to the in~ide of ma~k ~hsll 11 pa~ through it~
hole~ 27. Retainer clips 29 are ~hen placsd on each protru~ion 25 and pre~ed on to pinch mask shell 11 and filter liner~ 17 and 18 batween frame pieces 24 and 26 as ~hown in Figure 5. The rib~ of frame piece~ 24 and 26 hold filter liner~ 17 and 18 up again~t hole~ 12 through which inhaled air pa~ses.

~1~.

~3~ ~ 662 When fllter liner3 17 and 18 have holes around their periphery external filter liner 18 iQ first a~embled to frame piece 24 80 that protruQiOns 25 pais ~hrough the hole~. After frame piece 24 is asqembled to mask ihell 11 as de~cribed in the last paragraph, the inner filter liner 17 is assembled 90 the protru~ion~ 25 pas~ through the hole~ around it~ periphery. The frame piece 26 and clip~ 29 are ai~embled ai described in the last paragraph. It would be obvious that one skilled in the axt can devise many different way~ of jointly retaining inner and outer filter liner~ 17 and 18 to mask Qhell 11 ~o that inhaled air cannot pa~ around the edges of the liners.

In Figure 6 i9 shown an axemplary filter liner 17 or 18 that is a multilayer ~ilter liner. This exemplary multilayer filter liner has a first layer 29 of a fibrous material u~ed for filtering du~t and mi~t ~orm inhaled air. The ~econd layer 30 i~
a fibrou~ material that i3 impregnated with activated charcoal or other chemicals f or ab~orbing noxio~ or poiqonou~ ga~3es and mists and airborne particulate matter. Such a material is available from Extraction Systems~ Norwood, Massachusett~. A net li~e material forms the third layer 31. Layer 31 is that layer of inner filter liner 17 which faces the inside of mask shell 11, or i~ that layer of filter liner 18 that i~ seen on the out~ide of mask 10 and are provided for aegthetic appearance only. Layer 31 may be "Delnet", a nonwoven, porous net material manufactured by the Hercules Corporation.

In Figure 7 is shown an alternative embodiment of the invention in which the snap-in retainsr 19 or combination retainer 23 previously described are not utilized. Rather, proviqion is made to r~movably attach an external filter liner 18 by means o~ a self adhe~ive strip 32 attached to the edge of the llner. To implement this ambodiment a flat, rectangular, oval or .... - ' :' - ' '~ -, -. . ~ . - , ~ . . . : .
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. .: , ' . , ' ' ~L31 11 ~2 other plastic mounting piece 33 is attached to the front of mask Qhell 11 as qhown in Figuxe 7. The purpoqe of mounting piece 33 iq to provide a ba~e to which a Qelf adhesive filter liner 18 may be attached. Mounting piece 33 ~urrounds holeq 12 through which inhaled air paqse~ and it may be attached by thexmobonding, adhe~ive bonding or by qome other technique. The wearer of mask 10 takes a replacement external filter liner 18 that ha~ a self adheqive strip fa~tened around the adge thereof and peelq off an eaqy relea~a protective cover strip ~not shown) that i9 well known in the presYure sensitive self adhe3ive art. Filter liner 18 is then placed on mounting piece 33 so that the qelf adhesive strip fasten~ filter liner 18 thereto. When it iq time to replace filter liner 18 the edge thereof i9 gra~ped and it i3 peeled from mounting piece 33. A new ~elf adhesive filter liner 18 i9 then affixed to mounting piece 33. In an alternative embodiment of the invention mounting piece 33 is fa~tened to the in ide of foam mask shell 11 and qelf adheqive filter liners are attached thereto inside of tha mask rather than on the outside.

Where needed, a mounting piece 33 may be fastenad to both the inside and the outside of foam mask shell 11 and self adheRive filter liners 17 and 18 may be attached to both mounting pieces 33. In this manner ma~k 10 may be used to provide ~iltering again~t selective combinations of noxious and poisonou3 ga99e9, dusts and mists.

In an alternative embodiment filter liner~ 17 and/or 18 may be ~ub3tituted with a filter cartridge of types known in the art.
In yet another embodimen~ filter liners 17 and/or 18 may be permanently and directly mounted asainst foam ma3~ shell 11 covering all hole3 12 by a variety of teohnique~ weIl known in the art.

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In Figure S i9 ~hown another alternative embodiment of the invention that ha~ a foam maQk qhell 11 but which does not utilize filter liners a~ previouqly de~cribed. The air paqsage holeq 12 also are not punched through foam ma3k ~hell 11. Rather, at leaqt one larger hole 37 i~ punched through ~hell 11 and a collar 38 is thermobonded, friction snap-fit or adheqive bonded through the wall of mask shell 11 in hole 37. Alternatively, large hole 37 may be ~ub~tituted with a permeable formad cavity suitably ~haped to accept a ~ilter cartridge. For example, by having a plurality of holes for flow of air therethrough. Walls o~ ~uch a formed cavity may have a qtraight or a corrugated ~bellow~ like) ~hape. Alternatively, there may be two holes or cavities 37 and two collarq 38, but only ona i~ shown in Figure 8 for ease of representation. Collar 38 may be of cylindrical or other shape and a paqsage or hole 39 through it i~ u~ed to mount a replaceable cartridge filter 40 of the type well known in the art. Cartridge filter 40 has an extension 41 having, in essence, an out~ide dimension approximately equal to the in~ide dimen~ion of the cylindrical passage 39 through collar 38. To mount cartridge filter 40 it~ extension 41 i~ inserted into pa3sage 39 where it makes a relatively tight friction fit that retain~
filter 40 therein. In addition, no unfiltered air can pasq through this joint. To replace a cartridge filtex 4Q it i8 grasped and twisted back and forth while pulling it away from ma3k ~hell 11. When it i~ removed a new filter cartridge 40 i inqtalled. There are m~ny dif~erent type3 of filter cartridges that may be interchanged to u~e mask 10 in Figure 8 in many type3 o~ en~ironm~t Alternatively, filtar cartridge 40 may be attached to ma~k ~hell 11 in a permanent manner by a variety o~
30 methods well known in the art. Thi~ foam 3hell mask is then a replacement ~or the more conventional type of "gas ma~k" except that it i3 le~ expensive, much lighter and i9 more com~ortable to wear. Being le99 expensive, quch ma~ks will not be ~hared with .. . , . - - . . . .

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the attendant problems of mask care and communicable disea~e concerns deQcribed in the Summary of the Invention.

In Figure 9 iq ~hown a cro~qq sectional view of another alternative embodiment of the invention. An outer ma~k Qhell 34 is fabricated by thermoforming a sheet of ~ynthetic fiber, woven, knitted or nonwoven, filter material in a cup qhape. One ~uch filter material is marketed under the registered trademark VILE~ON MICRODON by tha Carl Freudenberg Company of Germany and marketed in the United Stateq by Pellon Corporation of Lowell, ~a~achu~etts. When thermoformed into maqX Ahell 34 the filter material is permanently ~et and retains its molded shape. Before or after thermoforming, a piece of fibrouq liner material 35 that is impregnated with activated charcoal iQ placsd against (shown in Figure 9 in~ide1 the material of the mask qhell 34 but not covering the edge or rim 36 that touches the face of the wearer. Through coating, fusion o~ fiber3, or use of impermeable ~oam or other laminate~, rim 36 i9 rendered impermeable to flo~ of air, thu~ localizing flow of all breathed air only through the area of shell 34 co~ered by liner 35. The two ~heet~ 34 and 35 may be assembled together in a variety of mannerq well known in the art. Altarnatively, liner 35 may be made o~ other material3 and may comprise more than one layer for functional, a~Yembly and/or ae~thetic purposes. One mask shell that may be u~ed as mask ~hell 34 to ~hich filter liner 35 may be as3embled i~ taught in U.S. Patent 4,641,645 a~signed to the ~ama a~ ignee as tha~
patent.

~ While what has been described hereinabove are the pxeferred embodiment~ of the invention, it will be ob~iou~ to thos~ skilled in the art that numerou~ change3 may be made wi~hout departing ~rom the spirit and scope of the invention. For exampl~ elastic strap~ 13 and 14 may be attached to mask ~hell 11 by pas~ing them through holes in rim 15 o~ the mask.
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Claims

1. A face mask for filtering air comprising:

a mask shell formed of a flexible, air impermeable foam material, said mask shell having one or more holes through the central portion thereof, and a first filter liner for filtering the air passing through said holes, said filter liner being fastened to said mask shell and covering all said holes to thereby filter all inhaled air passing through said holes.

2. The invention in accordance with claim 1 wherein said mask shell has a ridge formed surrounding said holes as the mask shell is formed, and further comprising:

a retainer having a rim which when forced into said ridge thereby fastens both said retainer and said first filter liner to said mask shell.

3. The invention in accordance with claim 1 further comprising a one-way exhaust valve mounted through the wall of said mask shell in a position that it is not covered by said first filter liner, said valve for venting exhaled air.

4. The invention in accordance with claim 3 further comprising one or more elastic straps attached to the edge of said mask shell and being used to hold the face mask over the nose and mouth of a mask wearer by passing around the head of the wearer.

5. The invention in accordance with claim 1 wherein said first filter liner is fastened to the interior of said mask and further comprising:

a second filter liner for filtering the air passing through said holes, said second filter liner being fastened in the exterior of said mask shell and covering all said holes to thereby filter all inhaled air passing through said holes.

6. The invention in accordance with claim 5 further comprising:

a retainer that mounts to said mask shell over said first and said second filter liners to fasten both said first and said second filter liners to said mask over said holes.

7. The invention in accordance with claim 4 wherein said foam mask shell is made of polymeric cross-linked, closed-cell foam that has physical properties that provide shape retention to said mask shell and elasticity that enables the edge of said mask to conform and seal to the face of a wearer around their nose and mouth.

8. The invention in accordance with claim 1 wherein said first filter liner comprises one or more layers including filtration medium layers.

9. The invention is accordance with claim 1 wherein said air impermeable foam material from which said face mask is fabricated is a laminate structure.

10. A face mask for filtering air comprising:

a mask shell formed of a flexible, air impermeable foam material, said mask shell having one or more holes through the central portion thereof, a first mounting means fastened to said mask shell, said first mounting means having an opening that surrounds said holes; and a first filter liner for filtering the air passing through said holes, said first filter liner having an adhesive strip around its periphery, and said adhesive strip being used to fasten said first filter liner to said face mask by being adhesively fastened to said first mounting mean , said first filter liner covering all said holes to thereby filter all inhaled air passing through said holes.

11. The invention in accordance with claim 10 further comprising a one-way exhaust valve mounted through the wall of said mask shell in a position that it is not covered by said first filter liner, said valve for venting exhaled air.

12. The invention in accordance with claim 11 further comprising one or more elastic straps attached to the edge of said mask shell and being used to hold the face mask over the nose and mouth of a mask wearer by passing around the head of the wearer.

13. The invention in accordance with claim 12 wherein said foam mask shell is made of polymeric cross-linked, closed-cell foam that has physical properties that provide shape retention to said mask shell and elasticity that enables the edge of said mask shell to conform and seal to the face of a wearer around their nose and mouth.

14. The invention in accordance with claim 10 wherein said first mounting means is fastened to the exterior of said mask and further comprising:

a second mounting means fastened to the interior of said mask shell, said second mounting means having an opening that surrounds said holes, and a second filter liner for filtering the air passing through said holes, said second filter liner having an adhesive strip around its periphery, and said adhesive strip being used to fasten said second filter liner to said face mask by being adhesively fastened to said second mounting means, said second filter liner covering all said holes to thereby filter all inhaled air passing through said holes.

15. The invention in accordance with claim 14 further comprising a one-way exhaust valve mounted through the wall of said mask shell in a position that is not covered by said first or said second filter liner, said valve for venting exhaled air.

16. The invention in accordance with claim 15 further comprising one or more elastic straps attached to the edge of said mask shell and being used to hold the face mask over the nose and mouth of a mask wearer by passing around the head of the wearer.

17. The invention is accordance with claim 10 wherein said air impermeable foam material from which said face mask is fabricated is a laminate structure.

18. A face mask for filtering air comprising:

a mask shell formed of a flexible, air impermeable foam material, said mask shell having one or more holes through the central portion thereof, and a filter cartridge mounted to cover said hole(s) to thereby filter all inhaled air passing through said holds.

19. The invention in accordance with claim 18 wherein during formation of said mask shell a recess is formed at the bottom of which are said holes and said filter cartridge is mounted by being force fit into said recess which expands due to the flexibility of said foam material from which said mask shell is formed, and the contact between the sides of said recess and said filter cartridge is an air tight seal.

20. The invention in accordance with claim 18 wherein during formation of said mask shel a recess is formed at the bottom of which are said holes and said filter cartridge is sealed in said recess so that all breathed air must pass through said filter cartridge.

21. The invention in accordance with claim 18 further comprising:

a first mounting means fastened in each of said holes, said first mounting means having an opening therethrough in which one of said filter cartridges mounts.

22. The invention in accordance with claim 18 further comprising a one-way exhaust valve mounted through the wall of said mask for venting exhaled air.

23. The invention in accordance with claim 18 further comprising one or more elastic straps attached to the edge of said mask shell and being used to hold the face mask over the nose and mouth of a mask wearer by passing around the head of the wearer.

24. The invention in accordance with claim 18 wherein said foam mask shell is made of polymeric cross-linked, closed-cell foam that has physical properties that provide shape retention to said mask shell and elasticity that enables the edge of said mask shell to conform and seal to the face of a wearer around their nose and mouth.

25. A face mask for filtering air and comprising:

a mask shell fabricated from a piece of fibrous material by being formed into a generally cup-shaped shell to fit over the mouth and nose of a wearer of the mask to filter inhaled air passing through the material, and a filter liner fastened against said mask shell but not covering the edge of said mask and generally conforming to the contour of said mask shell, said mask shell being impermeable to the flow of air in the area of said mask shell that is in contact with the wearer's face and that is not covered by said filter liner.

26. The invention in accordance with claim 25 further comprising a one-way exhaust valve mounted through the wall of said mask shell, said valve for venting exhaled air from the inside of the mask.