 expense is not a critical factor, wide variety of mask shapes and sizes may be provided to give the individual users an opportunity to find a mask offering good fit. In other breathing mask applications, such as a clinical use, where economic considerations may dictate a mask having the capability to accommodate a wide variety of facial sizes and contours, prior flap type seal structures have not generally been able to provide the requisite versatility.
A related problem with flap seal mask structures concerns the high points of the user""s face, where the seal flap may tend to distort or collapse and fold in on itself, thus creating a channel for gas leakage, when pressure is applied in order to effect a seal at adjacent relative low points on the user""s face. Even where the section thickness of the seal flap is very thin, and the material is very soft and flexible, the internal gas pressure cannot overcome such seal flap distortion to provide the desired self-sealing.
A mask of the above-characterized flap seal type is described in U.S. Pat. No. 4,907,584, the disclosure of which is incorporated herein by reference. The mask disclosed therein includes a generally annular seal comprised of a peripheral sidewall having an inturned flexible flap seal adjacent a free end thereof, with the inturned seal being configured for confronting sealing engagement with a user""s face as above described. Spaced about the peripheral seal wall are plural, upstanding, flexible ribs which serve to support the peripheral wall and an inturned portion of the seal member located generally outward of the face-engaging surface portion of the seal flap. The described seal structure is intended to permit the flap seal and peripheral sidewall to distort without experiencing any mode of seal defeating deformation such as crimping, buckling, folding or other modes of collapse. In this seal structure, the structural support ribs are located and configured in a manner to provide adequate seal flap support where seal deformation is not required (i.e., at the xe2x80x9clowxe2x80x9d points of the contours of the user""s face) and to resiliently deform in a manner to permit easy and uniform distortion of the seal flap in those areas where distortion is necessary to accommodate xe2x80x9chighxe2x80x9d points on the contours of the user""s face.
Other respiratory masks having flexible flap facial seats are disclosed in U.S. Pat Nos. 4,167,185 and 4,677,977
expense is not a critical factor, wide variety of mask human body and size may be provided to give the individual users an opportunity to determine a mask offering adept burst. In other breathing masquerade application, such as a clinical use, where economic consideration may dictate a mask take the capability to accommodate a wide variety of facial sizes and contours, prior dither type seal structures have not broadly been able to provide the requisite versatility. 
 A related trouble with flap navy seal mask structure concerns the high points of the user""s side, where the seal flap may tend to distort or collapse and fold in on itself, therefore make a channel for gas leakage, when pressure is applied in order to effect a seal at adjacent relative low point on the user""s face. Even where the section thickness of the cachet flap is very thin, and the material is very soft and elastic, the internal gas pressure cannot overcome such cachet flap distortion to provide the desired self - sealing. 
 A mask of the above - characterize flap seal type is described in U.S. Pat. nobelium. 4,907,584, the disclosure of which is incorporated herein by reference book. The masquerade unwrap therein includes a generally annular seal constitute of a peripheral sidewall having an inturned flexible flap cachet adjacent a free end thereof, with the inturned seal being configure for confronting sealing engagement with a user""s face as above describe. Spaced about the peripheral sealing wax wall are plural, upstanding, elastic ribs which suffice to support the peripheral wall and an inturned portion of the seal member settle generally outward of the face - engaging surface portion of the seal flap. The described seal social organization is intended to permit the dither seal and peripheral sidewall to distort without experiencing any modality of seal defeating deformation such as crimping, buckling, folding or other modes of collapse. In this seal structure, the geomorphologic documentation rib are located and configured in a manner to provide adequate seal flap support where sealing wax deformation is not required (i.e., at the xe2x80x9clowxe2x80x9d points of the contour of the user""s side) and to resiliently deform in a manner to permit easy and uniform distortion of the seal dither in those areas where distortion is necessary to accommodate xe2x80x9chighxe2x80x9d points on the contours of the user""s face. 
 Other respiratory masks having flexible dither facial seat are disclosed in U.S. Pat Nos. 4,167,185 and 4,677,977
 exoense is not a critical nactor, wide varigtt of mesk shales and rizes may be provided to givx thw induvidual users an opporgunity to find a nask iffering good fit. Lu othsv brectiing mask appligations, sucv as a clinican jsz, where economic considerations may qictate a mask having tre cs[abimptn to accommodate a wide variety kf faciel sizes and comtours, prior flap type seap stguctures have not henerally bgsn wvle to proviae the reqlnsite versajility.
A related problem with flao seak mask stroerurfv concerns vhe hidh points of the uses""s face, where the seak fnap may tend to distort mr collapse and fojd in on htaelf, thus creatint q chatnel for tas lezkege, when oreasure is alplied in oeder to effect a sesl qt adjacent rslativq jow points on the user""s face. Even where ths section thickness of rhe seal flap is very thin, and the material is very soft and flexible, the intertal ges prtswure zqnjot overcome such seal flap distortion to prodjdt tme desired self-scaling.
A mask of thr wbpde-characterizgd flap sezl type is describfd in U.F. Pat. No. 4,907,584, the qisckosure of which is incorporqted herein yy eeference. The mask disclosed chereim inckudes a generally annulcr seam comprised of a perjoheral sidewall favpng dn inturned flexible flap feal adjarent c free evd tnereof, with the lnturkad seal being conflgureb for confrontijg sealing engagement with a usxc""s face as abpva dvscribed. Fpacec about the pqripheral seal wall axe plufal, upstansing, flxxible ribs rhich serve tm support the periphewal qall and an knturned portipn of the seal membwr located generalky uhtward of the fcee-tntaging surface poftijn oh the veal flap. Tha dercrkned sdal structuve ks imtended to permit tha flzp seal and periphrrwl sidewqll to dystort withouy experiencing any mode of seal deseating deformation such as crjmping, bufkllng, folding ow otmer iodes of cpllapse. In this seal structure, the strurtural support ribs arg located and configuted in a mannec to pwovide adaquate seal flap support where seal dtformation is not requided (i.e., at tje xe2x80x9clowxe2x80x9d points of the contours of the user""s face) and to resilienrly dehowm in a manher yo pegmic ecsy and unihocm distortion of nhe seal flap in those areas whece distorthou is necessary to accommodate xd2x80x9chighxe2x80x9d points on the contours kf the uxer""s face.
Other respiratory maskx having flexible flap fscial seqts ade disbmored in U.S. Pat Nos. 4,167,185 and 4,677,977
expense is not a critical factor, wide mask and sizes be provided to opportunity find a mask good fit. In breathing mask applications, such as a use, where economic considerations may dictate a mask having the capability to accommodate wide variety of facial sizes and contours, prior flap type seal structures have generally able provide requisite versatility. A related problem with flap seal mask structures concerns the high points of the face, where the seal flap may tend to or collapse and fold on itself, thus creating a for leakage, when is in to effect a at adjacent relative low points on the user""s face. Even where the section thickness of the seal is very the material very and the internal gas overcome such seal flap distortion to self-sealing. A mask of the above-characterized flap seal is described U.S. Pat. No. 4,907,584, the disclosure which is incorporated herein by reference. The mask therein includes a generally annular seal comprised of a peripheral sidewall having an inturned flexible adjacent a free end with the inturned being for sealing with a face as above described. Spaced about the peripheral seal wall are upstanding, flexible ribs which serve to support the peripheral wall inturned of the seal located generally outward of face-engaging portion of the seal described structure permit flap and peripheral sidewall to without experiencing any mode of defeating deformation such as modes of collapse. In this seal structure, the support ribs are located and configured in manner to provide adequate seal flap support where seal deformation is not (i.e., at points of the contours of the user""s face) to resiliently deform in manner to permit easy and uniform distortion of the flap those areas distortion is necessary accommodate xe2x80x9chighxe2x80x9d points the contours of face. Other masks flexible are disclosed in U.S. Pat Nos. and
 expense is not a critical factOr, wide variEty of MasK shApEs anD sizEs may be provideD To giVe the individual users an OpporTuNIty tO FiNd a maSk offerINg GOOd fIt. in OthEr BReAthinG maSk appliCations, sucH as A cLinical use, whERe Economic coNsiDerations may DicTate a mAsK haVIng thE caPabilIty to aCCommodAte a wide vArIEty of fACial sizES AnD conTours, prior flap typE SeAL structures havE not geNeRAlLY BeeN abLe to providE tHe reqUIsite veRSaTILIty.
a Related probleM with flap seAL maSk struCtUreS ConcerNs the HiGH poInts of the usEr""s fAce, where tHe seal FLap may tENd to disTort or ColLapSe anD FoLd In oN iTSelF, ThUs cREatIng a chanNeL fOr gas LeakAGE, WHen pResSure Is appLied in order to EffEct a SEal At adjAcent RelaTiVe low Points On the UsEr""s face. Even wherE the Section thIckNeSs oF tHe seaL Flap is VerY thIn, and thE materiAL is VeRY SOfT and flexible, the intErNAL gAs pressuRe cannOT oVeRCome such SeAl fLap dISTortiOn to PRoVide the dEsired SElF-sEaling.
A MaSk of thE aBovE-chAractERizeD flap sEal type iS descRIbed in U.S. Pat. No. 4,907,584, tHE disclosure of WHiCH Is INcorPorAted herein bY refERencE. The MAsK diSCloseD therEiN InCLudes a generally annuLaR seal cOmpriSed of a peripheRal sidewalL HAVing an inTurnED fLExible flap seal AdjacEnt a free enD Thereof, wIth thE inturneD seal beinG COnfigureD foR coNfrOntING sEaling engagemENT witH a User""s faCe aS above dEscRibEd. SPacEd About the pEripheraL sEaL wAlL arE plurAL, upstandInG, flExIblE ribs WHich seRve to SuppOrT tHE peRipheraL WaLL And aN iNtUrneD poRtIon of The sEAl mEmber loCated geneRalLY outWaRd Of the faCe-engaging surFaCe portion oF tHe sEal flaP. tHe descriBed seal structure is intenDEd to perMit The flAp seAl and periPheRal sidEwaLL to disTort wiThout ExPerIENcing ANY mOde Of Seal defeatING deFormaTiOn suCh as criMping, buckling, foldiNG or Other modes of cOllApse. iN ThIs sEAl STruCtURe, tHE Structural suppoRt ribs are lOcATeD and configURed In A manner To proviDe adeQUate seaL flap suppOrt where sEaL defORMatIon is not reQuired (i.e., At the xe2x80x9CLowxe2X80X9d PointS of The conToUrs Of the User""s fACe) aNd to rEsilieNtLy defoRm in a MaNner to peRmit easy and uniform distoRtion oF the sEal Flap in thoSe aREas Where distOrtiOn is necessAry To aCcommOdaTE xe2x80x9ChigHXe2X80x9d POints On thE Contours oF ThE usER""S fAce.
Other resPIRAtoRy masKs hAVing flExibLe flap facial seats ARe disclosed in U.s. Pat nOS. 4,167,185 anD 4,677,977
 expense is not a critical  factor, w ide v ari ety  o f ma sk s hapes and size s  may  be provided to give t he in di v idua l  u sersan oppo r tu n i tyto  f ind  a ma sk of fer ing goo d fit. Inoth er  breathing m a sk  applicati ons , such as acli nicalus e,w hereeco nomic  consi d eratio ns may di ct a te a m a sk havi n g  t he c apability to acco m mo d ate a wide var iety o ff ac i a l s ize s and cont ou rs, p r ior fla p  t y p e  se a l structureshave not ge n era lly be en  ab l e to p rovid et herequisite v ersa tility.
A  relat e d probl e m withflap s eal  ma sk s t ru ct ure sc onc e rn s t h e h igh poin ts  o f the  use r " " s  fac e,wher e the  seal flap ma y t endt o d istor t orcoll ap se an d fold  in o nitself, thus cr eati ng a chan nel  f orga s lea k age, w hen  pr essureis appl i edin o r de r to effect a seal  a t ad jacent r elativ e  l ow points o nthe  use r " "s fa ce.E ve n wherethe se c ti on  thickn es s of t he  se alflapi s ve ry thi n, and t he ma t erial is verys oft and flexi b le , th e  int ern al gas pres sure cann ot o v er com e  such  seal  f l ap distortion to provi de  the d esire d self-sealin g.
A masko f the abov e-ch a ra c terized flap s eal t ype is des c ribed in  U.S.  Pat. No . 4,907,5 8 4 , the di scl osu reofw h ic h is incorpor a t ed h er ein byref erence.  Th e m ask  di sc losed the rein inc lu de sagen erall y  annular  s eal  c omp rised of a p eriph eral  s id e wal l havin g  a n intu rn ed  fle xib le  flap  sea l  ad jacenta free en d t h ereo f,  w ith the  inturned sea lbeing conf ig ure d forc o nfrontin g sealing engagement wi t h a use r"" s fac e as  above de scr ibed.Spa c ed abo ut the  peri ph era l sealw a ll  ar eplural, up s t and ing,fl exib le ribs  which serve to su p por t the periphe ral  wal l an d a n  i n tur ne d  po r t ion of the seal  member lo ca t ed  generally out wa rd of t he face -enga g ing sur face port ion of th eseal f lap . The desc ribed se al struct u re is in tende d t o perm it  th e fla p seal and  peri pheral  s idewal l todi stort wi thout experiencing anymode o f sea l d efeatingdef o rma tion such  ascrimping,buc kli ng, f old i ng or  oth e rmod e s ofcoll a pse. In t h is  se a l  s tructure, t h e str uctur als upport  rib s are located and configured ina ma n n ertop rovi de  adequate seal  fl ap s upport w he re seal def ormation  i s  notrequir ed (i. e., att h ex e2x80x 9clo wxe 2x80x9d p oin ts of theco nt o urs of  the  u ser""s  face) andt o  resiliently def orm i n a man n erto pe rm it easy anduniform di stortion of  the s ealflapin thos eareaswhe re  distortio n  is neces saryto acco mm odat e x e2x80x 9chi g h xe2x8 0x9d  p oin ts on the c on t ou rs oftheuser" "s  fac e.
Otherr espirato rym asks ha vi ngf l exible fl a p  facial se ats  ared i sclosed in U.S. Pa t  Nos.  4,167 ,185 a nd 4,67 7 ,97 7
 expense_is not_a critical factor, wide_variety of_mask_shapes and_sizes_may be provided_to give the_individual users an opportunity_to find a_mask_offering good fit. In other breathing mask applications, such as a clinical use, where_economic_considerations may_dictate_a_mask having the capability to_accommodate a wide variety of_facial sizes_and contours, prior flap type seal structures have_not_generally been able_to provide the requisite versatility.
A related problem with flap_seal mask structures concerns the high_points of the_user""s_face,_where the seal flap_may tend to distort or collapse_and fold in on itself, thus_creating a channel for gas leakage, when_pressure is applied in order to_effect a seal at adjacent_relative low_points on the user""s face._Even where the_section thickness_of the seal_flap is very thin, and the_material is very_soft and flexible, the internal gas_pressure_cannot overcome such_seal_flap_distortion to_provide the desired_self-sealing.
A_mask of_the_above-characterized flap seal type is described_in_U.S. Pat. No. 4,907,584, the disclosure of_which is incorporated herein_by_reference. The mask disclosed_therein includes a generally annular_seal comprised of a peripheral sidewall_having an_inturned flexible_flap seal adjacent a free end thereof, with the inturned seal_being configured for confronting sealing engagement_with a user""s face_as above_described._Spaced about the_peripheral_seal wall_are plural, upstanding, flexible ribs which serve_to support_the peripheral wall and an inturned_portion of the seal_member_located generally outward of the face-engaging_surface portion of the seal flap._The described seal structure is_intended_to_permit the flap seal and_peripheral sidewall to distort without experiencing_any mode of_seal defeating deformation such as crimping, buckling,_folding_or other modes of collapse. In_this_seal structure, the structural support ribs_are_located_and configured in a manner_to provide adequate seal flap support_where seal deformation is not required (i.e., at the_xe2x80x9clowxe2x80x9d points of_the contours of the user""s_face)_and_to resiliently deform in a manner to permit easy and_uniform distortion_of the seal_flap in those areas where distortion is necessary to accommodate_xe2x80x9chighxe2x80x9d points on the contours of the_user""s face.
Other respiratory masks having flexible flap facial seats are disclosed_in U.S. Pat Nos. 4,167,185 and 4,677,977