attention is first directed to fig1 and 2 a of the drawings illustrating the protective breathing hood generally designated 10 which in fig1 is in a flat position and in fig2 a is illustrated donned over an individual &# 39 ; s head 11 . the protective hood 10 comprises a hood 12 made of a stretchable fire resistant material , e . g . silicon rubber which may resist heat up to about 400 °- 600 ° c . and which is an extremely elastic material whilst being impermeable to gases and biologic material . the hood 12 has an opening 14 through which the head of an individual is introduced and a neck sealing portion 16 which as illustrated in the figures is plaited at 18 so as to allow good sealing engagement about the individual &# 39 ; s neck ( see fig2 a ) whilst not choking the individual or causing an uncomfortable feeling . the arrangement is such that when the hood is donned over a user &# 39 ; s head the sealing portion 16 sealingly engages about the user &# 39 ; s neck preventing ingress of obnoxious gases or biologic material therethrough . as can further be illustrated in fig1 and 2 a , the protective hood 10 further comprises a visor 20 which in the present example is a uniform translucent portion extending over both eyes made of a material which is also a heat resistant material . however , it is to be appreciated that the visor 20 may be formed in other shapes and forms , e . g . two eye pieces extending opposite the eye locations of the hood or , the arrangement may be such that the entire hood 12 may be transparent and accordingly no particular visor is provided . the protective hood 10 is formed with two respiratory units 26 disposed offset with respect to the nose / mouth location of the individual , indicated in the figures at 30 . the intersecting dashed lined marked f in fig1 indicate a fold line about which the hood may be folded and may be preserved in a sealed , pocket - sized package other folding patterns are possible as well . one other important character of the invention noticed in fig1 a and 2 b is the deformation of the hood at the nose / mouth location giving rise to forming an internal chamber c ( see fig2 b ) between the nose / mouth location 30 and the individual &# 39 ; s face , the purpose of which will become apparent hereinafter . however , it is noticed that the chamber c renders respiratory units 26 to be is in flow communication with the nose and mouth of the individual . turning now to fig3 a and 3b , there are illustrated a pair of respiratory units 26 articulated to one another by a supporting member 38 . the particular structure of the respiratory units 26 is disclosed hereinafter in detail with reference to fig4 - 6 . in the particular embodiment ( fig3 a and 3b ), deforming member 38 is made of a rigid plastic material formed with two ring - like portions 40 clampingly secured to each of a pair of respiratory units 26 , with an intermediate bridging portion consisting of two members 42 a and 42 b , though other constructions are possible as well and which at the assembled position , while donned over an individual &# 39 ; s head , extend at the nose / mouth location to thereby deform the hood 12 giving rise to forming chamber c ( see also dashed lines in fig1 and 2 a ). bridging portions 42 a and 42 b are interconnected to the circular portions by integral hinges at 44 . for the sake of clarity , the supporting member 38 is illustrated also in fig1 and 2 a , by dashed lines . whilst in fig1 to 3 the deforming member 38 is in the form of a rigid member extending between the two respiratory units , other arrangements for deformation of the mask may be employed as well , for the sake of forming a chamber c . for example , the respective nose / mouth portion 30 may be provided with deforming ribs . such ribs ( not shown ) may be integrally molded during the process of molding the hood , e . g . made of silicon , or may be attached thereto by other means , e . g . adhering or welding ( e . g . heat or sonic , etc ) the ribs may be made of a rigid material other than that of the hood or may constitute an integral part thereof . further attention is now directed to fig4 - 6 for understanding the assembly and mode of operation of the respiratory units 26 . in the present embodiment , each of the respiratory units comprises a multi - receptacle member 48 facing the inside of the protective hood and a cover member 50 facing the outside of the hood . multi - receptacle member 48 is formed with a plurality of receptacles 54 which in the present example have the shape of a honeycomb and a hexagonal section , though other shapes are possible as well , e . g . circular , etc . each of the receptacles 54 has an outlet opening 56 which is covered by a fine grid 58 , so as to prevent outflow of the activated charcoal particles recovered within the receptacles 54 . cover member 50 is similarly formed with a plurality of inlet openings , each such openings fitted with a fine grid 66 also serving to prevent outflow of the activated charcoal particles 59 ( seen in fig6 ) received within the receptacles 54 . co - axially received within each respiratory unit 26 there is a one - way exhaling valve 70 which is in the form of a mushroom - type membrane valve with a stem member 72 snapingly received within a central opening formed at the multi - receptacle member 48 . a plurality of exhaling apertures 74 are formed in the multi - receptacle member 48 to facilitate flow of exhaled gases from the chamber c of the protective hood to the surrounding environment , after deforming the mushroom - type valve and then via the outlet apertures 78 formed in the cover member 50 . typically , the respiratory units 26 are also fitted with a biologic - material barrier in the form of filtering paper 84 ( which for the sake of convenience and practicality is in the form of a single sheet though other arrangements are available as well , e . g . individual pieces received in each of the receptacles 54 ). whilst in the present example , the receptacles 54 are stuffed with particulated activated charcoal 59 ( fig6 ), it is to be appreciated other forms of gas treating media is possible as well , e . g . uniform or layers of impregnated charcoal cloth or other charcoal carrying media , e . g . particulated charcoal embedded within non woven material , e . g . in the form of pellets , etc . as can best be seen in fig4 and 6 , the size of inlet opening 62 and outlet openings 56 is smaller than the actual size of the receptacles 54 . this arrangement ensures that inflow through the respiratory units is continuously treated and obnoxious material is absorbed by the activated charcoal particles 59 obviating the need for thick filtration material on the one hand and on the other hand , providing extended effective use / filtration . as can further be seen in fig4 and 6 , the receptacle member 92 is formed with an annular rim 90 and the cover member 50 is formed with a corresponding annular rim 94 , the latter provided with gripping teeth 96 at a outward facing portion thereof . the arrangement is such that at the assembled position the circular portion 40 of the deforming member 38 is clampingly received between rim portions 92 and 94 . a retaining ring 100 has a plurality of annular teeth 102 corresponding with teeth 96 of the rim 94 and is adapted for clampingly receiving therebetween respective portions of the hood 12 ( fig6 ) wherein the ring 100 is snapingly secured over the periphery of the cover member 50 . reverting now to the issue of chamber c formed in the protective hood in accordance with the present invention , as illustrated , for example in fig1 and 2 , it is to be appreciated that such a chamber is advantageous as it minimizes the feeling of suffocation in case such a protective hood is stretched over an individual &# 39 ; s breathing organisms ( nose and mouth ). furthermore , the construction of a chamber ( at times referred to as a breathing chamber , mixing chamber , speaking chamber , and other similar terms ) enables an individual wearing the protective hood to speak clearly . this is not facilitated in case of a hood which is stretched over the individual &# 39 ; s mouth . still another advantage of the chamber resides in that the individual may breathe freely without having to direct the exhaled gases through an particular outlet opening in which case speech becomes complicated or impossible .
a protective breathing hood comprising a hood made of a stretchable fire resistant material and which is also impermeable to gases and biologic material . the hood is sized and shaped for placing over a head of a user in an airtight manner with an opening of the hood scalingly engaging a neck portion of the user . at least a visor portion of the hood is transparent and a pair of respiratory units are disposed offset with respect to the nose location . each respiratory unit comprises a housing formed with an inhalation flow path accommodating activated exhalation flow path fitted with a one way exhaling valve , wherein at a donned position of the hood a chamber is formed at a mouth / nose location thereof .