Patent Publication Number: US-11654310-B2

Title: Respirator

Description:
RELATED APPLICATIONS 
     This application is a continuation application of International Patent Application Serial No. PCT/US2021/022592, filed on Mar. 16, 2021, which claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 62/990,279, filed on Mar. 16, 2020, and U.S. Provisional Patent Application Ser. No. 63/198,865, filed on Nov. 18, 2020, the disclosure of each of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates generally to respirators with separate channels for inhaled air and exhaled air. 
     BACKGROUND 
     Today, three types of respirators are used as Respiratory Protective Devices (RPD) for respiratory organs: (1) a first type has an exhalation valve, and replaceable filtering elements (cartridges) that are installed in a housing made of plastic and silicone (reusable); (2) a second type has an exhalation valve and a filter housing made of filter material; and (3) a third type has a filter housing made of filter material without an exhalation valve, and inhalation and exhalation are filtered by the respirator housing. 
     There are a few disadvantages associated with these respirators. One disadvantage is that the under-mask space is closed, which forms the volumetric dead zone during breathing. This leads to an increased content of carbon dioxide in the inhaled air, increase in air humidity and temperature. As a result, increased fatigue, sweating, irritation of the facial skin. Another disadvantage is that a shared breathing air volume is created for the nose and mouth, which makes the use of respirators uncomfortable even in a state of calm. The coronavirus pandemic has exacerbated the disadvantages of these respirators. Accordingly, there is a need for a new type of respirators. 
     SUMMARY 
     In one aspect, the present disclosure provides a respirator, comprising: (i) a mouth aperture configured to be disposed about a mouth of a user; (ii) a nasal aperture configured to be disposed about a pair of nostrils of the user when the mouth aperture is disposed about the mouth of the user; (iii) a nasal fluid channel extending between the nasal aperture and a nasal inlet; (iv) an oral fluid channel extending from the mouth aperture to an oral outlet, such that fluidic communication between the nasal fluid channel and the oral fluid channel is prevented; (v) a nasal inhalation valve disposed within the nasal fluid channel between the nasal aperture and the nasal inlet and configured to transition between (a) an open configuration in which the nasal aperture is in fluidic communication with the nasal inlet to allow the user to inhale from the nasal inlet to the pair of nostrils, and (b) a closed configuration in which fluidic communication between the nasal aperture and the nasal inlet is prevented, the nasal inhalation valve configured to assume its open configuration in response to nasal inhalation by the user, and its closed configuration in response to nasal exhalation by the user; (vi) a nasal exhalation valve configured to transition between (a) an open configuration in which the nasal fluid channel is in fluidic communication with the oral fluid channel or an environment to allow the user to exhale from the pair of nostrils to the oral fluid channel or the environment, and (b) a closed configuration in which air is prevented from passing through the nasal exhalation valve, the nasal exhalation valve configured to assume its open configuration in response to nasal exhalation by the user, and its closed configuration in response to nasal inhalation by the user; and (vii) an oral exhalation valve disposed within the oral fluid channel between the mouth aperture and the oral outlet and configured to transition between (a) an open configuration in which the mouth aperture is in fluidic communication with the oral outlet, and (b) a closed configuration in which fluidic communication between the mouth aperture and the oral outlet is prevented. 
     In another aspect, the present disclosure provides (i) a mouth aperture configured to be disposed about a mouth of a user; (ii) a nasal aperture configured to be disposed about a pair of nostrils of the user when the mouth aperture is disposed about the mouth of the user; (iii) a nasal fluid reservoir configured to be in fluidic communication with the pair of nostrils; (iv) an oral fluid reservoir configured to be in fluidic communication with the mouth of the user; (v) a nasal inhalation valve disposed between the nasal fluid reservoir and an inhalation channel that is in fluidic communication with an inhalation inlet, and configured to transition between (a) an open configuration in which the nasal fluid reservoir is in fluidic communication with the inhalation channel, and (b) a closed configuration in which fluidic communication between the nasal fluid reservoir and the inhalation channel is prevented; (vi) a nasal exhalation valve disposed between the nasal fluid reservoir and an exhalation channel that is in fluidic communication with an exhalation outlet, and configured to transition between (a) an open configuration in which the nasal fluid reservoir is in fluidic communication with the exhalation channel, and (b) a closed configuration in which fluidic communication between the nasal fluid reservoir and the exhalation channel is prevented; (vii) an oral inhalation valve disposed between the oral fluid reservoir and the inhalation channel, and configured to transition between (a) an open configuration in which the oral fluid reservoir is in fluidic communication with the inhalation channel, and (b) a closed configuration in which fluidic communication between the oral fluid reservoir and the inhalation channel is prevented; and (viii) an oral exhalation valve disposed between the oral fluid reservoir and the exhalation channel, and configured to transition between (a) an open configuration in which the oral fluid reservoir is in fluidic communication with the exhalation channel, and (b) a closed configuration in which fluidic communication between the oral fluid reservoir and the exhalation channel is prevented. The nasal inhalation valve is configured to assume (a) its open configuration in response to nasal inhalation by the user, and (b) its closed configuration in response to nasal exhalation by the user. The nasal exhalation valve is configured to assume (a) its open configuration in response to nasal exhalation by the user, and (b) its closed configuration in response to nasal inhalation by the user. The oral inhalation valve is configured to assume (a) its open configuration in response to oral inhalation by the user, and (b) its closed configuration in response to oral inhalation by the user. The oral exhalation valve is configured to assume (a) its open configuration in response to oral exhalation by the user, and (b) its closed configuration in response to oral inhalation by the user. 
     In yet another aspect, the present disclosure provides a respirator comprising: (i) a mouth aperture configured to be disposed about a mouth of a user; (ii) a nasal aperture configured to be disposed about a pair of nostrils of the user when the mouth aperture is disposed about the mouth of the user; (iii) a nasal fluid channel extending between the nasal aperture and a nasal inlet; and (iv) an inhalation filter disposed between the nasal inlet and the nostrils, the inhalation filter being configured to include a liquid medium. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG.  1    is a schematic diagram illustrating a respirator  100 , in accordance with an embodiment. 
         FIG.  2 A  is a side view of a respirator  200 , in accordance with an embodiment of  FIG.  1   . 
         FIG.  2 B  is a top-down view of the respirator  200  of  FIG.  2 A . 
         FIG.  2 C  is a front view of the respirator  200  of  FIG.  2 A . 
         FIG.  2 D  is a rear view of the respirator  200  of  FIG.  2 A . 
         FIG.  2 E  is a cross-sectional view of the respirator  200  of  FIG.  2 A . 
         FIG.  2 F  is an exploded view of the respirator  200  of  FIG.  2 A . 
         FIG.  3    is a schematic diagram illustrating a respirator  300 , in accordance with an embodiment. 
         FIG.  4 A  is a front view of a respirator  400 , in accordance with an embodiment of  FIG.  3   . 
         FIG.  4 B  is a front view of the respirator  400  with an inhalation valve  442  disposed within the septum  440 . 
         FIG.  4 C  is a side view of the respirator  400 . 
         FIG.  4 D  is a rear view of the respirator  400 . 
         FIG.  4 E  is an explosive view of the respirator  400 . 
         FIG.  4 F  is a close-up view of the obturator shown in  FIG.  4 E . 
         FIGS.  4 G- 4 I  show open-type frame mechanisms for securing the respirator  400  on a user&#39;s head. 
         FIGS.  4 J- 4 K  depict a mechanism for opening the frame of the respirator  400 . 
         FIGS.  5 A- 5 C  are illustrations showing three different view of a respirator  500 , in accordance with an embodiment of  FIG.  3   .  FIG.  5 A  shows a front view,  FIG.  5 B  a side view, and  FIG.  5 C  a rear view. The respirator  500  can be secured to a user&#39;s head and face using any known mechanism, including but not limited to straps, mounts, and ear loops. The respirator  500  can be secured to a user&#39;s head and face using the head mounts described in  FIG.  2 A  or  FIG.  4 D . 
         FIG.  5 D  is an illustration of the respirator  500  where the outer wall is made transparent. 
         FIG.  5 E  is an illustration showing the air flow when inhaling through the nose. 
         FIG.  5 F  is an illustration showing the air flow when exhaling through the mouth. 
         FIG.  5 G  is a cross-sectional view of a filter device with liquid media  590   a  and  590   b , the right arrow shows the filtration pathway for inhalation, and the left arrow shows the filtration pathway for exhalation. 
         FIG.  5 H  is an illustration showing a filter device with a roll filter. 
         FIG.  5 I  is an illustration of a roll filter. 
         FIGS.  6 A- 6 C  are illustrations showing three different view of an industrial respirator  600 , in accordance with an embodiment.  FIG.  6 A  shows a front view,  FIG.  6 B  a side view, and  FIG.  6 C  a rear view. 
         FIG.  6 D  is an illustration of the respirator  600  where the outer wall is made transparent. 
         FIG.  6 E  is an illustration of a filter with liquid medium  690 . 
         FIG.  6 F  is a cross-sectional view of the filter shown in  FIG.  6 A . The arrow shows the filtration pathway for inhalation. 
         FIG.  6 G  is an illustration showing an inhalation filter with a filter cartridge. 
         FIG.  7 A  is an illustration of a respirator having roll filters as inhalation filters. 
         FIGS.  7 B and  7 C  are an illustration of a roll filter. The arrows show the directions of air flow. 
         FIG.  8 A  is an illustration of a respirator having droplet separators as inhalation filters. 
         FIG.  8 B  is an illustration of a droplet separator suitable for removing large aerosol particles that have high adhesion (e.g., a saliva particle or a sputum particle). 
         FIG.  8 C  is an illustration of the air flow in the droplet separator of  FIG.  8 B . The arrows indicate the air flow direction. 
         FIG.  9 A  is a front view of a respirator  900 , in accordance with an embodiment of  FIG.  1   . 
         FIG.  9 B  is a rear view of the respirator  900 . 
         FIG.  10    is a perspective view of a respirator  1000 , in accordance with an embodiment of  FIG.  1   . 
         FIG.  11    is a schematic diagram illustrating a respirator  1100 , in accordance with an embodiment. 
         FIG.  12 A  is a front view of a respirator  1200 , in accordance with an embodiment of  FIG.  11     
         FIG.  12 B  is a rear view of the respirator  1200 . 
         FIGS.  13 A- 13 B  are schematic diagrams showing an umbrella one-way valve, where the valve is closed ( FIG.  13 A ) and open ( FIG.  13 B ). 
         FIG.  14 A  is a front view of a hydro-respirator  1400 . 
         FIG.  14 B  shows an obturator  1428  of the hydro-respirator  1400 . 
         FIGS.  15 A- 15 B  show a perspective view ( FIG.  15 A ) and a top-down view ( FIG.  15 B ) of a hydro-respirator  1500 .  FIG.  15 B  shows an obturator  1528  of the hydro-respirator  1500 . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure describes embodiments of respirators with separate channels for inhaled air and exhaled air, thereby providing a user with better breathing experience than existing respirators. As used herein, the term “channel” means three-dimensional space enclosed by a closed surface. A channel can have a regular or irregular shape. The term “channel” does not mean that it must be elongated. In some implementations, a channel is elongated. In some implementations, a channel is not elongated. For example, a channel can be a chamber in some implementations. 
     As shown in  FIG.  1   , the respirator  100  comprises: (a) a nasal aperture  120 , (b) a mouth aperture  130 , (c) a nasal fluid channel  150 , (d) a nasal inlet  152 , (e) a nasal inhalation valve  154 , (f) a nasal exhalation valve  156 , (g) an oral fluid channel  160 , (h) an oral outlet  162 , and (i) an oral exhalation valve  164 . 
     The nasal aperture  120  is configured to be disposed about a pair of nostrils of a user. The mouth aperture  130  is configured to be disposed about a mouth of the user when the nasal aperture  120  is disposed about the nostrils of the user. The respirator  100  can further comprise an obturator (not shown) disposed on the circumferences of the nasal aperture  120  and the mouth aperture  130 . The obturator is configured to form a seal around the nostrils and the mouth so that fluidic communication between the nasal fluid channel  150  and the oral fluid channel  160  is prevented unless the nasal exhalation valve  156  is in an open configuration. 
     The nasal fluid channel  150  extends between the nasal aperture  120  and the nasal inlet  152 . The oral fluid channel  160  extends between the mouth aperture  130  and the oral outlet  162 . The nasal inhalation valve  154  is disposed within the nasal fluid channel  150  between the nasal aperture  120  and the nasal inlet  152 . The nasal inhalation valve  154  is configured to transition between an open configuration and a closed configuration. In the open configuration, the nasal aperture  120  is in fluidic communication with the nasal inlet  152 , thereby allowing the user to inhale from the nasal inlet  152  to the pair of nostrils. In the closed configuration, the fluidic communication between the nasal aperture  120  and the nasal inlet  152  is prevented. The nasal inhalation valve  154  is configured to assume its open configuration in response to nasal inhalation by the user, and its closed configuration in response to nasal exhalation by the user. 
     The respirator  100  can optionally comprises an inhalation filter  182  disposed between the nasal inlet  152  and the nasal inhalation valve  154 . In some implementations, the inhalation filter  182  is disposed within the nasal fluid channel  150 . In some implementations, the inhalation filter  182  is disposed at a distal end of the nasal fluid channel  150 . The inhalation filter  182  is configured to filter the air entering the nasal inlet  152  (e.g., to remove pathogens, particulates, or otherwise anything undesirable to the user). 
     The nasal exhalation valve  156  is configured to transition between an open configuration and a closed configuration. In the open configuration, the nasal fluid channel  150  is in fluidic communication with the oral fluid channel  160  or an environment, thereby allowing the user to exhale from the pair of nostrils to the oral fluid channel  160  or the environment, or inhale with the mouth from the nasal fluid channel  150  (and by extension from the nasal fluid channel  150 ) to the oral fluid channel  160 . In the closed configuration, air is prevented from passing through the nasal exhalation valve  156 . For example, in some implementations, in the closed configuration, fluidic communication between the nasal fluid channel  150  and the oral fluid channel  160  is prevented. In some implementations, the nasal exhalation valve  156  permits nasal exhalation to combine with mouth exhalation. 
     The oral exhalation valve  164  is disposed within the oral fluid channel  160  between the mouth aperture  130  and the oral outlet  162 . The oral exhalation valve  164  is s configured to transition between an open configuration and a closed configuration. In the open configuration, the mouth aperture  130  is in fluidic communication with the oral outlet  162 . In the closed configuration, the fluidic communication between the mouth aperture  130  and the oral outlet  162  is prevented. 
     The respirator  100  can optionally comprise an exhalation filter  184  disposed between the oral outlet  162  and the oral exhalation valve  164 . In some implementations, the exhalation filter  184  is disposed within the oral fluid channel  160 . In some implementations, the exhalation filter  184  is disposed at a distal end of the oral fluid channel  160 . The exhalation filter  182  is configured to filter the air exiting the oral exhalation valve  164  (e.g., to remove pathogens, particulates, or otherwise anything undesirable to the environment around the user). 
     The respirator  100  can optionally comprise a septum  140  disposed between the nasal fluid channel  150  and the oral fluid channel  160 . The septum  140  is configured to prevent fluidic communication between the nasal fluid channel  150  and the oral fluid channel  160 . In some embodiments, the septum  140  can include an obturator configured to form a seal on the face of the user to prevent fluidic communication between the nasal fluid channel  150  and the oral fluid channel  160 . The nasal exhalation valve  156  can be disposed within the septum  140 . While  FIG.  1    only shows one optional septum, some implementations of the respirator  100  can have two, three, four, or more septa. 
     In some implementations, the respirator  100  further comprises a housing having an inner layer and an outer layer, and a volume defined therebetween. The housing defines the nasal inlet  152  and the oral outlet  162 . The inner layer defines the nasal aperture  120  and the mouth aperture  130 . The volume includes the nasal fluid channel  150  and the oral fluid channel  160 , and the septum  140  is disposed between the inner layer and the outer layer to divide the volume into the nasal fluid channel  150  and the oral fluid channel  160 . 
     In some implementations, the nasal fluid channel  150  and the oral fluid channel  160  are not divided from a common volume by a septum. Rather, each of the nasal fluid channel  150  and the oral fluid channel  160  has its independent housing defining a volume. In such implementations, the nasal aperture  120  and the mouth aperture are defined by an aperture housing  110 ; and the nasal fluid channel  150  and the oral fluid channel  160  can be connected to each other by the aperture housing  110 , where the nasal exhalation valve  156  is disposed within the aperture housing  110  and provides fluidic communication between the nasal fluid channel  150  and the oral fluid channel  160 . Further, in some such implementations, the nasal inhalation valve  154 , the nasal exhalation valve  156 , and the oral exhalation valve  164  are disposed within the aperture housing  110 , as shown optionally in broken lines in  FIG.  1   . Alternatively, in some implementations, there is no fluidic communication between the nasal fluid channel  150  and the oral fluid channel  160 , as the nasal exhalation valve  156  is configured to permit the user to exhale into the environment, and the respirator  100  can further comprise an oral exhalation valve configured to permit the user to exhale into the environment. 
     Due to its configuration, the respirator  100  permits nasal and/or oral inhalation, and nasal and/or mouth exhalation. While  FIG.  1    only shows one nasal inhalation valve  154 , the respirator  100  can further include one additional nasal inhalation valve, so that there is one nasal inhalation valve on each side of the nose. Similarly, while  FIG.  1    only shows one oral exhalation valve  164 , the respirator  100  can further include one additional oral exhalation valve, so that there is one oral exhalation valve on each side of the mouth. 
     In some implementations, the respirator  100  can further comprise a head mount configured to be disposed about a parietal part of the user&#39;s head and thus to provide further mechanical stability for the respirator  100 . The head mount can optionally be adjustable to accommodate the different head sizes of users. 
     In some implementations, the respirator  100  can further comprise a coupling member (e.g., a strap) configured disposed about the cheeks of a user. In some implementations, the coupling member can optionally be adjustable to accommodate the different head sizes of users. 
     The inhalation filter  182  and exhalation filter  184  can operate accordingly a variety of filtering mechanisms. In some implementations, the inhalation filter  182  or the exhalation filter  184  is configured to include a liquid medium. In some implementations, the liquid medium is water or an antiseptic solution. Filtration can be achieved through a multi-stage process using various fluid properties. For example, large particles (e.g., dust, mucus, or saliva) can be removed by creating a vortex air that flows in the volume of the liquid, while finer filtering can be achieved through bubbling process when the air stream passes through a layer of unstable foam. In some implementations, the liquid medium can be replaced with a granular substance or a granular mixture, for example, activated carbon. In some embodiments, the inhalation filter  182  or the exhalation filter  184  is configured to include a roll filter. In some implementations, the inhalation filter  152  or the exhalation filter  184  is configured to include a mesh. The inhalation filter  182  or the exhalation filter  184  can be positioned horizontally or vertically, or somewhere therebetween. 
     Generally, the operating principle of the respirator  100  can be described as follows. When inhaling through the nose, under the influence of negative relative pressure, the nasal inhalation valve  154  opens and air enters from the nasal fluid channel  150  into the nasal aperture  120 . In some implementations, the air previously passes through an inhalation filter from the space external to the respirator  100 . When the user exhales through the nose, under the influence of positive relative pressure, the nasal inhalation valve  154  is closed, and the nasal exhalation valve  156  opens, and air enters the oral fluid channel  160 . Under the influence of positive relative pressure, the oral exhalation valve  164  opens, and the exhaled air exits the respirator  100  through the oral outlet  162  and optionally after passing through an exhalation filter. 
     The outer layer of the housing is transparent, opaque, or a combination thereof (e.g., a portion of the outer layer facing the user&#39;s mouth may be transparent to aid in communication between the user and others, while other portions of the outer layer may be less transparent or opaque). The outer layer of the housing can be made of any suitable material, e.g., plastic, silicone, or the like. 
     The housing can be made, partially or whole, from breathable (filtering) material. In some implementations, the respirator  100  is for single use. For example, the whole housing can be made of a spunbond meltblown spunbond (SMS) material. 
     In some implementations, the respirator  100  is reusable. For example, a portion of the housing (e.g., the obturator) can be made of silicone and/or thermoplastic elastomer; another portion of the housing can be made of acrylonitrile butadiene styrene (ABS) plastic, or polyethylene terephthalate (PET) plastic; and valves can be made of silicone or rubber. 
     In some implementations, only the obturator and the coupling member (e.g., a strap) are configured to be in contact with the skin when the user wears the respirator  100 . In some implementations where additional components are in contact with the skin, these additional components can be made of an air permeable material. 
     Regardless of whether the respirator  100  is for single use or reusable, in some implementations separate components are manufactured separately and then assembled into the respirator  100 . 
       FIGS.  2 A- 2 E  show different views of a respirator  200  that comprises the features of the respirator  100  shown in  FIG.  1   , according to an embodiment. As shown in  FIG.  2 A , the respirator  200  has a front-facing portion  270 , a rear-facing portion  280 , and a head mount  202  (in some embodiments a respirator may not include the head mount). The front-facing portion  270  is coupled to the rear-facing portion  280 . The front-facing portion  270  is configured to cover the lower half of a user&#39;s face so that a nasal aperture is disposed about the nostrils of the user and a mouth aperture is disposed about the mouth of the user. The rear-facing portion  280  is configured to be disposed about the occipital part of the user&#39;s head. The head mount  202  is coupled to the rear-facing portion  280 . The head mount  202  is configured to be disposed about a parietal part of the user&#39;s head and thus to provide further mechanical stability for the respirator  200 . 
     As shown in  FIG.  2 C , the front-facing portion  270  of the respirator  200  comprises a nasal aperture  220 , a mouth aperture  230 , a septum  240 , a nasal fluid channel  250 , an oral fluid channel  260 , two nasal inhalation valves  254 , a nasal exhalation valve  256 , two oral exhalation valves  264 , an obturator  266 , a coupling member  204 , and a rear-facing portion  280 . 
     Without reiterating the features discussed above and for the sake of brevity, the positions and functions of the nasal aperture  220 , the mouth aperture  230 , the septum  240 , the nasal fluid channel  250 , the oral fluid channel  260 , the nasal inhalation valves  254 , the nasal exhalation valve  256 , and the oral exhalation valves  264  are the same or substantially the same as those described for the respective counterparts in the respirator  100  of  FIG.  1   . 
     The obturator  266  is disposed on the circumferences of the nasal aperture  220  and the mouth aperture  230 . The obturator  266  is configured to form a seal around the nostrils and the mouth so that fluidic communication between the nasal fluid channel  250  and the oral fluid channel  260  is prevented unless the nasal exhalation valve  256  is in an open configuration. 
     The coupling member  204  is configured to connect the front-facing portion and the rear-facing portion  280 . In some embodiments, the coupling member  204  is flexible. The coupling member  204  can optionally be adjustable to accommodate the different head sizes of users 
     The details of the rear-facing portion  280  can be seen in  FIG.  2 D . Specifically, the rear-facing portion  280  comprises a housing, an inhalation filter  282 , and an exhalation filter  284 . The housing is configured to enclose the inhalation filter  282  and the exhalation filter  284 . The inhalation filter  282  is configured to filter the inhaled air, while the exhalation filter  284  is configured to filter the exhaled air. 
     As shown in  FIG.  2 D , each of the septum  240 , the nasal fluid channel  250 , and the oral fluid channel  260  extends from the front-facing portion  270  to the rear-facing portion  280 . The nasal inlet  252  is shown as a series of holes. The oral outlet  262  is shown as a series of holes. 
       FIG.  2 E  is a cross-sectional view of the respirator  200 . 
       FIG.  2 F  is an explosive view of the respirator  200 . The front-facing portion  270  is coupled to a filter block  286  through the coupling member  204 . A size adjuster  206  disposed on a distal end of the filter block  286  is configured to adjust the distance that the coupling member  204  can slide in so as to adjust the fitting of the front-facing portion  270  on a user&#39;s face. 
     The filter block  286  is configured to provide: (a) a volume for airtight installation of the filters  282  and  284 ; and (b) an airtight fluidic communication with the front-facing portion  270 . When the filter block  286  is connected to the front-facing portion  270 , a closed system is created to permit airtight flow of inhaled filtered air and exhaled filtered air for the nasal fluid channel and oral fluid channel respectively. 
     The inhalation filter  282  is disposed between an inhalation seal cover  281  and the filter block  286 . The exhalation filter  284  is disposed between an exhalation seal cover  283  and the filter block  286 . The inhalation seal cover  281  is configured to: (a) achieve an airtight press over the contour of the inhalation filter  282  to the filter block  286 ; and (b) provide a protective casing for the inhalation filter  282 . The exhalation seal cover  283  is configured to: (a) achieve an airtight press over the contour of the exhalation filter  284  to the filter block  286 ; and (b) provide a protective casing for the exhalation filter  284 . 
     The respirator  200  further comprises an attachment member  208  and an occipital support  209 . When a user wears the respirator  200 , the attachment member  208  is disposed on the crown of the user&#39;s head, and the occipital support  209  is disposed on the occipital part of the user&#39;s head. Both the attachment member  208  and the occipital support  209  are configured to provide mechanical stability when the user is wearing the respirator  200 . 
       FIGS.  9 A- 9 B  show front and rear views of a respirator  900  that comprises the features of the respirator  100  shown in  FIG.  1   , according to an embodiment. As shown in  FIGS.  9 A- 9 B , the respirator  900  comprises an aperture housing  910 , a nasal aperture  920 , a mouth aperture  930 , a nasal fluid channel  950 , two nasal inhalation valves  954 , two nasal exhalation valves  956 , an oral fluid channel  960 , two oral exhalation valves  964 , an inhalation filter  982 , and an exhalation filter  984 . Note that the inhalation filter  982  and the exhalation filter  984  are installed in filter blocks. 
     The aperture housing  910  defines the nasal aperture  920  and the mouth aperture  930 . Each of the nasal fluid channel  950  and the oral fluid channel  960  has its own housing defining a volume. The nasal fluid channel  950  is connected to the oral fluid channel  960  by the aperture housing  910 . 
     The nasal inhalation valves  954  are disposed about the nose such that there is one nasal inhalation valve  954  on each side of the nose. The nasal exhalation valves  956  are disposed below the nostrils such that there is one nasal exhalation valve  956  below each nostril. The oral exhalation valves  964  is disposed about the mouth such that there is one oral exhalation valve  964  on each side of the mouth. 
       FIG.  10    show a perspective view of a respirator  1000  that comprises the features of the respirator  100  shown in  FIG.  1   , according to an embodiment. The respirator  1000  comprises a nasal aperture  1020 , a mouth aperture  1030 , a nasal fluid channel  1050 , a nasal exhalation valve having a nasal portion  1056   a  and an oral portion  1056   b , an oral fluid channel  1060 , a nasal inhalation valve  1054 , and an oral exhalation valve  1064 , a nasal obturator  1066   a , and a mouth obturator  1066   b.    
     The nasal portion  1056   a  and oral portion  1056   b  of the nasal exhalation valve have the same flow direction. They are connected together to form the nasal exhalation valve that permits the air to be exhaled from the nostrils to the oral fluid channel  1060 . The nasal portion  1056   a  and oral portion  1056   b  can be disconnected. When they are disconnected, the nasal portion  1056   a  is configured to permit the user to exhale into the surrounding environment. For example, if the user decides to ingest a substance (e.g., food, drink, or a pill), the user can disconnect the nasal portion  1056   a  and oral portion  1056   b  by lowering the aperture housing for the mouth to ingest the substance, while being partially protected by inhalation through the nose and exhalation into the surrounding environment. 
     The nasal obturator  1066   a  is disposed on the circumferences of the nasal aperture  1020 . The nasal obturator  1066   a  is configured to form a seal around the nostrils. The mouth obturator  1066   b  is disposed on the circumferences of the mouth aperture  1030 . The mouth obturator  1066   b  is configured to form a seal around the mouth. 
       FIG.  3    shows an embodiment of a respirator  300  where inhalation can be done through the nose or mouth, each through a separate valve, and exhalation can also be done through the nose or mouth, each through a separate value. The inhaled air shares a common pathway, and the exhaled air shares a common pathway. 
     The respirator  300  comprises: (a) a housing having an inner layer and an outer layer defining volume  310  therebetween, (b) a nasal aperture  320 , (c) a nasal inhalation valve  322 , (d) a nasal fluid reservoir  324 , (e) a nasal exhalation valve  326 , (f) a mouth aperture  330 , (g) an oral inhalation valve  332 , (h) an oral fluid reservoir  334 , (i) an oral exhalation valve  336 , (j) a septum  340 , (k) an inhalation channel  350 , (l) an inhalation inlet  352 , (m) an exhalation channel  360 , and (n) an exhalation outlet  362 . 
     The nasal aperture  320  is defined by the inner layer and configured to be disposed about a pair of nostrils of a user. The mouth aperture  330  is defined by the inner layer and configured to be disposed about a mouth of the user when the nasal aperture  320  is disposed about the nostrils of the user. 
     The respirator  300  can further comprise an obturator (not shown) disposed on the circumferences of the nasal aperture  120  and the mouth aperture  130 . The obturator is configured to form a seal around the nostrils and the mouth so that fluidic communication between the inhalation channel  350  and the exhalation channel  360  is prevented unless at least one of the inhalation or exhalation valves ( 322 ,  326 ,  332 ,  336 ) is in an open configuration. 
     The septum  340  is disposed between the inner layer and the outer layer and divides the volume  310  into the nasal fluid reservoir  324  and the oral fluid reservoir  334 . The septum  340  is configured to prevent fluidic communication between the nasal fluid reservoir  324  and the oral fluid reservoir  334 . The nasal fluid reservoir  324  is configured to be in fluidic communication with the pair of nostrils. The oral fluid reservoir  334  is configured to be in fluidic communication with the mouth of the user. In some embodiments, the septum  340  can include an obturator configured to form a seal on the face of the user to prevent fluidic communication between the nasal fluid reservoir  324  and the mouth fluid reservoir  334 . 
     The nasal inhalation valve  322  is disposed between the nasal fluid reservoir  324  and the inhalation channel  350  that is in fluidic communication with the inhalation inlet  352 . The nasal inhalation valve  322  is configured to transition between an open configuration and a closed configuration. In the open configuration, the nasal fluid reservoir  324  is in fluidic communication with the inhalation channel  350 , and by extension, the inhalation inlet  352 . In the closed configuration, fluidic communication between the nasal fluid reservoir  324  and the inhalation channel  350 , and by extension, the inhalation inlet  352 , is prevented. The nasal inhalation valve  322  is configured to assume its open configuration in response to nasal inhalation by the user, and its closed configuration in response to nasal exhalation by the user, as described in more detail below. 
     The nasal exhalation valve  326  is disposed between the nasal fluid reservoir  324  and the exhalation channel  360  that is in fluidic communication with the exhalation outlet  362 . The nasal exhalation valve  326  is configured to transition between an open configuration and a closed configuration. In the open configuration, the nasal fluid reservoir  324  is in fluidic communication with the exhalation channel  360 , and by extension the exhalation outlet  362 . In the closed configuration, fluidic communication between the nasal fluid reservoir  324  and the exhalation channel  360 , and by extension, the exhalation outlet  362 , is prevented. The nasal exhalation valve  326  is configured to assume its open configuration in response to nasal exhalation by the user, and its closed configuration in response to nasal inhalation by the user. 
     The oral inhalation valve  332  is disposed between the oral fluid reservoir  334  and the inhalation channel  350  that is in fluidic communication with the inhalation inlet  352 . The oral inhalation valve  332  is configured to transition between an open configuration and a closed configuration. In the open configuration, the oral fluid reservoir  334  is in fluidic communication with the inhalation channel  350 , and by extension, the inhalation inlet  352 . In the closed configuration, fluidic communication between the oral fluid reservoir  334  and the inhalation channel  350 , and by extension, the inhalation inlet  352 , is prevented. The oral inhalation valve  332  is configured to assume its open configuration in response to oral inhalation by the user, and its closed configuration in response to oral exhalation by the user. 
     The oral exhalation valve  336  is disposed between the oral fluid reservoir  334  and the exhalation channel  360  that is in fluidic communication with the exhalation outlet  362 . The oral exhalation valve  336  is configured to transition between an open configuration and a closed configuration. In the open configuration, the oral fluid reservoir  334  is in fluidic communication with the exhalation channel  360 , and by extension, the exhalation outlet  362 . In the closed configuration, fluidic communication between the oral fluid reservoir  334  and the exhalation channel  360 , and by extension, the exhalation outlet  362 , is prevented. The oral exhalation valve  336  is configured to assume its open configuration in response to oral exhalation by the user, and its closed configuration in response to oral inhalation by the user. 
     In some implementations, the respirator  300  further comprises an inhalation filter  370  disposed between (1) the inhalation inlet  352  and (2) the nasal inhalation valve  322  and the oral inhalation valve  332 . In some implementations, the inhalation filter  370  is disposed within the inhalation channel  350 . In some implementations, the inhalation filter  370  is disposed at a distal end of the inhalation channel  350 . The inhalation filter  370  is configured to filter the air entering the inhalation inlet  352  (e.g., to remove pathogens, particulates, or otherwise anything undesirable to the user). 
     The respirator  300  can optionally comprise an exhalation filter  374  disposed between (1) the exhalation outlet  362  and (2) the nasal exhalation valve  326  and the oral exhalation valve  336 . In some implementations, the exhalation filter  374  is disposed within the exhalation channel  360 . In some implementations, the exhalation filter  374  is disposed at a distal end of the exhalation channel  360 . The exhalation filter  374  is configured to filter the air exiting the nasal exhalation valve  326  or the oral exhalation valve  336  (e.g., to remove pathogens, particulates, or otherwise anything undesirable to the environment around the user). 
     The inhalation filter  370  and exhalation filter  374  can operate accordingly a variety of filtering mechanisms. In some implementations, the inhalation filter  370  or the exhalation filter  374  is configured to include a liquid medium. In some implementations, the liquid medium is water or an antiseptic solution. Filtration can be achieved through a multi-stage process using various fluid properties. For example, large particles (e.g., dust, mucus, or saliva) can be removed by creating a vortex air that flows in the volume of the liquid, while finer filtering can be achieved through bubbling process when the air stream passes through a layer of unstable foam. In some implementations, the liquid medium can be replaced with a granular substance or a granular mixture, for example, activated carbon. In some implementations, the inhalation filter  370  or the exhalation filter  374  is configured to include a roll filter. In some implementations, the inhalation filter  370  or the exhalation filter  374  is configured to include a mesh. The inhalation filter  370  or the exhalation filter  374  can be positioned horizontally or vertically, or somewhere therebetween. 
     In some implementations, the respirator  300  further comprises a septal valve  342  disposed within the septum and configured to transition between an open configuration and a closed configuration. In the open configuration, the nasal fluid reservoir  324  is in fluidic communication with the oral fluid reservoir  334 . In the closed configuration, fluidic communication between the nasal fluid reservoir  324  and the oral fluid reservoir  334  is prevented. The septal valve  342  is configured to assume its open configuration in response to oral inhalation or nasal exhalation by the user, and its closed configuration in response to oral exhalation or nasal inhalation by the user. 
     While  FIG.  3    only shows one septum, some implementations of the respirator  300  can have two, three, four, or more septa. While  FIG.  3    only shows one optional septal valve, some implementations of the respirator  300  can have two, three, four, or more septal valves. While  FIG.  3    only shows one nasal inhalation valve, some implementations of the respirator  300  can have two, three, four, or more nasal inhalation valves. While  FIG.  3    only shows one nasal exhalation valve, some implementations of the respirator  300  can have two, three, four, or more nasal exhalation valves. While  FIG.  3    only shows one oral inhalation valve, some implementations of the respirator  300  can have two, three, four, or more oral inhalation valves. While  FIG.  3    only shows one oral exhalation valve, some implementations of the respirator  300  can have two, three, four, or more oral exhalation valves. 
     Generally, the operating principle of the respirator  300  can be described as follows. When inhaling through the nose or mouth, under the influence of negative relative pressure, the nasal inhalation valve  322  or the oral inhalation valve  332  opens, and air enters from the inhalation channel  350  into the nasal fluid reservoir  324  or the oral fluid reservoir  334 . The air previously passes through an optional inhalation filter (not shown) from the space external to the respirator  300 . When the user exhales through the nose or mouth, under the influence of positive relative pressure, the nasal inhalation valve  322  or the oral inhalation valve  332  is closed, and the nasal exhalation valve  326  or the oral exhalation valve  336  opens, and air enters the exhalation channel  360 . The exhaled air exits the respirator  300  through the outlet  362  and optionally after passing through an exhalation filter (not shown). 
     The outer layer of the housing is transparent, opaque, or a combination thereof (e.g., a portion of the outer layer facing the user&#39;s mouth may be transparent to aid in communication between the user and others, while other portions of the outer layer may be less transparent or opaque). The outer layer of the housing can be made of any suitable material, e.g., plastic, silicone, or the like. 
     The housing can be made, partially or whole, from breathable (filtering) material. In some implementations, the respirator  300  is for single use. For example, the whole housing can be made of a spunbond meltblown spunbond (SMS) material. 
     In some implementations, the respirator  300  is reusable. For example, a portion of the housing (e.g., the obturator) can be made of silicone and/or thermoplastic elastomer; another portion of the housing can be made of ABS plastic, or polyethylene terephthalate (PET) plastic; and valves can be made of silicone or rubber. 
     In some implementations, only the obturator and the coupling member (e.g., a strap) are configured to be in contact with the skin when the user wears the respirator  300 . In some implementations where additional components are in contact with the skin, these additional components can be made of an air permeable material. 
     Regardless of whether the respirator  300  is for single use or reusable, in some implementations separate components are manufactured separately and then assembled into the respirator  300 . 
     The respirator  400  of  FIG.  4 A  has features consistent with the schematic diagram of  FIG.  3   , according to an embodiment. The respirator  400  comprises a nasal aperture  420 , a nasal fluid reservoir  424 , a nasal inhalation valve  422 , a nasal exhalation valve  426 , an obturator  428 , a mouth aperture  430 , an oral fluid reservoir  434 , an oral inhalation valve  432 , an oral exhalation valve  436 , a septum  440 , an inhalation channel  450 , an exhalation channel  460 , an inhalation filter  470 , an inspiratory filter unit  472 , an exhalation filter  474 , and an expiratory filter unit  476 . 
     Without reiterating the features discussed above and for the sake of brevity, the positions and functions of the nasal aperture  420 , the nasal fluid reservoir  424 , the nasal inhalation valve  422 , the nasal exhalation valve  426 , the mouth aperture  430 , the oral fluid reservoir  434 , the oral inhalation valve  432 , the oral exhalation valve  436 , the septum  440 , the inhalation channel  450 , and the exhalation channel  460  are the same or substantially the same as those described for the respective counterparts in the respirator  300  of  FIG.  3   . 
     The obturator  428  is disposed on the circumferences of the nasal aperture  420  and the mouth aperture. The obturator  428  is configured to form a seal around nostrils and the mouth so that fluidic communication between the nasal fluid reservoir and the oral fluid reservoir is prevented. 
     The inhalation filter  470  is disposed between the inhalation inlet and the nasal inhalation valve  422 . The inhalation filter  470  is configured to filter the inhaled air. The exhalation filter  474  is disposed between the nasal exhalation valve  426  and the exhalation outlet. The exhalation filter is configured to filter the exhaled air. 
     The inhalation inlet  452  is shown as a series of holes in  FIG.  4 D . The exhalation outlet  462  is shown as a series of holes in  FIG.  4 D . 
       FIG.  4 E  is an explosive view of the respirator  400 . In this view, the physical relationships between the inhalation filter  470  and the inspiratory filter unit  472 , and between the exhalation filter  474  and the expiratory filter unit  476  are more easily understood. The inhalation filter  470  is disposed between the inhalation seal cover  481  and the inspiratory filter unit  472 . The exhalation filter  474  is disposed between the exhalation seal cover  483  and the expiratory filter unit  476 . 
     The inspiratory filter unit  472  is configured to provide: (a) a volume for airtight installation of the inhalation filter  470 ; and (b) an airtight fluidic communication with the inhalation channel  450 . When the inspiratory filter unit  472  is connected to the inhalation channel, a closed system is created to permit airtight flow of inhaled filtered air. 
     The inhalation seal cover  481  is configured to: (a) achieve an airtight press over the contour of the inhalation filter  470  to the inspiratory filter unit  472 ; and (b) provide a protective casing for the inhalation filter  470 . 
     The expiratory filter unit  476  is configured to provide: (a) a volume for airtight installation of the exhalation filter  474 ; and (b) an airtight fluidic communication with the exhalation channel  460 . When the expiratory filter unit  476  is connected to the exhalation channel, a closed system is created to permit airtight flow of exhaled filtered air. 
     The exhalation seal cover  483  is configured to: (a) achieve an airtight press over the contour of the exhalation filter  474  to the expiratory filter unit  476 ; and (b) provide a protective casing for the exhalation filter  474 . 
     In  FIG.  4 E , the first coupling member  404 , the second coupling member  406 , the occipital support  409 , the aperture housing  410 , and the obturator  428  are also shown. The first coupling member  404  is configured to lock the inspiratory filter unit  472  and the expiratory filter unit  476  together. The second coupling member  406  is configured to couple: (a) the inhalation channel  450  with the inspiratory filter unit  472 ; and (b) the exhalation channel  460  with the expiratory filter unit  476 . The occipital support  409  is configured to be disposed on the occipital part of a user&#39;s head and provide mechanical stability when the user wears the respirator  400 . 
       FIG.  4 F  is a close-up view of the obturator  428  shown in  FIG.  4 E . The obturator  428  is configured to: (a) be disposed on the circumferences of the nasal aperture and the mouth aperture; and (b) form a seal around the nostrils and the mouth. 
       FIG.  4 B  additionally comprises a second oral inhalation valve  442  as compared to the respirator in  FIG.  4 A . The second oral inhalation valve  442  is disposed within the septum  440 . The second oral inhalation valve  442  is configured to transition between an open configuration and a closed configuration. In the open configuration, the oral fluid reservoir  434  is in fluidic communication with the nasal fluid reservoir  424 , and by extension, the inhalation inlet (not shown). In the closed configuration, fluidic communication between the oral fluid reservoir  434  and the nasal fluid reservoir  424 , and by extension, the inhalation inlet, is prevented. The second oral inhalation valve  442  is configured to assume its open configuration in response to oral inhalation by the user, and its closed configuration in response to oral exhalation by the user. The second oral inhalation valve  442  can thus increase the breathing capacity by at least twice. In some implementations, the opening pressure required for opening the second oral inhalation valve  442  is greater than that for the oral inhalation valve  432 , thereby restricting the use of the second oral inhalation valve  442  to more intense oral inhalation, e.g., during exercising. 
     The respirator  400  can be secured to the head of a user through an open-type frame mechanism. For the convenience of putting on a respirator, each filter can be made of two or more parts, so that it can be opened. In this case, the attachment for the crown of the head can be made in the form of a ring or half ring or any appropriate form complimentary to user&#39;s head anatomy. The parts of each filter can be closed using any suitable mechanism, such as, for example, magnets, zip ties, glue, mechanical locks, snap fits, interference fits, hook and loop fasteners, etc. At the same time, each half of each filter has its own inhalation and exhalation filter (in the case of horizontal division of the internal cavity of the respirator frame).  FIGS.  4 G- 4 I  show the open-type frame mechanisms. As shown in  FIGS.  4 I- 4 K , a coupling member (e.g., a button, a screw, etc.)  404  can be used to lock the inspiratory filter unit and the expiratory filter unit together. By removing the coupling member, the inspiratory filter unit and expiratory filter unit are de-coupled from each other, thereby permitting the user to remove the respirator. 
       FIGS.  5 A- 5 F  show a respirator  500  that does not have a rear-facing portion. The respirator  500  of has features consistent with the schematic diagram of  FIG.  3   , according to an embodiment. As shown in  FIG.  5 D , the respirator  500  comprises a nasal fluid reservoir  524 , a nasal inhalation valve  522 , a nasal exhalation valve  526 , an obturator  528 , an oral fluid reservoir  534 , an oral inhalation valve  532 , an oral exhalation valve  536 , a septum  540 , an inhalation channel  550 , an exhalation channel  560 , an inhalation filter  570 , and an exhalation filter  574 . 
       FIG.  5 G  shows an inhalation filter  570  and an exhalation filter  574  each having a liquid medium  590   a  and  590   b  respectively for filtration purposes. The inhalation filter  570  and exhalation filter  574  comprise structures that force the air to pass through the liquid medium  590   a  and  590   b  when the air passes from the inlet to the outlet. The inhalation filter  570  is shown on the right-hand side of  FIG.  5 G , where the arrow illustrates the filtration pathway as the air enters and exits the inhalation filter  570 . The liquid medium  590   a  is disposed on the bottom of the inhalation filter  570 . As the inhaled air flows through the liquid medium  590   a , the inhaled air gets filtered. The exhalation filter  574  is shown on the left-hand side of  FIG.  5 G , wherein the arrow illustrates the filtration pathway as the air enters and exists the exhalation filter  574 . The liquid medium  590   b  is disposed on the bottom of the exhalation filter  574 . As the exhaled air flows through the liquid medium  590   b , the exhaled air gets filtered. 
     If the filter housing is made of transparent materials, it will be possible to visually determine the degree of contamination of the liquid medium and promptly make a decision if washing and refueling with a fresh liquid medium are needed. In addition, a colorographic or numeric chart can be used to determine the rate of contamination of the filter and the remaining time of use, based on the transparency of the liquid. 
     In some embodiments, instead of a liquid medium, a roll filter can be used for either the inhalation filter, the exhalation filter, or both. For example,  FIG.  5 H  is an illustration showing an inhalation filter  570  and an exhalation filter  574  each having a roll filter disposed therein. In the roll filter shown in  FIGS.  5 H and  5 I , the air flow moves across the filter material. The filter material can be arranged horizontally rather than vertically, in some implementations. The respirator case itself can have multiple walls, forming a cavity in which the filter material is located. 
     In some embodiments, instead of a liquid medium, a granular substance or a granular mixture, for example activated carbon, can be used as a filter material. 
     There are conditions, when while using RPD&#39;s there&#39;s no need to filter the exhaled air, for example, when performing construction. At the same time, the filter capacity (i.e., the ability to accumulate and retain pollutants) should be significantly higher than that of a civilian hydro-respirator. As shown in the industrial respirator  600  of  FIGS.  6 A- 6 D , the inhaled air, through the nose and/or mouth, passes through an inhalation filter, and the exhaled air leaves freely, without filtration. The respirator  600  comprises the features of the respirator  100  shown in  FIG.  1    except that the respirator  600  does not have an exhalation filter, according to an embodiment. 
     As shown in  FIG.  6 D , the respirator  600  comprises a nasal aperture  620 , a mouth aperture  630 , a septum  640 , a nasal fluid channel  650 , two nasal inhalation valves  654 , a nasal exhalation valve  656 , an oral exhalation valves  664 , an obturator  666 , a first coupling member  604   a , a second coupling member  604   b , and an inhalation filter  682 . 
     The first coupling member  604   a  connects the nasal fluid channel  650  with the second coupling member  604   b . The second coupling member  604   b  is connected to the inhalation filter  682 . In some embodiments, the first coupling member  604   a  is a joint or a connector. In some embodiments, the second coupling member  604   b  is a pipe. 
       FIGS.  6 E- 6 F  show the inhalation filter  682 . Notably, the inlet for inhaled air is disposed at a predetermined angle relative to the ground. The liquid medium  690  is disposed on the bottom of the inhalation filter  682 . As the inhaled air flows through the liquid medium  690 , the inhaled air gets filtered. 
     When inhaling through the nose, under the action of negative relative pressure, the nasal inhalation valves  654  open, and air enters the inhalation filter  682 , gets filtered, then enters the second coupling member  604   b , the first coupling member  604   a , the nasal fluid channel  650 , and the nasal aperture  620 . When inhaling through the mouth, in addition to the above process, the nasal exhalation valve  656  opens, and filtered air entered the mouth aperture  630 . 
     When exhaling through the nose, under the influence of positive relative pressure, the nasal inhalation valves  654  close, and the nasal exhalation valve  656  and the oral exhalation valve  664  open. The exhaled air enters the mouth aperture  630  and exits through the oral exhalation valve  664 . When exhaling through the mouth, under the influence of positive relative pressure, the nasal exhalation valve  656  closes and the oral exhalation valve  664  opens, thereby permitting the exhaled air to exit through the oral exhalation valve  664 . 
     After each use or a plurality of uses, the respirator  600  can be disassembled, washed, and filled with a clean liquid medium for future use. 
     In some embodiments, instead of a liquid medium, a granular substance or a granular mixture, for example activated carbon, can be used as a filter material. 
     In some embodiments, for example, at sub-zero ambient temperatures, standard filter cartridges can be used in the half mask of the same design.  FIG.  6 G  shows an example of an industrial respirator with a filter cartridge, which is a standard filter made of corrugated material. 
     In order to reduce the cost of operation and user convenience, filter elements for a respirator can be assembled from rolled filter materials to form a roll filter. In some embodiments, the filter can be a roll filter, where a filter element is rolled into a three-dimensional structure. For example, the filter elements can be located horizontally, and not vertically, as shown in  FIGS.  7 A- 7 C . In  FIG.  7 A , one inhalation filter is disposed on each side of the nose. As shown in  FIGS.  7 B- 7 C , in contrast to standard filter use, the air does not move across the filtering material, but moves along the filtering material. In this way, the filtration properties (e.g., thinness of filtration and dust capacity) are improved. 
     In some embodiments, when it is necessary to filter large aerosol particles that have high adhesion (e.g., particles of saliva, sputum), droplet separators can be used to clean the air by separation, as shown in  FIGS.  8 A- 8 C . As shown in  FIG.  8 C , the droplet separator comprises blocking structures on the air-flow pathway which permit the removal of large aerosol particles. 
     In some embodiments, the filter is configured to include a mesh. The mesh includes a plurality of cells. As the inhaled or exhaled air flows though the cells, particles are removed from the inhaled or exhaled air. The size of the cells determines the size of particles that the filter can remove from the air. 
     In some embodiments, the filter (e.g., an inhalation filter or an exhalation filter) can be a corrugated filter. The area of filter material is variable, e.g., from about one cm 2  to about 10, 000 cm 2 . The filter material can be of any type, depending of the filtration goal. For example, in order to filter aerosol particles, micro-fiberglass material or meltblown material can be used. To filter hazardous gases, activated charcoal can be used. To filter humid exhaled air we a Teflon-based membrane can be used, which can maintain its filtration properties when it is moisturized or wet. 
       FIG.  11    shows an embodiment of a respirator  1100  where inhalation can be done through the nose or mouth, each through a separate valve, and exhalation can also be done through the nose or mouth, each through a separate valve. 
     The respirator  1100  comprises: (a) a nasal aperture  1120 , (b) a nasal inhalation valve  1122 , (c) a nasal fluid reservoir  1124 , (d) a nasal exhalation valve  1126 , (e) a mouth aperture  1130 , (f) an oral inhalation valve  1132 , (g) an oral fluid reservoir  1134 , (h) an oral exhalation valve  1136 , (i) a nasal inhalation channel  1150   a  and an oral inhalation channel  1150   b , (j) a nasal inhalation inlet  1152   a  and an oral inhalation inlet  1152   b , (k) a nasal exhalation channel  1160   a  and an oral exhalation channel  1160   b , and (l) a nasal exhalation outlet  1162   a  and an oral exhalation outlet  1162   b.    
     The nasal aperture  1120  is configured to be disposed about a pair of nostrils of a user. The mouth aperture  1130  is configured to be disposed about a mouth of the user when the nasal aperture  1120  is disposed about the nostrils of the user. The respirator  1100  can further comprise an obturator (not shown) disposed on the circumferences of the nasal aperture  1120  and the mouth aperture  1130 . The obturator is configured to form a seal around the nostrils and the mouth so that fluidic communication between (a) the nasal fluid reservoir  1124  and (b) the oral inhalation channel  1150   a  and the oral exhalation channel  1160   a  is prevented unless the nasal inhalation valve  1122  or the nasal exhalation valve  1126  is in an open configuration. Similarly, the obturator is configured to form a seal around the nostrils and the mouth so that fluidic communication between (a) the oral fluid reservoir  1134  and (b) the oral inhalation channel  1150   b  and the oral exhalation channel  1160   b  is prevented unless the oral inhalation valve  1132  or the oral exhalation valve  1136  is in an open configuration. 
     The respirator  1100  can optionally comprise a septum  1140  disposed between the nasal fluid reservoir  1124  and the oral fluid reservoir  1134 . The septum  1140  is configured to prevent fluidic communication between the nasal fluid reservoir  1124  and the oral fluid reservoir  1134 . The nasal fluid reservoir  1124  is configured to be in fluidic communication with the pair of nostrils. The oral fluid reservoir  1134  is configured to be in fluidic communication with the mouth of the user. In some embodiments, the septum  1140  can include an obturator configured to form a seal on the face of the user to prevent fluidic communication between the nasal fluid reservoir  1124  and the oral fluid reservoir  1134 . 
     The nasal inhalation valve  1122  is disposed between the nasal fluid reservoir  1124  and the nasal inhalation channel  1150   a  that is in fluidic communication with the nasal inhalation inlet  1152   a . The nasal inhalation valve  1122  is configured to transition between an open configuration and a closed configuration. In the open configuration, the nasal fluid reservoir  1124  is in fluidic communication with the nasal inhalation channel  1150   a , and by extension, the nasal inhalation inlet  1152   a . In the closed configuration, fluidic communication between the nasal fluid reservoir  1124  and the nasal inhalation channel  1150   a , and by extension, the nasal inhalation inlet  1152   a , is prevented. The nasal inhalation valve  1122  is configured to assume its open configuration in response to nasal inhalation by the user, and its closed configuration in response to nasal exhalation by the user, as described in more detail below. 
     The nasal exhalation valve  1126  is disposed between the nasal fluid reservoir  1124  and the nasal exhalation channel  1160   a  that is in fluidic communication with the nasal exhalation outlet  1162   a . The nasal exhalation valve  1126  is configured to transition between an open configuration and a closed configuration. In the open configuration, the nasal fluid reservoir  1124  is in fluidic communication with the nasal exhalation channel  1160   a , and by extension the nasal exhalation outlet  1162   a . In the closed configuration, fluidic communication between the nasal fluid reservoir  1124  and the nasal exhalation channel  1160   a , and by extension, the nasal exhalation outlet  1162   a , is prevented. The nasal exhalation valve  1126  is configured to assume its open configuration in response to nasal exhalation by the user, and its closed configuration in response to nasal inhalation by the user. 
     The oral inhalation valve  1132  is disposed between the oral fluid reservoir  1134  and the oral inhalation channel  1150   b  that is in fluidic communication with the oral inhalation inlet  1152   b . The oral inhalation valve  1132  is configured to transition between an open configuration and a closed configuration. In the open configuration, the oral fluid reservoir  1134  is in fluidic communication with the oral inhalation channel  1150   b , and by extension, the oral inhalation inlet  1152   b . In the closed configuration, fluidic communication between the oral fluid reservoir  1134  and the oral inhalation channel  1150   b , and by extension, the oral inhalation inlet  1152   b , is prevented. The oral inhalation valve  1132  is configured to assume its open configuration in response to oral inhalation by the user, and its closed configuration in response to oral exhalation by the user. 
     The oral exhalation valve  1136  is disposed between the oral fluid reservoir  1134  and the oral exhalation channel  1160   b  that is in fluidic communication with the oral exhalation outlet  1162   b . The oral exhalation valve  1136  is configured to transition between an open configuration and a closed configuration. In the open configuration, the oral fluid reservoir  1134  is in fluidic communication with the oral exhalation channel  1160   b , and by extension, the oral exhalation outlet  1162   b . In the closed configuration, fluidic communication between the oral fluid reservoir  1134  and the oral exhalation channel  1160   b , and by extension, the oral exhalation outlet  1162 , is prevented. The oral exhalation valve  1136  is configured to assume its open configuration in response to oral exhalation by the user, and its closed configuration in response to oral inhalation by the user. 
     In some implementations, the respirator  1100  further comprises an nasal inhalation filter  1170   a  disposed between (1) the nasal inhalation inlet  1152   a  and (2) the nasal inhalation valve  1122 , and/or an oral inhalation filter  1170   b  disposed between (1) the oral inhalation inlet  1152   b  and (2) the oral inhalation valve  1132 . In some implementations, the nasal inhalation filter  1170   a  is disposed within the nasal inhalation channel  1150   a . In some implementations, the nasal inhalation filter  1170   a  is disposed at a distal end of the nasal inhalation channel  1150   a . In some implementations, the oral inhalation filter  1170   b  is disposed within the oral inhalation channel  1150   b . In some implementations, the oral inhalation filter  1170   b  is disposed at a distal end of the oral inhalation channel  1150   b . The inhalation filter(s)  1170   a/b  are configured to filter the air entering the inhalation inlet(s)  1152   a/b  (e.g., to remove pathogens, particulates, or otherwise anything undesirable to the user). 
     The respirator  1100  can optionally comprise a nasal exhalation filter  1174   a  disposed between (1) the nasal exhalation outlet  1162   a  and (2) the nasal exhalation valve  1126 , and/or an oral exhalation filter  1174   b  disposed between (1) the oral exhalation outlet  1162   b  and (2) the oral exhalation valve  1136 . In some implementations, the nasal exhalation filter  1174   a  is disposed within the nasal exhalation channel  1160   a . In some implementations, the nasal exhalation filter  1174   a  is disposed at a distal end of the nasal exhalation channel  1160   a . In some implementations, the oral exhalation filter  1174   b  is disposed within the oral exhalation channel  1160   b . In some implementations, the oral exhalation filter  1174   b  is disposed at a distal end of the oral exhalation channel  1160   b . The exhalation filter(s)  1174   a/b  are configured to filter the air exiting the nasal exhalation valve  1126  and/or the oral exhalation valve  1136  (e.g., to remove pathogens, particulates, or otherwise anything undesirable to the environment around the user). 
     The inhalation filter(s)  1170   a/b  and exhalation filter(s)  1174   a/b  can operate accordingly a variety of filtering mechanisms. In some implementations, the inhalation filter(s)  1170   a/b  or the exhalation filter(s)  1174   a/b  are configured to include a liquid medium. In some implementations, the liquid medium is water or an antiseptic solution. Filtration can be achieved through a multi-stage process using various fluid properties. For example, large particles (e.g., dust, mucus, or saliva) can be removed by creating a vortex air that flows in the volume of the liquid, while finer filtering can be achieved through bubbling process when the air stream passes through a layer of unstable foam. In some implementations, the liquid medium can be replaced with a granular substance or a granular mixture, for example, activated carbon. In some implementations, the inhalation filter(s)  1170   a/b  or the exhalation filter(s)  1174   a/b  are configured to include a roll filter. In some implementations, the inhalation filter(s)  1170   a/b  or the exhalation filter(s)  1174   a/b  are configured to include a mesh. The inhalation filter(s)  1170   a/b  or the exhalation filter(s)  1174   a/b  can be positioned horizontally or vertically, or somewhere therebetween. 
     In some implementations, the nasal aperture  1120  and the mouth aperture  1130  are defined by an aperture housing  1110 ; the nasal inhalation channel  1150   a  and the oral inhalation channel  1150   b , and the nasal fluid reservoir  1124  and the oral fluid reservoir  1134 , can be connected to each other by the aperture housing  1110 . Further, in some such implementations, the nasal inhalation valve  1122 , the nasal exhalation valve  1126 , the oral inhalation valve  1132 , and/or the oral exhalation valve  1136 , are disposed within the aperture housing  1110 , as shown optionally in broken lines in  FIG.  11   . 
     In some implementations, the respirator  1100  further comprises a septal valve  1142  disposed within the septum  1140  (and defined by or disposed within the aperture housing  1110 , when present) and configured to transition between an open configuration and a closed configuration. In the open configuration, the nasal fluid reservoir  1124  is in fluidic communication with the oral fluid reservoir  1134 . In the closed configuration, fluidic communication between the nasal fluid reservoir  1124  and the oral fluid reservoir  1134  is prevented. The septal valve  1142  is configured to assume its open configuration in response to oral inhalation or nasal exhalation by the user, and its closed configuration in response to oral exhalation or nasal inhalation by the user. In some implementations, the septum  1140  extends from one end of the aperture housing  1110  (when present) to another (e.g., opposite) end of the aperture housing  1110  to fluidically isolate the nasal fluid reservoir from the oral fluid reservoir, with fluid communication therebetween available through the septal valve  1142 , as described above. 
     While  FIG.  11    only shows one septum, some implementations of the respirator  1100  can have two, three, four, or more septa. While  FIG.  11    only shows one optional septal valve, some implementations of the respirator  1100  can have two, three, four, or more septal valves. While  FIG.  11    only shows one nasal inhalation valve, some implementations of the respirator  1100  can have two, three, four, or more nasal inhalation valves. While  FIG.  11    only shows one nasal exhalation valve, some implementations of the respirator  1100  can have two, three, four, or more nasal exhalation valves. While  FIG.  11    only shows one oral inhalation valve, some implementations of the respirator  1100  can have two, three, four, or more oral inhalation valves. While  FIG.  11    only shows one oral exhalation valve, some implementations of the respirator  1100  can have two, three, four, or more oral exhalation valves. 
     Generally, the operating principle of the respirator  1100  can be described as follows. When inhaling through the nose or mouth, under the influence of negative relative pressure, the nasal inhalation valve  1122  or the oral inhalation valve  1132  opens, and air enters from the nasal inhalation channel  1150   a  or the oral inhalation channel  1150   b  into the nasal fluid reservoir  1124  or the oral fluid reservoir  1134 , respectively. The air previously passes through optional inhalation filter(s)  1170   a/b  from the space external to the respirator  1100 . When the user exhales through the nose or mouth, under the influence of positive relative pressure, the nasal inhalation valve  1122  or the oral inhalation valve  1132  is closed, and the nasal exhalation valve  1126  or the oral exhalation valve  1136  opens, and air enters the nasal exhalation channel  1160   a  or the oral exhalation channel  1160   b , respectively. The exhaled air exits the respirator  1100  through the outlets  1162   a/b  and optionally after passing through an exhalation filter(s)  1174   a/b.    
     The outer layer of the housing is transparent, opaque, or a combination thereof (e.g., a portion of the outer layer facing the user&#39;s mouth may be transparent to aid in communication between the user and others, while other portions of the outer layer may be less transparent or opaque). The outer layer of the housing can be made of any suitable material, e.g., plastic, silicone, or the like. 
     The housing can be made, partially or whole, from breathable (filtering) material. In some implementations, the respirator  1100  is for single use. For example, the whole housing can be made of a spunbond meltblown spunbond (SMS) material. 
     In some implementations, the respirator  1100  is reusable. For example, a portion of the housing (e.g., the obturator) can be made of silicone and/or thermoplastic elastomer; another portion of the housing can be made of ABS plastic, or polyethylene terephthalate (PET) plastic; and valves can be made of silicone or rubber. 
     In some implementations, only the obturator and the coupling member (e.g., a strap) are configured to be in contact with the skin when the user wears the respirator  1100 . In some implementations where additional components are in contact with the skin, these additional components can be made of an air permeable material. 
     Regardless of whether the respirator  1100  is for single use or reusable, in some implementations separate components are manufactured separately and then assembled into the respirator  1100 . 
       FIGS.  12 A- 12 B  show front and rear views of a respirator  1200  that comprises the features of the respirator  1100  shown in  FIG.  11   , according to an embodiment. As shown in  FIGS.  12 A- 12 B , the respirator  1200  comprises an aperture housing  1210 , a nasal aperture  1220 , a mouth aperture  1230 , a septum  1240 , a nasal inhalation channel  1250   a , an oral inhalation channel  1250   b , a nasal fluid reservoir  1224 , an oral fluid reservoir  1234 , a nasal exhalation channel  1260   a , an oral exhalation channel  1260   b , a nasal inhalation valve  1222 , a nasal exhalation valve  1226 , an oral inhalation valve  1232 , an oral exhalation valve  1236 , a nasal inhalation filter  1270   a , a nasal exhalation filter  1274   a , an oral inhalation filter  1270   b , an oral exhalation filter  1274   b , and two septal valves  1242   a/b . Note that the nasal inhalation filter  1270   a , the nasal exhalation filter  1274   a , the oral inhalation filter  1270   b , and the oral exhalation filter  1274   b  are installed in filter blocks. 
     The aperture housing  1210  defines the nasal aperture  1220  and the mouth aperture  1230 . Each of the nasal inhalation channel  1250   a , oral inhalation channel  1250   b , nasal exhalation channel  1260   a , and the oral exhalation channel  1260   b , has its own housing defining a volume. Those four channels are interconnected by the aperture housing  1210 . 
     The nasal inhalation valve  1222  and the nasal exhalation valve  1226  are configured to be disposed about the nose such that there is one nasal valve on each side of the nose. The septal valves  1242   a/b  are configured to be disposed below the nostrils such that there is one septum valve below each nostril. The oral inhalation valve  1232  and the oral exhalation valve  1236  are disposed about the mouth such that there is one oral valve on each side of the mouth. 
     In addition to  FIGS.  5 G,  6 E, and  6 F , embodiments of hydro-respirators are shown in  FIGS.  14 A- 14 B  and  FIGS.  15 A- 15 B . As used herein, the term “hydro-respirator” refers to a respirator that uses a liquid medium for filtering inhaled air, exhaled air, or a combination thereof. 
     In  FIG.  14 A , a hydro-respirator  1400  comprises an inhalation hydrofilter  1482   a , an inhalation or exhalation hydrofilter  1482   b , an aperture housing  1410 , and an exhalation valve  1484 .  FIG.  14 B  shows an obturator  1428  that is configured to form a seal around the nostrils and mouth of a user. As used herein, the term “hydrofilter” refers to a filter that uses a liquid medium for filtration. In some embodiments, the liquid medium is water. In some embodiments, the liquid medium is an antiseptic solution. 
     In  FIG.  15 A , a hydro-respirator  1500  comprises an inhalation hydrofilter  1582   a , an inhalation or exhalation hydrofilter  1582   b , an aperture housing  1510 , and an exhalation valve  1584 .  FIG.  15 B  shows an obturator  1528  that is configured to form a seal around the nostrils and mouth of a user. 
     Different filters are described in conjunction with the drawings. It should not be construed that those filters can only be used in those respirators depicted in the drawings. Rather the filters can be used in any one of the respirators described throughout the present application. 
     Various configurations of filters, filter housings, inlets and outlets, are described in conjunction with the drawings. It should be understood that in any of the embodiments described herein, the filters can be exposed to the environment, and those filters can define the inlet and outlets, rather than the inlets and outlets being defined by a separate housing or filter housing. 
     Similarly, different head mounts are described in conjunction with the drawings. It should not be construed that those head mounts can only be used in those respirators depicted in the drawings. Rather the head mounts can be used in any one of the respirators described throughout the present application. 
     In some implementations, the valve (e.g., an inhalation valve, an exhalation valve, or a septal valve) described throughout the present application is a one-way valve. The one-way valve thus permits the transition from an open configuration to a closed configuration, and vice versa. The one-way valve can utilize any known designs, including but not limited to, umbrella, duckbill, mushroom, flap, Archimedes&#39; screw, and membrane. In some implementations, the one-way valve is an umbrella valve, e.g., having an opening pressure of about two to about five pascals.  FIGS.  13 A- 13 B  show an umbrella one-way valve, where the valve is closed ( FIG.  13 A ) and open ( FIG.  13 B ). 
     While various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto; inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure. 
     Also, various inventive concepts may be embodied as one or more methods, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments. 
     All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. 
     The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” 
     The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc. 
     As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of” or, when used in the claims, “consisting of” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of” “only one of” or “exactly one of” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law. 
     As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc. 
     The terms “substantially,” “approximately,” and “about” used throughout this Specification and the claims generally mean plus or minus 10% of the value stated, e.g., about 100 would include 90 to 110. 
     In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.