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CHEMICAL/BIOLOGICAL SPECIAL
OPERATIONS MASK
GOVERNMENTAL INTEREST 5
The invention described herein may be manufactured, licensed, and used by or for the U.S. Government.
FIELD OF THE INVENTION
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The present invention relates generally to respiratory masks, more particularly to full-face respiratory masks adapted for protecting the wearer against biologically/ chemically hazardous materials especially in the form of airborne particulates, vapors and aerosols. 15
BACKGROUND OF THE INVENTION
Respiratory masks that are adapted to protect the wearer's face, eyes, and lungs from the effects of hazardous airborne particles of a chemical or biological nature were first used to 20 protect soldiers during war against poison gases. Today such masks have evolved and developed for use in many capacities, including, but not limited to firefighting, environmental cleanup, manufacturing, medical hazard handling, quarantining of patients with highly contagious 25 pathogens, biological and chemical warfare, mining, paint applications, construction, and other applications where persons may come into contact with hazardous substances especially those of airborne nature.
Typically, the mask is worn over the wearer's face sealed 30 from the ambient atmosphere and cleans the air entering the mask by means of a filter device generally comprised of chemically impregnated fibers or a bed of adsorbent material usually activated charcoal. During operation, a one-way inlet valve in the mask allows air drawn in by the wearer's 35 lungs into a filter containing the absorbent material, whereby the filtered air then flows into the mask. Thus, the air is filtered and cleaned as it enters the mask. As the wearer exhales, the exhaled gas is expelled through a one-way exit valve out of the mask and the process is repeated with each 40 breath.
Full-face respiratory masks are typically uncomfortable and difficult to wear for long periods of time and impose significant burden on the wearer. Such masks are typically 4J heavy and bulky, restrict vision, generate heat stress and discomfort for the wearer, difficult to breathe through, and trap moisture vapors and perspiration causing lens fogging and discomfort. In addition, when the masks are not worn, they are cumbersome to carry and often cannot be folded 5Q without damage into a compact form.
For the foregoing reasons, there is a need for a full-face respiratory mask useful for protecting the wearer against hazardous chemical and biological agents in the form of aerosols, vapors and the like, while maintaining long-term 55 wearability, improved long-term chemical and biological protection, and capacity to be packed into a small compact package. The full-face respiratory mask of the present invention as described herein overcomes the shortcomings described above. 60
SUMMARY OF THE INVENTION
The present invention provides a respiratory mask assembly for protecting a wearer from biological and/or chemical agents that may be present in an atmosphere. The respiratory 65 mask of the present invention provides a military level of protection against biological and chemical agents over a
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long period of time without similar level of burden and discomfort often associated with full-face mask configurations. The respiratory mask is configured to be highly compact and portable so that it may be conveniently carried and/or packed into a tightly compact hermetically sealed package prior to wear. The mask is easily manufactured using inexpensive and readily available component parts and equipment. In addition, the design of the mask provides the wearer a wide unobstructed field of vision while allowing the wearer to effectively communicate with others. The mask is further adapted to minimize moisture-related fogging and accumulation of carbon dioxide in the interior thereof and facilitate the dissipation of heat and perspiration unavoidably generated by the wearer, while providing a high level of chemical/biological protection suitable especially for military use.
In one aspect of the present invention there is provided a respiratory mask assembly for filtering airborne biological and/or chemical agents from air for breathing, which comprises:
an outer hood adapted to seal with and encompass at least the head and neck of a wearer from ambient atmosphere;
at least one transparent lens attached to the outer hood for providing visual sight to the wearer;
at least one filter assembly attached to the outer hood, the filter assembly adapted for filtering airborne biological and/or chemical agents from air passing therethrough;
an airflow regulator located in the outer hood, the airflow regulator including an outlet adapted for expelling exhaled air to ambient, and an inlet adapted for drawing air thereinto; and
air conveying means located in the outer hood for conveying air filtered through the filter assembly from ambient to the inside surface of the transparent lens for drawing into the airflow regulator inlet.
BRIEF DESCRIPTION OF THE DRAWINGS
Various embodiments of the invention are described in detail below with reference to the drawings, in which like items are identified by the same reference designation, wherein:
FIG. 1 is a front elevational view of the respiratory mask for one embodiment of the present invention;
FIG. 2 is a side elevational view of the respiratory mask according to the present invention;
FIG. 3 is a rear elevational view of the respiratory mask according to the present invention;
FIG. 4 is an enlarged view of the cross sectional area indicated by "A" in FIG. 3;
FIG. 5 is an exploded assembly view of a faceplate assembly of the respiratory mask according to the present invention; and
FIG. 6 is a side elevational view of the respiratory mask partially in phantom showing a neck seal component located inside thereof according to the present invention.
DETAILED DESCRIPTION OF THE
INVENTION
The present invention is directed to respiratory masks adapted for filtering biologically/chemically hazardous particulates, aerosols and the like from ambient air for providing safe breathable life sustaining air to the wearer. The respiratory mask of the present invention provides the
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wearer with suitable protection against biological and chemical atmospheric fallout while minimizing the limitations and problems associated with conventional full-face respiratory masks. The respiratory mask of the present invention is designed to possess low bulk and weight for 5 increased wear comfort, and may be packaged in a compact form for easy portability. In addition, the respiratory mask is simple and inexpensive to manufacture while providing the high level of protection especially suitable for military use.
The present invention is generally directed to a respiratory 1° mask that includes means contained therein for conveying to the wearer's mouth and/or nose, ambient air filtered through a filter medium located on hood of the mask. The air conveying means and the mask is further adapted, in combination, to remove or wick moisture away from the :5 wearer's skin enclosed thereunder, thus reducing the discomfort associated with heat stress and moisture retainment, while preventing the penetration of harmful aerosols and particulates to the wearer.
Referring to FIGS. 1 and 2, a respiratory mask assembly 20 10 of the present invention is shown for one embodiment of the present invention. The respiratory mask assembly or mask 10 comprises generally a head portion 12, a neck portion 14, and a lower portion 16. The mask 10 further includes an outer hood 18, an inner elastic hood 20, a 25 faceplate assembly 22 adapted to fit over a wearer's face and one or more filter assemblies 24 for filtering air drawn into the mask 10. The faceplate assembly 22 further includes an airflow regulator 26 for regulating the flow of air into and out of the wearer's lungs, and a transparent lens piece 28 for 30 providing the user with visual sight through the mask 10. The mask 10 is designed to completely cover and seal the wearer's neck and head from ambient atmosphere.
With reference to FIG. 3, the outer hood 18 and the inner 3J hood 20 is configured to maintain a spaced-apart arrangement to form a gap space 30 therebetween (see also FIG. 4). The gap space 30 serves as a channel or passage whereby filtered air passing through the filter assemblies 24 is effectively conveyed to the wearer through the airflow regulator 4Q 26 of the faceplate assembly 22. The outer and inner hoods 18 and 20 are connected and hermetically sealed along the edge portions thereof to partition the gap space 30 from the ambient atmosphere. Since the wearer breathes the air conveyed through the gap space 30, it is critical to the 4J operation of the mask 10 that the gap space 30 is sealed off from the ambient atmosphere that may contain biologically or chemically hazardous contaminants.
The inner hood 20 is generally composed of a lightweight, breathable fabric material. The fabric material of the inner 50 hood 20 is adapted to allow vapor moisture to pass therethrough from the wearer's skin. The fabric material is stretchable and conforms to the surface of the wearer's head and neck. Optionally, the inner hood 20 may be adapted to prevent penetration of biological or chemical agents for 55 providing additional protection to the wearer.
The outer hood 18 is generally composed of a lightweight, breathable fabric material that is wind-resistant and adapted to allow vapor moisture to pass out to the ambient atmosphere. The fabric material of the outer hood 18 is stiffer and 60 capable of holding its own shape apart from the inner hood 20 to form the gap space 30 therebetween. In addition to its wind resistant and moisture wicking capabilities, the fabric material of the outer hood 18 is further impermeable to airborne aerosol or particulates and liquid water and pre- 65 vents penetration of hazardous chemical and biological agents into the mask 10.
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In an alternative embodiment, the mask 10 may be configured to include a duct or tubing extending between the airflow regulator 26 and filter assemblies 24 in a single layer, outer hood-only arrangement. The duct may include any shape and volume occupying the interior of the mask 10 and conforms substantially along the surface of the wearer's head. The duct may be composed of any suitable material capable of effectively conveying a fluid. In this embodiment, the filtered air passing through the filter assemblies 24 is conveyed through the duct to the airflow regulator 26 of the faceplate assembly 22.
As shown in FIG. 3, the filter assemblies 24 are securely connected to and hermetically sealed along the edges thereof with the outer hood 18. The filter assemblies 24 are fluidly connected to the airflow regulator 26 by the gap space 30. The filter assemblies 24 may be mounted at any location on the mask 10, preferably on the neck portion 14 on the anterior side of the mask 10. Preferably, at least one filter assembly 24 is provided in each mask 10. Each filter assembly 24 includes a multi-laminar filter media 32 that is comprised of a plurality of discrete filter layers securely retained between a pair of mesh screen layers 38. The mesh screen layers 38 are made of thin screen mesh material such as nylon, for example, and are configured to protect the outside and inside surfaces of the filter media 32. The filter media 32 comprises one or more electrostatic, particulate filter layers 34 having a minimum collection efficiency of about 99.97% and one or more carbon activated sorbent layers, or chemical filter layers 36 for absorbing chemical contaminants. Preferably, the filter media 32 possesses low airflow resistance for facilitating comfortable and relatively unlabored breathing, and excellent filtering capacity for protection against hazardous airborne chemicals and biological agents.
The particulate filter layer 34 is generally comprised of a suitable flat-sheet, electrostatically charged, air filtration media (i.e. electrets) that are commercially available. The particulate filter layer 34 is preferably made from an electrostatic media. The electrostatic media material of the particulate filter layer 34 is available from 3M and marketed as ADVANCED ELECTRET MEDIA (AEM). The material offers excellent aerosol filtration and very low pressure drop characteristics. The electrostatic media of the particulate filter layer 34 is optimized to provide near HEPA performance at a thickness of about 0.1 of an inch. The effective surface area of the particulate filter layer 34 may range from about 125 to 300 cm2.
In the preferred embodiment, the chemical filter layer 36 is made from a carbon loaded web. The carbon loaded web material is available from and marketed by 3M. The carbon loading material is commercially available and marketed under CALGON ASZM-TEDA. The carbon loaded web media offers excellent sorbent filtration and low pressure drop characteristics. The web media is preferably loaded to 300 grams/m2 of carbon loading material and layered to provide effective chemical 10 o protection. Preferably, the chemical filter layer 36 comprises four (4) layers of carbon loading material. The effective surface area of the chemical filter layer 36 may range from about 125 to 300 cm2. As shown in FIG. 3, the chemical filter layer 36 is positioned between the particulate filter layers 34. It is noted that the present invention is not limited to the above filtering media and may include the use of any suitable filtration media with low airflow resistance effective for chemical and particulate filtration.
The filter media 32 retained between the pair of mesh screens 38 is mounted in a hood inlet 40 of the outer hood
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