MXPA01000871A - Face mask that has a filtered exhalation valve - Google Patents

Abstract

A filtering face mask that covers at least the nose and mouth of a wearer and that includes an exhalation valve. The exhalation valve opens in response to increased pressure when the wearer exhales to allow the exhaled air to be rapidly purged from the mask interior. An exhale filter element is placed in one of several locations in the exhale flow stream to remove contaminants from the exhaled air. The face mask is beneficial in that it provides comfort to the wearer by allowing warm, moist, high-CO2-content air to be rapidly evacuated from the mask interior through the valve and also protects the wearer from splash fluids and polluted air while at the same time protecting other persons or things from being exposed to contaminants in the exhale flow stream.

Description

FACIAL MASK THAT HAS A FILTERED EXHAUSTION VALVE FIELD OF THE INVENTION The present invention pertains to a face mask having a filter element associated with an exhalation valve. The filter element allows the face mask to remove contaminants from the exhalation flow stream.

BACKGROUND OF THE INVENTION Facial masks are worn over a person's airway for two common purposes: (1) prevent contaminants from entering the user's respiratory tract; and (2) protect other people or things from being exposed to pathogens and other pollutants expelled by the user. In the first situation, the facial mask is carried in an environment where the air contains substances harmful to the user, for example, in a car workshop. In the second situation, the facial mask is carried in Ref: 126986 an environment where there is a high risk of infection or contamination towards another person or thing, for example, in an operating room or in a clean room. Facial masks that have been designed to protect the user are commonly referred to as "respirators", while masks that have been designed primarily with the second scenario in mind-namely, protecting other people and things-are generally referred to as "facial masks" "or simply" masks ". A surgical mask is a good example of a face mask that often does not qualify as a respirator. Some surgical masks are loosely fitted facial masks, designed primarily to protect other people from contaminants that are expelled by the user. Substances that are expelled from the mouth of a user are frequently aerosols, which generally contain suspensions of fine solids or particles of liquid in gas. Surgical masks are very capable of filtering these particles. U.S. Patent No. 3,613,678 to Mayhew discloses an example of a loose fitting surgical mask.

Masks that do not seal around the face, such as some known surgical masks, typically do not have an exhalation valve to purge the exhaled air from inside the mask. The masks are sometimes loose fitting to allow the exhaled air to escape easily from the sides of the mask so that the user does not feel discomfort, particularly when breathing heavily. Because these masks are loose fitting, however, they can not completely protect the user from inhaling contaminants or from being exposed to fluid splashes. In view of the various contaminants that are present in hospitals, and of the many pathogens that exist in bodily fluids, the loose fitting feature is a notable drawback for such surgical masks. In addition, masks that are not sealed around the face are known to allow exhaled breathing to pass around the edges of the mask, known as "adjunctive breath," and such masks could not benefit from having an exhalation valve attached to the body of the mask. the mask Facial masks have also been designed to provide a tighter or airtight, more tight fit between the wearer's face and the mask. Some tight or tight fitting masks have a non-porous rubber face piece that supports removable or permanently attached filter cartridges. The facepiece also has an exhalation valve to purge the exhaled, moist, high C02 content of the inside of the mask. Masks that have this construction are commonly called more descriptively as respirators. U.S. Patent No. 5,062,421 to Burns and Reischel describes an example of such a mask. Commercially available products include the masks of the 5000 and 6000MR series sold by the 3M Company of Saint Paul, Minnesota. Other tight or tight fitting masks have a porous mask body that is shaped and adapted to filter the inhaled air. Usually these masks are also referred to as respirators and frequently have an exhalation valve, which opens under the increased pressure of internal air when the user exhales - see, for example, U.S. Patent No. 4,827,924 to Japuntich. Additional examples of filtration facial masks having exhalation valves are shown in U.S. Patent Nos. 5,509,436 and 5,325,892 to Japuntich et al., U.S. Patent No. 4,537,189 to Vicenzi, U.S. Pat. No. 4,934,362 to Braun, and U.S. Patent No. 5,505,197 to Scholey. Typically, the exhalation valve is protected by a valve cover - see, for example, United States Patent Nos. Des. 347,299 and Des. 347,298- that can protect the valve from physical damage caused, for example, by accidental impacts. Known tight or tight-fitting masks that have an exhalation valve can prevent the user from directly inhaling harmful particles, but masks have limitations when protecting other people or things from being exposed to contaminants expelled by the user. When a user exhales, the exhalation valve opens into ambient air, and this temporary opening provides a conduit from the user's mouth and nose to the outside of the mask. The temporary opening can allow the aerosol particles generated by the user to pass from the inside of the mask to the outside. Conversely, projectiles such as splashed fluids may pass from the outside of the mask into their interior through the temporary opening. In many applications, especially in surgical rooms and clean rooms, the open duct that the exhalation valve provides temporarily, could possibly lead to a patient's infection or contamination of a precision part. The Nurses Association of Operations Rooms (Association of Operating Room Nurses) has recommended that masks are 95% efficient in retaining expelled viable particles. Proposed Recommended Practice for OR Wearing Apparel, AORN JOURNAL., V. 33, n. 1, pp. 100-104 (January 1981); see also D Vesley et al., Clinical Implications of Surgical Mask Retention Efficiencies for Viable and Total Particles, INFECTIONS IN SURGERY, pp. 531-536, 533 (July 1983). Consequently, facial masks that use exhalation valves are not currently recommended for use in such environments. See for example, Gui del i nes para Preventing the Transmis sion of Mycobac t eri um Tubercul osi s i n Heal th Care Fa cili ti es, MORBIDITY AND MORTALITY WEEKLY REPORT, U.S. Dept. Health & Human Services, v. 43, n. RR-13, pp. 34 and 98 (October 28, 1994). Facial masks have been produced that are capable of protecting the user and nearby people or objects from contamination. Commercially available products include the masks of the 1800MR, 1812MR, 1838MR, 1860MR, and 8210MR brands sold by the 3M Company. Other examples of masks of this type are described in U.S. Patent Nos. 5,307,706 to Kronzer et al., 4,807,619 to Dyrud and 4,536,440 to Berg. The masks are relatively tight or watertight to prevent liquid gases and contaminants from entering and leaving the inside of the mask at their perimeter, but masks commonly lack an exhalation valve that allows exhaled air to be quickly purged from inside the mask. the mask Thus, although masks remove pollutants from inhalation and exhalation flow streams and provide protection against splash fluids, masks are generally incapable of maximizing user comfort. U.S. Patent No. 5,117,821 to White discloses an example of a mask that removes the odor of exhaled air. This mask is used for hunting purposes, to prevent the hunted animal from detecting the hunter. This mask has an inhalation valve that allows the ambient air to be pulled into the mask, and has a purification can held on the user's torso to receive the exhaled air. A long tube directs the exhaled air towards the remote can. The device has exhalation valves placed on the ends of the can to control the passage of purified respiration into the atmosphere, and to prevent retroinhalation of respiration from the can. The can can contain particles of mineral coal to eliminate the odors of breathing. Although the hunting mask prevents the exhaled organic vapors from being transported to the environmental area (and may provide the hunter with an unfair advantage), the mask is not designed to provide a source of clean air. Neither does this provide a coupling for an intake or collection filter, and it is somewhat problematic and may not be practical for other applications. German publication 43 077 54 discloses a mask using a hose or long tube extending from the body of the mask to be additionally coupled to another air tube, which in turn, is connected to a flow control device. air. The airflow control device controls the supply and elimination of respiration, for which it comprises an air pump that sucks the exhaled air towards an air filter, to purify or decontaminate the exhaled air. In addition, the device can also be used to supply the purified to the user. With this, the air control device sucks the breath and directs the filtered air towards the user. The airflow control device provides a power source and a clamp to fix the device in a user's clothing.

European Patent EP-A-0 171, 511 discloses a breathing mask comprising an inhalation and exhalation valve and a filter device coupled exclusively to the exhalation valve, which filters the carbon dioxide exhaled by the patient. user before entering the atmosphere. Therefore, the filtration device comprises a lithium hydroxide cartridge, LiOH, which includes lithium hydroxide granules, LiOH, as a carbon dioxide absorber (C02), and a fabric as a filter material to prevent the LiOH lithium hydroxide powder from coming into contact with the user's organism and causing chemical burn. US Patent No. 5,016,625 discloses a respirator for filtering air from the fumes of a fire in order to prevent a user from inhaling too much poisonous gas, such as carbon monoxide. A ventilation device is used which provides a textile material such as a filter which is moistened by an actuator, so that the filter can filter the inhaled air from poisonous gases and smoke.

BRIEF DESCRIPTION OF THE INVENTION In view of the above, a filtering face mask is needed which can prevent contaminants from passing from the user into the ambient air, which can prevent splash fluids from entering the interior of the mask, and which allows the air hot, humid, with high C02 content is quickly purged from the inside of the mask. This invention provides such a mask, which in brief summary comprises: (a) a mask body; (b) an exhalation valve that is positioned on the body of the mask and has at least one orifice that allows the exhaled air to pass from an interior gas space to an exterior gas space during an exhalation; Y (c) an exhalation filter element placed on the face mask of filtration in the exhalation flow stream, to prevent contaminants from passing from the interior gas space to the exterior gas space with the exhaled air. The invention differs from known facial masks in that it has an exhalation valve and because the invention includes for the first time an exhalation filter element which can prevent contaminants in the exhalation flow stream from passing from the interior gas space of the exhalation. mask towards the outer gas space. This feature allows the facial mask to be particularly beneficial for use in surgical procedures or for use in clean rooms where it could not have been used in the past. Also, contrary to some previously known facial masks, the invention may be in the form of a tight or tight fitting mask which provides the user with good protection against airborne contaminants and splash fluids. And because the face mask of the invention has an exhalation valve, this can provide the user with good comfort by being able to quickly purge hot, moist, high-C02 air coming from inside the mask. In this way, the invention provides increased comfort to users by decreasing the temperature, humidity, and carbon dioxide levels within the mask, while at the same time protecting the user and preventing the particles of other contaminants from passing into the mask. the environment. These and other advantages and features that characterize the invention are illustrated below in the detailed description and in the accompanying drawings.

GLOSSARY With reference to the invention, the following terms are defined as described below: "aerosol" means a gas containing particles suspended in solid and / or liquid form, "clean air" means a volume of atmospheric air that has been filtered to eliminate the pollutants; "contaminants" means particles and / or other substances which in general may not be considered as particles, (for example, organic vapors, etc.) but which may be suspended in the air including air in an exhalation flow stream; "exhalation valve" means a valve designed for use over a filtering face mask, to open in response to the pressure of the exhaled air and to remain closed when a user inhales and between breaths; "exhaled air" is the air that is exhaled by a user of the filtering face mask; "exhalation filter element" means a porous structure through which exhaled air can pass, and which is capable of removing contaminants from an exhalation flow stream; "exhalation flow current" means the air current that passes through an orifice of an exhalation valve .; "outer gas space" means the space of ambient atmospheric air within which the exhaled gas enters after passing significantly beyond the exhalation valve; "filtering face mask" means a mask that covers at least one user's nose and mouth, and that is capable of supplying clean air to a user; "inhalation filter element" means a porous structure through which the inhaled air passes before being inhaled by the user, so that contaminants and / or particles can be removed therefrom; "interior gas space" means the space within which the clean air enters before being inhaled by the user and into which the exhaled air passes before passing through the orifice of the exhalation valve; "mask body" means a structure that can be adjusted at least over a person's nose and mouth, and that helps define an interior gas space separate from an exterior gas space; "particle" means any liquid and / or solid substance that is capable of being suspended in the air, for example, pathogens, bacteria, viruses, mucus, saliva, blood, etc. "porous structure" means a mixture of a volume of solid material and a volume of empty spaces, which defines a three-dimensional system of tortuous interstitial channels through which a gas can pass.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the drawings, where similar reference characters are used to indicate structures corresponding to the entire length of the various views: Figure 1 is a perspective view of a face mask 20 of filtration that is equipped with an exhalation valve 22; Figure 2 is a sectional side view of an exhalation valve 22, illustrating a first embodiment of an exhalation filter element 31 according to the invention; Figure 3 is a front view of a valve seat 30, which is used in connection with the valve 22, Figure 4 is a sectional side view of an exhalation valve 22, illustrating a second embodiment of a filter element 32 of exhalation according to the invention; Figure 5 is a sectional side view of an exhalation valve 22, illustrating a third embodiment of an exhalation filter element 33 according to the invention; Figure 6 is a side sectional view of an exhalation valve 22, illustrating a fourth embodiment of an exhalation filter element 34 according to the invention; Figure 7 is a sectional side view of a mask 20 'similar to the mask 20 shown in Figure 1, illustrating a fifth embodiment of an exhalation filter element 35 according to the invention; Figure 8 is a sectional side view of a mask 20"similar to the mask 20 shown in Figure 1, illustrating a sixth embodiment of an exhalation filter element 36 according to the invention; Figure 9 is a sectional side view of a mask 20 '' 'similar to the mask 20 shown in Figure 1, illustrating a seventh embodiment of an exhalation filter element 37 according to the invention; Figure 10 is a sectional side view of an exhalation valve 22 having an exhalation filter element 38 according to the invention; Figure 11 is a sectional side view of an exhalation valve 22 having an exhalation filter element 39 detachable according to the invention; Figure 12 is a front view of a filtering face mask 60 having an exhalation filter element 40 according to the invention; Figure 13 is a front view of a complete face filtration mask 70, illustrating an exhalation filter element 41 according to the invention; and Figure 14 is a schematic view illustrating the air flows when performing a "Valve Proof of Flux or Side by Side Percentage".

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES This invention has utility with many types of facial filtration masks including the mascaras masks that cover the user's nose and mouth; the full-face respirators that cover the user's nose, mouth, and eyes; full body suits and hoods that provide clean air to a wearer; Air masks supplied and energized; self-contained breathing apparatus; and essentially any other filtering face mask that can be equipped with an exhalation valve. The invention is particularly suitable for use with facial filtration masks having a porous mask body that acts as a filter. According to various embodiments of the present invention, the exhalation filter element can be placed upstream to the exhalation valve orifice inside the mask, so that the aerosol particles are collected before passing through the mask. the exhalation valve. In yet another embodiment, the exhalation filter element can be placed between the body of the mask and the opening towards the exhalation valve. In other additional embodiments, the exhalation filter element may be placed downstream of the exhalation valve, so that the air passing through the exhalation valve subsequently passes through the exhalation filter element. Other embodiments include an exhalation filter element that covers not only the valve housing but larger portions of the mask body and even the entire exterior of the mask body, to provide increased filter surface area and decrease the resistance to exhalation or pressure drop through the exhalation filter element. The invention may also include embodiments wherein the mask covers layers of networks or conformation layers that act as the exhalation filter element or where the valve cover is the exhalation filter element. In Figure 1, a face mask 20 is shown having an exhalation valve 22 positioned centrally on the body 24 of the mask. The body 24 of the mask is configured in a generally cup-shaped configuration when worn to fit snugly over a person's nose and mouth. The mask 20 is formed to maintain a substantially leak-free contact with the user's face at its periphery 21. The body 24 of the mask is pulled tightly against the face of a user around the periphery 21 of the mask by the bands 26. that extend behind the head and neck of the user when the mask is carried. The facial mask 20 forms an interior gas space between the body 24 of the mask and the face of the user. The interior gas space is separated from the ambient atmospheric air or the exterior gas space by the body 24 of the mask and the exhalation valve 22. The body of the mask can have a conformable nose clamp 25 (see Figures 7-). 9) mounted on the inside of the body 24 of the mask (or outside or between the layers) to provide a tight or tight fit over the nose and where the nose meets the cheekbone. A mask having the configuration shown in Figure 1 is described in U.S. Patent Application Serial No. 08 / 612,527 to Bostock et al., And in U.S. Pat. Series 29 / 059,264 to Henderson et al., 29 / 059,265 to Bryant et al., And 29 / 062,787 to Curran et al. Facial masks of the invention can take many other configurations, such as planar mascaras and cup-shaped masks shown, for example, in U.S. Patent No. 4,807,619 to Dyrud et al. The nose clamp may have the configuration described in U.S. Patent No. 5,558,089 to Castiglione. The masks could also have a thermochromic adjustment indicator seal on their periphery, to allow the user to easily assess whether an appropriate adjustment has been established - see, U.S. Patent No. 5,617,849 to Springett et al. The exhalation valve 22 that is provided on the body 24 of the mask is opened when a user exhales in response to the increased pressure within the mask, and must remain closed between the breaths and during an inhalation. When a user inhales, the air is pulled through the filtration material, which may include a non-woven, fibrous filtration material 27 (Figures 2, 4-9 and 12-13). Filtering materials that are common on respirators of half-masks of negative pressure, such as respirator 20 shown in Figure 1, frequently contain a tangled network of melt blown, electrically-charged (BMF) raicrofibers. BMF fibers typically have an average fiber diameter of about 10 micrometers (μm) or less. When they are randomly entangled in a network, they have enough integrity to be handled as a mesh. Examples of fibrous materials that can be used as filters in a mask body are described in U.S. Patent No. 5,706,804 to Baumann et al., U.S. Patent No. 4,419,993 to Peterson, the Reissue Patent. from U.S. No. 28,102 to Mayhew, U.S. Patent Nos. 5,472,481 and 5,411,576 to Jones et al., and U.S. Patent No. 5,908,598 to Rousseau et al. Fibrous materials may contain additives to increase filtration performance, such as the additives described in U.S. Patent Nos. 5,025,052 and 5,099,026 to Crater et al., and may also have low levels of extractable hydrocarbons to improve performance; see, for example, U.S. Patent Application Serial No. 08 / 941,945 to Rousseau et al. Fibrous networks can also be manufactured to have increased resistance to oily mist, as shown in U.S. Patent No. 4,874,399 to Reed et al and in U.S. Patent Applications Nos. 08 / 941,270 and 08 / 941,864, both to Rousseau et al. An electrical charge may be imparted to the nonwoven fibrous webs using techniques described in, for example, U.S. Patent No. 5,496,507 to Angadj ivand et al., U.S. Patent No. 4,215,682 to Kubik et al. ,., and U.S. Patent No. 4,592,815 to Nakao. Figure 2 shows the exhalation valve 22 in cross section mounted on the body 24 of the mask. The body 24 of the mask acts as an inhalation filter element and includes a filter layer 27, an outer cover network 29, and an inner cover network 29 '. The inhalation filter element is integral with the body 24 of the mask. That is, it is part of the body of the mask and is not a part that subsequently becomes attached to the body. The outer and inner cover networks 29 and 29 'respectively protect the filter layer 27 from the abrasive forces and retain any fibers that may become detached from the filter layer 27. The cover networks 29, 29' may also have filtration abilities, although typically not as clearly as good as the filtration layer 27. The cover networks can be made of nonwoven fibrous materials containing polyolefins and polyesters (see for example U.S. Patent Nos. 4,807,619 and 4,536,440 and U.S. Patent Application No. 08 / 881,348 filed June 24, 1997). The exhalation valve 22 includes a valve seat 30 and a flexible flap 42. The flexible flap 42 rests on a seal surface 43 when the flap closes, but rises from that surface 43 at the free end 44 when a flap is reached. significant pressure during an exhalation. The seal surface 43 of the valve is generally curved in a concave cross section when viewed from a lateral elevation. Figure 3 shows the seat 30 of the valve from a front view. The seat 30 of the valve has a hole 45 which is positioned radially inwardly to the seal surface 43. The hole 45 may have transverse members 47 that stabilize the seal surface 43 and ultimately the valve 22 (Figure 2). The transverse members 47 can also prevent the flap 42 (Figure 2) from reversing towards the hole 45 during an inhalation. The flexible flap 42 is secured in its fixed portion 48 (Figure 2) to the seat 30 of the valve on the flap retaining surface 49. The flap retention surface 49, as shown, is positioned outside the region encompassed by the hole, and may have spigots 51 to assist in mounting the flap to the surface. The flexible flap 42 (Figure 2) can be secured to the surface 49 using sonic welding, an adhesive, mechanical fastening, and the like. The seat 30 of the valve also has a flange 46 extending laterally from the valve seat 30 in its base, to provide a surface that allows the exhalation valve 22 (Figure 2) to be secured to the body 24 of the mask . Valve 22 shown in Figures 2 and 3 is more fully described in U.S. Patent Nos. 5,509,436 and 5,325,892 to Japuntich et al. Contrary to the valve described in these two patents, valve 22 shown in Figure 2 has an exhalation filter element 31 placed in the exhalation flow stream. The exhalation filter element 31 shown in Figure 2 is placed between the filter material 27 in the body 24 of the mask and the base 46 of the exhalation valve 22. The exhalation filter element 31 is thus positioned downstream to the opening 52 in the body 24 of the mask. The air that is exhaled by the user enters the interior gas space of the mask, which in Figure 2 could be located to the left of body 24 of the mask. The exhaled air leaves the interior gas space as it passes through an opening 52 in the body 24 of the mask. The opening 52 is circumscribed by the valve 22 at its base 46. Before passing through the orifice 45 of the valve, the exhaled air passes through the exhalation filter element 31. The exhalation filter element 31 removes contaminants that may be present in the exhalation flow stream, for example, particles suspended in the aerosol exhaled by the user. After passing through the exhalation filter element 31, the exhaled air then exits the valve orifice 45 as the free end 44 of the flexible flap is lifted from the seal surface 43 in response to a force generated by the exhaled air by the user. All exhaled air must pass through the filtration material 27 of the body of the mask or through the element 31 of the exhalation filter. The exhaled air passing through the filtration material 27 of the mask body or the exhalation filter element 32 then enters the atmosphere. Under ideal conditions, the exhaled air is not allowed to enter the atmosphere, without filtering, unless it accidentally escapes from the mask, for example at its periphery 21 (Figure 1). The exhaled air leaving the interior gas space through the valve orifice 45 then proceeds through the gate 53 in the valve cover 54 to enter the outside gas space. The cover 54 of the valve extends on the exterior of the valve seat 30 and includes the gates 53 on the side portions and on the upper part of the cover 54 of the valve. A valve cover having this configuration is shown in U.S. Patent No. Des. 347,299 to Bryant et al. Other configurations of other exhalation valves and valve covers may also be used (see U.S. Patent No. Des 347,298 to Japuntich et al. For another valve cover). The resistance or pressure drop across the exhalation filter element is preferably less than the resistance or pressure drop across the inhalation filter element of the mask body. Because the exhaled air will follow the path of least resistance, it is important to use an exhalation filter element that shows a lower pressure drop than the mask body, preferably less than the filter media in the mask body , so that a larger portion of the exhaled air passes through the exhalation filter means, rather than through the filter medium of the mask body. For this purpose, the exhalation valve, which includes the exhalation filter element, must demonstrate a pressure drop that is less than the pressure drop through the filter medium of the mask body. The majority or substantially all of the exhaled air will thus flow from the interior of the mask body, outwardly through the exhalation valve, and through the exhalation filter element. If the resistance of the air flow due to the exhalation filter element is too great, so that the air is not easily expelled from the inside of the mask, the humidity and carbon dioxide levels inside the mask can be increased. and may cause discomfort to the user. Figure 4 shows an exhalation filter element 32 placed at another site. In this embodiment, the exhalation filter element 32 is placed on the inside of the body 24 of the mask upstream of the opening 52 in the filter medium. As in the previous embodiment, the exhaled air lifts the flexible flap 42 over the outlet hole 45 and then passes to the gates 53 in the cover 54 of the valve. The exhaled air passes through the exhalation filter element 32 before passing through the opening 52 of the filter medium and orifice 45 of the valve. As in other modalities, the exhalation filter element 32 can be secured to the mask at this site, for example by mechanical clamping (eg, snap or friction fit), ultrasonic welding, or the use of an adhesive. Figure 5 shows an exhalation filter element 33 extending over and around the valve cover 54 of the exhalation valve 22. The exhalation filter element 33 is preferably juxtaposed tightly against the outside of the exhaust cover. the valve and is maintained between the body 24 of the mask and the seat 30 of the valve and the cover 54 of the valve. When placed at this site, the exhaled air passes through the element 33 of the exhalation filter after passing through the gates 53 on the cover 54 of the valve. Modes such as this can be advantageous in that placing the element 33 of the exhalation filter downstream to the valve orifice 45 and the flap 42 allows the exhalation flow stream to strike the flap 42 of the valve without hindrance. That is, the downstream placement of the exhalation filter element can prevent a decrease in momentum in the exhalation flow stream that could impede the opening operation of the valve. Downstream placement can also be advantageous since it provides better prophylactic coverage of the valve and can collect particles that could be generated by the rupture of a condensation meniscus between the flap 42 of the valve and the valve seat 30. Figure 6 shows an exhalation filter element 34 which is located on the interior of the cover 54 of the valve. The exhalation filter element 34 is maintained between the seat 30 of the valve and the body 24 of the mask, and between the seat 30 of the valve and the cover 54 of the valve. The air that is exhaled thus passes through the element 34 of the exhalation filter before passing through the gate 53 in the cover 54 of the valve but after passing through the orifice 45 of the valve. The downstream location of the exhalation filter element 34 in this embodiment can likewise be advantageous as described above with reference to Figure 5. Figure 7 also shows an exhalation filter element that is located downstream to the flap 42 of the valve. Element 35 of the exhalation filter has an expanded surface area relative to the other embodiments. The exhalation filter element 35 extends completely on the outside of the exhalation valve 22 and the body 24 of the mask. Because the exhalation filter element 35 has a surface area that is slightly greater than the surface area of the body 24 of the mask (or the filter means 27 in the body 24 of the mask), it could be shown that there is a smaller drop of pressure through the exhalation filter element 35 that the body 24 of the mask (when the same filter medium is used in each), and therefore the exhaled air will easily pass from the interior gas space to the gas space outside through the opening 52 in the body 24 of the mask and through the orifice 45 of the exhalation valve. The filter medium 27 which is used in the body 24 of the mask is typically a high performance medium which shows very low particle penetration (see the description and the above patents and the patent applications cited above with respect to the medium of BMF filter, electric charge and fiber additives). Penetration of the particles is usually sufficient to meet the NIOSH requirements described in 42 C.F.R. part 84. Particle penetration and pressure drop move inversely to each other (lower penetrations are commonly accompanied by higher pressure drops). Because the lower pressure drop could be demonstrated by the element 35 when compared to the body 24 of the mask, the embodiment shown in Figure 7 is advantageous since the filter medium used in the exhalation filter element 35 can be a high performance medium such as that used in the body of the mask. In Figure 8, the exhalation filter element 36 is also placed downstream to the composite 53 on the cover 54 of the valve. Contrary to the embodiment illustrated in Figure 7, however, the surface area of the exhalation filter element 36 is less than the surface area of the body 24 of the mask. The element 36 of the exhalation filter is secured to the body 24 of the mask where the central panel 55 of the body of the mask meets the top panel 56 and the bottom panel 57. Although the exhalation filter element 36 does not cover an area superficial that is greater than the body 24 of the mask, this is nevertheless an enlarged surface area when compared to other modalities. In this way, the exhalation filter element 36 may not necessarily be able to demonstrate the penetration and pressure drop values that are shown by the filter means 27, but may nonetheless be a very good filtering means. that shows low particle penetration. If the inner and outer cover networks 29 and 29 'are significantly added to the total pressure drop of the body 24 of the mask, then it may be possible that the exhalation filter element 36 could be able to be such a good filter medium. as the filter means 27 used in the body 24 of the mask. In Figure 9, the exhalation filter element 37 is the outer cover network 29. This embodiment is advantageous since it can be relatively easy to manufacture. The product can be made by puncturing a hole through the other layers 27, 29 'in the body 24 of the mask, followed by the application of the outer cover network 29 after the holes are punctured. The modality can be beneficial for a continuous line manufacturing process. Alternatively, the inner cover network 29 'could act as the exhalation filter element, and the outer cover network 29 could have a hole placed therein. Or both layers 29, 29 'could act as an exhalation filter element.

In Figure 10, the exhalation valve 22 has an exhalation filter element shown as a filtration cover 38 constructed of a sintered plastic or other material having sufficient rigidity, as well as a porous structure that provides filtration capabilities. Examples of materials that could be used to produce a sintered valve cover include, VYLON HP (grain size 1 mm), VYLON HP (grain size 2 mm), BYLON TT1 / 119, and VYLON HP (grain size 2.5 mm) all made with a polypropylene base material available from Porvair Technology Ltd., Wrexham, Clwyd, Wales, United Kingdom.

The sintered or porous valve covers can be made from sheets produced from the grains. The sheet material can be cut into pieces that are mounted in the form of a valve cover. Alternatively, the grains can be heated and pressed onto a tool adapted to form a valve cover. The valve cover 38 does not have the gates 53 as the valve cover 50 shown in Figures 2, 5-9 and 11. Rather, the air flowing through the valve 24 passes through the porous structure of the valve. cover 38 of the filtration valve. Using this integrated configuration, an exhalation filter element separate from the valve cover is not required. Figure 11 shows an exhalation valve 22 having an exhalation filter element 39 that is removable and preferably replaceable. The removable filter element 39 is extended over and snapped onto the valve cover 54 using conventional or other means of fastening. An impermeable layer (not shown) can be placed between the cover 54 of the valve and the body 24 of the mask, to prevent the reentry of exhaled moisture. The removable filter element 39 can be configured to fit tightly over and form an airtight seal to the valve cover 54, or it can be coupled in other ways known in the art, for example pressure-sensitive or reclosable adhesive bond. The removable filter element 39 may have a porous structure such as a thermally bonded fibrous nonwoven web, or may be made from a sintered or porous material as described above. This mode allows the exhalation filter element to be replaced before the mask has fulfilled its service life. Figure 12 illustrates a second embodiment of a cup-shaped face mask, generally designated 60. The face mask 60 includes the bands 62 that are connected to the body 64 of the mask and extend around the back of the head and the user's neck to hold the mask against the face. The body 64 of the mask acts as an inhalation filter element and is generally made of fibrous filtration material as described above and may also include inner and / or outer covering network layers - see, for example, the U.S. Patent No. 5,307,796 to Kronzer et al., U.S. Patent No. 4,807,619 to Dyrud, and U.S. Patent No. 4,536,440 to Berg. Similar to the embodiment shown in Figures 1-7, the face mask 60 may include an exhalation valve similar to the valve in the other embodiments. An exhalation filter element 40 covering the exterior of the valve cover (not shown) can be used to prevent contaminants from entering the exterior gas space. The exhalation filter element may be coupled as illustrated above in Figure 5. The exhalation filter element may also be positioned as described above with reference to the other figures. The face mask can also be configured in cup shapes different from the modalities shown in Figure 12, and the figures described above. The mask could, for example, having the configuration shown in U.S. Patent No. 4,827,924 to Japuntich. Figure 13 illustrates a full-face respirator 70, including a mask body 72, which typically includes a facial seal 73 of plastic and / or non-porous rubber, and a transparent shield 74. The mask body 72 is configured to Cover the eyes, nose, and mouth of the user, and form a seal against the user's face. The body 72 of the mask includes inhalation gates 76 that are configured to receive the removable filter cartridges (not shown) as described in the Environmental Health and Safety booklet of Minnesota Mining and Manufacturing Company 70-0701-5436-7 (535) BE, dated April 1, 1993. Gates 76 should include a one-way inhalation valve that allows air to flow into the mask. The filter cartridges filter the air drawn towards the mask before it passes through the gates 76. The mask 70 includes bands or a harness (not shown) to extend over the top of the user's head or back of the head and neck of the user to hold the mask70 against the user's face. A face mask of this construction is also shown and described in U.S. Patent No. 5,924,420 to Reischel et al. and in U.S. Pat. No. Des 388,872 to Grannis et al, and Des. 378,610 to Reischel et al. The body 72 of the mask includes an exhalation valve 78 in general in the central lower portion of the mask 70. The exhalation valve 78 may include a circular flap type diaphragm (not shown) retained at its center with a tongue extending through a hole in the center of the flap. Such exhalation valves are described, for example, in U.S. Patent No. 5,062,421. The present invention also includes an exhalation filter element 41 positioned on the outer portion of the valve housing. The exhalation filter element 41 can be placed at other positions along the exhalation flow stream and close to the exhalation valve similar to the sites shown in other figures. The element 41 of the exhalation filter can be designed to be uncoupled and replaceable. The exhalation filter element is preferably adapted such that its placement in the exhalation flow stream allows the exhalation filter element to reside in the path of least resistance, so that the exhalation filter element substantially does not oppose the exhalation filter element. flow through the exhalation valve. In all the modes shown, under normal circumstances substantially all the exhaled air passes through either the body of the mask or the exhalation filter element 31-41. Although the air can be coupled to the exhalation filter element at various points in the exhalation flow stream, no matter where it is placed, the exhalation filter element makes it possible for the contaminants to be removed from the exhalation flow stream to provide Some level of protection to other people or things while at the same time provides improved comfort to the user and allows the user to put on a tight or tight fitting mask. The exhalation filter element may not necessarily remove all contaminants from an exhalation flow stream, but preferably eliminates at least 95%, and more preferably at least 97%, and still more preferably at least 99% when tested in accordance with the Ba ct eri Ana Filtration Effi cient Test, described later. To provide the user with good comfort while wearing the masks of the invention, the mask preferably makes it possible for at least 50% of the air entering the interior gas space to pass through the exhalation filter element. More preferably, at least 75%, and still more preferably at least 90% of the exhaled air passes through the exhalation filter element, as opposed to traveling through the filter medium or possibly escaping to the periphery of the mask. When the valve described in U.S. Patent Nos. 5,509,436 and 5,325,892 to Japuntich are used on the respirator, and the exhalation filter element demonstrates a lower pressure drop than the body of the mask, more than 100 percent of the air can pass through the exhalation filter element. As described in the Japuntich et al. Patents, this can occur when the air is passed to the filtering face mask at a rate of at least 8 meters per second under a Fluvial Test of Fl uj or Percent ual Side by Side (described later). Because more than 100 percent of the exhaled air passes through the valve, there is a net influx of air through the filter medium. The air that enters the interior gas space through the filter medium is less humid and colder, and therefore improves user comfort. The modes of the exhalation filter element, which are filters that cover larger portions of the mask body, have an increased surface area, so that the resistance through the exhalation filter element is effectively decreased. The lower resistance in the exhalation flow stream increases the percentage of exhaled air that passes through the exhalation valve, rather than through the body of the mask. Different materials and sizes for the body of the mask and the exhalation valve filter can create different patterns of flow and pressure drop. Many types of commercially available filter media, such as meltblown microfiber networks, described above or spunbonded fibrous nonwoven media, have been found to be acceptable filter media for exhalation filter elements. A preferred exhalation filter element comprises a spunbonded network of polypropylene. Such a network can be obtained from PolyBond Inc., Waynesboro, Virginia, product number 87244. The exhalation filter element could also be an open cell foam.

In addition, if the mask uses conformation layers to provide support for the filter medium (see for example, U.S. Patent No. 5,307,796 to Kronzer, U.S. Patent No. 4,807,619 to Dyrud, and U.S. Patent No. 4,536,440 to Berg), the conformation layers (also referred to as as the molded mask shielding material) could be used as an exhalation filter element.

Or the exhalation filter element could be made from the same materials that are commonly used to form conformation layers. Such materials typically include fibers that have bonding components that allow the fibers to be bonded to one another at points of intersection of the fibers. Such thermally bonded fibers typically fall into the form of monofilaments or bicomponents. The construction of non-woven fibers of the shaping layer provides a filtration capacity - although typically not as large as a filter layer - that allows the shaping layer to sift larger particles such as saliva from the user. Because these fibrous webs are made of thermally bonded fibers, it may be possible to mold the webs into a three-dimensional configuration designed to fit over an exhalation valve, for example, in the form of a valve cover. In general, any porous structure that is capable of filtering contaminants is contemplated for use as an exhalation filter element in the invention. To decrease the pressure drop across the exhalation filter element, it could be configured in a form of expanded surface area. For example, this could be corrugated or folded, or it could be in the form of a pancake filter, which could be removably attached. The exhalation filter element preferably contains one or more fluorochemical additives to impart better protection to the mask of the splash fluids. Fluorochemical additives that may be suitable for such purposes are described in U.S. Patent No. 5,025,052 and 5,099,026 to Crater et al., U.S. Patent No. 5,706,804 to Baumann et al., And the patent application. of the United States Serial No. 08 / 901,363 to Klun et al. filed July 28, 1997. The fluorochemical additive can be incorporated into the volume of the solid material that is present in the porous structure of the exhalation filter element, and / or this can be applied to the surface of the porous structure. When the porous structure is fibrous, the fluorochemical additive is preferably incorporated into at least some or all of the fibers in the exhalation filter element.

The fluorochemical additive (s) that may be used in connection with the exhalation filter element to inhibit the passage of liquid through the element may include, for example, fluorochemical oxazolidinones, fluorochemical piperazines, fluoroaliphatic radical containing compounds, fluorochemical esters, and combinations thereof. Preferred fluorochemical additives include the fluorochemical oxazolidinones such as C8F? 7S02N (CH3) CH2CH (CH2C1) OH (see Example 1 of the Crater et al. Patents) and the fluorochemical dimer acid esters (see Example 1 of the application for Klun et al.). A preferred commercially available fluorochemical additive is the protector of the FX-1801 Scotchban ™ brand from 3M Company, Saint Paul, Minnesota. In addition to or in place of the annotated fluorochemical additives, other materials for inhibiting the penetration of the liquid such as waxes or silicones may be employed. Essentially any product that can inhibit the penetration of the liquid but not at the expense of significantly increasing the pressure drop through the exhalation filter element, is contemplated for use in this invention. Preferably, the additive could be processable in molten form so that it can be incorporated directly into the porous structure of the exhalation filter element. The additives desirably impart repellency to aqueous fluids and thereby increase oleophobicity and hydrophobicity or are surface energy reducing agents. The exhalation filter element is not only useful for removing contaminants and inhibiting the penetration of liquid, but it can also be useful for eliminating unwanted vapors. In this way, the exhalation filter element can have sortive qualities to eliminate such contaminants. The exhalation filter element can be made from active particulate material such as activated carbon joined together by the polymeric particulate, to form a filter element which can also include a particulate non-woven filter as described above, to provide characteristics of elimination of vapors, as well as filtration capacity of particulates, satisfactory. An example of a bonded particulate filter is described in U.S. Patent Nos. 5,656,368, 5,078,132, and 5,033,465 to Braun et al. and U.S. Patent No. 5,696,199 to Senkus et al. An example of a filter element having combined gas and particle filtration abilities is described in U.S. Patent No. 5,763,078 to Braun and Steffen. The exhalation filter element could also be configured as a non-woven network of, for example, blown microfibers in molten form, which possess the active particulate as described in U.S. Patent No. 3,971,373 to Braun. The active particulate can also be treated with topical treatments to provide vapor elimination; see, for example, United States Patents Nos. 5,496,785 and 5,344,626 both to Abler. Massage masks having an exhalation filter element according to the invention have been found to meet or exceed industrial standards for features such as fluid resistance, filter efficiency, and user comfort. In the medical field, bacterial filter efficiency (BFE), which is the ability of a mask to remove particles, usually bacteria issued by the user, is typically evaluated for facial masks. The BFE tests are designed to evaluate the percentage of particles that escape from the inside of the mask. There are three tests specified by the Department of Defense and published under Military Specification MIL-M-36954C: Surgical, Disposable Mask (June 1, 1975) that evaluates BFE. As a minimum industry standard, a surgical product must have an efficiency of at least 95% when evaluated under these tests. BFE is calculated by subtracting the percent penetration of 100%. Percent penetration is the ratio of the number of particles downstream to the mask, to the number of particles upstream to the mask. Facial filtering masks using an electrically charged network of polypropylene BMF, and having an exhalation filter element according to the present invention, are capable of exceeding the minimum industrial standard and may even have an efficiency greater than 97%. Facial masks must also meet a fluid resistance test where 5 synthetic blood challenges are forced against the mask under a pressure of 35.15 kg / cm (5 pounds per square inch psi). If synthetic blood does not pass through the mask, it passes the test, and if any synthetic blood is detected, it fails. The masks having an exhalation valve and an exhalation filter element according to the present invention, have been able to pass this test, when the exhalation filter element is placed on the outside or the ambient air of the valve as well as on the inner or facial side of the exhalation valve. In this way, the filter mascaras of the present invention can provide good protection against splash fluids when in use. The comfort of the user improves when a large percentage of exhaled air passes freely through the exhalation valve, as opposed to the body of the mask or its periphery. Tests have been conducted where a stream of compressed air is directed into the interior gas space of a face mask, while the pressure drop across the body of the mask is measured. Although the results vary depending on the filter material used for the inhalation filter element and also with respect to the site and type of the exhalation filter element in the present invention, it was found that at a flow rate of approximately seventy-nine liters per minute, above 95% of the air can leave the interior gas space through the valve, and less than 5% through the filtration material in the body of the mask, when using a network material joined by spinning , polypropylene, commercially available (87244 available from PolyBond of Waynesboro, Virginia) as the exhalation filter element.

EXAMPLES Facial masks having an exhalation filter element were prepared as follows. The exhalation valves that were used are described in U.S. Patent No. 5,325,892 to Japuntich et al., And are available on the 3M Company's mascaras such as the 3M Cool Exhalation Valves.

Flow MR An orifice two centimeters in diameter was cut in the center of the 3M 1860MR ventilator to accommodate the valve. The valve was attached to the ventilator using a sonic welder available from Branson (Danbury, Connecticut). The 3M brand 8511MR facemask respirators that already had a valve were also used. The filter element was coupled to the valve in various ways. In one embodiment, the filter element was welded in place between the valve seat and the body of the mask as shown in Figure 2. In yet another construction, the exhalation filter element was placed on the cover of the mask. the valve and cut to extend approximately 12.7 mm (one half inch) beyond the valve on all sides. The exhalation filter element was then ultrasonically welded to the outer edge of the valve cover as shown in Figure 5, using a sonic welder available from Branson (Danbury, Connecticut). The exhalation filter element can also be coupled in this manner using an adhesive. In yet another construction, the exhalation filter element was placed on the valve seat and under the valve cover as shown in Figure 6. The net-like material extending beyond the seat of the The valve was then folded under the seat, and the wrapped valve was placed on the body of the mask above the opening. The respirator assembly, the filter net, and the valve were then ultrasonically welded together. From the inner part of the mask, the excess filter net was cut, leaving the valve orifice unobstructed and the filter net covering the valve and being sealed around the periphery of the valve. In yet another construction, the exhalation filter element was coupled to the outer edge of a filtering face piece using sonic welding or an adhesive to enable the filter element to essentially cover the entire exterior of the mask, including the exhalation valve as shown in Figure 7.

Bac teri ana Filtration Effi cient Test Facial masks as described above were tested for bacterial filtration efficiency (BFE) in a modified test of, but based on, the MIL-M-36954C standard from the Department of Defense, Military Specifications: Surgical, Disposable Mask (12 June 1975) 4.4.1.1.2 Method II as described by William H. Friedrichs, Jr. In "The Journal of Environmen tal Sci ences", p. 33-40 (November / December 1989). The facial masks described in Table I below were sealed in an airtight chamber. Vacuum air was drawn into the chamber through a high efficiency particulate air (HEPA) filter and then passed through the -spirator, from the interior gas space to the exterior gas space, to a flow constant of 28.3 liters per minute to simulate a constant state of exhalation. This caused the valve to remain open. A nebulizer (part number FT-13, 3M Company, Division of Occupational Health and Environmental Safety, Saint Paul, Minnesota) was used to generate a challenge aerosol, polystyrene latex spheres (PSL) (available from Duke Scientific Corp ., Palo Alto, California) that has a size similar to that of the aerosols created for the nebulization of Staphyl ococc us a ure us, of 2.92 μm of aerodynamic diameter, on the internal part or the facial side of the respirator. The challenge aerosol was not neutralized in its charge. The challenge was generated by squeezing the nebulizer at a rate of one squeeze per second and samples were taken upstream in the interior gas space and then downstream in the outside gas space, using an Aerodynamic Particle Size Meter (APS 3310 from TSl Company, Saint Paul, Minnesota). Percent penetration was determined by dividing the concentration of the particles downstream to the valve between the concentration of the particles upstream to the valve, and multiplying by 100. Only the concentrations of the particles in the size range of 2.74- 3.16 μm were used to calculate the penetration. BFE was calculated as 100 less penetration. In vi tro methods, such as this one, have been found more stringent than in vi ve methods, such as a Creene and Vesl ey test, described by Donald Vesley, Ann C. Langholtz, and James L. Lauer in " Tn.fect_.on in Surgery ", pp. 531-536 (July 1983). Therefore, it is expected that achieving 95% BFE using the method described above would be equivalent to or greater than achieving 95% BFE using the modified Greene and Vesl ey test. The results of the evaluation using the test method described above are shown in Table 1.

TABLE 1 Results of the BFE Test of the Valves of 3MMR Cool Flow ™ Exhalation Having Exhalation Filter Elements Mounted on Respirators 3M 1860MR valve cover as shown in Figure 5 All nets attached by polypropylene spinning 87244 of 35.37 g (1.25 ounces) were obtained from Poly Bond, Inc. Waynesboro, Virginia. * * Percentages are expressed in these examples as percentages by weight, unless otherwise stated. *** See Example 1 of the Patent Application of the United States Serial No. 08 / 901,363 to Klun et al., For the description of this additive. The continuous reference to this fluorochemical dimer acid ester in these Examples refers to the compound mentioned in Example 1 of the application of Klun et al. All the additives in the Examples were processed in molten form in the fibers. The data in Table 1 show that exhalation valves that have exhalation filter elements can achieve more than 95% efficiency in a simulated bacterial filtration efficiency test.

Proof of Resistance to Fl ui two In order to simulate blood splashing from a patient's ruptured artery, a known volume of blood can be impacted on the valve at a known rate, in accordance with Australian Standard AS 4381-1996 (Appendix D) for Surgical Masks , published by Standards Australia (Australian Standards Association), 1 The Crescent, Homebush, NSW 2140, Australia. The test performed was similar to the Australian method with a few changes described later. A synthetic blood solution was prepared by mixing 1000 milliliters of deionized water, 25.0 g of Acrysol G110 (available from Rohm and Haas, Philadelphia, Pennsylvania), and 10.0 g of Red dye 081 (available from Aldrich Chemical Co., Milwaukee, Wisconsin). ). The surface tension was measured and adjusted so that it was in the range between 40 and 44 dynes / cm when adding Brij 30MR, a nonionic surfactant available from ICI Surfactants, Wilmington, Delaware as necessary.

The valve with the diaphragm of the valve properly open was placed 46 cm (18 inches) from a 0.084 cm (0.033 inch) orifice (18 gauge valve). The synthetic blood was made to sprout from the hole and went directly into the opening between the valve seat and the diaphragm of the open valve. The timing was adjusted so that a volume of 2 ml of synthetic blood was released from the orifice at a reservoir pressure of 34,000 Newtons per square meter (5 PSI). A piece of blotting paper was placed on the inside of the valve directly below the valve seat to detect any synthetic blood that penetrated towards the front side of the respirator body, through the valve. The valve was challenged with synthetic blood 5 times. Any detection of synthetic blood on the blotting paper, or anywhere within the facial side of the respirator, after five challenges, is considered a failure; The test is considered to pass when there is no blood detection within the faceplate of the ventilator after five challenges. The respirator body was not evaluated.

The results of the fluid resistance test according to the method described above on the constructions with exhalation filter elements of different materials, and assembled in different positions, are shown in Table 2.

TABLE 2 Fluid Resistance of 3MMR Cool FlowMR Exhalation Valves Having an Exhalation Filter Element Mounted on the 3M 8511MR Respirator **** E The molded shell material used in these examples weighed approximately 4 to 35.37 grams per 0.09 m2 (square foot) and had the following composition: 70% crushed fiber of white polyester Cellbond ™ core / cover 63/35 type 254 of 4 denier x 5 cm (2 inches) from Hoechst-Celanese Corp. (Salisbury, North Carolina). 30% Type 259, Trevira ™ with shredded white polyester finish fiber 70107 3.0 denier x 2.5 cm (1 inch) from Hoechst-Celanese Corp. (Salisbury, NC).

The data in Table 2 show that the exhalation valves of the invention were able to provide good resistance to splash fluids.

Proof of Val va of Fl uj or Per cent ual from Side to Side Exhalation valves that have exhalation filter elements were tested to evaluate the percentage of exhaled air flow that exits the ventilator through the exhalation valve, as opposed to the exit through the respirator filter portion. This parameter was evaluated using the test described in Examples 8-13 of U.S. Patent No. 5,325,892 and described herein again briefly for ease of reference.

The efficiency of the exhalation valve to purge breathing is a major factor that affects the comfort of the user. The filtering facepiece respirators were mounted on a metal plate such that the exhalation valve was placed directly on a 0.96 square centimeter (cm2) hole through which the compressed air was directed, with the flow directed towards the inner part of the mask, like the exhaled air. The pressure drop through the filter medium of the mask can be determined by placing a probe of a manometer with the inside of the filter face mask. The total percentage flow was determined by the following method with reference to Figure 14 for better understanding. First, the linear equation describing the ratio of the volumetric flow of the filter medium of the mask (Qf) to the pressure drop (ΔP) through the face mask was determined while the valve was closed. The pressure drop through the facial mask with the valve left open was then measured at a specified volume flow of exhalation (Qr). The flow through the Qf filter medium of face mask was determined at the pressure drop measured from the linear equation. The flow through the valve alone (Qv) is calculated as The percentage of the total exhalation flow through the valve is calculated If the pressure drop across the face mask is negative at a given Qt, the air flow through the mask mask filter medium towards the interior of the mask will also be negative, giving the condition that the outward flow through the valve orifice Qv is greater than the exhalation flow Qt. Thus, when Q_- is negative, the air is effectively pulled inward through the filter during exhalation, and sent through the valve, resulting in a total percent exhalation flow greater than 100%. This is called aspiration and provides cooling to the user. The results of the test on constructions having an exhalation filter element of different materials and mounted in different positions are shown in Table 3 below.

TABLE 3 Percent Flow Through the Valve at 42 and 79 liters / minute (LPM) of the Exhalation Valves 3M MR Cool FlowMR Having Filter Elements Exhalation Mounted on Respirators 3M 1860 MR The data in Table 3 demonstrate that good flow percentages through the exhalation valve can be achieved by the facial masks of the invention.

All patents and patent applications cited above are incorporated by reference in this document, in their entirety.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (10)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A filtering face mask, characterized in that it comprises: a) a mask body; b) an exhalation valve that is positioned on the body of the mask and having at least one orifice that allows the exhaled air to pass from an interior gas space to an exterior gas space during an exhalation; and c) a fibrous exhalation filter element positioned in the exhalation flow stream, to prevent contaminants from passing from the interior gas space to the exterior gas space with the exhaled air.

2. The filtering face mask according to claim 1, characterized in that it further comprises an inhalation filter element for filtering the inhaled air.

3. The filtering face mask according to claim 2, characterized in that the inhalation filter element is integrally positioned in the body of the mask, and wherein the exhalation filter element shows a pressure drop through it, when a person exhales, whose pressure drop across the exhalation filter is less than a pressure drop through the inhalation filter element during an exhalation.

The filtering face mask according to claim 2, characterized in that the inhalation filter element is not integral to the body of the mask, and wherein the exhalation filter element is adapted such that the placement in the flow of Exhalation flow puts the exhalation filter element in a path of least resistance when a person exhales.

5. The filtering face mask according to claim 3, characterized in that the filtering face mask has a cup-shaped mask body.

The filtering face mask according to claim 3, characterized in that the body of the mask has an opening placed therein, the exhalation valve being placed on the body of the mask in the opening.

The filtering face mask according to claim 6, characterized in that the body of the mask includes a layer of filter material, and wherein the exhalation filter element is placed between the filter material and the base of the filter. exhalation valve, or wherein the exhalation filter element is placed upstream of the opening in the filter material, or where the exhalation valve includes a valve cover and the exhalation filter element extends over and around of the valve cover on its outside, or where the exhalation valve includes a valve cover and the exhalation filter element is located on the inside of the valve cover, or where the exhalation filter element is located. it extends over the outside of the exhalation valve and the body of the mask, and the surface area of the exhalation filter element is larger than the surface area of the filter material in the body of the mask, or where the exhalation filter element is placed downstream to the exhalation valve, and is coupled to the body of the mask, and has a surface area that is less than the surface area of the filter material in the body of the mask.

The filtering face mask according to claim 3, characterized in that the inhalation filter element includes a layer of filtration material and a cover network, and wherein the cover network acts as the exhalation filter element. .

9. The filtering face mask according to claim 1, characterized in that the exhalation valve has a valve cover placed on it which is a porous structure that makes it possible for the valve cover to act as an exhalation filter element. .

10. The filtering face mask according to claim 1, characterized in that the exhalation filter element eliminates at least 95% of what is required when tested in accordance with the Bacterial Filtration Efficacy Test.