Face mask that has a filtered exhalation valve

The present invention relates to a filtering face mask comprising a filter element associated with an exhalation valve. The filter element allows the mask to remove impurities from the exhaled stream.

Face masks are put on the human respiratory tract to prevent dirt from entering the user's respiratory tract and to protect other people or objects from pathogens and other contaminants exhaled by the user. In the first situation, the face mask is worn in an environment where the air contains substances harmful to the user, e.g. in a car body repair shop. In the second situation, a face mask is put on in an environment where there is a high risk of infection or contamination for another person or thing, e.g. in an operating room or in a sterilized room.

Face masks intended to protect the user are usually called respirators, while masks intended primarily for use in the second scenario, namely to protect other people and things, are usually called face 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 fitting face masks, mainly intended to protect others from contaminants that are exhaled by the user. Substances that are exhaled from the user's mouth are often aerosols, which are usually suspensions of fine solids or liquid particles in gas. Surgical masks filter such particles quite well. U.S. Patent No. 3,613,678 (Mayhew) describes an example of a loosely fitting surgical mask.

Masks that are not tight around the face, such as some known surgical masks, usually do not have an exhalation valve designed to clean the exhaled air from inside the mask. These masks are sometimes loosely fitted so that the exhaled air can easily escape from the sides of the mask, so that the user does not feel uncomfortable, especially when breathing heavily. However, because these masks are loosely fitted, they cannot completely protect the user against inhalation of dirt or splashing liquids. Due to the various impurities that occur in hospitals, and the many pathogens that exist in body fluids, loose fitting is a clear disadvantage of such surgical masks. In addition, masks that are not tight around the face allow, as you know, the passage of exhaled air around the edges of the mask, and the exhalation valve attached to the mask body does not provide any benefits in such masks.

Face masks have also been constructed to ensure a tighter, more hermetic fit between the wearer's face and the mask. Some tight-fitting masks have a non-porous rubber face that supports removable or permanently attached filter cartridges. This part of the face also has an exhalation valve for cleaning warm, moist, high CO2 content, exhaled air from inside the mask. Masks with this design are usually called more descriptively respirators. U.S. Patent No. 5,062,421 (Burns and Reichsel) describes an example of such a mask. Commercially available products include 5000 and 6000 Series ™ masks, sold by the 3M Company, St. Paul, Minnesota.

Other tightly fitted face masks have a porous mask body that is shaped and designed to filter inhaled air. Usually, these masks are also called respirators and often have an exhalation valve that opens under increased internal air pressure when the user exhales - see, e.g., US Patent No. 4,827,924 (japuntich ^).

190 442

Additional examples of filtering face masks that have exhalation valves are provided in US Patent Nos. 5,599,436 and 5,325,892 (japuntich et al.), 4,537,189 (Vicenzi), 4,934,362 (Braun) and 5,505,197 (Scholey).

Typically, the exhalation valve is protected by a valve cover - see, e.g., US Patents Nos. 347.299 and 347.298 - which can protect the valve against physical damage caused, for example, by unintentional impacts.

Known close-fitting masks that have an exhalation valve can protect the user from directly inhaling harmful particles, but these masks have some limitations when it comes to protecting other people or things from being exposed to user exhaled contaminants. When the user exhales, the exhalation valve opens to the ambient air, and such temporary opening causes a duct from the user's mouth and nose to place outside the mask. Conversely, liquid splashes can get from the outside of the mask to its interior through such temporary opening.

In many applications, especially in surgery and sterilized rooms, the open duct temporarily formed by the exhalation valve may possibly lead to patient infection or contamination of the precision part. The instrumentalists association recommended that masks be 95% effective in retaining exhaled viable particles. Proposed Recommended Practice for OR Wearing Apparel, AORN Journal, v. 33, nl, pp. 100-104, 101 (January 1981); see also D. Vesley et al., Clinical Implications of Surgical Mask Retention Effeciencies for Viable and Total Particles, INFECTIONS IN SURGERY, pp. 531-536, 533 (July 1983). Consequently, face masks that have exhalation valves are not currently recommended for use in such environments. See e.g. Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health Care Facilities, MORBIDITY AND MORTALITY WEEKLY REPORT, US Dept. Health & Human Services, v. 43, n. RR-13, p. 34 & 98 (October 12, 1994).

Face masks are produced that can protect both the user and nearby persons and objects from contamination. Commercially available products include 1800 ™, 1812 ™ m 1838 ™, 1869 ™ and 8210 ™ grades sold by the 3M Company. Other examples of such masks are described in US Patent Nos. 5,307,706 (Kronzer et al.), 4,807,619 (Dyrud) and 4,536,440 (Berg). These masks are fitted relatively tightly so that gases and liquid contaminants cannot enter or leave the interior of the mask at its perimeter, but these masks usually do not have an exhalation valve that allows quick removal of exhaled air from the interior of the mask. Thus, although these masks remove impurities from the inspiratory and expiratory streams and provide protection against liquid splashes, they cannot, however, substantially improve user comfort.

U.S. Patent No. 5,117,821 (White) describes an example of a mask that removes vapors from exhaled air. This mask is used when hunting so that the animal cannot sense the hunter. This mask has an inhalation valve that allows the ambient air to be drawn into the mask, and also has a cleansing container supported on the user's body and designed to collect exhaled air. A long pipe directs the exhaled air into this distant tank. This device has an exhalation valve located at the ends of the tank to control the passage of the purified exhalation to the atmosphere and to exclude inhalation of air from the tank. The reservoir may contain charcoal particles to remove fumes from the breath.

Although the hunting mask prevents the exhaled organic vapors from entering the ambient air (and can give the hunter a lot of benefits), this mask is not intended to create a source of clean air for the user. Nor does it provide for an inlet filter attachment, is somewhat troublesome and would be impractical in other applications.

German publication 43 077 54 describes a mask that uses a long hose or tube extending from the mask body to further connect to another air tube which in turn is attached to an air flow regulating device. This air flow regulating device controls the inflow and outflow of breath, including an air pump that draws the exhaled air into the air filter to clean the exhaled

190 442 air. In addition, this device can also be used to supply purified air to the user. The air regulating device draws a breath and directs the filtered air to the user. The air flow regulating device includes an energy source and a clamp for attaching the device to the user's clothing.

EP-A-0 171 511 describes a respiratory mask that includes an inspiration and expiratory valve and a filter device attached solely to the exhalation valve, which filter carbon dioxide exhaled by the user before venting into the atmosphere. The filter device contains a lithium hydroxide LiOH insert for this purpose, containing lithium hydroxide LiOH as a carbon dioxide (CO?) Absorber, and is woven as a filter material to prevent lithium hydroxide dust from coming into contact with the user's body and causing chemical burns.

U.S. Patent No. 5,016,625 describes a respirator to filter smoke and fumes from air from a fire to prevent the user from inhaling too much toxic gas such as carbon monoxide. A ventilation device was used using the textile material as a filter, which is wetted by an executive member, so that the filter can filter toxic gas and smoke from the inhaled air.

SUMMARY OF THE INVENTION

A filtering face mask comprising a mask body and an exhalation valve that is located on the mask body and has at least one opening to allow exhaled air to pass from the internal gas space to the external gas space during exhalation, characterized by having a fibrous exhalation filter element located in the exhaust stream, so that pollutants cannot pass from the internal gas space to the external gas space with the exhaled air.

It is preferred that the filtering mask includes an inspiratory filter element for filtering the inhaled air, and furthermore, the inspiratory filter element is integrally located in the mask body, the expiratory filter element having a lower pressure drop on exhalation than the pressure drop on the inspiratory filter element during exhalation. The inspiratory filter element is not integral with the mask body, and furthermore the expiratory filter element is adapted such that placement in the exhaust stream causes the position of the exhaust filter element in the path of least resistance at the exhalation. The filtering mask has a cup-shaped body, the mask body having an opening therein, and the exhalation valve is located on the mask body at this opening. Also preferably, the mask body includes a layer of filter material and the expiratory filter element is located between the filter material and the expiratory valve base, or the expiratory filter element is located in front of the opening in the filter material, or the expiratory valve includes a valve cover and the expiratory filter element extends over and around the valve cover on the outside of the valve, or the exhaust valve includes a valve cover, and the expiratory filter element is located on the inside of the valve cover, or the expiratory filter element extends over the outside of the expiratory valve and the mask body, and the surface area of ​​the expiratory filter element is larger than the surface area of ​​the filter material in the mask body, or the expiratory filter element is located behind an exhaust valve and is attached to the mask body and has a surface area, which is smaller than the surface area of ​​the mask body filter material. In addition, the inspiratory filter element includes a filter material layer and cover material, the cover material acting as an expiratory filter element. The exhalation valve has a valve cover disposed thereon, which is a porous structure that acts as an expiratory filter element, the expiratory filter element removing at least 95% of the hazard when tested according to a bacterial filtration efficiency test.

The invention differs from known face masks that have an expiratory valve in that the invention for the first time has an expiratory filter element that can prevent impurities in the expiratory stream from moving from the internal gas space to the external gas space. This property allows the face mask to be particularly advantageous when used in surgical or in congestive procedures

190 442 in sterilized rooms, where it has not been used so far. In addition, unlike some previously known face masks, the solution of the invention can be in the form of a tight-fitting mask that provides the user with good protection against air pollution and liquid splashes. And because the face mask according to the invention has an exhalation valve and can provide the user with comfort due to the ability to quickly remove warm, humid air with a high CO content? from inside the mask. The invention therefore provides greater convenience for users by reducing the temperature, humidity and carbon dioxide content within the mask, while at the same time protecting the user and preventing particles and other contaminants from entering the environment.

With reference to the invention, the following terms have the meanings given below: aerosol - means a gas containing suspended particles in solid and / or liquid form; clean air - means the volume of air or oxygen that has been filtered to remove impurities or otherwise becomes safe to breathe;

impurities - means particles and / or other substances that in principle cannot be considered as particles (e.g. organic vapors, etc.) but which may be suspended in the air, including air in the exhaled stream;

exhalation valve - means a valve intended to be used on a filtering face mask to open under the pressure of exhaled air and remain closed when the user inhales and between breaths;

exhaled air - means air that is exhaled by the user of a filtering face mask;

expiratory filter element - means a porous structure through which exhaled air can pass and which is capable of removing impurities from the exhaled stream;

exhaled stream - means the air stream that passes through the exhaust valve opening;

external gas space - means the space in which the exhaled gas enters after passing significantly beyond the exhalation valve;

filtering face mask - means a mask that covers at least the nose and mouth of the user and is able to provide clean air to the user;

inspiratory filter element - means a porous structure through which the inhaled air passes before inhalation by the user, so that impurities and / or particles can be removed from it;

internal gas space - means the space in which clean air enters before being inhaled by the user and in which exhaled air passes before passing through the exhaust valve opening;

mask body - means a structure that fits at least on the nose and mouth of a person and which helps to create an internal gas space separated from the external gas space;

particles - means a liquid substance and / or steel that can be suspended in the air, for example pathogens, bacteria, viruses, fungi, mucus, saliva, blood, etc .;

Porous structure - means a mixture of a certain amount of solid material and pore volume, which creates a three-dimensional system of interstitial, winding channels through which gas can pass.

The subject of the invention is illustrated in the embodiments in the drawing, in which:

figure 1 is a perspective view of a filtering face mask 20 that is equipped with an exhaust valve 22;

figure 2 is a cross-sectional view of the exhaust valve 22 showing the first embodiment of an exhaust filter element 31 according to the invention;

figure 3 is a front view of the valve seat 30 that is used in conjunction with the exhaust valve 22;

figure 4 is a cross-sectional view of the exhaust valve 22 showing a second embodiment of an exhaust filter element 32 according to the invention;

190 FIG. 442 is a cross-sectional view of the exhaust valve 22 illustrating the third embodiment of an exhaust filter element 33 according to the invention;

figure 6 is a side view of the exhaust valve 22 showing a fourth embodiment of an exhaust filter element 34 according to the invention;

figure 7 is a cross section of a mask 20 'similar to mask 20 shown in figure 1, illustrating a fifth embodiment of an exhaust filter element according to the invention;

figure 8 is a cross section of a mask 20 similar to the mask 20 shown in figure 1, illustrating a sixth embodiment of the exhaust filter element 36 according to the invention;

figure 9 is a section of a mask 20 'similar to mask 20 shown in figure 1, illustrating a seventh embodiment of an exhaust filter element 37 according to the invention;

figure 10 is a section through the exhaust valve 22 with an exhaust filter element 38 according to the invention;

figure 11 is a cross-sectional view of the exhaust valve 22 with a detachable exhaust filter element 39 according to the invention;

figure 12 is a front view of a filtering face mask 60 having an exhaust filter element 40 according to the invention;

Figure 13 is a front view of a full-face filter mask 70 illustrating the exhaust filter element 41 of the invention; and Figure 14 is a schematic view illustrating the air flow when performing a percentage flow through the valve.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention is applicable to many types of facial filtering masks, including half-masks that cover the user's nose and mouth, respirators that cover the user's nose, mouth and eyes, full-body coveralls and hoods that supply clean air to the user, powered masks air, self-contained breathing devices and essentially all other filtering masks that may be equipped with an exhalation valve. The invention is particularly suitable for use with facial filter masks that have a porous mask body that acts as a filter.

According to various embodiments of the present invention, an exhalation filter element may be located in front of the exhalation valve opening, so that the particles contained in the aerosols are collected before passing through the exhalation valve. In another embodiment, the exhalation filter element may be located between the mask body and the exhalation valve opening. In yet other embodiments, the expiratory filter element may be located downstream of the expiratory valve so that air passing through the expiratory valve then passes through the expiratory filter element. Other embodiments include an expiratory filter element covering 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 less exhalation resistance, or pressure loss on the expiratory filter element. The invention may also include embodiments in which the fabric covering the mask or the shaping layers act as an exhalation filter, or the valve cover is an exhaust filter.

Figure 1 shows a mask 20 that has an exhalation valve 22 positioned centrally on the mask body 24. The mask body 24 has a substantially cup-shaped shape so that it fits snugly against the nose and mouth of the man after putting on the mask. The mask 20 is generally intended to maintain tight contact with the user's face at its circumference 21. The mask body 24 is tightly sealed to the user's face around the perimeter 21 of the mask by straps 26 that extend behind the user's head and neck after the mask is on. The mask 20 creates an internal gas space between the mask body 24 and the user's face. This internal gas space is separated from the ambient air or external gas space by the mask body 24 and by the exhalation valve 22. The mask body may have an adjustable nose clip 25 (see Fig. 7-9) mounted on the inside of the mask body 24 (or outside or between layers) to ensure a snug fit on the nose and where the nose meets the cheekbone. A mask with the configuration shown in Fig. 1 is described in US Patent Application Serial No. 08 / 612,527 (Bostock et al.) And in US Model Application Serial No. 29 / 059.264 (Henderson et al.), 29 / 059.265 (Bryant et al. )

190 442 and 29 / 062.787 (Curran et al.). The masks of the invention may have many other configurations, such as flat masks or bowl-shaped masks, as exemplified in US Patent No. 4,807,619 (Dyrud et al.). The nose clip may have the configuration described in US Patent No. 5,558,089 (Castiglione). The mask may also have a thermochromic fit signaling the seal around its perimeter so that the user can easily make sure that a proper fit is provided - see US Patent No. 5,617,849 (Springett et al.).

The exhalation valve 22, which is provided on the mask body 24, opens when the user exhales, under the effect of increased pressure inside the mask, and should remain closed between breaths and during inspiration. When the user inhales, the air is drawn through the filter material, which may contain non-woven filter material 27 (Figures 2, 4-9 and 12-13). Filter materials that are commonly used on vacuum half-mask respirators, such as the respirator shown in Figure 1, often contain a tangled web of molten microfibers (BMF) having electric charges. BMF fibers usually have an average diameter of about 10 (or smaller). When these fibers are accidentally entangled in the web, they have sufficient integrity to be treated as a mat. Examples of fibrous materials that can be used as filters in the mask body are described in U.S. Patent No. 5,706,804 (Baumann et al.), U.S. Patent No. 4,419,993 (Peterson), U.S. Patent Publication No. Re 28.102 ( Mayhew), in US Patent Nos. 5,472,481 and 5,411,576 (Johnes et al.) And in US Patent Application 08 / 514.866 (Rousseau et al.). Fibrous materials may contain additives to increase filtration, such as the additives described in US Patent Nos. 5,025,052 and 5,099,026 (Crater et al.), And may also have low extractable hydrocarbon content to improve performance (see, for example, US Patent Application Serial No. 08 / 941.945 (Rousseau et al.)). Fibrous webs having increased oil mist resistance may also be produced, as described in U.S. Patent No. 4,874,399 (Reed et al.) And in U.S. Patent Applications 08 / 941.270 and 08 / 941.864 (both Rousseau et al.). Electric charges can be introduced into the nonwoven webs of BMF fibers by the methods described, for example, in US Patent No. 5,416,507 (Angadjivand et al.), In US Patent No. 4,215,682 (Kubik et al.) And in US Patent No. 4,592,815 ( Nakao).

Figure 2 is a cross sectional view of the exhaust valve 22 mounted on the mask body 24. The body 24 functions as an inspiratory filter element and includes a filter material layer 27, an outer fabric cover material 29 and an inner fabric cover material 29 '. The inspiratory filter element is integral with the mask body 24. That is, it forms part of the mask body, and is not the part that is later attached to the body. The outer and inner fabric material 29 and 29 'of the cover protects the filter material layer 27 against frictional forces and stops any fibers that may detach from the filter material layer 27. The fabric materials 29, 29' of the cover may also have filtration ability, although usually not similar to the filtration capacity of the fabric constituting the filtering material layer 27. Covering fabrics may be made of nonwovens containing polyolefins and polyesters (see e.g. U.S. Patent Nos. 4,807,619 and 4,536,440 and U.S. Patent Application 08 / 881.348 issued June 24, 1997). The exhalation valve 22 includes a seat 30 and a flexible flap 42. This flexible flap 42 rests on the sealing surface 43 when the flap is closed, but is lifted from the sealing surface 43 at the free end 44, when significant pressure is achieved during exhalation. The valve sealing surface 43 is generally concave curvilinear in cross section when viewed from the side.

Figure 3 shows the valve seat 30 in a front view. The valve seat 30 has an opening 45 that is located radially inside the sealing surface 43. The opening 45 may have cross members 47 that stabilize the sealing surface 43 and, as a result, exhalation valve 22 (Fig. 2). The cross members 47 may also prevent the flap 42 (Fig. 2) from turning into the opening 45 during inspiration. The flexible flap 42 is attached to its fixed part 48 (fig. 2) to the valve seat 30 on the flap holding surface 49. The flap holding surface 49, as shown, is located outside the area covered by the opening and may have posts 51 to assist in mounting the flap on that surface. The flexible flap 42 (Fig. 2) can be attached to the surface 49 by ultrasonic welding, by means of glue, by mechanical clamping, etc. The valve seat 30 also has a flanged base 46 that extends sideways from the valve seat 30 at its base to form a surface enabling attachment of the exhaust valve 22 (Fig. 2) to the mask body 24. The exhalation valve 22 shown in Figs. 2 and 3 is more fully described in US Patent Nos. 5,599,436 and 5,325,892 (Japuntich et al.). Unlike the valve described in these two patents, the exhaust valve 22 shown in Fig. 2, has an expiratory filter element 31 located in the expiratory stream.

The exhalation filter element 31 shown in Fig. 2 is located between the filter material layer 27 in the mask body 24 and the exhalation valve base 22. The expiratory filter element 31 is therefore located behind the opening 52 in the mask body 24. The air exhaled by the user enters the inner gas space of the mask, which in Figure 2 is located on the left side of the mask body 24. Exhaled air exits the internal gas space passing through the opening 52 in the mask body 24. The opening 52 is surrounded by the exhaust valve 22 at its base 46. Before passing through the valve opening 45, the exhaled air passes through the exhaust filter element 31. The expiratory filter element 31 removes impurities that may be present in the exhaled air stream, e.g., particles suspended in a user exhaled aerosol. After passing through the expiratory filter element 31, the exhaled air exits from the valve opening 45 when the free end 44 of the flexible flap is lifted from the sealing surface 43, under the force generated by the exhaled air of the user. All exhaled air should pass through the mask body filter material layer 27 or the exhaust filter element 31. Under ideal conditions, the exhaled air cannot leave the internal gas space without filtering, unless it unintentionally escapes from the mask e.g. at its circumference 21 (Fig. 1).

Exhaled air that exits the internal gas space through the valve opening 45 then passes through the holes 53 in the valve cover 54 to enter the external gas space. The valve cover 54 is located on the outside of the valve seat 30 and includes holes 53 on the sides and at the top of the valve cover 54. A valve cover with this configuration is shown in US Patent 347.299 (Bryant et al.). Other configurations of other exhaust valves and valve covers may also be used (see US Patent Model 347.298 (Japuntich et al.) For a different valve cover).

The resistance or pressure drop on the expiratory filter element is preferably smaller than the resistance or pressure drop on the inspiratory filter element of the mask body. Because the exhaled air will travel along the path with the least resistance, it is important to use an expiratory filter element that has a lower pressure drop than the mask body, preferably smaller than the filter media in the mask body, so that most of the exhaled air passes through the exhaust filter materials rather than through mask body filter media. For this purpose, the exhalation valve containing the exhalation filter element should have a pressure drop less than the pressure drop over the filter media of the mask body. Thus, most or substantially all of the exhaled air flows from the inside of the mask body out through the exhalation valve and through the exhalation filter element. If the resistance to the flow of air through the exhaust filter element is so great that the air cannot be easily pushed out of the mask, then the moisture and carbon dioxide content of the mask may increase and cause discomfort to the user.

Figure 4 shows an expiratory filter element 32 located at another location. In this embodiment, the exhalation filter element 32 is located inside the mask body 24 in front of the opening 52 in the filter media. As in the previous embodiment, the exhaled air raises the flexible flap 42 at the outlet opening 45, and then passes through the holes 53 in the valve cover 54. The exhaled air passes through the expiratory filter element 32 before passing through the opening 52 in the filter media and through the valve opening 45. As in other embodiments, the exhaust filter element 32 can be attached to the mask at this point, for example, by means of

190 442 mechanical (e.g. snap or friction fastening), by ultrasonic welding or using glue.

Figure 5 shows an expiratory filter element 33 that extends above and around the valve cover 54 of the expiratory valve 22. The expiratory filter element 33 is preferably located just off the outside of the valve cover and is held between the mask body 24 and the valve seat 30 and the valve cover 54. In this position, the exhaled air passes through the exhalation filter element 33 after passing through the holes 53 in the valve cover 54. Such designs can be advantageous because the location of the exhaust filter element 33 behind the valve opening 45 and the flap 42 allows the expiratory stream to hit the valve flap 42 unhindered. The placement of the exhalation filter element behind the valve cover may thus avoid reducing the momentum of the exhaled air stream, which could worsen valve opening. The location behind the valve cover can also be advantageous in that it provides better prophylactic valve protection and enables the collection of particles that could arise as a result of a break in the condensation meniscus between the valve flap 42 and the valve seat 30.

Figure 6 shows an expiratory filter element 34 that is located on the inside of the valve cover 54. The exhalation filter element 34 is held between the valve seat 30 and the mask body 24 and between the valve seat 30 and the valve cover 54. The exhaled air therefore passes through the exhalation filter element 34 before passing through the holes 53 in the valve cover 54, but after passing through the valve opening 45. The positioning of the exhaust filter element 34 downstream of the valve in this embodiment may likewise be advantageous as described above with reference to Fig. 5.

Figure 7 also shows an exhaust filter element that is located behind the valve flap 42. The exhaust filter element 35 has an increased surface area compared to other embodiments. The exhalation filter element 35 extends completely on the outside of the exhalation valve 22 and mask body 24. Because the exhaust filter element 35 has a surface area slightly larger than the surface area of ​​the mask body 24 (or filter material layer 27 in the mask body 24), on the exhaust filter element 35 there will be less pressure drop than on the mask body 24 (if the same filter material is used in each of these elements) and therefore the exhaled air will easily pass from the internal gas space to the external gas space through the opening 52 in the mask body 24 and through the exhaust valve opening 45. The filter material 27, which is used in the mask body 24, is usually a high-efficiency material that exhibits very low particle penetration (see description above, and the patents and patent applications listed above for BMF filter materials, static charge introduction and fibrous additives) . Particle passage is usually sufficient to meet the NlOSH requirements set out in 42 CFR Part 84. Particle permeation and pressure drop change inversely relative to each other (lower permeability is usually accompanied by larger pressure drops). Since the element 35 will exhibit a lower pressure drop compared to the mask body 24, the embodiment shown in Fig. 7 is advantageous because the filter materials used in the exhaust filter element 35 can be high efficiency materials such as those used in the mask body.

In Figure 8, the exhalation filter element 36 is also located behind the holes 53 in the valve cover 54. However, unlike the embodiment shown in Fig. 7, the surface area of ​​the exhaust filter element 36 is smaller than the surface area of ​​the mask body 24. The exhalation filter element 36 is attached to the mask body 24 in a place where the middle panel 55 of the mask body meets the upper panel 56 and the lower panel 57. Although the exhalation filter element 36 does not cover a surface area that is larger than the mask body 24, it is, however, an increased surface area compared to other embodiments. The exhaust filter element 36 need not necessarily be able to exhibit the permeation and pressure drop values ​​that are exhibited by the filter materials 27, however, it can be a very well-functioning filter material that has low particle penetration. If the inner and outer material 29 and 29 'cover

190 442 contribute significantly to the total pressure drop across the mask body 24, then it may be possible that the exhaust filter element 36 is as well suited as filter material as the filter materials 27 used in the mask body 24.

In Figure 9, the exhalation filter element 37 is the outer cover material 29. This embodiment is advantageous because it is relatively easy to manufacture. Such an article can be made by piercing the hole through other layers, such as a filter material layer 27, or outer material 29 'in the mask body 24, and after piercing the holes, the outer cover material 29 is applied. This implementation can be advantageous in a continuous process in the production line. Alternatively, the inner cover material 29 may act as an exhalation filter element, and the outer cover material 29 may have holes arranged therein. Or, both layers of material 29, 29 'can act as part of the exhaust filter.

In Figure 10, the exhalation valve 22 has an expiratory filter element shown as a filter cover 38 of sintered plastic or other material with sufficient rigidity and as a porous structure providing filtration properties. Examples of materials that can be used to make the sintered valve cover include VVLON HP (grain size 1 mm), VVLON HP (grain size 2 mm), VVLON TT1 / 119 and VVLON HP (grain size 2.5 mm), all of polypropylene base material available from Porvair Technology Ltd., Wrexham, Clwyd, Wales, United Kingdom. Sintered or porous valve covers can be made from sheets made of grains. The sheet material can be cut into pieces, which are mounted in the form of a valve cover. Alternatively, the beans can be heated and pressed in a device adapted to shape the valve cover. The valve cover 38 has no openings 53, such as the valve cover 50 shown in Figs. 2.5-9 and 11. The air flowing through the exhalation valve 22 rather passes through the porous structure of the exhaust filter element 38 constituting the cover. When using this integrated design, no exhaust filter element separate from the valve cover is needed.

Figure 11 shows the exhalation valve 22 which has the exhalation filter element 39 removable and preferably replaceable. The replaceable filter element 39 extends over and snaps into the valve cover 54 using conventional or other fasteners. An impermeable layer (not shown) is placed between the valve cover 54 and the mask body 24 to prevent exhaled moisture from entering again. The replaceable filter element 39 can be designed to snap into and seals onto the valve cover 54, or it can be attached by other known methods, e.g., pressure sensitive adhesive bonding, or allowing adjustment. The exchangeable filter element 39 may have a porous structure, such as a thermally bonded non-woven fabric, or it may be made of sintered or porous material as described above. This allows the exhaust filter element to be replaced before the end of the mask's life.

Figure 12 shows a second embodiment of the cup-shaped face mask generally indicated by 60. Mask 60 includes straps 62 that are attached to the mask body 64 and which extend behind the user's head and neck to hold the mask against the face. Mask body 64 acts as an inspiratory filter element and is essentially made of fibrous filter material as described above, and may also include layers of inner and / or outer cover material - see, for example, US Patent No. 5,307,796 (Kronzer et al.), Patent U.S. Patent No. 4,807,619 (Dyrud) and U.S. Patent No. 4,536,440 (Berg). Similarly to the embodiment shown in Figs. 1-7, the face mask 60 may include an exhalation valve similar to the valve in other embodiments. An exhaust filter element 40 that covers the outside of the valve cover (not shown) can be used to prevent dirt from entering the external gas space. The exhalation filter element can be attached as shown above in Fig. 5. The exhalation filter element can also be positioned as described above with reference to other drawings. The face mask may also have bowl shapes other than the embodiments shown in Fig. 12 and in the drawings described above. This mask may, for example, have the shape shown in US Patent No. 4,827,924 (Japuntich).

190 442

Figure 13 shows a mask 70 in the form of a full-face respirator that includes mask body 72, comprising a substantially non-porous face seal 73 made of plastic and / or rubber, and a transparent lens 74. Mask body 72 has a shape that covers the eyes, nose and the user's mouth and provided a seal around the user's face. Mask body 72 includes inspiratory holes 76 that are used to accommodate removable filter cartridges (not shown) such as those described in the Minnesota Mining and Manufacturing Company Health and Environmental Safety 70-0701-5436-7 (535) BE brochure April 1 1993. Openings 76 should include a one-way inspiration valve that allows air to flow into the mask. Filter cartridges filter the air drawn into the mask before it passes through the holes 76. Mask 70 includes stripes (not shown) extending through the top of the user's head and behind his head and neck to hold the mask 70 against the user's face. A face mask of this design is also shown and described in US Patent Application 08 / 727.340 (Reischel et al.) And in US Patent No. 388.872 (Grannis et al.) And 378.610 (Reischel et al.).

Mask body 72 includes an exhalation valve 78 substantially in the middle bottom portion of the mask 70. Exhalation valve 78 may include a circular flap type membrane (not shown) held in its center by a chin extending through the opening in the center of the flap. Such exhaust valves are described, for example, in US Patent No. 5,062,421. The present invention also includes an exhaust filter element 41 disposed on the exterior of the valve housing. This exhalation filter element 41 may be located at other locations along the exhalation flow stream and near the exhalation valve similar to the locations shown in other drawings. The exhaust filter element 41 can be made removable and replaceable. The expiratory filter element is preferably adjusted so that its placement in the expiratory flow stream allows the expiratory filter element to rest on the path with the least resistance, such that the expiratory filter element essentially does not inhibit flow through the expiratory valve.

In all embodiments shown, under normal circumstances, substantially all exhaled air passes either through the mask body or through the exhalation filter element 31-41. Although air may contact the expiratory filter element at various points in the expiratory flow stream, regardless of its location the expiratory filter element allows the removal of impurities from the expiratory flow stream to provide some level of protection to other people or things while providing better user comfort and enabling the user putting on a tightly fitting mask. The expiratory filter element need not necessarily remove all impurities from the exhalation flow stream, but preferably retains at least 95%, and more preferably at least 97%, and even more preferably at least 99% when tested according to the bacterial filtration efficiency test described above.

To provide the user with comfort when wearing the masks of the invention, the mask preferably allows at least 50% of the air entering the internal gas space to pass through the exhaust filter element. More preferably, at least 75%, and even more preferably at least 90% of the exhaled air passes through the exhalation filter element instead of escaping through the filter material or possibly around the perimeter of the mask. When the valve described in US Patents 5,509,436 and 5,325,892 (Japuntich) is used in a respirator and the exhaust filter element has a lower pressure drop than the mask body, then more than 100% of air can pass through the exhaust filter element. As described in these patents, this may occur when air flows into the filter face mask at a speed of at least 8 meters per second when testing the percentage flow through the valve (described below). Because more than 100% of the exhaled air passes through the valve, there is a net supply of air through the filter material. The air that enters the internal gas space through the filtering material is less humid and cooler, and therefore improves the user's comfort.

Embodiments of the exhalation filter element, which are filters covering larger portions of the mask body, have an increased surface area such that the flow resistance through the expiratory filter element is effectively reduced. Less resistance for the expiratory flow stream increases the percentage of exhaled air passing through

190 442 exhalation valve and not through the mask body. Different materials and dimensions of the mask body and exhalation valve filter can create different flow distributions and pressure drops.

It has been found that many types of commercially available filter materials, such as melt-blown microfibers, described above, or spin-bonded nonwovens are acceptable filter materials for exhaust filter components. A preferred exhaust filter element comprises spin-bonded polypropylene material. Such material may be obtained from PolyBond Inc., Waynesboro, Virginia, product number 87244. The exhalation filter element can also be an open-cell foam. In addition, if the mask uses shaping layers to provide support for filter materials (see, e.g., US Patent No. 5,307,796 (Kronzer), US Patent No. 4,807,619 (Dyrud) and US Patent No. 4,536,440 (Berg), then the shaping layers (also called shell-shaped mask material) can be used as part of the exhaust filter. Or the exhaust filter element can be made of the same materials that are usually used to create shaping layers. Such materials usually contain fibers that have bonding components that allow the fibers to be bonded to each other at the intersection of these fibers. Such thermally bonded fibers typically exist as single filaments or in multi-component form. The non-woven structure of the shaping layer gives it filterability, although usually not as large as the filter layer, which allows the shaping layer to retain larger user particles such as saliva. Because such materials are made of thermally bonded fibers, they can be formed into three-dimensional shapes that fit into the exhalation valve, such as in the form of a valve cover, for example. In general, any porous structure that is capable of filtering contaminants is contemplated for use as an exhaust filter element according to the invention.

To reduce the pressure drop on the exhaust filter element, it can be made with an enlarged surface area. For example, it may be crinkled or braided, or it may be in the form of a cake-shaped filter that is detachably attached.

The exhalation filter element preferably contains fluorochemical additives to improve the mask's protection against liquid splashes. Fluorochemical additives that may be suitable for such purposes are described in US Patent Nos. 5,025,052 and 5,099,026 (Crater et al.), In U.S. Patent No. 5,706,804 (Baumann et al.) And in U.S. Patent Application Serial No. 08 / 901.363 (Klun et al.) Of July 28, 1997. The fluorochemical additive may be contained in the volume of solid material that occurs in the porous structure of the exhaust filter element and / or may be applied to the surface of the porous structure. When the porous structure is fibrous, the fluorochemical additive is preferably included in at least some or all of the fibers of the exhalation filter element.

Fluorochemical additives that can be used in conjunction with an expiratory filter element to suppress liquid passage through this element may include, for example, fluurochemical oxazolidinones, fluorochemical piperazines, fluoroaliphatic radical containing compounds, fluorochemical esters and combinations thereof. Preferred fluorochemical additives include fluorochemical oxazolidinones such as CsFi₇SC2 (CH3) CH₂CH- (CH ₂Cl) OH (see example 1 in Crater and other patents) and fluorochemical esters of dimeric acid (see example 1 of the application Klun et al.). A preferred commercially available fluorochemical additive is brand name FK-1801 Scotchban ™ from the 3M Company, Saint Paul, Minnesota.

In addition to or instead of the fluorochemical additives listed, other materials may be used to prevent the passage of liquids, such as waxes or silicones. In principle, any product that prevents fluid passage, but not at the expense of significantly increasing the pressure drop across the exhaust filter element, is contemplated for use in the present invention. Preferably the additive is suitable for melt processing so that it can be included directly in the porous structure of the exhaust filter element. Such additives have a beneficial effect on the repulsion of aqueous fluids, and thus increase oleophobicity and hydrophobicity, or are factors that reduce surface energy.

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The exhalation filter element is not only useful to remove impurities and prevent fluid from passing through, but it can also be useful to remove unwanted fumes. The exhaust filter element may therefore have sorption properties for removing such impurities. The exhaust filter element may be made of active granular material, such as activated carbon; bonded together by a polymeric granular material to form a filter element that may also contain a nonwoven granular filter as described above to provide vapor removal properties as well as satisfactory filtering efficiency for the particulate materials. An example of a bonded particulate filter is described in US Patent Nos. 5,656,368, 5,078,322 and 5,033,465 (Braun et al.) And in US Patent No. 5,696,199 (Senkus et al.). An example of a filter element that combines the ability to filter gases and particulate materials is described in US Patent No. 5,763,078 (Braun and Steffen). The exhalation filter element can also be constructed as a non-woven material, for example, from melt-blown microfibers that support active particulate material, such as described in US Patent No. 3,971,373 (Braun). Active particulate material may also be subjected to local treatment to ensure vapor removal, see, e.g., US Patent Nos. 5,466,785 and 5,344,626 (Abler).

Face masks that have an exhalation filter element according to the present invention meet. as stated, the conditions of industrial standards (or exceed them) on properties such as fluid resistance, filtering efficiency and user convenience. In the medical field, the effectiveness of bacterial filtering (BFE) is usually assessed in the case of facial masks, which means the mask's ability to retain particles, ordinary bacteria, exhaled by the user. BFE tests are to assess the percentage of particles that escape from the inside of the mask. The Department of Defense reports three studies for BFE assessment, which are published in MIL-M-36954C, Military Specification: Mask, Surgical, Disposable (June 12, 1975). According to the minimum requirement of the industry standard, a surgical device should have a minimum efficiency of 95% when evaluated according to these tests.

The BFE is calculated by subtracting the percentage penetration from 100%. The percentage penetration is the ratio of the number of particles behind the mask to the number of particles before the mask. Filtering face masks that use electrostatically charged polypropylene BMF and have an exhaust filter element according to the present invention may be better than the minimum values ​​of the industry standard and may even have an efficiency greater than 97% by.

Face masks should also meet the fluid test conditions, where five strokes of synthetic blood are directed at the mask at 5 psi (34.5 kPa). If the blood does not pass through the mask, the test result is positive, and if synthetic blood is detected, the test result is negative. Masks that have an expiratory valve and exhalation filter element according to the present invention may pass this test when the expiratory filter element is placed outside or on the side of the valve contacting the ambient air, as well as on the inside or on a steep face exhaust valve. The filtering face masks of the present invention can therefore provide good protection against liquid splashes during use.

User comfort is improved when a large percentage of exhaled air exits freely through the exhalation valve, not through the mask body or rim. Tests were carried out in which a stream of compressed air is directed into the inner gas space of the face mask while measuring the pressure drop over the mask body. Although the results varied depending on the filter material used for the inspiratory filter element as well as the location and type of the exhaust filter element according to the present invention, it was found that at a flow rate of approximately 79 l / min above 95% air can leave the internal gas space through valve, and less than 5% through filtering material in the mask body, when commercially available polypropylene material bonded to spinning (87244 available from PolyBond of Waynesboro, Virginia) is used as an exhaust filter element.

EXAMPLES

Face masks having an expiratory filter element were prepared as follows. Exhalation valves used are described in US Patent No. 5,325,892 (Japuntich et al.) And are available on face masks from 3M Company as 3M exhaust valves

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Cool Flow ™. A 2 cm diameter hole was cut inside the 3M 1860 ™ ventilator to accommodate the valve. The valve was attached to the respirator using an ultrasonic welding machine available from Branson (Danbury, Connecticut). Respirators with a 3M 8511 ™ face mask were used that already had a valve. The filter element was attached to the valve in several ways. In one embodiment, the filter element was welded in place between the valve seat and the mask body, as shown in Figure 2. In another design, the exhaust filter element was placed on the valve cover and cut to protrude about half an inch (13 mm) beyond the valve on all sides. The exhalation filter element was then ultrasonically welded to the outer lip of the valve cover as shown in Fig. 5 using an ultrasonic welder available from Branson (Danbury, Connecticut). The exhaust filter element can also be attached in this way using glue. In another design, the exhalation filter element was placed above the valve seat and below the valve cover, as shown in Fig. 6. Then the material protruding beyond the valve seat was hidden under the seat, and the wrapped valve was placed on the mask body above the opening. The assembly consisting of a respirator, filter material and valve was then ultrasonically welded together. From the inside of the mask, excess filter material was cut off, leaving the valve opening uncovered and filter material covering the valve and sealed around the valve circumference. In another design, the exhalation filter element is attached to the outer edge of the filtering face element by ultrasonic welding or gluing so that the filter element can cover substantially the entire outside of the mask, including the exhalation valve, as shown in Fig. 7.

BACTERIA FILTER PERFORMANCE TEST

The face masks described above were tested for bacterial filtration efficiency (BFE) in a test modified with, but based on, the Department of Defense MIL-M-36954C, Military Specifications: Mask, Surgical, Disposable (June 12, 1975) standard. 4.4.1.1.2 Method II , as described by William H. Friedrichs, junior in The Journal of Environmental Sciences, pp. 33-40 (November / December 1989).

The face masks listed in Table 1 below were sealed in a gas-tight chamber. The air was extracted by creating a vacuum in this chamber through a highly effective particulate trap (HEPA) air filter, and then passed through the ventilator from the internal gas space to the external gas space at a constant flow rate of 28.3 l / min to simulate constant state of exhalation. As a result, the valve remained open. A nebulizer (part no. FT-13, 3M Company, Occupational Health and Environmental Safety Division, St. Paul, Minnesota) was used to aerosolize polystyrene latex (PSL) beads (from Duke Scientific Corp., Paloalto, California) with dimensions similar to aerosols produced by nebulization of Staphylococcus aureus, with an aerodynamic diameter of 2.92 pm, on the inside or face of the ventilator. The provoking aerosol was not neutralized in terms of electrostatic charge. The challenge was caused by squeezing the nebulizer at a rate of one squeeze per second and sampling in the internal gas space and then in the external gas space using an aerodynamic particle size determination instrument (APS 3310 from TSI Company, St. Paul, Minnesota). Percent penetration was determined by dividing the particle concentration behind the valve by the concentration of the particles before the valve and multiplying by 100. Only particle concentrations in the size range 2.74-3.16 pm were used to calculate the penetration. BFE calculated as 100 minus penetration. In vitro methods such as this have been found to be more reliable than in vivo methods such as modified Greene and Vesley test, described by Donald Vesley, Ann C. Langholtz and James L. Lauer in Infection in Surgery, p. 531-536 (July 1983). Therefore, achieving 95% BFE using the method described above is expected to be equivalent to or greater than achieving 95% BFE using the modified Greene and Vesley test. The results of the assessment using the method described above are shown in Table 1.

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Tables © 1

The results of testing the efficiency of filtering bacteria 3M ™ exhaust valves with mounted elements of the exhaust filter on 3M 1860 ™ respirators

<td>Example</td><td>Material and design of the exhaust filter element</td><td>BFE</td>

<td> 1</td><td>The material of the molded shell adhered to the valve cover, as shown in Fig. 5</td><td> &gt;98%</td>

<td> 2</td><td>2 layers of bonded spinning * polypropylene material 872444 turquoise colored 1.25 oz per square yard (34.2 g / m2) welded to the valve cover as shown in Fig. 5</td><td> &gt;97,5%</td>

<td>Π 3</td><td>1 layer of bonded material when spinning from polypropylene with a weight of 50.1 g / m2²containing 115% ** of the fluorochemical additive *** dimeric acid ester welded to the valve cover as shown in figure 5</td><td> &gt;97%</td>

<td> 4</td><td>1 layer of 40 g / m2 polypropylene bonded spinning material, heat sealed to the valve cover as shown in Fig. 5</td><td> &gt;97%</td>

* All materials bonded when spinning from polypropylene 87244, 34.2 g / m2² were obtained from Poły Bond, Inc., Waynesboro, Virginia.

** In the examples, these values ​​are given in percentages by weight, unless otherwise stated.

*** See example 1 in US Patent Application Serial No. 08 / 901.363 (Klun et al.), Where this appendix is ​​described. Further information on this fluorochemical dimeric acid ester in these examples is given in Example 1 of said application (Klun et al.). All of the additives in the examples were melted into fibers.

The data in Table 1 show that expiratory valves that have expiratory filter components can achieve greater than 95% efficiency in testing the effectiveness of simulated bacterial filtration.

TANK RESISTANCE TEST

To simulate blood splatter from a damaged patient's artery, you can cause a known volume of blood to strike a valve at a known speed according to Australian Standard AS 4381-1996 (Annex D) on surgical face masks, published by Standards Australia (Standards Association of Australia), 1 The Crescent , Homebush, NSW 2140, Australia ...

The study was similar to the Australian method with the slight changes described below. A synthetic blood solution was prepared by mixing 1000 ml deionized water, 25.0 g Acrysol G110 (from Rohm and Haas, Philadelphia, Pennsylvania) and 10.0 g Red 081 dye (from Aldrich Chemical Co., Milwaukee, Wisconsin). The surface tension was measured and set so that it was in the range of 40-44 dyne / cm, by adding as needed Brij 30 ™, a nonionic surfactant from ICI Surfactants, Wilmington, Delaware.

The valve with the diaphragm supported when open was positioned 18 inches (46 cm) from the 0.033 inch (0.084 cm) bore (valve number 18). Synthetic blood was discharged from the nozzle by a stream directed straight into the hole between the valve seat and the open valve membrane. This was set in time so that 2 ml of synthetic blood was discharged from the nozzle under a tank pressure of 5 psi (34 kN / m²). A piece of paper was placed inside the valve directly under the valve seat to detect synthetic blood leaking onto the face of the ventilator body through the valve. The valve was attacked with synthetic blood five times. Any detection of synthetic blood on tissue paper or anywhere inside the ventilator's face after five strokes with blood is treated as a malfunction. The correct result is no detection of blood inside the ventilator's face after five blood strokes. Ventilator body not rated.

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The results of the fluid resistance test as described above on the constructions of exhaust valve components made of different materials and mounted in different positions are shown in Table 2.

Table 2

Fluid resistance of 3M ™ Cool Flow ™ exhalation valves with an exhaust filter element mounted on the 3M 8511 ™ ventilator

<td>Example</td><td>Location of the exhaust filter element</td><td>Material of the exhaust filter element</td><td>Fluid resistance test result</td>

<td> 1</td><td> 2</td><td> 3</td><td> 4</td>

<td> 5</td><td>lack</td><td>lack</td><td>negative</td>

<td>6a</td><td rowspan="3">The element mounted between the valve seat and the mask body, as in fig. 2</td><td>1 layer of 1.24 ounce per square yard (34.2 g / im) polypropylene 87244 bonded material spinning</td><td>negative</td>

<td>6b</td><td>2 layers of bonded polypropylene 87244 fabric weighing 1.25 oz per square yard (34.2 g / m2)</td><td>negative</td>

<td> 7</td><td>material bonded to spinning from polypropylene with a basis weight of 110, 6 g / m ', containing 0.65% of the flame retardant FX-1801 Scotchban ™</td><td>positive</td>

<td> 8</td><td rowspan="3">The element mounted on the valve cover as in Fig. 5</td><td>material bonded while spinning from polypropylene with a weight of 50.6 g / inr, swirling 0.66% FX- ™ -1801 '</td><td>positive</td>

<td> 9</td><td>material bonded while spinning from polypropylene with a basis weight 50 g / them</td><td>positive</td>

<td> 10</td><td>1 layer of material bonded when spinning from turquoise-colored polypropylene 87244 with a basis weight of 1.25 oz per square yard (34.2 g / m2) and 1 layer of melted blown material with a basis weight of 75-85 g / m2, 85% polypropylene, 15% polyethylene</td><td>positive</td>

<td>11a</td><td rowspan="3"></td><td>2 layers of material bonded when spinning in turquoise-colored polypropylene 87244 with a basis weight of 1.25 oz per square yard (34.2 g / m)</td><td>positive</td>

<td>11b</td><td>1 layer of bonded material when spinning from turquoise-colored polypropylene 87244 with a basis weight of 1.25 oz per square yard (34.2 g / m)</td><td>negative</td>

<td> 12</td><td>2 layers of material bonded when spinning from 20.7 g / m polypropylene containing 0.62% FX-1801 ™ '</td><td>positive</td>

190 442 cd of table 2

<td> 1</td><td> 2</td><td> 3</td><td> 4</td>

<td> 13</td><td></td><td>1 layer of material bonded when spinning from turquoise-colored polypropylene 87244 1.25 oz per square yard (34.2 g / m2) and 1 layer of melted blown polypropylene material, 0.53 oz, approximate fiber diameter 7 pm</td><td>positive</td>

<td> 14</td><td></td><td>1 layer of bonded material when spinning from polypropylene with a weight of 40 g / m2</td><td>positive</td>

<td> 15</td><td></td><td>molded shell material</td><td>positive</td>

<td> 16</td><td></td><td>1 layer of material bonded when spinning from polypropylene with a basis weight of 50.1 g / m, containing 114% fluorofluoric ester of aimlrowl acid</td><td>positive</td>

<td> 17</td><td></td><td>1 layer of bonded material when spinning from 10.6 g / m2 polypropylene, containing 0.65% FX-1801 ™</td><td>positive</td>

<td> 18</td><td></td><td>1 layer of bonded material when spinning from polypropylene with a weight of 1.5 ounces square meters (1.81 g / m2)</td><td>positive</td>

**** The molded crust material used in these examples weighed approximately 4-6.5 grams per square foot (44.4-72.2 g / m²) and had the following composition: 70% type 254 white polyester staple fiber, 65/35 Cellbond ™ 4 den * 2 core sheath from Honshsa-Celknnse Corp. (Salisbury, North Carolina)

The data from Table 2 show that the exhaust valves according to the invention were able to provide good splash resistance.

VALVE PERCENTAGE FLOW TEST

Exhalation valves having expiratory filter components have been tested to determine the percentage of exhaled breath exhaled from the ventilator through the exhalation valve as opposed to the air exiting through the filter portion of the ventilator. This parameter was determined using the test described in Examples 8-13 of US Patent No. 5,325,892 and briefly described herein.

The effective removal of breath through the exhalation valve is a major factor in user comfort.

Respirators with a face filter mask were mounted on a metal plate so that the exhalation valve was located directly above the 0.96 cm2 opening through which the compressed air was directed with the flow directed into the interior and the masks as exhaled air. The pressure drop over the mask filter material was determined by placing the pressure gauge probe inside the filtering face mask.

The total percentage flow rate was determined by the following method described for better understanding based on Fig. 14. First, a closed equation describing the relationship of the volume flow rate (Qf to pressure drop (AP) on the face mask was determined with the valve closed. Then measured at the specific volume flow rate ( Qt) exhalation pressure drop over the face mask when the valve can open. The flow rate through the face mask filter material was determined

190 442 at a measured pressure drop based on this linear equation. Flow rate through the valve itself (Q_v) calculated as Qv = Qt - 0 / · The percentage of total exhaust flow through the valve was calculated as 100 (Qt - Q /) Qf.

If the pressure drop on the face mask is negative at a given Qt, the flow rate through the face mask filter material into the mask will also be negative, which means that the flow through the valve opening Qv is greater than the flow Q_T exhalation. So when Q is negative, the air is actually drawn in through the filter during exhalation and flows through the valve, whereby the percentage of total exhaust flow rate is greater than 100%. This is called aspiration and provides cooling to the user. The results of research on constructions having an exhaust filter element made of various materials and mounted in different places are given in Table 3 below.

Table 3

Percentage flow through the valve at 42 l / min and 79 l / min for 3M ™ Cool Flow ™ exhaust valves with exhaust filter components mounted on 3M 1860 ™ ventilators

<td rowspan="2">Example</td><td rowspan="2">Location of the exhaust filter element</td><td rowspan="2">Material of the exhaust filter element</td><td colspan="2">Exhaled air flow rate through the valve</td>

<td>at 42 l / min</td><td>at 79 l / min</td>

<td> 1</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td>

<td> 19</td><td>lack</td><td>lack</td><td> 76%</td><td> 104%</td>

<td> 20</td><td>Mounted between the valve seat and the ventilator body as shown in figure 2</td><td>2 layers of material bonded when spinning from turquoise-colored polypropylene 87244 with a basis weight of 1.25 oz per square yard (34.2 g / m2)</td><td> 31%</td><td> 41%</td>

<td> 21</td><td></td><td>1 layer of material bonded when spinning from polypropylene with a weight of 50.1 g / m2 containing 1.14% fluorochemical ester of dimer acid</td><td> 19%</td><td> 24%</td>

<td> 22</td><td rowspan="3">Under the valve housing but above the valve diaphragm as shown in Figure 6</td><td>Material bonded when spinning from polypropylene with a basis weight 50.6 g / m2 containing 0.66% FX-1801 ™</td><td> 41%</td><td> 50%</td>

<td> 23</td><td>Material bonded when spinning from polypropylene with a basis weight 50 g / m2</td><td> 58%</td><td> 70%</td>

<td> 24</td><td>1 layer of material bonded when spinning from turquoise-colored polypropylene 87244 with a basis weight of 1.25 oz per square yard (34.2 g / m2) and 1 layer of melted blown material with a basis weight of 75-85 g / m2 with 85% polypropylene 1 15% polyethylene</td><td> 53%</td><td> 61%</td>

190 442 cd of table 3

<td> 1</td><td> 2</td><td> 3</td><td>And 4</td><td> 5</td>

<td> 25</td><td>Above the valve housing as shown in figure 5</td><td>2 layers of material bonded when spinning from turquoise-colored polypropylene 87244 with a weight of 1.25 oz per square yard (34.2 g / m)</td><td> 65%</td><td> 96%</td>

<td> &lt;26</td><td>Above the entire respirator and valve as shown in Figure 7</td><td>2 layers of material bonded when spinning from polypropylene 87244 grammage 1.25 oz per square yard (34.2 / m ')</td><td> 88%</td><td> 112%</td>

<td> 27</td><td>On the valve housing as shown in fig. 5</td><td>1 layer of bonded material when spinning from white polypropylene with a basis weight 1.5 ounces per square yard 1.8 g / m2</td><td> 47%</td><td> 71%</td>

<td> 28</td><td>On the entire respirator and valve as shown in Figure 7</td><td>1 layer of material bonded by spinning from polypropylene with a basis weight of 50.1 g / m, containing 1.14% fluorochemical ester of dimer acid</td><td> 78%</td><td> 97%</td>

<td> 29</td><td>Above the entire respirator and valve as shown in Figure 7</td><td>1 layer of material bonded by spinning from polypropylene with a basis weight of 97.4 g / m ', containing 116% fluorochemical ester of dimer acid</td><td> 48%</td><td> 73%</td>

<td> 30</td><td>Above the entire valve housing as shown in figure 5</td><td>molded shell material</td><td> 57%</td><td> 93%</td>

<td> 31</td><td>Above the entire respirator and valve as shown in Figure 7</td><td>2 layers of bonded material for a spinning basis weight 20.7 g / m ', containing 0.62% FX-1801 ™</td><td> 66%</td><td> 96%</td>

<td> 32</td><td>Above the entire respirator and valve as shown in Figure 7</td><td>1 layer of material bonded when spinning from turquoise-colored polypropylene 87244 with a basis weight of 1.25 oz per square yard (34.2 g / m ') and 1 layer of polypropylene material with a basis weight of 0.53 oz per square yard (0.64 g / m2 ') with approximate fiber diameter 7 pm</td><td> 66%</td><td> 99%</td>

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The data in Table 3 show that good percentage flow rates through the exhalation valve can be achieved using the filtering face masks according to the invention.

This application refers in its entirety to all patents and patent applications listed above.

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Fig. 12

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Fig 14

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