WO2023134907A1

WO2023134907A1 - Breathing zone arrangement

Info

Publication number: WO2023134907A1
Application number: PCT/EP2022/082170
Authority: WO
Inventors: Andras Gedeon
Original assignee: Mincor Ab
Priority date: 2022-01-17
Filing date: 2022-11-17
Publication date: 2023-07-20
Also published as: SE2250038A1

Abstract

A breathing zone arrangement comprising at least one air flow generating device (4) structured to generate a defined air flow through at least one air flow outlet into at least one air flow conduit (8), at least one filter arrangement (10) configured to receive air generated by said at least one air flow generating device (4) via said at least one air flow conduit (8) and to filter received air, an air guiding device (12) configured to receive filtered air from said at least one filter arrangement (10) via said at least one air flow conduit (8), wherein said air guiding device (12) is structured to define a breathing zone space (14) provided in front of the mouth of a user (16) when said air guiding device (12) is mounted in front of the user (16), wherein said breathing zone space (14) has a predetermined volume and an extension large enough to cover the mouth of the user (16). The air guiding device (12) comprises an air flow distributor member (20) configured to distribute said filtered air flow into two essentially perpendicular and laminar air flows wherein said predetermined position immediately in front of the mouth allows one air flow (22) to be directed towards and confined to the mouth and the other air flow to be directed towards and confined to the nostrils. Thereby no sealing is required between said air guiding device (12) and the user (16).

Description

Breathing zone arrangement

Technical field

The present disclosure relates to a breathing zone arrangement in particular intended for protecting a user from airborne contagion, e.g. viruses, by creating a clean zone just in front of the mouth and nose.

Background

The standard method used today to protect a health care worker from inhaling infected aerosol droplets is to breathe through a disposable mask that filters (removes) the particles that carries the contagion.

These masks (also called respirators) are placed over both mouth and nose and must provide a tight seal against the skin of the face. They represent a closed system because the breathing zone is separated from the surrounding air by the mask. The seal is critical since any leakage will reduce the filtrating function (as shown by Samy Rengasamy et al, Journal of Occupational and Environmental Hygiene, 2014;l 1(6), pp 388-396). The mask has low but noticeable resistance. On inspiration this creates a negative pressure inside the mask. Even if the area of the leakage is very small (for instance with dimensions ~5xlmm or ~5 mm²), a significant amount of unfiltered air will enter into the mask reducing filtrating efficiency typically from 95% to about 85% (allowing three times more particles into the breathing zone).

The problem is compounded by the fact that there is no easy way for the user to discover if a leak has arisen. Thus, the specified protection offered by the mask can in practice never be taken for granted. The pressure needed to maintain a tight seal, the breathing resistance and the added dead space all contribute to the discomfort of the user. The requirement of a low breathing resistance limits the density of the filter media and hence the filtration efficiency of the mask. The best mask in common use today (i.e. the so called N95 mask) is a compromise between these conflicting requirements. When no leak is present it has a 95% filtration efficiency for a particle with a size of 0.3 pm that is, it allows 50 such particles through out of 1000. Another significant drawback with single use masks is the manual handling when removing/exchanging them. To avoid the risk for subsequent contact infection, the handling of used masks must therefore be according to strictly adhered instructions.

So-called High-efficiency particulate air (HEPA) filters are frequently used in equipment like vacuum cleaners in the prevention of the spread of airborne particles including those carrying bacterial and viral organisms. The specification used in the European Union: European Standard EN 1822-1:2009,5 defines several classes of HEPA filters by their retention at the given most penetrating particle size (MPPS), namely 0.3 pm. The efficiency to remove particles at 0.3 pm is therefore the standard way of expressing the protection efficiency of a HEPA filter. This measure, the protection efficiency at 0.3 pm, can also be applied when comparing different breathing arrangements including the semiclosed systems where a more or less controlled leakage is arranged, and the open systems where a filtered airflow into an open breathing zone is the main component of the protective arrangement.

Semi-closed devices, sometimes called Powered Air Purifying Respirators (PAPR), operate with high filtered flows (up to 6 liters/s) creating a clean air volume under positive pressure that keeps the contagion out. Clean air is let into and leave the volume in a variety of ways. Semi-closed systems have good protection efficiencies but they are very clumsy to wear and are expensive, and they are not suited for routine clinical work.

Open systems have many configurations and largely lack the drawbacks associated with closed or semi-closed arrangements. In the following, prior art documents describing such systems will be identified and briefly discussed.

US5878742 shows a helmet and visor assembly with a fan blower using filtered air creating a distributed flow over the face of the user thereby protecting the wearer from the ambient environment.

JP2006326475 shows an arrangement, which creates an air flow in front of a face of a person by means of a filter/fan unit and an optional visor. Air positively charged by positive ions generated by a positive ion generator is blown by a blower so as to pass in front of a face. Since an air curtain of positively charged air is formed in front of the face, flying positively charged pollen and dust are repelled by electrostatic repulsion and protected from entering the eyes and nose.

US20190009114 shows a health mask that blocks entry of external substances air by means of forming an air curtain in front of the body part. A filter and a fan are placed into the same unit, and the filter-fan unit is placed close to the ear of the wearer.

DE102018005650 shows a facemask comprising a filter and may have an integrated air fan. The mask arrangement is worn on the head. A visor is additionally mounted on the mask. At least one clean air gap is created.

US20190351360 shows a handheld fan. In front of the fan portion, a HEPA filter is provided. Air is blown through the HEPA filter to clean the air and to remove viruses and other unhealthy particles in front a person.

KR1020190130891 relates to an air purifying portable fan carried by the user by means of e.g. a fixing band around the arm. A mask is worn on the user's face. In addition to the fan, a HEPA filter may be present.

Other disclosures are US 5878742 where a filtered airflow is distributed and passed down the face of the user who is also protected by a helmet and a face shield and

US20170113075 where the filtered air passes the face from below and where the airflow is said to create at least partial shielding with respect to the surrounding.

All these open systems introduce filtered air at one or at many distributed locations around the face and generate clean airflows in various directions passing the mouth/nose region.

However, all open systems described above have unspecified properties with regard to the actual protection efficiency and in particular no indication is given of the resulting protective factor at particle size 0.3 pm. Nor are they specified as regards their resilience against external draft or as regards interference due to the movement of the user.

In fact, it can be shown by measurements and tests performed by the inventor, that they all suffer from the same common problem that the protection efficiencies at 0.3 pm are very low compared to the 95% of the state of the art N95 mask. Irrespective of the magnitude and the direction of the filtered air flow used, attainable protection efficiencies are only in the range of 40-80%. The reason for this is that in all these systems the expired air from the user is allowed to flow out and mix freely with the more or less contaminated air in the open breathing zone and at particle size 0.3 pm this turbulent uncontrolled mixing inevitably contaminates the inhaled air irrespective of how clean the filtered air is initially. This is not surprising since A.S. Sakharov, K Zhukov: Physics 2020,2, 340-351 has recently calculated that to get any protection (at around 0.3 pm particle size) from an airflow barrier, huge and in practice totally unacceptable flows of the order 10 m/s are needed.

In summary regarding the present state of the art, the closed N95 mask gives good protection provided that it is tight, but adds breathing resistance and dead space and is inconvenient in use. The semi-closed systems are expensive and awkward to wear and while open systems do not have these drawbacks they do not provide satisfactory clinical protection compared to 95 % at 0.3 pm, of the N95 mask.

The object of the present invention is to achieve an improved open arrangement intended to eliminate all the above stated drawbacks. Avoiding the problems with the use of tight- fitting masks and PAPR-devices and at the same time providing high protection efficiency at 0.3 pm particle size also when the user moves around and breathes up to 1000 ml tidal breaths. In particular, to design an inexpensive open arrangement that is comfortable to wear, has no breathing resistance, no dead space, and still achieves a protection efficiency in excess of 95% at 0.3 pm under all normal indoor conditions.

Furthermore, the arrangement should be easy to attach/detach to/from a standard face shield and preferably provide at least 8 hours of continuous protection.

Summary

The above-mentioned objects are achieved by the present invention according to the independent claims.

Preferred embodiments are set forth in the dependent claims.

The general object achieved by the breathing zone arrangement according to the present invention is to create a small “clean zone” immediately in front of the mouth and nose of the person to be protected. According to the present invention, possibly contaminated air is sucked in by an air flow generating device, e.g. a small fan, and passed through a filter arrangement, comprising e.g. two filters, being high performance (99.5% HEPA 12) filter(s), before being introduced in a controlled manner into a small breathing zone space just in front of the mouth. There, the filtered air is distributed by an air guiding device, comprising an air flow distributer member, in two directions: nearly horizontally, that is towards the mouth and nearly vertically towards the nostrils of the user. The filtered air is continuously flushing the small breathing zone space, thereby establishing a protected volume with the size of approximately 5x3x2 cm just in front of the mouth and up to the nose, from which the user can breathe totally unhindered.

It is an important aspect of the arrangement according to the present invention that there is no contact with the face, and that the air guiding device is placed 2 cm, or less than 2 cm, in front of the mouth of the user. The air flow distributor member directing the flows in the required directions, produces laminar air flows, where the so-called Reynolds number is significantly less than 2000. These flows exceed the peak inspired flows and results in a dynamic overpressure during inspiration and even more importantly, a temporary static overpressure (due to the opposing flows directions) during expiration thereby preventing mixing with air outside the breathing zone.

In one embodiment the flow generated by the air flow generating device is divided into two parts, each passing a filter (a HEPA-12-filter with 99.5% efficiency). This reduces the flow through the filters and thus the pressure drops over the filters and allows the use of a smaller, less expensive, less noisy fan used as the air flow generating device.

Having two separate airflow conduits are also beneficial since in this way the dimensions of each conduit can be kept smaller and so it is easier to fit them between a face shield and the users face.

Measurements and tests performed by the inventor have shown that using a face shield according to this embodiment results in a protection efficiency of 97%, i.e. only 30 particles sized 0.3 pm enter the breathing zone out of 1000. This is 60% better protection than that provided by the N95 mask. Protection efficiency remains the same for any tidal breath up to 1000 ml and is not affected by the movement of the head or the presence of draft flows of 0.3 m/s. This value exceeds the maximal allowed indoor draft by about 70% according to ASHRAE Standard 170-2017, ANSI Standard 62.2-2019 and also the value established by the Public Health Agency of Sweden.

Brief description of the drawings

Figure 1 is a block diagram schematically illustrating the breathing zone arrangement according to the present invention.

Figure 2 is a schematic side view of the head of a user using the breathing zone arrangement according to the present invention.

Figure 3 is a perspective view of the air guiding device applied in the breathing zone arrangement according an embodiment of the present invention.

Figure 4 is a schematic view from above of the head of a user using the breathing zone arrangement according to an embodiment of the present invention.

Detailed description

The breathing zone arrangement will now be described in detail with references to the appended figures. Throughout the figures the same, or similar, items have the same reference signs. Moreover, the items and the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

A breathing zone arrangement 2 is provided that comprises at least one air flow generating device 4 structured to generate a defined air flow through at least one air flow outlet 6 into at least one air flow conduit 8, e.g. flexible tubing.

The arrangement 2 further comprises at least one filter arrangement 10 configured to receive air generated by the at least one air flow generating device 4 via the at least one air flow conduit 8 and to filter received air. The filter arrangement 10 fulfils the requirement of a High-Efficiency Particulate Air (HEP A) filter of at least class 12.

The arrangement 2 also comprises an air guiding device 12 configured to receive filtered air from the at least one filter arrangement 10 via the at least one air flow conduit 8. The air guiding device 12 is structured to define a breathing zone space 14 provided in front of the mouth of a user 16 when the air guiding device 12 is mounted in front of the user 16. The breathing zone space 14 has a predetermined volume and an extension large enough to cover the mouth of the user 16. This is illustrated in figure 2.

A mounting arrangement 28 is provided (see figure 4) structured to position the air guiding device 12 in a predetermined position immediately in front of the mouth of the user 16.

The air guiding device 12 comprises an air flow distributor member 20 configured to distribute the filtered air flow into two essentially perpendicular and laminar air flows 22, 24. This is specifically illustrated in figure 2. Herein, by essentially perpendicular is meant an angle interval of 75-105 degrees. The predetermined position immediately in front of the mouth allows one air flow 22 to be directed towards and confined to the mouth and the other air flow 24 to be directed towards and confined to the nostrils. The directions of the laminar air flows should be aligned with the inhalation flows to the mouth and to the nostrils. The laminar air flows 22, 24 in the defined breathing zone space 14 are such that they create a dynamic overpressure during inspiration by the user 16 and a static overpressure during expiration by the user 16, to ensure that no sealing is required between the air guiding device 12 and the user 16.

According to an embodiment, the mounting arrangement 18 is structured to position the air flow distributor member 20 less than a predetermined distance D in front of the mouth of the user 16. The predetermined distance D is 2 cm. Thus, the flow distributer member should be positioned e.g. 2 cm, 1.5 cm, 1.0 cm, or 0.5 cm, or any values therebetween, from the mouth of the user.

According to another embodiment, the cross section of the laminar air flow is about 3x5 cm towards the mouth, and about 2x5 cm towards the nose. This size is expected to cover most situations. However, the sizes of the cross-sections could be adapted to different users’ anatomy, e.g. a smaller sized air guiding device could be applied for a user having a smaller mouth/nose, and larger sized air guiding device could be applied for a user having a larger mouth/nose. According to an embodiment a cross section of each of the laminar air flows is essentially rectangular. By essentially rectangular is meant a rectangle optionally having rounded corners. Other cross-sectional shapes of the laminar air flows are also possible, e.g. elliptical shapes.

In a further embodiment, the directions of the flows towards the mouth and the nose are within +/- 15 degrees from flow directions of the inspired gas.

According to another embodiment, the air flow generating device 4 and/or air guiding device 12 is/are structured such that the air flow 24 towards the nostrils is less than the air flow 22 towards the mouth. This may e.g. be performed by providing one or many constrictions of the air flow intended for the nostrils, or having air flow conduits of smaller dimension in comparison with the dimension of the air flow conduits intended for the air flow towards the mouth.

In another embodiment, the air flow distributor member 20 comprises a plurality of parallel channels, each transporting a small fraction of the total air flow. One variation of this embodiment is illustrated in figure 3 showing the air guiding device 12. The air flow distributer member 20 is in the illustrated variation provided with three rows of parallel channels in each of the perpendicular directions. Each row comprises a plurality of openings that in the illustrated variation are essentially rectangular/quadratic. Naturally, the number of rows could be higher or lower than three. These openings could have any other shape, e.g. circular, or elliptical, and need not be arranged in rows.

According to still another embodiment, the total air flow through the air flow distributor member 20 is in the range of 1.5 -2.5 1/s. Larger flows would reduce the efficiency of the filter and shorten operation time. Significantly lower flows risk to come close to the peak inspiratory flow rates (normally about 0.5 1/s) which could create less dynamic overpressure in the inspiratory phase and thereby endanger the clean zone. A suitable fan used as the air flow generating device 4 that can be attached to a waistline, weighs approximately 0.5 kg and is provided with a 6000 mAh rechargeable battery that can deliver about 1.8 1/s filtered flow for more than 8 hours, and alarms at the end of its operating time.

In a further embodiment, the Reynolds number within the defined breathing zone space 14 is less than 2000. The Reynolds number (Re) helps predict flow patterns in different fluid flow situations. At low Reynolds numbers, flows tend to be dominated by laminar (sheetlike) flow, while at high Reynolds numbers flows tend to be turbulent. The turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow (eddy currents). These eddy currents begin to churn the flow, using up energy in the process, which for liquids increases the chances of cavitation. Reynolds numbers are an important dimensionless quantity in fluid mechanics.

In one embodiment, illustrated in figure 4, the breathing zone arrangement 2 comprises one air flow generating device 4 structured to generate two defined air flows through two air flow outlets 6 respectively connected to an air flow conduit 8. One filter arrangement 10 is arranged along each of the air flow conduits 8 to filter air flowing through the air flow conduits 8 before reaching the air guiding device 12.

In figure 4 is illustrated an embodiment where the mounting arrangement 18 comprises a face shield 26 provided with attachment members 28 structured to attach/detach the at least one air flow conduit 8 to the face shield 26, e.g. to the rim of the standard face shield. The air guiding device 12 is then held and positioned in the intended position via the air flow conduits 8 which have the necessary structural capabilities for that. Further attachment members 28 may e.g. be provided to directly connect the air guiding device to the inner surface of the face shield 26, which is indicated in figure 4 as a dashed rectangle. It should be noted that the face shield 26 may be applied to any of the embodiments disclosed herein.

The present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.

Claims

1. A breathing zone arrangement (2) comprising:

- at least one air flow generating device (4) structured to generate a defined air flow through at least one air flow outlet (6) into at least one air flow conduit (8),

- at least one filter arrangement (10) configured to receive air generated by said at least one air flow generating device (4) via said at least one air flow conduit (8) to filter received air, wherein said filter arrangement (10) fulfils the requirement of a High- Efficiency Particulate Air (HEPA) filter of at least class 12,

- an air guiding device (12) configured to receive filtered air from said at least one filter arrangement (10) via said at least one air flow conduit (8), wherein said air guiding device (12) is structured to define a breathing zone space (14) provided in front of the mouth of a user (16) when said air guiding device (12) is mounted in front of the user (16), wherein said breathing zone space (14) has a predetermined volume and an extension large enough to cover the mouth of the user (16), and

- a mounting arrangement (18) structured to position said air guiding device (12) in a predetermined position immediately in front of the mouth of the user (16), c h a r a c t e r i z e d i n that said air guiding device (12) comprises an air flow distributor member (20) configured to distribute said filtered air flow into two essentially perpendicular and laminar air flows (22, 24), said air flow distributor member (20) comprises a plurality of parallel channels each transporting a small fraction of the total air flow, wherein said predetermined position immediately in front of the mouth allows one air flow (22) to be aligned with the inhalation flow to the mouth and confined to the mouth and the other air flow (24) to be aligned with the inhalation flow to the nostrils and confined to the nostrils, wherein said mounting arrangement (18) is structured to position said air flow distributor member (20) less than a predetermined distance D, being 2 cm, in front of the mouth of the user (16), and wherein the total air flow through the air flow distributor member (20) is in the range 1.5 -2.5 1/s resulting in that the laminar air flows (22, 24) in said defined breathing zone space (14) are such that they ensure that no sealing is required between said air guiding device (12) and the user (16).

2. The breathing zone arrangement (2) according to claim 1, wherein a cross section of the laminar air flow is about 3x5 cm towards the mouth, and about 2x5 cm towards the nose.

3. The breathing zone arrangement (2) according to any of claims 1-2, wherein a cross section of each of the laminar air flows is essentially rectangular.

4. The breathing zone arrangement (2) according to any of claims 1-3, wherein the direction of the flow towards the mouth and the nose is within +/- 15 degrees from flow directions of the inspired gas.

5. The breathing zone arrangement (2) according to any of claims 1-4, wherein the Reynolds number for the flows (22) and (24) within said defined breathing zone space (14) is less than 2000.

6. The breathing zone arrangement (2) according to any of claims 1-5, comprising one air flow generating device (4) structured to generate two defined air flows through two air flow outlets (6) respectively connected to an air flow conduit (8), and wherein one filter arrangement (10) is arranged along each of said air flow conduits (8) to filter air flowing through the air flow conduits (8).

7. The breathing zone arrangement (2) according to any of claims 1-6, wherein said mounting arrangement (18) comprises a face shield (26) provided with attachment members (28) structured to attach/detach said at least one air flow conduit (8) to said face shield (26).