HK1119993A - Microbicidal air filter - Google Patents

Description

Microbicidal air filter

Technical Field

The present invention relates to air filters, and more particularly to microbicidal air filters.

Background

The removal of airborne pathogens and environmental allergens is of great importance in environments where high levels of air purity are required, such as in hospitals and in the rooms of people suffering from severe allergic reactions to the aforementioned allergens. Typically, devices in the form of a hood or air duct filter out particulate matter during air circulation, or in the case of a face mask, during inhalation and exhalation. Face masks and air duct filters can temporarily trap pathogens and allergens, as well as particulate matter such as dust, on the surface of the filter material. Once the filters reach a threshold limit or are used once, they are typically discarded or, in some cases, cleaned and reused. Many designs of filtration devices exist, examples of which are as follows:

U.S. Pat. No. 1,319,763 to Drew, entitled "Air filter for wall registers", published 10, 28.1919;

U.S. patent No. 3,710,948 to Sexton, published on 16.1.1973, "Self-stabilizing pocket type filter";

U.S. Pat. No. 3,779,244, "dispersible face respiratory rate", Weeks, issued on 12, 18, 1973;

U.S. patent No. 3,802,429 to Bird, issued on 9.4.4.1974, "Surgical face mask";

U.S. Pat. No. 4,197,100 to Hausher, 8.4.4.1980, "Filter members for filters";

U.S. Pat. No. 4,798,676 to Matkovich, published 17.1.1989, "Low pressure drop bacterial filter and method";

U.S. patent No. 5,525,136 to Rosen, issued 6, 11, 1996, "Gasketed Multi-media air cleaner";

U.S. Pat. No. 5,747,053 to Nashimoto, 5.5.1998, "Antiviral filter air cleaned infected with tea extract";

U.S. patent No. 5,906,677 to Dudley, 25.5.1999, "electric supercharger screen";

U.S. patent No. 6,036,738 issued to Shanbroom at 3/14/2000, "dispensing gas filters";

U.S. patent No. 6,514,306, "Anti-microbial fibers media," issued on 4.2.2003 to Rohrbach et al.

The above design suffers from a number of important disadvantages. Disadvantageously, in the above-described designs, removal of the dirty filter or mask after use can result in the immediate dispersal of the unfixed pathogens or particles into the air surrounding the user, which if inhaled, can be harmful to the user. Furthermore, the design does not immobilize and kill airborne pathogens in situ. Some of these designs incorporate a sticky substance into the filter material to trap particulate matter. Some designs introduce a complex arrangement of filters into the box, which may be impractical for application to an air conduit or mask. In some cases, glass fibers are used as part of the filter media, which may be harmful to humans if located near the nose and mouth. In one design, cotton yarn soaked with disinfectant appears to be placed in an air duct to atomize into the chamber to maintain moisture content. The use of such wet disinfectants can be harmful to people in the vicinity of the disinfectant and may not be suitable for use in a face mask. Another filter media uses fibers having cavities filled with an antibacterial agent to allow slow release of the antibacterial agent therefrom. Another design discloses that the fibers are processed to contain an antibacterial agent therein, which can leave freely once the fibers are opened. These fiber designs have the problem of rapidly losing their antibacterial activity once they are cleaned or washed.

Accordingly, there is a need for an improved microbicidal air filter.

Disclosure of Invention

The present invention reduces the difficulties and disadvantages of the prior art and solves the problems of the prior art by providing a microbicidal air filter that traps and kills pathogenic microorganisms on a novel immobilized fibrous web. To this end, the fibers include an antimicrobial agent incorporated into their structure during processing of the fibers so that the latter substantially kill microorganisms in proximity thereto. The antimicrobial agent is inherently and externally secured to the fiber structure with strong molecular bonds. This significantly reduces or substantially eliminates the problems associated with further release of microorganisms from the filter after use and during processing. Advantageously, the filter can be used as a mask or in an air circulation duct, typically as an after-filter or downstream of a filter, and can capture and kill a variety of microorganisms. The fibers may be made of a material, such as, but not limited to, a polyvinyl chloride (PVC) based material, which enables the filter to be washed and reused almost indefinitely without significant loss of antimicrobial activity due to molecular bonds between the antimicrobial agent and the fiber structure.

In one aspect of the present invention, there is provided a microbicidal air filter for use through an air passageway, the air filter comprising: an immobilization network comprising a plurality of fibers having an amount of at least one antimicrobial agent incorporated and molecularly bonded into the structure thereof sufficient to substantially immobilize, retain and at least inhibit the growth of, or typically kill, microorganisms suspended in a volume of air moving through said air passageway, said immobilization network being substantially permeable to said air.

In one embodiment, the immobilization network is a post-filter, whereby the air is pre-filtered before reaching the air channel.

In one embodiment, the air filter is a mask shaped and sized to fit over and secure around the nose and mouth of a user.

In one embodiment, the air filter is an air duct filter shaped and sized to fit within an air duct system that defines the air passageway.

Typically, the air filter further comprises: first and second air permeable screen elements securable together along respective peripheral edges, the screen elements being shaped and sized to fit within and be secured in an air duct system; the air permeable immobilization network is disposed substantially between the first and second screen elements.

Conveniently, a fastening member connects the first and second air permeable screen elements together to sandwich the immobilization network therebetween.

Typically, the fastening means comprises a frame for connecting the first and second screen elements together.

Conveniently, the fastening member further comprises a plurality of sutures disposed through the immobilization network to divide the immobilization network into sub-portions.

In another aspect of the present invention, there is provided a microbicidal mask comprising: first and second air permeable screen elements secured together along respective peripheral edges, the screen elements defining a gap therebetween, the screen elements being shaped and sized to fit over and be secured to a user's mouth and nose; an air permeable immobilization network disposed in and substantially filling the gap, the immobilization network comprising a plurality of fibers having an amount of at least one antimicrobial agent incorporated and molecularly bonded into the structure thereof sufficient to substantially immobilize, retain and at least inhibit the growth of, or typically kill, microorganisms suspended in a volume of air moving through the network.

In one embodiment, the first air permeable screen element includes a slit disposed therein and of sufficient size to allow the immobilization network to be placed in the gap.

Other advantages and objects of the invention will in part be apparent from a review of the drawings and from a careful consideration of the following description.

Drawings

In the drawings, like reference numerals refer to like elements throughout.

FIG. 1 is a simplified exploded view of an embodiment of a filter;

FIG. 2 is a simplified partial cross-sectional view of a mask having the filter;

FIG. 2a is a simplified partial cross-sectional view of an alternative embodiment of a face mask;

FIG. 3 is a simplified exploded view of an embodiment of a filter in a frame;

FIG. 4 is a simplified exploded view of the filter with the primary filter;

FIG. 5 is a simplified exploded view of an air circulation system having a filter;

FIG. 6 is a simplified front view of an alternative filter for use in the system of FIG. 5;

FIG. 7 is a simplified front view of an alternative filter for use with the system of FIG. 5, showing sutures as the securing members;

FIG. 8 is a simplified front view of an alternative filter for use with the system of FIG. 5, showing rivets as fastening members;

fig. 9 is a cross-sectional view taken along line 9-9 of fig. 7.

Detailed Description

Preferred embodiments of the present invention will now be described for purposes of illustration and not limitation, with reference to the accompanying drawings.

Definition of

As used herein, the term "microorganism" or "microbial" means a microorganism including, but not limited to, bacteria, protozoa, viruses, molds, and the like. Also included in this definition are dust mites.

As used herein, the term "antimicrobial agent" means a compound that inhibits, prevents, or destroys the growth or proliferation of microorganisms, such as bacteria, protozoa, viruses, molds, and the like. Examples of antimicrobial agents for use herein include antibacterial, antiviral, antimycotic and antimycotic agents, or any combination thereof.

As used herein, the terms "antibacterial agent," "bactericide" and "bacteriostatic agent" mean a compound that inhibits, prevents the growth of, and/or kills bacteria.

As used herein, the term "antiviral agent" means a compound that inhibits, prevents the growth of, or kills a virus.

As used herein, the term "antimycotic agent" means a compound that inhibits, prevents the growth of, or kills a mold.

As used herein, the term "anti-yeast agent" means a compound that inhibits, prevents the growth of, or kills yeast.

As used herein, the term "anti-dust mite agent" means a compound that inhibits, prevents the growth of, or kills dust mites.

As used herein, the terms "microbicidal", "biocidal" and "sterilized" mean the inhibiting, growth arresting or killing properties of any of the foregoing "agents" used alone or in combination with one another.

Description of the preferred embodiments

Referring now to FIG. 1, a first embodiment of a microbicidal air filter is shown generally at 10. Broadly speaking, the filter 10 comprises an air permeable immobilization network 12, an air permeable first screen 14 and an air permeable second screen 16. The first screen 14 and the second screen 16 merely serve to support the web 12 and define a working area 18. One skilled in the art will recognize that the immobilization network 12 may be used independently of the screens 14 and 16.

The mesh 12 comprises a network of fibers 20, which may be non-woven or woven, depending on whether a soft or hard (rigid) mesh is desired. The web 12 may also comprise yarn, such as cotton, having fibers 20 interwoven therein. Each fiber 20 includes an amount of at least one antimicrobial agent that is completely incorporated and stabilized on the structure of the fiber 20 via very strong molecular bonds, thereby providing a large and constant concentration of antimicrobial agent over a large surface area throughout the life of the fiber 20. In other words, the antimicrobial agent is in the center of the fiber 20, cohesively mixing and diffusing therealong, onto and into it. The fibres 20 are arranged in a fine layer which makes them permeable to air throughout the mesh, typically a so-called angel hair (ang1 e's hair), a sheet mesh or the like.

Preferably, the mesh is a fibrous material. More preferably, the fibrous material is commercially available RHOVOL' AS +^TM、RHOVYL’AS^TM("AS" means "sterilized"), THERMOVOL-L9B^TM、THERMOVYL-ZCB^TM、THERMOVYL-MXB^TM("B" means "biocidal") or by TRICLOSAN^TMTreated polyvinyl chloride (PVC) -based organic fibers, and the like.

RHOVYL’AS+^TM、RHOVYL’AS^TM、THERMOVYL-L9B^TM、THERMOVYL-MXB^TMAnd THERMOVOL-ZCB^TMAre all made of RHOVOL^TMSA, said material having an inherent antimicrobial and/or biocidal activity. In particular, RHOVOL' AS^TMFiber, THERMOVOL-L9B^TMFiber and THERMOVOL-ZCB^TMThe fiber incorporates an antibacterial agent which is molecularly bonded to the fiber structure and RHOVOL' AS^TMFiber antibacterial agent, RHOVYL' AS +^TMFiber and THERMODYL-MXB^TMThe fiber also contains an acaricide, an anti-dust mite agent. TRICLOSAN^TMIs a well-known antimicrobial agent that at least reduces the growth of, and typically even kills, microorganisms, such as bacteria, yeasts and molds.

The fibrous material may be used undoped (100%) or blended with at least 30% volume percent of other types of fibers in woven or non-woven fabrics and meeting the Individual Protective Equipment (IPE) requirements. The fibrous material may also have other properties including, but not limited to, non-flammability, chemical resistance, fire suppression, thermal insulation, and moisture wicking (moisture wicking).

Preferably, the antimicrobial agent comprises an antibacterial agent, an antiviral agent, an anti-dust mite agent, an anti-mold agent and an anti-yeast agent.

The antibacterial agent is preferably TRICLOSAN^TM。

The preferred anti-dust mite agent is benzyl benzoate.

Typically, the fibrous material has a porosity in the range of about 0.1 μm to about 3 μm, however this also depends on the size of the microorganism to be retained.

Typically, the fibrous material has two grams per square foot (2 gr/ft)²) To thirty grams per square foot (30 gr/ft)²) The density of (c). More preferably, the density is about ten grams per square foot (10 gr/ft)²)。

As best shown in fig. 2, the filter 10 may be part of a conventional mask 24 for hospital workers and the mask 24 may be expandable (soft mask) or non-expandable (rigid mask), the filter 10 sometimes being used in areas with pre-filtered air. The screens 14 and 16 are typically joined around a peripheral edge 22 and define a gap 23 therebetween. The mesh 12 may be attached to one of the screens described above to provide a physical barrier to particulate matter and, more importantly, pathogenic microorganisms. The mesh 12 may be passed through VELCRO^TMFasteners, sutures, bonding, etc. are attached to the screens 14 or 16 or are located within the interior of a portable mask 24 for an individual worn in front of the individual's nose/mouth. The front face mask screen 25 of the face mask 24 acts as a primary filter upstream of the mesh 12 to pre-filter the air by removing particulate matter and microorganisms from the air passing through the air passage as indicated by the arrows.

Alternatively, as best shown in FIG. 2a, the mesh 12 may be positioned between a front screen 25 and a rear screen 27, such as a commercially available filter mask, in the gap 23 of the mask 24 to create a bi-directional filtration system, as indicated by the arrows. The front screen 25 may include a slit 29 to allow the mesh 12 to be inserted into the gap 23. This type of mask 24 can be used for persons who have respiratory infections but still wish to work, but do not wish to infect others by exhaling breath contaminated with pathogenic microorganisms.

The screen elements 14, 16 may be of various sizes and shapes, and may be simple conventional flexible or semi-flexible type screens as shown in fig. 1, made of aluminum, nylon, thermoplastic materials, fiberglass type materials (not normally permitted for use as a face mask), woven type fabrics, and the like. As shown in fig. 3, the screen elements 14, 16 and the mesh 12 may be supported by a rigid frame 26, such as a standard aluminum screen frame, which is divided into two portions 28, 30 and integrated with the screen elements 14, 16, respectively, to ensure rigidity and ease of installation. The fastening members 32 may be used to releasably connect the two screen elements 14, 16 together with the mesh 12 sandwiched therebetween and compressed to prevent movement by air flowing therethrough. The securing member 32 may be a pivoting retainer that pivots on one of the portions 28, 30 to retain the other portion relative to the portion. Alternatively, as best shown in FIG. 4, a rigid screen 34 of any conventional air filter 36 may be used.

Referring now to fig. 5 and 6, the filter 10 is illustratively mounted within an air duct 38 downstream of the air filter 36 and upstream of the air heating system 40 (the air passage is shown by the arrows in fig. 5) so that air passing through the web 12 can be pre-filtered so that the web 12 acts as a post-filter, thereby being more effective because most of the particulate matter or dust contained in the air is removed therefrom before reaching the web. The frame 26 generally encloses the sealed screen elements 14, 16, but also includes intermediate reinforcing rods 42 for subdividing the screen elements 14, 16 into a plurality of smaller sub-elements 44 to restrain the mesh 12 from remaining in position between the two elements 14, 16. Alternatively, as best shown in fig. 6, the frame 26 is a thin metal rod to which the screen elements 14, 16 are attached, with reinforcing rods 42 providing additional support to the screen elements 14, 16 and the mesh 12, and sub-elements 44 as previously described.

Referring now to fig. 5,7, 8 and 9, other types of fastening members 32 are illustrated. One preferred type of fastening member 32 includes a plurality of stitches 46 that may be arranged in a variety of patterns, such as wavy lines or straight lines. The stitches 46 pass through the mesh 12 and divide the mesh into sub-portions 44 as previously described. Alternatively, as best shown in FIG. 8, the fastening member 32 may also include a rivet 48 that passes through the web 12.

Examples

The invention is illustrated in further detail by the following non-limiting examples.

Example 1

Evaluation of microbicidal and filterability in rigid and soft masks

Two masks of the present invention were compared to a commercially available mask as shown in Table 1^1，2，3A comparison was made of them against a panel of bacteria and molds of various sizes^{4，5，6，7}Antimicrobial and retention ability. The NB rigid and soft masks used in examples 1 and 2 were each equipped with a TRICLOSAN containing a molecular linkage^TMA network 12 of PVC based organic fibers. The NB soft face mask consisted of a double layer of peripherally stitched woven fabric containing 76% w/w of THERMOYL-ZCB^TMFibres and 24% w/w polyester (however any other woven fabric, such as cotton etc. may be used) and a mesh 12 (see figure 2a above) is provided inside the double coating. The NB rigid mask was made of two conventional commercially available dust resistant masks, one inserted into the other with a TRICLOSAN containing insert between them^TMA network of PVC based organic fibers.

Using air pollution chambers^5，8，9The filtration capacity of the mask containing the mesh was measured. The chamber including a chamber containing a predetermined quantity of frozenA perforated bottle of dry microorganisms. The chamber was mounted on a microbial air sampler. The test mask was mounted at the interface between the contaminated air chamber and the air sampler. A negative pressure is created in the air chamber which causes the freeze-dried microorganisms to move towards the mask. A media is placed downstream of the mask to detect any penetrations of the mask.

TABLE 1

Microorganisms	Size (mum)	Filtration Rate (%)
					NBRM	NBSM	3M*
		Bacteria
Mycobacterium tuberculosis (Mycobacterium tuberculosis)	0.2-0.7×1.0-10				100	100	95
		Proteus (Proteus spp.)	0.4-0.8×1-3	100				100
Pseudomonas aeruginosa (Pseudomonas aureginosa)	0.5-1.0×1.5-5				100	100
		Staphylococcus aureus (Staphylococcus aureus)	0.5×1.5	100				100
Golden Streptococcus (Streptococcus pneumniae)	0.5-1.5				100	100
		Haemophilus influenzae (Haemophilus influenze)	1	100				100
Anthrax (Anthrax)	1-1.5×3-5				100	100
		Mould fungus
Acremonium strictum (Acremonium strictum)	3.3-5.5(7)×0.9×1.8				100	100	96
		Aspergillus versicolor (Aspergillus versicolor)	2-3.5	100				100
Penicillium griseofulvum (Penicillium griseofulvum)	2.5-3.5×2.2-2.5				100	100
		Neosartorya fischeri	2×2.5	100				100

NBRM (rigid face mask)

NBSM ═ Soft face mask

^*From technical specifications²Data of (2)

Example 2

Evaluation of Small particle filtration Capacity

The three masks of example 1 were tested for their filtering ability on two particulate materials of 0.3 μm size using essentially the same apparatus as in example 1. In this case, a cassette type trapping membrane is provided downstream of the air pump to trap the particles passing therethrough. The air pump generates a negative pressure downstream of the mask. The two particulate materials selected were sodium chloride and dioctyl phthalate.

TABLE 2

Particulate material	Size (mum)	Filtration Rate (%)
					NBRM	NBSM	3M*
		Sodium chloride (NaCl)	0.3	100				100	95
Dioctyl phthalate (DOP)	0.3				100	100

NBRM (rigid face mask)

NBSM ═ Soft face mask

^*From technical specifications²Data of (2)

Example 3

Evaluation of microbicidal and filterable capacities of ventilated system filters

Will have RHOVOL' AS +^TMThe antimicrobial capacity of the filter of the fig. 3 embodiment of the fiber was evaluated 0, 7, 14, and 21 days after installation in an indoor ventilation system.

The results are illustrated in tables 3-6 below.

After the above time the filter was removed and the Samson method used¹⁰And (6) carrying out analysis. The fibrous material (1g) of each filter was diluted with sterilized demineralized water (9ml) and then serially diluted.

The total amount of bacteria, yeast and mold was calculated by a blood cell count method. The total amount of viable bacteria, yeasts and moulds was calculated after serial dilution culture on the appropriate medium. Aerobic viable bacteria were grown on soy agar (TSA, Quelab), while yeasts and molds were grown on HEA supplemented with gentamicin (0.005% p/v) and oxytetracycline (0.01% p/v) to limit bacterial growth. A pH of 4.8+/-0.2 for HEA allows spore germination and hyphal (myceen) formation. After the incubation period, a colony calculator (Accu-Lite) was used^TMFisher) was performed on the microbial colonies. The morphotypes of the bacterial colonies were identified by gram staining (see table 5).

With respect to yeast and mold calculations, each macroscopically distinct mold colony was identified by gender (gender) and/or species using a microscope.

Using adhesive tape¹¹To prepare a mold slide. This technique maintains its structural integrity by securing the mold to the tacky side of the tape. Once the mold was collected, the mold was stained with lactophenol and observed at magnifications of 10 × and 40 × respectively. By using look-up tables^{12，13，14，15}And identifying the mould. In this experiment, only spore-forming colonies were identified.

Table 3: bacterial filtration

After filtration	Calculated bacteria count (UFC/g)
				Time (sky)	Can survive	Non-viable	Total amount of
0	6000(3.43％)	169000(96.57％)	175000(100％)
				7	9000(2.75％)	318000(97.25％)	327000(100％)
14	27000(2.21％)	1193000(97.79％)	1220000(100％)
				21	70000(1.88％)	3650000(98.12％)	3720000(100％)

Table 4: fungus filtration

After filtration	Calculated number of fungi (UFC/g)
				Time (sky)	Can survive	Non-viable	Total amount of
0	29000(11.74％)	218000(88.26％)	247000(100％)
				7	110000(10.19％)	970000(89.81％)	1080000(100％)
14	230000(8.75％)	2400000(91.25％)	2630000(100％)
				21	1640000(7.24％)	21000000(92.76％)	22640000(100％)

Table 5: identification of bacterial morphotypes

After filtration (sky)	Bacterial morphotype
		0	78.4% cocci gram-positive 21.6% bacilli gram-negative
7	84.3% cocci gram-positive 15.7% bacilli gram-negative
		14	86.7% cocci gram-positive 13.3% bacilli gram-negative
21	88.9% cocci gram-positive 11.1% bacilli gram-negative

Table 6: identification of mould species

After filtration (sky)	Species of mould
		0	Aspergillus niger (Aspergillus niger), Cladosporium cladosporioides (Cladosporium cladosporioides), Cladosporium herbarum (Cladosporium herbarum), Geotrichum species (Penicillium sp.), Saccharomyces cerevisiae
7	Aspergillus niger, cladosporium cladosporioides, Cladosporium herbarumPenicillium, yeast
		14	Alternaria alternata (Alternaria alternata), Arthrinium sp, Aspergillus niger, Cladosporium sp, Geotrichum sp, Penicillium sp, Saccharomyces cerevisiae
21	Aspergillus niger, Cladosporium gemmifolium, Cladosporium herbarum, Penicillium, yeast

Example 4

Evaluation of antimicrobial Activity of antibacterial Agents for woven fiber samples after deep washing

To ensure that the antimicrobial fibers of the present invention retain their antimicrobial activity after multiple cleanings and washings, the antimicrobial fibers are conjugated to TRICLOSAN having molecular bonding^TMEach weave of reagent THERMOVOL-L9B^TMAnd THERMOVOL-ZCB^TMFiber samples were tested. Three (3) samples of each fiber type were each subjected to multiple successive cleanings and tested for antibacterial activity against the growth of two bacteria, namely staphylococcus aureus and Escherichia coli, after five (5), ten (10) and one hundred (100) washes. A similar test was also performed on one (1) reference sample of each fiber type without any antimicrobial agent after five (5) washes. The results are summarized in table 7 below.

TABLE 7

Bacteria	Fiber	Number of washes	Bacterial inhibition zone size (mm)	Bacterial growth/antimicrobial Rate
					Staphylococcus aureus	Thermovyl-L9B	5	12.5	None/high
10	13	None/high
			100	14.75			None/high
Thermovyl-ZCB	5	12.125						None/high
			10	12.625		None/high
	100	16.75					None/high
			Thermovyl-L9*	5		0		Mean/difference
Thermovyl-ZC*	5	0					Mean/difference
			Escherichia coli	Thermovyl-L9B		5		5.125	None/high
10	6.125	None/high
					100	8.125	None/high
Thermovyl-ZCB	5	5						None/high
				10	5.375	None/high
	100	9.375					None/high
				Thermovyl-L9*	5	0		Mean/difference
Thermovyl-ZC*	5	0					Mean/difference

Microbial free agent

Discussion of the related Art

To date, commercially available masks have been hampered by their inability to capture and kill over 95% of microorganisms. Studies of microbicidal meshes in the form of filters in the face masks and ventilation systems of the present invention have demonstrated significant improvements in capture and kill efficiency (tables 1-6).

Tables 1 and 2 illustrate the compositions containing TRICLOSAN^TMThe PVC-based organic fibers of (a) are effective as particulate filters, antibacterial and antifungal filters. The antimicrobial and particle filtration capabilities of both soft and rigid masks were 100% compared to the corresponding capabilities of commercial masks (95-96%).

Tables 3-7 illustrate the highly effective levels of antimicrobial and filtration capabilities of the filters of the present invention. Specifically, the inventors have demonstrated in tables 3 and 4 that the combined antibacterial, antifungal and retention abilities are all 100%.

Furthermore, as shown in table 5, the inventors have confirmed that 96.6% of the entire bacterial population present on the filter fibers after day zero (0) (78.8% of coccal gram-positive bacteria and 21.6% of bacillal gram-negative bacteria, respectively) of different bacterial morphology types were captured on the filter. 98.1% (88.9% coccal gram-positive bacteria and 11.1% bacillal gram-negative bacteria, respectively) were present on the fibers of the filter twenty-one days (21). This confirms that the effectiveness of the filter persists over a longer period of time. As illustrated in table 6, a number of pathogenic molds were identified on the filters of the present invention for twenty-one days.

If desired, the filter can be cleaned, washed and subjected to other treatments, and can be reused without significant loss of the above-described capacity, or even the above-described capacity also increases with increasing number of washes, as illustrated in Table 7.

One of the most significant features of the filter 10, whether in the mask described above or in the circulatory system ducting filter, is its ability to immobilize, retain and kill or inhibit the growth of a wide variety of microorganisms that come into contact with the network 12 of fibres 20. Air that is pre-filtered in the case of a circulatory system, or inhaled/exhaled through the user's mask, typically includes residual microorganisms that pass through the primary filter or filters without fixing them. A person with an upper respiratory infection, such as influenza, tuberculosis, anthrax, Severe Acute Respiratory Syndrome (SARS), etc., can have significantly reduced or substantially eliminated further infection to others using the face mask of the present invention. Similarly, air contaminated with pathogenic microorganisms may be filtered prior to entering the nose and mouth area of the user. The flow of air is shown by the arrows in figures 2, 2a and 5, where air contaminated with microorganisms is shown by hatched lines and the unshaded arrows indicate clean filtered air.

Reference to the literature(incorporated by reference in this specification)

1.National lnstitute for Occupational Safety and Health.NIOSH respiratordecision logic.Cincinnati，Ohio：Department of Health and Human Services，Public Health service，CDC，1987：13-9；DHHS publication no.(NIOSH)87-108.

2.TB Respiratory Protection Program In Health Care FacilitiesAdministrator′s Guide，(http://www.cdc.gov/niosh/99-143.html).

3.3M Soins de santéCahada；Une protection fiable a chaque respiration；3M®2002.

4.MMWR；Laboratory Performance Evaluation of N95 Filtering FacepieceRespirators，1996(December 11，1998).

5.Edwin H.Lennette，Albert Balows，William J.Hausler，Jr.H.JeanShadomy，1985，Manual of Clinical Microbiology.

6.Robert A.Samson，Ellen S.van Reenen-Hoekstra，1990，Introduction tofood-borne Fungi.

7.G.Nolt，Noel R.Krieg，Peter H.A.Sneath，James T.Staley，Stanley，T.Williams，1994，Bergey′s Manual of Determinative bacteriology.

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14.Malloch，D.1981.Moulds，their isolation，cultivation and identification.Toronto；University of Toronto Press.97 p.

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Claims (23)

1. A microbicidal air filter (10) for use through an air passage, the air filter (10) comprising:

-an immobilization network (12) comprising a plurality of fibers (20) having an amount of at least one antimicrobial agent incorporated and molecularly bonded into the structure thereof sufficient to substantially immobilize, retain and at least substantially inhibit growth of suspended microorganisms in a volume of air moving through said air passage, said immobilization network (12) being substantially permeable to said air.

2. The filter (10) according to claim 1, wherein the at least one antimicrobial agent kills microorganisms suspended in the volume of air.

3. The filter (10) of claim 1, wherein said plurality of fibers (20) are arranged in a lattice, said lattice defining a plurality of air spaces between said fibers (20).

4. The filter (10) according to claim 3, wherein the fibers (20) are tightly woven or loosely woven.

5. The filter (10) according to claim 4, wherein said fibers (20) are treated PVC-based organic fibers.

6. The filter (10) according to claim 1, wherein said antimicrobial agent is selected from the group consisting of an antibacterial agent, an antiviral agent, an anti-dust mite agent, an anti-mold agent, and an anti-yeast agent.

7. Filter (10) according to claim 6, wherein the antimicrobial agent is TRICLOSAN^TMOr benzyl benzoate.

8. The filter (10) of claim 1, wherein the immobilization network (12) is a post-filter, whereby the air is pre-filtered before reaching the air channel.

9. The filter (10) of claim 1, wherein said air filter (10) is a mask (24) shaped and sized to fit over and secure around the nose and mouth of a user.

10. The filter (10) of claim 1, wherein said air filter (10) is an air duct filter shaped and sized to fit within an air duct system (40) defining an air passageway.

11. The filter (10) of claim 10, wherein said air filter (10) further comprises:

-first and second air permeable screen elements (14, 16) securable together along respective peripheral edges (22), the screen elements (14, 16) being shaped and sized to fit within and be secured in an air duct system (40);

-said air-permeable immobilization network (12) being arranged substantially between said first and second screen elements (14, 16).

12. A filter (10) according to claim 11 wherein a fastening member (32) connects said first and second air permeable screen elements (14, 16) together to sandwich said immobilization network (12) therebetween.

13. The filter (10) of claim 12, wherein said fastening member (32) includes a frame (26) for connecting said first and second screen elements (14, 16) together.

14. The filter (10) of claim 13, wherein said fastening member (32) further comprises a plurality of stitches (46) disposed through said immobilization network (12) to divide said immobilization network (12) into sub-portions (44).

15. A microbicidal mask (24) comprising:

-first and second air permeable screen elements (14, 16) secured together along respective peripheral edges (22), said screen elements (14, 16) defining a gap (23) therebetween, said screen elements (14, 16) being shaped and sized to fit over and be secured to a user's mouth and nose;

-an air permeable immobilization network (12) disposed in said gap (23) and substantially filling said gap (23), said immobilization network (12) comprising a plurality of fibers (20) having an amount of at least one antimicrobial agent incorporated and molecularly bonded into its structure sufficient to substantially immobilize, retain and at least substantially inhibit the growth of microorganisms suspended in a volume of air moving through said network (12).

16. The face mask (24) according to claim 15, wherein said at least one antimicrobial agent kills microbes suspended in said volume of air.

17. The facemask (24), according to claim 15, in which said immobilization network (12) includes a plurality of fibers (20) arranged in a lattice, said lattice defining a plurality of air spaces between said fibers (20).

18. The face mask (24) according to claim 17, wherein said fibers (20) are tightly woven or loosely woven.

19. The facemask (24), according to claim 18, in which said fibers (20) are treated PVC-based organic fibers.

20. The face mask (24) according to claim 15, wherein said antimicrobial agent is selected from the group consisting of an antibacterial agent, an antiviral agent, an anti-dust mite agent, an anti-mold agent, and an anti-yeast agent.

21. The face mask (24) according to claim 15, wherein said antimicrobial agent is TRICLOSAN^TMOr benzyl benzoate.

22. The facemask (24), according to claim 15, in which said immobilization network (12) is a post-filter, whereby air is pre-filtered before reaching the air passage.

23. The facepiece (24), according to claim 15, in which said first air permeable screen element (14) includes a slit (29) disposed therein and of sufficient size to allow said immobilization network (12) to be placed in said gap (23).