We have studied the filter materials in the most popular foreign breathing filters. We have established that the filter set for a bacterial/viral heat and moisture exchange (HME) filter consists of a primary filtering layer which provides highly efficient removal of bacteria and viruses from the air as a result of mechanical or electrostatic filtration; barrier layers, preventing migration of fibers and moisture droplets into the primary filtering layer; and a heat and moisture exchange layer, providing the needed humidity and temperature for the air inspired by the patient.As a result of our studies, we have selected or designed de novo filter materials to make a filter set for a domestic breathing filter. We have determined the parameters of the material for the heat and moisture exchange layer: weight percent of fibers, thickness, surface and volume density, air permeability, hygroscopicity, weight percent calcium chloride.In designing domestic filter materials for breathing filters, we studied materials in the most widely used imported breathing filters: Pharma Systems (Sweden), Pall (an international company), and Venticaire (UK).As a result of our studies, we have established that there are two basic types of filter sets: -a filter set for bacterial/viral filters, consisting of a primary filtering layer ensuring efficient removal of bacteria and viruses from breathing mixtures, plus two barrier layers which are mainly intended to keep droplets of liquid from entering the primary filtering layer; -a filter set for bacterial/viral heat and moisture exchange filters, consisting of a primary filtering layer, a heat and moisture exchange layer that humidifies and warms the breathing mixtures, and two barrier layers.Furthermore, there are breathing filters in which only one type of filter material is used, designed only for humidification and warming of the breathing mixtures ("artificial nose"). Primary filtering layerThe primary filtering layer is designed for highly efficient bacterial/viral filtration. As follows from the results of analysis of filter materials in imported breathing filters providing highly efficient removal of bacteria and viruses from air, two types of materials are used:-filter materials consisting of fine glass, ceramic, or other fibers of diameter down to 1 µm and having a dense, fine-pored structure, and which accomplish mechanical filtration of the breathing mixtures;-electret (electrostatic) filter materials, consisting of polyester, polypropylene, or polyacrylonitrile fibers of diameter 20-35 µm, providing high-efficiency filtration largely due to electrostatic attraction forces between aerosol particles and the fibers of the material. These materials are most promising for breathing filters, since they have low aerodynamic resistance and significantly cheaper materials for mechanical filtration.
The goal of the research was to fabricate non-fabric filter materials with antimicrobial drugs for purification of air from microorganisms and mechanical particles. The properties of antimicrobial drugs used for treatment of fibrous materials were analyzed. Drugs for preparing antimicrobial filter materials were selected. Equipment for producing viscose fiber with antimicrobial drugs such as the AVK-0.6 IM system for preparing technical viscose threads and the ShA-5K spinning system were selected. Processes for treating viscose thread with antimicrobial drugs for forming cord of linear density 80-90 ktex and its embossing, drying, and cutting were developed. Experimental batches of non-fabric needle-punch material with antimicrobial drugs were produced. The antimicrobial activity was determined by the zone method and in liquid medium against test cultures including various classes and species of microorganisms.Chemical fibers and textile and non-fiber materials containing antimicrobial drugs are broadly incorporated into world practice. They are used primarily in medical articles such as suturing agents, gurney accoutrements, clothing, and everyday items such as shoes, stockings, military uniforms, etc. [1][2][3].The use of fibrous materials with antimicrobial drugs for fabricating air filters is significantly less developed although the use of such materials for them is most advantageous.As a rule, the purification of process air and air supplied to clean rooms is a multi-stage process. Imported highefficiency particulate filters (HEPA, ULPA) that provide a purification efficiency class according to GOST 51251 [1] and H10-H14 and U15-U17 are used in the final stage [4].The high efficiency of solid particle filtration by these filters is common knowledge. However, high energy demands and workplace noise, high aerodynamic resistance, and high costs are characteristic of air-purification systems using HEPA filters.Air filters for antimicrobial treatment of air could be developed by creating antimicrobial filtering materials of class F8-F9 with bactericidal, fungicidal, and virucidal properties in combination with low aerodynamic resistance and low energy demands. In several instances HEPA filters are highly competitive, especially in systems with full or partial air recirculation.Air filters using filter material with an antimicrobial drug deactivate microorganisms on the surface and within the bulk of the material and ensure that the air is not secondarily contaminated. This advantage persists with prolonged use of the air filters.The filter material with antimicrobial drugs can be used in the last and penultimate stages of air filtration. It is advisable to use a filter material with a filtering element containing an antimicrobial drug in the final filtration stage for the following instances:− purification of air in ventilation systems of up to class F9 pharmaceutical rooms and therapeutic medical institutions;
Comprehensive tests of experimental bacterial and viral heat and moisture exchanging breathing filters were performed using filter cartridges of domestic non-fabric materials from various production methods based on chemical fibers on a stand that enabled the specific loss of moisture from the humidifying loop of the breathing filters to be determined according to the requirements of ISO 9360-1:2000 (E). Results from tests of the specific moisture loss from the humidifying loop for the experimental breathing filters and analogous filters from foreign companies were compared.Comprehensive tests of experimental bacterial and viral heat and moisture exchanging (BVHME) breathing filters were carried out in order to evaluate their heat and moisture exchanging and aerodynamic properties. Chemical safety, toxicological, and clinical tests were also performed.The filtering element of the tested breathing filters was a filter cartridge consisting of domestically produced filter materials prepared from chemical fibers:-the main filtering layer of electrostatic filter material made of fiber prepared by electro-forming of a solution of styrene and acrylonitrile copolymer; -a heat and moisture exchanging layer of filter material made of a mixture of viscose and polypropylene bicomponent fibers containing the hydrophilic adsorbent calcium chloride;-barrier layers made of non-fabric material, thermally bonded polypropylene located between the main filtering and heat and moisture exchanging layers in addition to the outer sides of the filter cartridge.A stand satisfying requirements of the standard ISO 9360-1:2000 (E) was constructed to carry out the tests of the heat and moisture exchanging properties of the breathing filters [1].The test stand (Fig. 1) included a bidirectional flow generator (1) that mimicked human breathing; a moisture generator (2); an electronic unit for controlling the test process (3); a calibrator for tuning the stand apparatus (4), and measuring equipment such as a TRM202-Shch1.SS meter-regulator; CUW 4200S analytical balance (CAS, South Korea); a CS Medica Sphygonomanometer Cerfied No. 109180493; an IVTM-7K moisture and temperature meter; and a Testo 830-T-2 contact infrared thermometer.The bidirectional air-flow generator was a mechanically drive piston that created an air flow that had a sinusoidal wave shape.The moisture generator consisted of a thermally isolated chamber containing a water bath, a special valve mechanism, a heat source, and an air bladder.
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