Portable air sterilizer for respiratory equipment used in infectious environments

Abstract

A portable air sterilization device attached to a respirator has been disclosed for personal protection of individuals working for long periods in highly infectious environments. This air sterilization device neutralizes 99.99% to 100% of aerosolized viruses and bacteria present in infected air and is portable. To sterilize infected air, the device uses a method of thermal stress (Grinshpun et al., 2010).

Description

Technical Field

[0001] This invention relates to a portable air sterilizer attached to a personal protective respirator used by individuals working for long hours in an infectious environment.

Background Art

[0002] The protection of personnel working in an infectious environment for long hours is partly solved by using masks or respirators that filter air and hold bacteria and viruses. Filters mechanically capture particles based on the spacing between material fibers and hold approximately 45 - 55% of particles of 1 micron or more. However, the dimensions of the SARS-COV-2 virus that causes COVID-19 are in the range of 0.14 - 0.016 microns. Reducing the spacing between fibers to hold finer particles may reduce the air flow through the filter, making breathing difficult or impossible.

[0003] The ability to hold submicron fine particles has been made possible by the development of filtering media using electret technology. These fibers are charged with static electricity on the surface and can attract and bind fine particles even when the particle size is smaller than the distance between the fibers. (JP2006528549)

[0004] All high-performance particle filter respirators that meet government health standards (i.e., N95, NK95, and FFP2) use electret-based filtering and hold at least 95% of particles of 0.3 microns or more. Also, respirators based on filters do not fit tightly to the face, allowing additional penetration up to a maximum of 8% of the inhaled air volume. Therefore, even when using performance masks compliant with N95, NK95, and FFP2 standards, a small amount of virus may pass through unfiltered into the body. In cases where the environment is highly contaminated and the exposure time is long (days or weeks), these small amounts of virus can accumulate and cause disease.

[0005] The latest generation of masks addresses the reduced airflow caused by electret filters by adding an electric air pump / turbine (see US7469699B2). However, even with these high-performance masks, 1% of unfiltered viruses can enter the body, accumulating over time and potentially causing illness.

[0006] By using a disinfectant air generator as a component of the respiratory system, the inactivation rate of viruses and bacteria increases from 99.99% to 100%. In other words, the concentration of active viruses after passing through the air device is 100 times lower than the concentration of viruses that would pass through unfiltered using a top-of-the-line electret fiber mask. The disinfectant air generator presented here does not use filtration to retain viruses. It uses heat stress to inactivate viruses and bacteria so that they cannot reproduce or transmit disease.

[0007] Heat stress requires a very short processing time (1 / 10 to 1 / 100 of a second) to inactivate the virus. Therefore, this inactivation method provides a feasible solution for the construction of portable respirators.

[0008] Inactivating viruses using UV-C radiation requires a processing time of several tens of seconds and generates respiratory irritants, particularly ozone (O3) and nitrogen oxides (NOx). Inactivation using high-voltage discharges in air, such as corona discharge and dielectric barrier discharge plasma, requires a shorter processing time but also generates ozone (O3) and nitrogen oxides (NOx).

[0009] The paper by Grinshpun et al. (2010), "Inactivation of aerosolized viruses in continuous airflow by axial heating," established the conditions necessary for virus inactivation. They analyzed the degree of inactivation of the MS2 bacteriophage virus by varying air temperature and treatment time. A 99.99% inactivation rate was achieved at a temperature of 175°C with a treatment time of 0.3–0.5 seconds. Above this critical temperature, the time required for inactivation decreases exponentially. All viruses are composed of the same type of proteins that make up the viral genome. Since viral inactivation is achieved by the spatial degradation of the proteins that encode viral activity, the results observed in the study of the MS2 virus can be extrapolated to all other viruses.

[0010] The design of the sterile air generator described in this patent meets the necessary conditions to ensure thermal stress and virus inactivation. The device ensures that an average of 8 liters / minute of air, the amount of air normally needed for breathing, is exposed to a temperature of 175°C or higher in the processing chamber for 0.3–0.5 seconds. [Overview of the project]

[0011] The objective of this invention is to design a portable air sterilization device that guarantees a 99.99% inactivation rate of viruses and bacteria. The technical challenge overcome by this invention is maintaining low thermal inertia of the overall device while achieving a high percentage of heat recovery necessary for processing the input air by thermal stress.

[0012] This invention describes a portable air sterilizer that attaches to a respirator and is used for personal protection of individuals working for extended periods in highly infectious environments. The air sterilizer is portable and neutralizes 99.99% to 100% of aerosolized viruses and bacteria present in infected air. To sterilize infected air, the device utilizes a heat stress method (Grinshpun et al., 2010). This device consists of the following components: • Air treatment module (1) ·Power(2) • Flexible hose (3) for supplying air to the full-face mask (11).

[0013] The heat-treated air treatment module (1) consists of an air treatment heat reactor (4) housed in a helical backflow heat exchanger (5). This spatial configuration of the heat reactor (4) and helical heat exchanger (5) allows the air to cool after heat treatment, recovering heat and minimizing heat loss into the environment. The recovered heat is transferred to the infected air before it reaches the heat treatment reactor (4) to preheat it. Air sterilization is achieved by heating the air to over 175°C and treating it for 0.3–0.5 seconds. Other air sterilization models using thermal stress have been proposed (US Patent Nos. US5874050 and US7332140B2). However, these devices are heavy and require a large power input, making them unsuitable for portable use. Portable devices for air purification by thermal treatment are also known, such as US Patent Nos. US6488900B1 and US9968809B2. However, the design choices of the thermal reaction chamber and heat exchanger unit in the devices proposed in the above patents resulted in large thermal inertia and heat loss, increasing the need for heavy power sources. As a result, the above patents could not become commercially viable products.

[0014] The design of the air sterilization device offers a novel solution by placing the heat reactor inside a reverse-flow helical heat exchanger. This eliminates the need for insulation to prevent increased thermal inertia of the device, and does not compromise the device's portability, even with the need for a larger energy supply.

[0015] To reach the critical temperature of 175°C of thermal stress within a 3-5 minute timeframe, heat loss must be kept low (low power consumption in the electrical resistance of the heat reactor), and thermal inertia must also be kept low.

[0016] The following are Figures 1-5 illustrating the design of the air purifier. [Brief explanation of the drawing]

[0017] [Figure 1] It is a schematic diagram of the parts of the sterilized air generator of the first design version. [Figure 2] It is the horizontal and vertical cross-sections of the heat treatment chamber of the first design version. [Figure 3] It is the cross-section of the heat treatment chamber in the second design version. [Figure 4] [[ID=!3]]It is a schematic diagram of the parts of the air sterilizer in the second design version. [Figure 5] It is the horizontal and vertical cross-sections of the heat treatment chamber in the second design version.

Embodiments for Carrying Out the Invention

[0018] Figure 1 schematically shows the first design version of an air sterilizer configured as follows. A. Hot air treatment module (1) B. Power supply (2) [[ID=……]]C. Flexible hose (3) for supplying sterilized air to the full-face mask (11)

[0019] Figure 2 shows the heat treatment module (1) composed of a heat treatment reactor (4) and a countercurrent spiral heat exchanger (5).

[0020] In the design version shown in Figure 2, the spiral heat exchanger (5) surrounds the heat treatment reactor (4). Therefore, the heat loss from the reactor (4) is used to preheat the air before treatment. This spatial arrangement eliminates the need for insulation material that would have increased the thermal inertia of the device.

[0021] A. The heat treatment air treatment module (1) is composed of the following. a. Heat treatment reactor (4) b. Spiral countercurrent heat exchanger (5) surrounding the heat treatment reactor (4). [[ID=...]]

[0022] A.a. The heat treatment reactor (4) is designed to reach a temperature of 175 °C or higher in a short time (3 - 5 minutes) while using minimal power. The low power usage is achieved by recovering the heat used in the process and using it to preheat the contaminated air, and by reducing the thermal inertia of the heat treatment reactor (4) / spiral countercurrent heat exchanger (5) assembly. The heat loss of the heat treatment reactor is reduced by placing the heat treatment reactor (4) at the center of the spiral heat exchanger. In this way, the heat lost in the reactor is used to preheat the air to be treated. This spatial arrangement eliminates the need for additional thermal insulation materials that would have been required to increase the thermal inertia of the device.

[0023] [[ID=X]]The heat treatment reactor consists of a self - standing nickel wire electrical resistance (6) attached to a 17 - mm diameter channel within a ceramic fiber block (7). The resistance coil (6) heats the air passing through the channel to a temperature of 175 °C or higher. The dimensions of the ceramic fiber block are 120 mm × 25 mm × 50 mm.

[0024] A.b. The spiral countercurrent heat exchanger (5) has countercurrent air channels (8) arranged in a double - spiral configuration that cools the sterilized hot air, recovers heat from the treated air, and preheats the air entering the heat treatment reactor. The two countercurrent air channels (8) are formed between two aluminum (9) sheets, which are wound in a diametric spiral with a width of 50 mm and a length of 110 mm. The sheets are wound leaving a space of 3 - 6 mm between them. The two countercurrent air channels (8 are formed by two ceramic fiber lids (10) and the aluminum sheets (9). For weight reduction, low thermal inertia, and efficient heat exchange between the air channels (8), the aluminum sheets (9) are only 0.07 - 0.1 mm thick and are corrugated transversely with respect to the length. The corrugation of the aluminum sheets (9) ensures the stability and rigidity of the final spiral shape, while at the same time contributing to the turbulent air flow within the channels (8) and increasing the heat transfer between the countercurrent air flows.

[0025] Note: In the original text, there was a mistake in the numbering in the English translation part. I've corrected it to match the correct sequence. Also, in the translation of the text in item [ID = 4], I've changed the beginning word "熱処理反応器は" to "The heat treatment reactor" for better English expression. If this is not allowed according to strict rules, please let me know and I'll adjust accordingly.B. Power source (2)

[0026] The power source consists of two 5000mA lithium-ion rechargeable batteries connected in series. The power source is also equipped with voltage control and adjustment circuits, as well as LED battery charge indicators. When used correctly within the 4.2V to 3V range, the batteries should provide 500 to 1000 charge cycles.

[0027] To extract maximum energy from the battery without affecting the appropriate operating range (4.2V~3V), the power supply incorporates voltage boosting and regulating circuits. The power generated along the resistor in the reactor (6) is 15W~12W, ensuring that the processing temperature is maintained above 175°C. The generated power depends on the voltage (U) and current (I) applied to the resistor, i.e., U(W) = U(V) x I(A). If the voltage on the battery leads drops during operation, the power generated along the resistor also decreases. If the power is initially sufficient to reach 175°C in a short time (3~5 minutes) and maintain it at 200~210°C, when the battery output drops between 3.5V~3.4V, the available power generated across the resistor becomes insufficient to maintain a temperature above 175°C. Under these conditions, the use of the respirator must be stopped before the full capacity of the battery is used. The battery will continue to supply power without adversely affecting its lifespan until the output reaches 3V.

[0028] By introducing a control and boost circuit as needed, a constant voltage can be provided to the resistor (6) of the heat treatment reactor (4) throughout the entire range of the battery's optimal power output from 4.2V to 3V. This ensures that the power radiated from the resistor remains constant until the battery's entire capacity is used.

[0029] Using a potentiometer, the tension control circuit can set a stable voltage to a value of 8.4V (4.2 + 4.2) or higher, which is higher than the total battery voltage at the start of the discharge cycle. The constants of the tension control circuit are related to the reactor resistance and ensure that the power required to maintain a temperature of 175°C or higher throughout the entire battery discharge cycle is dissipated.

[0030] A 32mm diameter flexible tube (3) guides air into the full-face mask (11), dissipating heat and cooling the germicidal air flowing into the mask by about 2-3 degrees. As a result, the germicidal air reaches the mask at a temperature of 2-3 degrees, slightly higher than the ambient temperature. This improves breathing comfort compared to filter masks. The temperature of the germicidal air guided into the mask is lower than the temperature of the air between a normal woven surgical mask and the user's face. In a normal filter mask, the temperature of the air rises due to exhaled air at 37°C, and the mask's fibers act as a heat exchanger.

[0031] C. The flexible tube (3) has a 32mm diameter opening and is used to collect air into a full-face mask (11) with a silicone rubber seal and a clear polycarbonate visor. The internal space of the mask (11) is divided into a nose and mouth area and the rest of the face by a flexible rubber wall. Two one-way valves are installed in the wall to circulate air from the mask's intake to the mouth area near the forehead. This division into two areas is necessary to prevent CO2 buildup inside the mask by mixing the exhaled air with the fresh air. Another one-way valve is installed in the mouth and nose area to allow the exhaled air to escape from the mask and to prevent infectious air from entering from the outside.

[0032] Figure 4 shows a second design version of the portable air sterilizer. In this version, the air heat treatment module (1) is mounted directly on the top of the full-face mask (11). In this version, the heat treatment reactor (4) is surrounded by a spiral heat exchanger (5), and there are also other plate heat exchangers above and below, which also operate with a backflow action.

[0033] Figure 5 shows vertical and longitudinal sections of the treatment module (1) in a second design version of the present invention. The backflow channels of the helical heat exchanger are formed from aluminum sheets (9) and aluminum end caps (12). The plate heat exchanger is formed from aluminum end caps (12) and two additional aluminum plates (13). Thus, two backflow air channels are formed on two faces of the helical heat exchanger (5). The air channels adjacent to the helical heat exchanger (5) are inlet channels for drawing in ambient cold infected air. The cold air drawn in through these channels is preheated by the aluminum end caps (12) of the helical heat exchanger (5) and reaches the pre-chamber (16) of the helical heat exchanger (5) through circular holes (15). From there, it enters the heat reactor (4) via another air channel (8). After being processed in the heat reactor chamber (4), the air flows along the other air channel (8) and backflows with the inlet air that is converted into heat. After this partial cooling, the treated air reaches the germicidal air receiving chamber (19) and flows through the cylindrical channel (18) to the main germicidal air channel (17). After reaching the main germicidal air channel (17), the germicidal air is further cooled by transferring heat to the untreated air in the reverse-flowing inlet channel (14). Once cooled, the germicidal air is guided through the fixing device (20) to the full-face mask (11).

[0034] The respirator with an air sterilizer described in this patent has the following advantages compared to existing respirators on the market: 1) This device provides users with sterile air after inactivating 99.99% of viruses. The concentration of residual active viruses is approximately 100 times lower than the concentration of viruses that can pass through the N95 electret-type filtration mask, which is considered the most effective. 2) Healthcare workers and frontline workers can be fully protected from all three main routes through which the virus enters the body (eyes, nose, and mouth). 3) This device does not contain any disposable parts, and therefore does not pose any environmental safety challenges. 4) The rechargeable power supply is lightweight and compact. The use of tension adjustment and lift circuits maximizes the battery's capacity. Under these operating conditions, the battery provides 500-1000 discharge and charge cycles. 5) Using heat stress as a method of virus inactivation is very safe and does not cause toxic byproducts that are harmful or irritating to sterile airflow. 6) This proposed air sterilization design has made it possible to construct the first portable full-face respirator using a method for inactivating aerosolized viruses with thermal stress. The following factors contribute to its portability: a. Spatial arrangement of the heat treatment reactor (4) and the spiral heat exchanger (5). The heat exchanger is designed to surround the reactor. b. Very low thermal inertia due to the design of the reactor-exchanger system. c. Use tension adjustment and lift circuits to ensure optimal use of power supplied from the rechargeable power source.

Claims

1. A device used in personal protective equipment systems that decontaminates air using heat, A heat treatment module configured to decontaminate air using heat, wherein the heat treatment module comprises an electrical resistor and a helical reverse heat exchanger having at least one corrugated surface surrounding the electrical resistor, A conduit for supplying sterilized air treated by the heat treatment module to a personal respirator, A mountable power supply electrically connected to the aforementioned electrical resistor, A device equipped with the following features.

2. The apparatus according to claim 1, wherein the electrical resistor is arranged within a ceramic fiber block.

3. The apparatus according to claim 1, wherein the electrical resistor is surrounded by the helical backflow heat exchanger.

4. The apparatus according to claim 1, wherein the attachable power supply comprises at least one storage battery, a voltage boosting and voltage regulating circuit, the voltage boosting and voltage regulating circuit is configured to maintain and supply a constant power to the electrical resistor over the entire period of battery discharge.

5. The apparatus according to claim 1, wherein the heat treatment module is configured to heat incoming air to a temperature exceeding 175°C for at least 0.3 seconds.

6. The apparatus according to claim 1, wherein the heat treatment module is configured to heat the incoming air to over 175°C and inactivate 99.99% of viruses, bacteria, and pathogens by heat.

7. The apparatus according to claim 1, wherein the helical backflow heat exchanger comprises a pair of sheets wound in a concentric helical manner, two ceramic fiber lids, and a pair of countercurrent air passages formed between the sheets.

8. The apparatus according to claim 1, wherein a countercurrent air passage is formed by the corrugated surface of the helical inverse heat exchanger and the ceramic fiber lid.

9. The apparatus according to claim 1, further comprising at least one air inlet channel adjacent to the helical backflow heat exchanger, wherein the air inlet channel is configured to take in outside air.

10. The apparatus according to claim 1, further comprising a port for fixing an air sterilizer to a personal respirator and for airtight connection.

11. A device for use in a personal protective equipment system, which decontaminates air by heat, A heat treatment module comprising an electrical resistor, a helical reverse heat exchanger having at least one corrugated surface surrounding the electrical resistor, and two plate heat exchangers, A conduit for supplying processed air from the heat treatment module, A device comprising a rechargeable battery and an attachable power supply including a voltage boosting and adjustment circuit.

12. The apparatus according to claim 11, wherein the two plate heat exchangers include two aluminum end caps and two aluminum plates, and have the function of extending the paths through which treated air and untreated air pass.

13. The apparatus according to claim 11, wherein the two plate heat exchangers and the helical backflow heat exchanger surround the heat treatment module from all sides.

14. The apparatus according to claim 11, wherein the helical backflow heat exchanger and the plate heat exchanger operate in a backflow manner.

15. The apparatus according to claim 11, wherein the helical backflow heat exchanger includes a channel through which treated heated air circulates while flowing back through untreated air.

16. The apparatus according to claim 11, wherein the voltage boosting and adjustment circuit is configured to supply a constant power to an electrical resistor over the entire discharge period of the storage battery.

17. The apparatus according to claim 11, further comprising at least one air intake channel adjacent to the helical backflow heat exchanger, wherein the at least one air intake channel is configured to take in outside air.

18. The apparatus according to claim 11, further comprising a port for fixing an air sterilizer to a personal respirator and for airtight connection.

19. The apparatus according to claim 11, wherein the heat treatment module is configured to heat the incoming air to over 175°C for at least 0.3 seconds.

20. The apparatus according to claim 11, wherein the heat treatment module is configured to heat incoming air to over 175°C and inactivate 99.99% of viruses, bacteria, and pathogens by heat.

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