Method for evaluating disinfection effectiveness of air purifier on bacterial aerosol

Abstract

The invention relates to a method for evaluating the disinfection effectiveness of an air purifier on bacterial aerosol, and relates to the technical field of disinfection effect evaluation. Comprising the following steps: (1) arranging an aerosol infection cabin; (2) starting an aerosol generator to generate bacterial aerosol, and injecting the bacterial aerosol into the aerosol infection cabin until a set time; (3) starting a fan cycle of the air purifier, under the condition that the disinfection mode is started and not started, enabling the air purifier to act for a set time, sampling the bacterial aerosol, taking out the gel filter membrane after sampling is finished, carrying out a bacterial content test, and carrying out viable bacteria counting culture; (4) carrying out disinfection and air filtration and purification on the aerosol infection cabin; (5) viable bacteria culture counting and data analysis; . The method is simple and convenient to operate and high in safety performance.

Description

Technical Field

[0001] The present application relates to the technical field of disinfection effect evaluation, and in particular to a method for evaluating the effectiveness of air purifiers in disinfecting bacterial aerosols. Background Art

[0002] The outbreak of the novel coronavirus has heightened public concern and anxiety about the biological quality of indoor air. Airborne viruses, bacteria, and other microorganisms can easily enter the human body through the respiratory tract, posing a serious threat to human health. Therefore, air purification is crucial.

[0003] At present, there are a wide variety of air purification products based on various principles on the market, and there are different opinions on the disinfection effects of these air purification products. A set of effective air disinfection effect evaluation methods is extremely necessary for both the development of new products and the supervision and inspection of product quality. Publication No. CN103805499A discloses an air disinfection effect evaluation system, which includes a microbial aerosol generating device, an airtight cabinet, two samplers and a vacuum pump; the microbial aerosol generator host is placed outside the airtight cabinet, the atomizing cup containing the microbial solution is placed in the airtight cabinet, and the microbial aerosol generator host and the atomizing cup are connected by a hose; the vacuum pump of one sampler is pre-placed in the airtight cabinet, the sampling head is placed outside the airtight cabinet, and the inlet and outlet of the sampling head of the sampler are independently connected to the airtight cabinet to form a closed loop; the air purifier is placed outside the airtight cabinet, its air inlet is connected to the airtight cabinet, the air outlet is connected to the inlet of another sampler, and the outlet of the other sampler is connected to the airtight cabinet to form a closed loop; an air filter is installed on the airtight cabinet. The present invention effectively evaluates the one-time disinfection effect of an air purifier on aerosol microorganisms passing therethrough, while also solving the biosafety problem in microbial aerosol experiments.

[0004] The disadvantages of the above patent documents are: 1. Whether the biosafety issues in microbial aerosol experiments are safe depends on the airtightness of the airtight cabinet on the one hand, and on the disinfection effect of the air and items in the airtight cabinet on the other hand. If the airtightness and disinfection effect of the airtight cabinet cannot be guaranteed, the biosafety issues in the above patent documents cannot be guaranteed. Furthermore, the above documents do not specifically disclose the product models of the airtight cabinets. For those skilled in the art, it is not clear how the airtight cabinets involved ensure their airtightness. Therefore, there are great safety risks when performing disinfection verification on some pathogenic microorganisms.

[0005] 2. In the above literature, when performing disinfection verification, since two samplers are involved, not only is sampling cumbersome but the calculation after sampling is also complicated.

[0006] Therefore, how to provide a method for evaluating the effectiveness of air disinfection effects of air purifiers that is easy to operate and has high safety performance is a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0007] In order to solve the problems existing in the related art, the present application provides a method for evaluating the effectiveness of air purifiers in disinfecting bacterial aerosols. The method is easy to operate and has high safety performance.

[0008] The method for evaluating the effectiveness of an air purifier for bacterial aerosol disinfection in this application includes the following steps: (1) Aerosol infection cabin layout: Place the benchtop airborne microorganism sampler, air purifier, and aerosol generator in the center of the aerosol infection chamber in sequence, with the airflow direction from the aerosol generator to the benchtop airborne microorganism sampler. At the beginning of each experiment, close the airtight valves and airtight door of the aerosol infection chamber to ensure the airtightness of the aerosol infection chamber. (2) Turn on the aerosol generator to generate bacterial aerosol and inject it into the aerosol infection chamber for the set time; (3) Turn on the fan cycle of the air purifier, and let the air purifier work for the set time when the disinfection mode is turned on as the experimental group; at the same time, let the air purifier work for the same time when the disinfection mode is not turned on as the control group; The control group and the experimental group were respectively sampled with a desktop airborne microbial sampler to collect bacterial aerosols. After sampling, the gel filtration membrane was removed for bacterial count testing and viable bacteria count culture was performed. (4) Disinfection and air filtration and purification of the aerosol infection cabin; (5) Live bacterial culture counting and data analysis; .

[0009] Furthermore, the bacterial aerosol in step (2) is a Bacillus subtilis spore aerosol, the volume of the Bacillus subtilis spore solution is 10 ml, and the air compressor is turned off after 5 minutes of injection to stop aerosol generation.

[0010] Furthermore, in step (3), an MD8 airscan desktop airborne microorganism sampler and a specially prepared gel filtration membrane 17528-080ACD were used for sampling, with a sampling flow rate of 100 L / min and a sampling volume of 1000 L.

[0011] Furthermore, after the sampling in step (3) is completed, the gel filtration membrane is taken out for bacterial content test. The specific operation is as follows: after the sampling is completed, the gel filtration membrane is taken out and placed in a 90 mm sterile culture dish, and then 10 ml of sterilized pure water solution is added in a biological safety cabinet, and the dish is placed on an electric heater at 40 ° C for 5 minutes to completely dissolve the gel filtration membrane and then the bacterial content test is performed.

[0012] Beneficial effects of this application: The evaluation method in this application is that the bacterial aerosols generated diffuse in the aerosol infection cabin, and the fan circulation of the air purifier drives part of the air to flow and pass through the air purifier. When the disinfection mode is turned on, the air purifier is allowed to act for a set time as the experimental group; at the same time, when the disinfection mode is not turned on, the air purifier is allowed to act for the same time as the control group, and the control group and the experimental group are respectively turned on with a desktop air planktonic microorganism sampler to sample the bacterial aerosols. After the sampling is completed, the gel filtration membrane is taken out for a bacterial content test, and the live bacteria count culture is performed to calculate the disinfection killing rate. This method is simple to operate and has high safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above and other objects, features and advantages of the present application will become more apparent through a more detailed description of exemplary embodiments of the present application in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the present application.

[0014] Figure 1 This is a schematic diagram of the layout of the aerosol infection cabin in this application; Figure 2 Schematic diagram of the Bacillus subtilis spore colony count results when the wind speed is set to level 1; Figure 3 Schematic diagram of the Bacillus subtilis spore colony count results when the wind speed is set to level 2. DETAILED DESCRIPTION

[0015] The following describes embodiments of the present application in more detail with reference to the accompanying drawings. Although the accompanying drawings illustrate embodiments of the present application, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art. Example 1

[0016] The method for evaluating the effectiveness of air purifiers in disinfecting bacterial aerosols in this application includes the following: 1. Experimental equipment and materials 1.1 Air Purifier The core component of the Chenxing brand SKAiR DF-1900 electrostatic air disinfector (air purifier), manufactured by a Zhejiang manufacturer, is an integrated circular electrostatic module installed at the air inlet of the air conditioner. It utilizes high-voltage electrostatic technology, with a voltage strength of 4000 V to 7000 V. The technical principles are as follows: 1. The electric field breaks down the outer structure of pathogens such as bacteria or viruses (such as bacterial cell membrane or viral envelope); 2. Reactive oxygen destroys the biofield of microorganisms (including bacteria); 3. Ozone disrupts the outer structure of pathogens (such as bacterial cell membranes or viral envelopes); 4. High pressure instantaneous carbonization of protein bodies.

[0017] 2.2 TSI 3079A Aerosol Generator The TSI 3079A is a rugged, compact aerosol generator that produces high-concentration polydisperse aerosols for both water-based and alcohol-based solutions. It can generate aerosols ranging in size from <10 nm to 200 µm at concentrations up to 108 particles / cm 3 The nebulizer is a compact, lightweight, and portable aerosol generator with an adjustable flow rate from 1.2 to 5.0 L / min. A built-in, low-noise compressor provides compressed air, and the nebulizer head is constructed entirely of stainless steel. Operating components are protected by a protective cover, making this aerosol generator highly portable and suitable for acceptance testing.

[0018] 2.3 MD8 airscan desktop airborne microbial sampler Sartorius MD8 airscan desktop airborne microbial sampler, flow rate: 2.0m 3 / h - 8.0 m 3 / h, 0.1 m per level 3 / h; Timer: Adjustable from 1 to 99 minutes, 1 minute per step; Temperature range: 15°C-35°C, maximum error ±5%; Noise level ≤ 62 dB(A); Weight: 6.5 kg; Dimensions (L × W × H): 375 × 242 × 228 mm. The specially formulated gel filtration membrane is water-soluble, with a nominal pore size of 3 μm and an 80 mm diameter. The gel filtration membrane is 250 μm thick and provides depth filtration, with a 99.9995% retention rate for Bacillus subniger spores and a 99.94% retention rate for bacteriophage T3.

[0019] 2.4 Experimental strains Bacillus subtilis (ATCC 9372) spore suspension was purchased from Mesalab, Inc., USA. The main experimental reagents involved are shown in Table 1 , and the main instruments and equipment are shown in Table 2 .

[0020] Table 1 Main experimental reagents

[0021] Table 2 Main instruments and equipment

[0022] 3. Experimental Methods 3.1 Aerosol infection cabin layout The air purifier, aerosol generator and desktop airborne microbial sampler were placed in the center of the aerosol infection chamber (volume of about 22 m³) ( Figure 1 Each time the laboratory closes the airtight valves and airtight doors of the aerosol infection chamber to ensure the airtightness of the aerosol infection chamber.

[0023] 3.2 Experimental design The experimental group consisted of cells in which the fan was activated and disinfection mode was used, and the control group consisted of cells in which the fan was activated and disinfection mode was not used, and the cells were injected 60 minutes after the injection of the aerosol. In each experiment, 1 ml of sterile water was inoculated as a negative control.

[0024] Experimental steps: First, the new gel filtration membrane should be installed on the benchtop planktonic microorganism sampler; Set the air purifier's gear, ionization state, and action time before turning it on and closing the aerosol infection chamber. Turn on the aerosol generator and inject Bacillus subtilis spore aerosol for the set time; After the procedure is completed, start the planktonic microorganism sampler to collect samples, and remove the gel filtration membrane after the sampling is completed; The aerosol infection cabin is disinfected and the air is filtered and purified.

[0025] 3.3 Aerosol generation Before each experiment, 10 ml of Bacillus subtilis spore suspension was injected into the aerosol generator solution. The air compressor flow rate was set to 20 L / min. After 5 minutes of injection, the air compressor was turned off to stop aerosol generation.

[0026] 3.4 Aerosol sampling Sampling was performed using an MD8 airscan desktop airborne microbial sampler and a specially designed gel filtration membrane 17528-080ACD, with a sampling flow rate of 100 L / min and a sampling volume of 1000 L.

[0027] 3.5 Gel filtration membrane treatment After sampling, the gel filtration membrane was removed and placed in a 90 mm sterile culture dish. Then, 10 ml of sterilized pure water solution was added in a biosafety cabinet and placed on an electric heater at 40 °C for 5 min to completely dissolve the gel filtration membrane before conducting a bacterial count test.

[0028] 3.6 Live bacteria culture count 3.6.1 Use a 10 ml pipette to pipette the dissolved gel membrane filtrate into a sterile test tube (25 mm × 100 mm) and vortex for 20 seconds.

[0029] 3.6.2 Place the test tube in a water bath at 80-85°C for 10 minutes. Then remove the test tube and place it in an ice bath (0-4°C) for 2 minutes.

[0030] 3.6.3 Pipette 1.0 ml of solution from each tube into a blank dilution tube containing 9.0 ml of sterile water and vortex for 20 seconds. Then transfer 1.0 ml of solution from this dilution tube into the second blank dilution tube, and so on until the dilution reaches 10. -4 .

[0031] 3.6.4 Select a test tube with an appropriate dilution (preferably one with an expected colony count of 15 to 300 cfu per plate), vortex for 20 seconds, and pipette 1.0 ml of the mixed suspension into a sterile Petri dish. Inoculate two Petri dishes for each dilution. Generally, two to three different dilutions are needed. Before adding samples to the Petri dishes, number them according to group number to avoid mixing the diluted solutions.

[0032] 3.6.5 Cool the melted soybean casein digest agar to 45-50 °C, then pour 20 ml into each culture dish, swirl by hand 10 times, left and right, and front and back twice to mix thoroughly, and place in a safety cabinet to solidify.

[0033] 3.6.6 Seal the solidified plate with sealing film and incubate it upside down at 37°C for 48 hours.

[0034] 3.6.7 Place the plates on a colony counter and record the number of colonies. Calculate the average colony count for each experimental group by dividing the average plate count by the dilution factor. Then, calculate the disinfection kill rate according to "2.1.3 Air Disinfection Effectiveness Assessment Test, 2.1.3.5 Field Test" in the "Technical Specifications for Disinfection" (2002 Edition). Calculate the kill rate using the following formula:

[0035] 4 Experimental results 4.1 Concentration of Bacillus subtilis (ATCC 9372) spore suspension The concentration of Bacillus subtilis (ATCC 9372) spore suspension was 4.0×10 7 cfu / ml.

[0036] 4.2 Disinfection test results In the laboratory aerosol infection chamber with an average temperature of 21-23.5℃ and a relative humidity of 45%-55%, with or without the air purifier disinfection mode turned on, Bacillus subtilis spores were collected and viable bacteria were counted and cultured. Each group of experiments was repeated three times, and the average value of the three experiments was calculated.

[0037] When the air purifier was set to the first wind speed (0.94 m / s) and the disinfection mode was not turned on, the concentration of Bacillus subtilis (ATCC 9372) suspension was 9.25×10 4 cfu / m 3 After the air purifier was turned on in disinfection mode for 60 minutes, the concentration of Bacillus subtilis spore suspension dropped to 3.6×10 2 cfu / m 3 ,like Figure 2 shown.

[0038] Therefore, when the air purifier was set to speed 1 and the disinfection function was turned on, the killing rate of Bacillus subtilis spores was 96.1% after 60 minutes (Table 3).

[0039] Table 3 The results of aerosol disinfection of Bacillus subtilis spores when the air purifier is set to wind speed 1

[0040] When the air purifier was set to the second wind speed (wind speed of 1.71m / s) and the disinfection function of the air purifier was not turned on, the concentration of Bacillus subtilis (ATCC 9372) suspension was 6.08×10 4 cfu / m 3 After the air purifier disinfection function was turned on, the concentration of Bacillus subtilis spore suspension dropped to 2.07×10 2 cfu / m 3 .

[0041] Therefore, when the air purifier was set to speed 2 and the machine was turned on for 60 minutes, the killing rate of Bacillus subtilis spores was 96.6% (Table 4), and no colonies grew in the negative control culture dishes.

[0042] Table 4 The results of aerosol disinfection of Bacillus subtilis spores when the air purifier is set to wind speed 2

[0043] 5 Conclusion 5.1 When the air purifier was set to speed 1 (0.94 m / s) and the disinfection function was turned on for 60 minutes, the killing rate of Bacillus subtilis spores was 96.1%.

[0044] 5.2 When the air purifier is set to wind speed level 2 (wind speed of 1.71m / s), the killing rate of Bacillus subtilis spores exceeds 96.6% after the disinfection function of the machine is turned on for 60 minutes.

[0045] The embodiments of the present application have been described above. The above description is illustrative and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to the technology in the market, or to enable other persons skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for evaluating the effectiveness of air purifiers in disinfecting bacterial aerosols, characterized in that: The following steps are involved: (1) Aerosol infection cabin layout: Place the benchtop airborne microorganism sampler, air purifier, and aerosol generator in the center of the aerosol infection chamber in sequence, with the airflow direction from the aerosol generator to the benchtop airborne microorganism sampler. At the beginning of each experiment, close the airtight valves and airtight door of the aerosol infection chamber to ensure airtightness. (2) Turn on the aerosol generator to generate bacterial aerosol and inject it into the aerosol infection chamber for the set time; (3) Turn on the fan cycle of the air purifier, and let the air purifier work for the set time when the disinfection mode is turned on as the experimental group; at the same time, let the air purifier work for the same time when the disinfection mode is not turned on as the control group; The control group and the experimental group were respectively sampled with a desktop airborne microbial sampler to collect bacterial aerosols. After sampling, the gel filtration membrane was removed for bacterial count testing and viable bacteria count culture was performed. (4) Disinfection and air filtration and purification of the aerosol infection cabin; (5) Live bacterial culture counting and data analysis; 。 2. The method according to claim 1, wherein The bacterial aerosol in step (2) is a Bacillus subtilis spore aerosol and the volume of the Bacillus subtilis solution is 10 ml, and the air compressor is turned off after 5 minutes to stop the aerosol generation.

3. The method according to claim 1, wherein In step (3), an MD8 airscan desktop airborne microbial sampler and a specially prepared gel filtration membrane 17528-080ACD were used for sampling, with a sampling flow rate of 100 L / min and a sampling volume of 1000 L.

4. The method according to claim 1, wherein After sampling in step (3), the gel filtration membrane is removed for bacterial content testing. The specific operation is as follows: after sampling, the gel filtration membrane is removed and placed in a 90 mm sterile culture dish, and then 10 ml of sterilized pure water solution is added in a biological safety cabinet. The dish is placed on an electric heater at 40°C for 5 minutes to completely dissolve the gel filtration membrane and then the bacterial content test is performed.

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