Microbial clean air delivery rate test method based on solid impactor sampler

Abstract

Provided is a microbial clean air delivery rate test method based on a solid impactor sampler. In the method, a solid impactor sampler is used to perform sampling; and on the basis of a proposed method for establishing sampling time schemes corresponding to different microbial clean air delivery rates, testing is performed to obtain a purification decay curve of microbial aerosol concentration for an air purification product in an enclosed environment, linear fitting is performed on exponential concentration to obtain a decay constant, and then conversion is performed to obtain a microbial clean air delivery rate value. The method has the advantages of high reproducibility, low test cost, high test efficiency, wide detection range, etc., can achieve the effective characterization of the purification rate of air purification products for airborne microbial particles, and can realize differentiation between air purification products having different microbial purification rates. Therefore, a test method for evaluating the microbial purification rate performance in the field of air purification products is provided.

Description

A microbial clean air quality test method based on a solid impact sampler Technical Field

[0001] The present invention relates to the technical field of air purifier microbial purification performance test methods, and in particular to a microbial clean air volume test method based on a solid impact sampler. Background Art

[0002] Currently, the domestic air purifier product standard system primarily uses the following indicators to characterize the microbial purification performance of air purifiers: the antibacterial rate (GB / T 21551.2-2008), the sterilization rate (GB 21551.3-2010), and the virus removal rate (GB / T 18801-2022). These indicators all measure the percentage of microorganisms removed per unit time. However, for air purifiers with strong purification performance on the market, their antibacterial / sterilization / virus removal rates are generally above 99.9%. Therefore, these three indicators cannot directly reflect the microbial purification ability of air purifiers.

[0003] Since air purifiers were developed and popularized earlier abroad, the mainstream air purifier purification performance standards mainly include the American standard AHAMAC series standards, the Canadian standard NRCC 54013, the Japanese standard JEM 1467, the Korean standard SPS-KACA002-132, the international standard IEC 63086, etc. Among them, the 2022 American standard AHAM AC-5 released the microbial clean air volume test method for the first time. This standard uses the liquid impact method to sample and measure the activity concentration of microbial aerosols in a closed test chamber, which is a sign of the formation of the microbial clean air volume indicator. Microbial clean air volume is currently an effective indicator of the microbial purification rate of air purifiers, but there are no research reports on the microbial clean air volume test method in my country.

[0004] The American standard AHAMAC-5 microbial clean air quality test method is based on the "concentration decay method" to measure the clean air quality value of the target pollutant. It is divided into two parts: natural decay test (without turning on the purifier) ​​and total decay test (with turning on the purifier). The specific steps are as follows:

[0005] A) Natural attenuation test:

[0006] a) Before starting the test, place the test prototype in the center of the test chamber as required, pre-operate the test prototype for a period of time, confirm the prototype's maximum operating gear, and control the temperature and humidity inside the test chamber within the ranges of 20°C ± 3°C and 50% ± 10%, respectively. Before testing, disinfect the environment inside the test chamber and clean the air background.

[0007] b) Transfer the prepared microbial suspension to the atomizer, atomize the microbial suspension, and turn on the stirring fan in the test chamber to ensure that the initial concentration range can be controlled within 5×10 6 CFU / m 3 or PFU / m 3 to 2×10 9 CFU / m 3 or PFU / m 3 within the range.

[0008] c) Sampling was performed using an SKC Biosampler liquid impactor at a minimum of three concentration points every 20 min. Each sampling period lasted 1 min, corresponding to a sampling volume of 12.5 L. PBS (pH 7.2, supplemented with 0.005% Tween 80) was used as the absorption solution. If the sampling efficiency was insufficient, multiple liquid impactors were connected in series to improve the sampling efficiency.

[0009] d) The sampled absorption liquid is serially diluted and transferred to nutrient agar plates in triplicate, and cultured and counted according to the test strain or strain type.

[0010] e) After the test, the test chamber shall be disinfected and the air filtered.

[0011] B) Total attenuation test:

[0012] a) The steps for pre-experimental preparation, background control and atomization of microbial suspension are the same as steps a) to c) of the natural attenuation test.

[0013] b) After the initial concentration points are collected, run the air purifier prototype and perform continuous sampling at 2-minute intervals for the first 10 minutes. Then, select sampling at 15 minutes, 30 minutes, and 45 minutes based on the performance of the air purifier prototype. The default sampling time is 1 minute, and the sampling flow rate is 12.5 L / min. For low concentration points, the sampling time needs to be extended to more than 1 minute.

[0014] However, the above-mentioned microbial clean air quality test method proposed by American Standard AHAMAC-5 has the following problems:

[0015] (1) The detection range is narrow and is only suitable for detecting high concentrations of bacteria, viruses and other microbial particles:

[0016] This method uses the liquid absorption method for sampling. The default value of the standard sampling time is 1 minute. For low concentration points, the sampling time needs to be extended until the microbial concentration can be effectively detected. For air purification products with high purification rates, it usually only takes 10 to 15 minutes to purify microorganisms to low concentration points. However, the corresponding low concentration point sampling time of the liquid impact method is usually as long as 10 minutes or more. At this time, the problem of overlapping sampling intervals and sampling times arises. Therefore, when a single set of samplers is used, the detection range can only be limited to high concentration points, resulting in a low upper limit of its MCADR detection range.

[0017] Therefore, when testing the microbial clean air volume of air purification products with high purification rates, it is necessary to use multiple sets of SKC Bio samplers simultaneously for cross-sampling at different time points. This leads to increased equipment costs and a significant increase in the workload of the corresponding sampling absorption liquid dilution and incubation operations. In addition, it is difficult to match and debug the sampling times of multiple sets of samplers, and the stability of the concentration decay curve fitting results is difficult to ensure, resulting in low validity of the results.

[0018] (2) Low test efficiency:

[0019] Since this method uses liquid absorption sampling, it is not possible to directly use a set of absorption bottles for efficient sampling. Therefore, the American standard clearly stipulates that multiple sets of absorption bottles need to be connected in series or adhesives need to be added to improve sampling efficiency. In addition, during the test, the test personnel are required to transfer the sampled absorption liquid to a biosafety cabinet for serial concentration dilution, and then set up 3 groups of parallel transfers to nutrient agar culture medium for constant temperature culture counting. The above sampling operations are time-consuming and laborious, resulting in low efficiency of the entire test.

[0020] (3) High test cost:

[0021] The SKC Bio sampler liquid impact sampler used in conjunction with this method is relatively expensive. The price of a single set of equipment is about 50,000 to 70,000 yuan, and the price of a liquid absorption sampling bottle is about 5,000 to 8,000 yuan. In addition, the American standard microbial clean air volume test method requires the use of at least 6 liquid absorption sampling bottles. Therefore, the cost of using only a single set of equipment plus sampling bottles is estimated to be at least 80,000 to 110,000 yuan. If, as mentioned in point (1) above, multiple sets of sampler equipment and multiple absorption bottles are required in series, the equipment cost required for the test may be as high as hundreds of thousands of yuan.

[0022] Summary of the Invention

[0023] The purpose of the present invention is to provide a microbial clean air volume test method based on a solid impact sampler, which has the characteristics of strong reproducibility, low test cost, wide detection range and high test efficiency.

[0024] The present invention specifically adopts the following technical solutions to achieve the above objectives.

[0025] A microbial clean air volume test method based on a solid impact sampler comprises the following steps:

[0026] (1) Natural attenuation test:

[0027] (1.1) Place the test sample in the center of a test chamber equipped with an aerosol atomizer, a stirring fan, and a circulating fan;

[0028] (1.2) Place the solid impact sampler containing the nutrient agar plate in the test chamber, transfer the prepared microbial suspension to the aerosol atomizer, clean the test chamber environment, and then maintain the test chamber sealed until the end of the natural attenuation test;

[0029] (1.3) Turn on the stirring fan, circulation fan, and aerosol atomizer to spray the test chamber with bacteria; after the aerosol atomizer has finished spraying, turn off the aerosol atomizer and continue to operate the stirring fan until the microbial aerosol in the chamber is uniform, then turn off the stirring fan;

[0030] (1.4) Use a sampler to sample the air at different time points. After sampling, disinfect and clean the environment in the test chamber;

[0031] (1.5) After sampling, transfer the nutrient agar plate from the sampler to a constant temperature incubator for incubation. After incubation, count the number of colonies on the nutrient agar plate and, based on the corresponding sampling volume, determine the colony count concentration at different decay times. Plot a microbial natural decay curve based on the logarithmic values ​​of the colony count concentration at different decay times, and calculate the natural decay constant.

[0032] (2) Total attenuation test:

[0033] (2.1) Perform the test according to steps (1.2) and (1.3) in sequence;

[0034] (2.2) After step (2.1) is completed, the air is sampled as the initial concentration point; after the initial concentration point sampling is completed, the prototype is immediately operated to the gear to be tested, and timing is performed at the same time, and then the air is sampled at different time nodes;

[0035] (2.3) After sampling, the nutrient agar plate in the sampler is transferred to a constant temperature incubator for incubation. After incubation, the number of colonies on the nutrient agar plate is counted, and the colony count concentration at different decay times is obtained based on the corresponding sampling volume. The total microbial decay curve is plotted based on the logarithmic values ​​of the colony count concentration at different decay times, and the total decay curve constant is calculated. Finally, the microbial clean air volume (hereinafter referred to as MCADR) of the test sample at the test gear is obtained.

[0036] As a specific embodiment of the present invention, the solid impact sampler is an Anderson six-stage sieve impact microbial sampler. The present invention can also use other types of solid impact samplers to achieve the purpose.

[0037] In step (1.4), the time point of the first sampling is taken as the initial concentration point. After the initial concentration point is sampled, continuous sampling is performed at intervals of 20 minutes. Each sampling time is 10 seconds, and the number of samplings is ≥5, that is, at least 5 concentration data are obtained.

[0038] In step (2.2), the number of colonies obtained at each time point must be within the effective count range of the total colony count of the solid impact sampler used. In other words, the sampling time plan of the total decay test, including the sampling time points (i.e., sampling intervals) and sampling duration, is determined based on the effective count range of the total colony count of the solid impact sampler used. Specifically, the time plan of the total decay test is established by the following steps:

[0039] ① According to the sampler flow rate and the effective range of the culture dish count, set the effective counting range of the total colony count of the sampler to ensure that the deviation of the colony count concentration statistical results is within an acceptable range. Under low-concentration sampling conditions, the impact of sampling fluctuation deviation caused by the low number of air microbial particles on the colony count concentration results can be reduced by setting the effective lower limit of the total colony count of the culture dish. Under high-concentration sampling conditions, the overlap of colonies on the culture dish will significantly reduce the colony count concentration results. By setting the effective upper limit of the allowable total colony count, the impact of colony overlap on the colony count concentration results can be reduced.

[0040] ② Set the lower limit of the sampling time according to the start and stop time allowed for the sampler, and set the upper limit of the sampling time according to the minimum sampling time interval determined by the time required for the sampling operation, so as to obtain the allowable range of the sampling time;

[0041] ③ The upper limit of the initial concentration is calculated from the lower limit of the sampling time and the upper limit of the allowable effective counting range. The lower limit of the initial concentration is set according to the estimated MCADR range of the test. For example, if the initial concentration is too low, the MCADR test range will be reduced. Therefore, the lower limit of the initial concentration can be set according to actual needs.

[0042] ④ Combine the MCADR calculation formula (Formula ②) and the attenuation curve linear formula (Formula ①) to derive the total colony count at each concentration point corresponding to different sampling time nodes (sampling time intervals), different sampling durations, different MCADR values ​​and selected sampling flow rates, and determine whether it is within the effective counting range of the total colony count of the sampler; if so, integrate the sampling time nodes and sampling durations of each concentration point into the corresponding sampling time plan of the MCADR detection range, and then establish the sampling time plan of the total attenuation test corresponding to the MCADR range; if not, reselect the sampling time nodes and sampling duration ranges until the total colony count at each concentration point is within the effective counting range of the total colony count of the sampler.

[0043] Preferably, the MCADR range of the test prototype's gear to be tested is estimated first, and then the sampling time scheme of the total attenuation test is selected accordingly; specifically, the MCADR range is estimated based on the air volume or particulate clean air volume corresponding to the test prototype's gear to be tested multiplied by the estimation coefficient. The estimation coefficient is related to factors such as the purification principle of the purifier product and the air duct structure. The typical range of the estimation coefficient is 0.7 to 1.0.

[0044] In steps (1.5) and (2.3), the natural attenuation constant and the total attenuation constant are calculated by fitting the linear formula of the attenuation curve, i.e., formula ①;

[0045] Ln C t =-kt+Ln C0 ①

[0046] Where:

[0047] C t ——Colony count concentration at time t, in CFU / m 3 ;

[0048] C0 is the colony count concentration at time t = 0, which is the colony count concentration at the initial concentration point, in CFU / m 3 ;

[0049] k——decay constant, in min -1 ;

[0050] t——decay time. The decay time is measured at the midpoint of the sampling time, specifically the midpoint between the start sampling time node and the completion sampling time node of the node, in minutes.

[0051] In step (2.3), the MCADR value is calculated based on the total attenuation constant using the MCADR calculation formula, i.e., the following formula ②:

[0052] MCADR=60V(k t -k n) ②

[0053] Where:

[0054] MCADR - Microbial Clean Air Delivery, in m 3 / h;

[0055] V——test chamber volume, in m 3 ;

[0056] k n ——Natural attenuation constant, in min -1 ;

[0057] k t ——Total attenuation constant, in min -1 .

[0058] Preferably, during the test, after the aerosol atomization device has completed spraying, the aerosol atomization device is turned off and the stirring fan is maintained to work for 5 minutes to make the microbial aerosol in the cabin uniform, and then the stirring fan is turned off. After the circulation fan in the cabin has worked for 5 minutes, sampling is carried out; the circulation fan remains on during the test until the entire natural attenuation test or the total attenuation test is completed.

[0059] Preferably, in step (1.4), the air colony count concentration corresponding to the initial concentration point in the test chamber should be controlled at 1.0×10 5 CFU / m 3 ~3.0×10 5 CFU / m 3 , and the linear fitting R of the natural attenuation curve is drawn 2 It should not be less than 0.9, otherwise the natural attenuation test should be repeated.

[0060] Preferably, in step (2.2), the microbial concentration corresponding to the initial concentration in the test chamber should be controlled at 1.0×10 5 CFU / m 3 ~3.0×10 5 CFU / m 3 , and the linear fitting R of the total microbial decay curve was drawn 2 It should not be less than 0.9, otherwise the total attenuation test should be repeated.

[0061] Preferably, after conducting a total attenuation test, the present invention repeats the total attenuation test again, and the deviation percentage of the total attenuation constant of the two tests is less than ±10%. Otherwise, the test is repeated until the relative deviation of the total attenuation constant of two consecutive total attenuation tests does not exceed ±10% to ensure the validity of the data; finally, the smaller value, larger value or average value of the two total attenuation constants can be selected and substituted into formula ② to calculate the MCADR value of the test sample at the specified gear.

[0062] Preferably, the solid impact sampler is placed in the test chamber so that the sampling port that is in direct contact with the air in the chamber is away from the air inlet and outlet, and is greater than 0.3m away from the wall and 0.7m to 1.2m above the ground of the test chamber.

[0063] Preferably, in step (1.2), the test chamber environment background is disinfected and the air is purified so that the cleanliness level in the chamber is not less than Class 7 (Class 10,000); then the ambient temperature and relative humidity of the test chamber are adjusted to 20°C to 25°C and 50% to 70%, the temperature and humidity control device is turned off, the test process is no longer turned on, and the test chamber is maintained sealed until the end of the natural attenuation test.

[0064] Preferably, in step (1.1), after the test prototype is placed into the test chamber, the prototype is debugged and confirmed to be operating normally, and the prototype is shut down after confirming that it can operate normally.

[0065] The present invention can be applied to detecting different microorganisms, such as bacteria, mold and other air microbial particles.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] The present invention provides a microbial clean air quality test method based on a solid impact sampling method, and establishes a sampling time scheme suitable for different microbial clean air quality ranges. Compared with the microbial clean air quality test method based on a liquid absorption method proposed in the American standard AHAM AC-5, the present invention has the advantages of low test cost, high test efficiency, simple operation, wide detection range, and strong reproducibility. Specifically:

[0068] 1) Low test cost: The solid impact sampler can use the domestically produced Anderson six-stage sieve solid impact sampler. The cost of a single set of equipment including the sampler is only about 20,000 yuan, and no additional matching sampling bottles are required. Compared with the SKC Bio sampler liquid impact sampling device specified by the American Standard, the equipment cost of the present invention is lower. Furthermore, the present invention only requires a single set of solid impact samplers to complete the test, significantly saving equipment costs.

[0069] 2) High test efficiency and simple operation: The Anderson six-stage sieve solid impact sampler generally has a collection efficiency of over 95%. A nutrient agar plate is directly installed in its sampling port. After collection, the sample can be directly transferred to a constant temperature incubator for culture and counting. Compared with the liquid absorption method used in the American standard method, the present invention not only has high collection efficiency but also is easier to operate, thereby improving the overall test efficiency.

[0070] 3) Wide detection range: The solid impact sampling method adopted by the present invention can effectively sample at high concentration points, and can also be completed efficiently within a few minutes when sampling at low concentration points. There is no problem of overlapping sampling intervals and sampling times. Therefore, the microbial clean air volume test method based on the solid impact sampler established by the present invention can have a wider detection range and can more accurately reflect the ability of the air purifier to purify microorganisms; with a 30m 3 Taking the test chamber as an example, the maximum MCADR measured by the Anderson six-stage sieve impact air microbial sampler is 915.5m 3 / h;

[0071] Figure 3 shows an example of the total attenuation curve test results of the microbial clean air volume of an air purifier with high purification capacity. The corresponding total attenuation test time is only 14 minutes, and the corresponding microbial clean air volume measured value is 685m 3 / h, and the relative deviation of the total decay constant re-measurement is less than 3%, which shows that the upper limit of the MCADR detection range of the present invention is higher than that of the existing method;

[0072] 4) Strong reproducibility: Based on the characteristics of the six-stage sieve solid impact sampler, the present invention proposes a method for establishing a sampling time scheme for different microbial clean air quantities, which can make the test results of the microbial clean air quantity more repeatable and ensure the stability of the test results; as shown in the total attenuation curve test data of Figures 1 to 3, the relative deviation of the total attenuation constant of two repeated total attenuation tests is less than ±3%, the repeated test results have little fluctuation, and are sufficiently reproducible.

[0073] The method of the present invention can effectively characterize the purification rate of air purification products for microbial particles in the air, distinguish air purification products with different microbial purification rates, and make up for the defect of low differentiation of sterilization rate and virus removal rate of traditional domestic microbial purification performance indicators. It provides a test method for evaluating the microbial purification rate performance in the field of air purification products, and also provides a reference basis for improving the microbial purification performance indicator method of the national standard system of air purifiers. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] FIG1 is a comparison diagram of two total attenuation curves of the test sample 1 in Example 2;

[0075] FIG2 is a comparison diagram of two total attenuation curves of test sample 2 in Example 2;

[0076] FIG3 is a comparison diagram of two total attenuation curves of the test sample 3 in Example 2;

[0077] FIG4 is a natural attenuation curve diagram in Example 2. DETAILED DESCRIPTION

[0078] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0079] The test chamber used in the following embodiments of the present invention is equipped with an aerosol atomization device, a stirring fan and a circulation fan. The specific test chamber can be selected to meet the requirements of the standard QB / T 5364-2019 "Technical Requirements and Evaluation Methods for Test Chambers for Air Purifier Testing"; the solid impact sampler used is the Anderson six-stage sieve impact air microorganism sampler.

[0080] Example 1 Determine the sampling time scheme for the total attenuation test (30m 3 Take the test chamber as an example)

[0081] 1) Set the effective counting range of the total colony count of the sampler: The number of sieve holes at each level of the Anderson six-stage sieve impact-type air microbial sampler used in this embodiment is 400. The diameters of the sieve holes from the first to the sixth stage are 1.18mm, 0.91mm, 0.71mm, 0.53mm, 0.34mm, and 0.25mm, respectively. The sampling flow rate is 28.3L / min, and the culture dish diameter specification is 90mm. Under the above conditions, if the total colony count of the six-stage sampler is too high, it is easy to cause colony overlap and reduce the colony count result; if the total colony count of the six-stage sampler is too low, such as below 10CFU, the sampling process fluctuates by one or more colony numbers, which will cause the colony count concentration to deviate from the actual concentration by ≥10%. Therefore, preferably, the effective counting range of the total colony count of the six-stage sampler of this embodiment is set to 10CFU~2400CFU;

[0082] 2) Set the sampling time range: The lower limit of the sampling time range should be set based on the premise that the start and stop time of the sampling pump interferes with the results as little as possible. The lower limit of the time is usually set to 5s to 10s. In this embodiment, 10s is taken as the lower limit of the sampling time. In order to reduce human operation errors and reduce the difficulty of operation, and the time required for sampling operations such as pre-sampling preparation of the sampling equipment, sampling settings, and data recording should be as sufficient as possible, the minimum interval between the start sampling time nodes of each concentration point set in this embodiment is 3 minutes. At the same time, to avoid cross-sampling operations of adjacent concentration points, the upper limit of the sampling time range should not exceed the minimum interval between the start sampling time nodes of each concentration point of the total attenuation. Taking the above situation into account, the minimum interval between the start sampling time nodes of each concentration point of the total attenuation in this embodiment is set to 120s. Therefore, preferably, the sampling time range set in this embodiment is 10s to 120s.

[0083] 3) Setting the initial concentration range: The upper limit of the initial concentration range is determined by the ratio of the upper limit of the effective count range of the total colony count of the six-stage sampler, 2400 CFU, and the sampling volume corresponding to the shortest sampling time, 4.72 L. The upper limit obtained by theoretical calculation is 5.1×10 5 CFU / m 3 Considering the interference factors such as human operation and equipment hardware error, this embodiment conservatively sets the upper limit of the initial concentration range to 3.0×10 5 CFU / m 3 Considering that a lower initial concentration would reduce the effective detection range of MCADR and the operability of the initial concentration range control, the lower limit of the initial concentration was set to 1.0×10 5 CFU / m 3 Therefore, preferably, the initial concentration range set in this embodiment is 1.0×10 5 CFU / m 3 ~3.0×10 5 CFU / m 3 .

[0084] 4) Determine the MCADR detection range: The test chamber volume selected in this embodiment is 30m 3 The effective concentration points of the linear fitting of the decay curve are set to no less than 5, and the natural decay constant is usually 0.005min -1 ~0.02min -1 About, in this embodiment, the typical value is 0.01min -1 As an example, from formula ①, we can know that under the condition of certain initial concentration and final concentration, the total decay time is inversely proportional to the total decay constant. The shorter the total decay time, the higher the total decay constant. Substituting it into formula ②, we can know that the corresponding MCADR is higher. Therefore, when the initial concentration takes the minimum value of 1.0×10 5 CFU / m3 The final concentration is the minimum colony count allowed, 1.18×10 2 CFU / m 3 (The corresponding sampling time is 120s, and the total colony count of the six-stage sampler is taken as the minimum value 10CFU), the end concentration point is taken as the corresponding shortest decay time 13min (the starting sampling time of each concentration point is set to the minimum interval of 3min, and the number of concentration points is 5, then the starting sampling time of the end concentration point is 12min, and the corresponding decay time is 13min). Substituting into formula ①, the maximum detection value of the total decay constant is 0.5186min -1 Then substitute into formula ② to get the maximum detection value of MCADR, which is 915.5m 3 / h. Taking into account the interference of human operation, equipment hardware errors, etc., the upper limit of the MCADR detection range is set to 800m. 3 / h; The total attenuation constant corresponding to the lower limit of the MCADR detection range should be at least twice or more of the natural attenuation constant to reduce the interference of the natural constant test deviation on the MCADR test results. In this embodiment, the lower limit of the MCADR detection range is 30m 3 / h, the corresponding total decay constant is 0.0267min -1 Therefore, preferably, the MCADR detection range determined in this embodiment is 30m 3 / h~800m 3 / h.

[0085] 5) Establish a total attenuation test with different MCADR ranges - adopt a time plan: set the sampling time node after the initial concentration point and the sampling time of each concentration point, and take the test chamber volume as 30m 3 The natural attenuation constant takes a typical value of 0.01min -1 , set the target MCADR value, and substitute the initial concentration upper and lower limits into formulas ① and ②, respectively, to obtain the colony count concentration value at each concentration point. Then, combined with the sampling duration and a sampling flow rate of 28.3 L / min, the corresponding total colony count is calculated. Finally, a list is used to check whether each concentration point with the target MCADR value meets the set sampler colony count effective range of 10 CFU to 2400 CFU. If the total colony count at the concentration point corresponding to the MCADR value exceeds the set effective count range, modify the sampling time node and sampling duration range. Multiple sampling time plans can be set according to the MCADR size range.

[0086] In this embodiment, 30m 3 / h~120m 3 / h、120m 3 / h~450m 3 / h and 450m 3 / h~800m3 / h, three feasible total attenuation tests were established using three time schemes, with the upper limit of initial concentration being 3.0×10 5 CFU / m 3 The colony count tables at each concentration point are shown in Table 1, Table 2, and Table 3, respectively. The lower limit of the initial concentration is 1.0×10 5 CFU / m 3 The colony count tables for each concentration point are shown in Tables 4, 5, and 6. As can be seen from the results in Tables 1 to 6, the sampling time nodes and sampling durations corresponding to MCADR selected in Tables 1 to 6 do not exceed the effective counting range of the sampler. Therefore, these sampling time nodes and durations are the effective sampling time schemes for the total attenuation test that measures MCADR.

[0087] Table 1 MCADR 30m 3 / h~120m 3 / hList of total colony counts at each concentration point (unit: CFU)

[0088] Table 2 MCADR 120m 3 / h~450m 3 / hList of total colony counts at each concentration point (unit: CFU)

[0089] Table 3 MCADR 450m 3 / h~800m 3 / hList of total colony counts at each concentration point (unit: CFU)

[0090] Table 4 MCADR 30m 3 / h~120m 3 / hList of total colony counts at each concentration point (unit: CFU)

[0091] Table 5 MCADR 120m 3 / h~450m 3 / hList of total colony counts at each concentration point (unit: CFU)

[0092] Table 6 MCADR 450m 3 / h~800m 3 / hList of total colony counts at each concentration point (unit: CFU)

[0093] As an example, the present invention can obtain the following total attenuation test-sampling time schemes in Tables 7, 8 and 9 through the above steps; those skilled in the art can also calculate other different total attenuation test-sampling time schemes based on the steps of the present invention, or appropriately increase or decrease the sampling time nodes or extend or shorten the sampling time based on the present invention. 3 / h and above detection range, by increasing the volume of the test chamber, similarly according to the above steps to calculate the applicable MCADR at 800m 3 Total attenuation test for detection range above / h - sampling time plan.

[0094] Table 7 30m 3 / h≤MCADR<120m 3 / h Total decay test-sampling time plan

[0095] Table 8 120m 3 / h≤MCADR<450m 3 / h Total decay test-sampling time plan

[0096] Table 9 450m 3 / h≤MCADR<800m 3 / h Total decay test-sampling time plan

[0097] Example 2 MCADR test of different air purifiers

[0098] This embodiment uses 30m 3 In the test chamber, the microorganism used in the test is Staphylococcus albus CGMCC 1.3374.

[0099] (1) Natural attenuation test:

[0100] (1.1) Place the test prototype in the center of the test chamber, debug and confirm whether the prototype is running normally, and shut down the prototype after confirming that it can operate normally;

[0101] (1.2) Place the solid impact sampler containing the nutrient agar plate in the test chamber so that the sampling point is away from the air inlet and outlet, 0.5 m ± 0.2 m from the wall, and 0.9 m ± 0.2 m above the test chamber floor.

[0102] Transfer the prepared microbial suspension to the aerosol atomization device, and then disinfect and purify the interior of the test chamber to ensure that the cleanliness level inside the chamber is not less than Class 7 (Class 10,000); adjust the internal ambient temperature of the test chamber to a range of 20°C to 25°C, and the relative humidity in the chamber to a range of 50% to 70%, then turn off the temperature and humidity control device, and do not open it during the test process, and keep the test chamber sealed until the end of the natural attenuation test;

[0103] (1.3) Turn on the stirring fan, circulation fan, and aerosol atomizer to spray the test chamber with bacteria; after the aerosol atomizer has finished spraying, turn off the aerosol atomizer, continue to run the stirring fan for 5 minutes, and then turn off the stirring fan;

[0104] (1.4) Stirring fan off: After the circulating fan has been running for 5 minutes, the air is sampled at different time points using a sampler. The circulating fan remains on during the test until the entire natural decay test is completed. This embodiment specifically adopts the natural decay test-sampling time scheme shown in Table 10 below:

[0105] Table 10 Natural decay test - sampling time plan

[0106] (1.5) After sampling, transfer the nutrient agar plate in the sampler to a constant temperature incubator for incubation. After incubation, count the colonies on the nutrient agar plate sampled at each time point, and calculate the number of colonies at each concentration point based on the sampling volume. The unit of colony count is CFU / m 3 ;

[0107] The microbial concentration corresponding to the initial concentration point in the test chamber is controlled at 1.0×10 5 CFU / m 3 ~3.0×10 5 CFU / m 3 , and the natural decay curve of microorganisms drawn according to the number of colonies, linear fitting R 2 It should not be less than 0.9; if so, the natural attenuation test is passed, otherwise the natural attenuation test is repeated;

[0108] After the natural attenuation test is passed, the natural attenuation constant is calculated according to formula ①, and then the total attenuation test is carried out.

[0109] (2) Total attenuation test:

[0110] (2.1) Repeat the above natural attenuation test steps (1.2) to (1.3);

[0111] (2.2) After the stirring fan is turned off and the circulating fan has been running for 5 minutes, the air is sampled using the sampler as the initial concentration point (t = 0 min); after sampling the initial concentration point, the prototype is immediately operated to the test gear and the timing is started synchronously. The air is sampled at different time points according to the schemes in Tables 7 to 9; the circulating fan remains on during the test until the entire total attenuation test is completed;

[0112] (2.3) After sampling, transfer the nutrient agar plate in the sampler to a constant temperature incubator for incubation. After incubation, count the colonies on the nutrient agar plate sampled at each time point, and calculate the number of colonies at each concentration point based on the sampling volume. The unit of colony count is CFU / m 3 ;

[0113] The microbial concentration corresponding to the initial concentration point in the test chamber is controlled at 1.0×10 5 CFU / m 3 ~3.0×10 5 CFU / m 3 , and the total microbial decay curve drawn according to the colony count, linear fitting R 2 Should not be less than 0.9; if so, the total attenuation test is passed, otherwise the total attenuation test is repeated;

[0114] (2.4) Repeat the above steps (2.1) to (2.3) and conduct another total attenuation test. Compare the total attenuation constants obtained from the two total attenuation tests. If the relative deviation percentage of the two total attenuation constants is less than ±10%, the test passes. Take the arithmetic mean of the total attenuation constant and substitute it into formula ② to calculate the MCADR value of the prototype in the test gear.

[0115] First, the MCADR range is estimated by multiplying the air volume corresponding to the gear to be tested of the test prototype by the estimation coefficient. The estimation coefficient is related to factors such as the purification principle of the purifier product and the air duct structure. In this embodiment, an estimation coefficient of 0.7 is taken as an example, and then the corresponding total attenuation test-sampling time scheme is selected. Then, the above steps are tested on the test prototypes numbered 1, 2, and 3. The results are shown in Table 11, the total attenuation curve test results are shown in Figures 1 to 3, and the natural attenuation curve results are shown in Figure 4.

[0116] Table 11 Example 2 Test Results

[0117] The results in Table 11 show that the test method of the present invention can detect a wide MCADR range, and the deviation percentage of the total attenuation constant between two tests of different test samples is less than ±3%, indicating that the repeated test results have little fluctuation and are sufficiently reproducible.

Claims

1. A microbial clean air volume test method based on a solid impact sampler, characterized in that: The following steps are involved: (1) Natural attenuation test: (1.1) Place the test sample in the center of a test chamber equipped with an aerosol atomizer, a stirring fan, and a circulating fan; (1.2) Place the solid impact sampler containing the nutrient agar plate in the test chamber, transfer the prepared microbial suspension to the aerosol atomizer, clean the test chamber environment, and then maintain the test chamber sealed until the end of the natural attenuation test; (1.3) Turn on the stirring fan, circulation fan, and aerosol atomizer to spray the test chamber with bacteria; after the aerosol atomizer has finished spraying, turn off the aerosol atomizer and continue to operate the stirring fan until the microbial aerosol in the chamber is uniform, then turn off the stirring fan; (1.4) Use a sampler to sample the air at different time points. After sampling, disinfect and clean the environment in the test chamber; (1.5) After sampling, transfer the nutrient agar plate in the sampler to a constant temperature incubator for incubation. After incubation, count the number of colonies on the nutrient agar plate and, based on the corresponding sampling volume, obtain the colony count concentration at different decay times. Plot the microbial natural decay curve based on the logarithmic values ​​of the colony count concentration at different decay times, and calculate the natural decay constant. (2) Total attenuation test: (2.1) Perform the test according to steps (1.2) and (1.3) in sequence; (2.2) After step (2.1) is completed, the air is sampled as the initial concentration point; after the initial concentration point sampling is completed, the prototype is immediately operated to the gear to be tested, and timing is performed at the same time, and then the air is sampled at different time nodes; (2.3) After sampling, the nutrient agar plate in the sampler is transferred to a constant temperature incubator for incubation. After incubation, the number of colonies on the nutrient agar plate is counted, and the colony count concentration at different decay times is obtained based on the corresponding sampling volume. The total microbial decay curve is plotted based on the logarithmic values ​​of the colony count concentration at different decay times, and the total decay curve constant is calculated. Finally, the microbial clean air volume of the test sample at the test position is obtained.

2. The microbial clean air volume test method based on a solid impact sampler according to claim 1 is characterized in that: In step (1.4), the time point of the first sampling is taken as the initial concentration point. After sampling the initial concentration point, continuous sampling is performed at intervals of 20 minutes. Each sampling time is 10 seconds, and the number of sampling times is ≥5.

3. The microbial clean air volume test method based on a solid impact sampler according to claim 2, characterized in that: In step (2.2), the sampling time node and sampling duration of the total attenuation test are determined based on the effective counting range of the total colony count of the solid impact sampler used.

4. The microbial clean air volume test method based on a solid impact sampler according to claim 3 is characterized in that: The time protocol for the total decay experiment was established by the following steps: ① According to the sampler flow rate and the effective range of culture dish counting, set the effective counting range of the total colony count of the sampler to ensure that the deviation of the statistical results of the colony count concentration is within an acceptable range; ② Set the lower limit of the sampling time according to the start and stop time allowed for the sampler, and set the upper limit of the sampling time according to the minimum sampling time interval determined by the time required for the sampling operation, so as to obtain the allowable range of the sampling time; ③ The upper limit of the initial concentration is calculated by the lower limit of the sampling time and the upper limit of the allowable effective counting range, and the lower limit of the initial concentration is set according to the estimated MCADR range of the test; ④ Combine the MCADR calculation formula and the linear formula of the attenuation curve to derive the total colony count at each concentration point corresponding to different sampling time nodes, different sampling durations, different MCADR values ​​and selected sampling flow rates, and determine whether it is within the effective counting range of the total colony count of the sampler; if so, integrate the sampling time nodes and sampling durations of each concentration point into the corresponding sampling time plan of the MCADR detection range, and then establish the sampling time plan of the total attenuation test corresponding to the MCADR range; if not, reselect the sampling time nodes and sampling duration range until the total colony count at each concentration point is within the effective counting range of the total colony count of the sampler.

5. The microbial clean air volume test method based on a solid impact sampler according to claim 4 is characterized in that: In steps (1.5) and (2.3), the natural attenuation constant and the total attenuation constant are calculated by fitting the linear formula of the attenuation curve, i.e., formula ①; Ln C t =-kt+Ln C0 ① Where: C t ——Colony count concentration at time t, in CFU / m 3 ; C0 is the colony count concentration at time t = 0, which is the colony count concentration at the initial concentration point, in CFU / m 3 ; k——decay constant, in min -1 ; t——decay time, the decay time is measured at the midpoint of the sampling time, the unit is min.

6. The microbial clean air volume test method based on a solid impact sampler according to claim 5, characterized in that: In step (2.3), the MCADR value is calculated based on the total attenuation constant using the MCADR calculation formula, that is, the following formula ②: MCADR = 60V (k t -k n )② Where: MCADR - Microbial Clean Air Delivery, in m 3 / h; V——test chamber volume, in m 3 ; k n ——Natural attenuation constant, in min -1 ; k t ——Total attenuation constant, in min -1 .

7. The microbial clean air volume test method based on a solid impact sampler according to claim 6 is characterized in that: During the test, after the aerosol atomization device has finished spraying, turn off the aerosol atomization device and continue to maintain the stirring fan working for 5 minutes to make the microbial aerosol in the cabin uniform. Then turn off the stirring fan and wait for the circulation fan in the cabin to work for 5 minutes before sampling. The circulation fan remains on during the test until the entire natural attenuation test or total attenuation test is completed.

8. The microbial clean air volume test method based on a solid impact sampler according to claim 7, characterized in that: In steps (1.4) and (2.2), the air colony count concentration corresponding to the initial concentration point in the test chamber should be controlled at 1.0×10 5 CFU / m3~3.0×10 5 CFU / m 3 , and the linear fitting R of the natural attenuation curve is drawn 2 It should not be less than 0.9, otherwise the natural attenuation test or total attenuation test should be carried out again.

9. The microbial clean air volume test method based on a solid impact sampler according to claim 8, characterized in that: After conducting a total attenuation test, repeat the total attenuation test again. The deviation percentage of the total attenuation constant of the two tests is less than ±10%. Otherwise, repeat the test until the relative deviation of the total attenuation constant of two consecutive total attenuation tests does not exceed ±10% to ensure the validity of the data.

10. The microbial clean air volume test method based on a solid impact sampler according to claim 9, characterized in that: The solid impact sampler is placed in the test chamber so that the sampling port that comes into direct contact with the air in the chamber is away from the air inlet and outlet, and is greater than 0.3m from the wall and 0.7m to 1.2m above the floor of the test chamber. In step (1.2), the test chamber environment background is disinfected and the air is purified to make the cleanliness level in the chamber not less than Class 7; then the ambient temperature and relative humidity of the test chamber are adjusted to 20℃~25℃ and 50%~70%, the temperature and humidity control device is turned off, and the test process is not opened again, and the test chamber is kept sealed until it is automatically cooled. The decay test is then completed.

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