key: cord-0812825-6uyrwfnp authors: Yi, Yayi; Shi, Dianlong title: The influence factors of mean particle size and positive quality control of bacterial filtration efficiency system date: 2021-12-20 journal: bioRxiv DOI: 10.1101/2021.12.20.473569 sha: fc00732827b840726c1fcae3f276b59657ae1df7 doc_id: 812825 cord_uid: 6uyrwfnp Background The Coronavirus Disease 2019 (COVID-19) has swept the whole world with high mortality. Since aerosol transmission is the main route of transmission, wearing a mask serves as a crucial preventive measure. An important parameter to evaluate the performance of a mask is the bacteria filtration efficiency (BFE). Aerosol mean particle size (MPS) and positive quality control value are two key indexes of BFE system. Aim To study the major influence factors of the mean particle size of bacterial aerosols and positive quality control value of BFE system. Method and Results In this study, we investigated the influence of Anderson sampler, spray flow, medium thickness, and peristaltic pump flow on the MPS of bacterial aerosols and positive quality control value of BFE system, respectively. The results show that the machining accuracy of Anderson sampler has great influence on aerosol MPS and positive quality control value. With the increase of aerosol spray flow rate, the positive quality control value will increase gradually, but the effect on aerosol MPS is not a simple linear relationship. As the agar medium thickness increased, the positive quality control value and aerosol MPS increased gradually. With the increase of peristaltic pump flow, the positive quality control value increased gradually, while the aerosol MPS was basically in a downward trend. When the peristatic pump flow rate was 0.1mL/min, the spray flow rate was 7.2L/min, the agar plate thickness was 27mL, and the Anderson sampler of Beijing Mingjie was used for the experiment, the aerosol MPS and positive quality control value were both within the acceptable range and were the optimal parameters. Conclusions This study provides guidance for the manufacturers of the BFE system and improves the protective performance of masks, which is important for the human health, especially during the occurrence of viral pandemics such as “COVID-19”. wearing a mask serves as a crucial preventive measure. An important parameter to 21 evaluate the performance of a mask is the bacteria filtration efficiency (BFE). Aerosol Organization (WHO) [1] . The occurrence of viral pandemics with extensive 52 transmission and the associated health impact is a big concern around the globe, which 53 raises the importance of respiratory protection against the viral transmission. Aerosol 54 transmission is the main routes of COVID-19 transmission. Coughing, sneezing, and 55 talking can transmits microbial aerosols through the air, potentially carrying infectious 56 diseases [2] . The associated risk can be exacerbated when pathogenic microbials 57 including bacteria and virus are present in the air [3, 4] . The role of respiratory protection 58 becomes particularly important in the occurrence of viral pandemics such as "COVID-59 19", SARS, and H1N1 influenza [3] [4] [5] [6] . Mask has been used for more than 100 years to prevent the spread of respiratory 61 infectious diseases and surgical infections [7] [8] [9] [10] [11] . The role of mask is to prevent harmful 62 aerosols from the human body instead of being inhaled into the lungs, including dust, 63 smoke, bacteria, and virus. Using masks to prevent viral transmission has been 64 recommend by many international guidelines [12] [13] [14] . MacIntyre et al. [15] reported that respectively [19, 20] . An important parameter to evaluate the performance of a mask is the bacteria 78 filtration efficiency (BFE) [21] . BFE refers to the percentage of the respirator material A strain of staphylococcus aureus was vaccinated into 100mL TSB, then exposed 103 to an incubator under 100r/min at 37℃. After 24h, the bacterial suspension was 104 obtained. 1mL bacterial suspension was added to the test tube with 9mL peptone 105 solution (1.5%), then diluted step by step to 10 -7 , and 0.1mL diluted bacterial 106 suspension from 10 -5 to 10 -7 test tubes was added to TSA plate for culture. Two parallel 107 plates were made for each gradient, then put them into the incubator at 37℃ for 24h. Statistic the bacterial count of each TSA plate, then take the colony number of (0- Requirements and test methods [24] specifies, positive quality control value should be 126 within the scope of the (1700-3000) CFU. the MPS should be within the scope of (3.0±0.3) um. (1) Table 147 2. Table 3 . The layer number The positive pole count (r) Viable "particle" plate count (C) The positive pole count (r) Viable "particle" plate count (C) MPS and positive quality control value, including 6.0, 6.5, 7.0, 7.2, 7.5, and 8.0 L/min. parameters. This study provides guidance for manufacturers of BFE detector and 287 theoretical basis for testing institutions to test the BFE of masks, which is important for 288 the human health, especially during the occurrence of viral pandemics such as WHO. 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