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Brief analysis of filtration efficiency test of anti-particulate mask

by:GESTER Instruments     2021-03-26
Air particulate matter is the main component of air pollution and becomes productive dust in the production environment, which is also called haze in the living environment. Productive dust is the most serious occupational hazard factor in my country. Occupational disease pneumoconiosis accounts for more than 80% of new occupational diseases in my country. In addition to dust control through industrial reforms, wearing anti-particulate masks is the last barrier to protect workers’ respiratory health . In recent years, my country’s environmental air pollution has become more and more serious. The haze formed by particulate matter from industry and daily life is serious for residents’ health. Anti-particulate masks have gradually become an important item for respiratory protection for the majority of residents, especially in the season when infectious diseases of the respiratory system are prevalent. , Anti-particulate masks also have a certain protective effect on respiratory infectious diseases. The US Department of Labor approved the use of effective anti-particulate masks in hospitals in 1995 to prevent respiratory infectious diseases such as tuberculosis. With the widespread use of anti-particulate masks, their protective effects have also received increasing attention. The filtration efficiency of the mask filter material is a key factor affecting the protective performance of protective masks. At present, the detection equipment for the filtration performance of protective masks in my country is complicated and only owned by professional institutions, and it is difficult for ordinary manufacturers and ordinary users to test. Therefore, in order to meet the filter efficiency test of anti-particulate masks and effectively carry out respiratory protection, according to the filterability test principle of masks, that is, the difference between the concentration of particles of different particle sizes in the internal and external environments of the mask, consider the shape and type of masks currently used in the market to carry out protection The design of a simple device for filterability testing of particulate masks is designed to meet the needs of different types of mask design, production and users. 1. Materials and methods 1. 1 Principle of the filter efficiency test device for anti-particulate masks The filtration efficiency of the anti-particulate mask filter material refers to the percentage of particulate matter removed. The principle of measuring filtration efficiency is to measure the number or concentration of particles inside and outside the mask or on both sides of the mask when a certain flow of air passes through the filter material of the mask. The ratio of the number/concentration of particles inside the mask divided by the number/concentration of particles outside the mask is the filtration efficiency. Based on the measurement principle of filtration efficiency. The measuring device mainly includes a fixing device of the mask filter material, a device for controlling the air flow through the mask, and a device for measuring the concentration of particles inside and outside the mask. 1. 2 The mask filter material fixing device uses smooth surface steel as the design material of the mask fixing device. Its shape and opening shape match the commonly used anti-particle masks in the market. In order to prevent the edge leakage of the mask filter material from affecting the filtering effect, a three-level Connection: Steel base, rubber pad and steel mask holder (Figure 1), tighten with screws to ensure sealing. A silicone tube is connected to the bottom of the base for air extraction. Before the test, place the mask filter material on the fixed base of the mask with a hole in the middle. Before use, heat the hot melt glue to coat and fix the lower side of the mask edge. After the hot melt glue is cold, it will form a sealant on the edge of the mask to ensure the edge seal. 1. 3 Air flow control device and interface connection The air flow control device is composed of an air suction pump (exhaust flow range: 10L/min ~ 100L/min) and a flow meter in series. The flow meter is connected to the base of the filter fixing device through a silicone tube connection. The connection between the silicone tube and the pipe at the base of the mask fixing device is a 180-degree straight extension connection, which avoids the problems of poor sealing, easy loosening of the connection, and unstable airflow caused by the distortion of the silicone tube. The silicone tube is used as the connection material of each component (Figure 2). The silicone tube has excellent elasticity and resilience, and has good sealing properties to ensure that the interfaces are tightly connected; in the connection method, connect the silicone tube with the appropriate diameter to the interface of each component The telescopic connection uses the good shrinkage of the silicone tube to make the silicone tube and the interface tightly connected. 1. 4 The particulate matter concentration measurement device is calculated based on fluid mechanics. The filter material mainly filters particulate matter through retention and electrostatic action. The particle size of the most filtered particulate matter is an aerodynamic diameter of 0.3μm. The design uses a special instrument for respirator suitability testing PortaCount ( TSI8030, USA) is used as a particle concentration measuring device to measure the concentration of particles inside and outside the mask. The instrument uses the coagulometer method to measure 0.3 ± 0.015 μm on both sides of the mask. The number of air particles in the range is converted to the particle count concentration, and the ratio of the particle concentration inside and outside the mask is the filtration efficiency. The particulate matter concentration measuring instrument has two connecting tubes, one is placed in the ambient air to measure the concentration of particulate matter outside the mask; the other is connected to the silicone tube under the base of the mask fixing device to measure the concentration of particulate matter in the mask. PortaCount's own FitPlusTM software can dynamically display the concentration of particles in the internal and external environment of the mask. The software counts for 1 minute, removes the first 20s and the last 20s, records the concentration of particles in the middle 20s, and automatically calculates the filtration efficiency. Filtration efficiency u003d within C /C outside, where C inside and C outside represent the particle concentration measured in the environment inside the mask and outside the mask, respectively. 1. 5 Actual test analysis This device was used to test the filtration efficiency of the filter media of 4 brands of self-priming filter-type particulate protective masks and 1 medical mask in common use in the city. Each mask is tested with 10 samples, a total of 60 masks. Before the test, the inhalation resistance of various masks was tested. Under a flow of 85L/min, the resistance was less than 100Pa, which met the requirement that the inhalation resistance of the relevant respiratory protector was less than 350Pa [8].
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