关键词: 气溶胶浓度, 泄漏率, 校准, 粒径分布, 空间均匀性

Abstract: Masks are an important defense line to prevent respiratory infectious diseases. The mask respirator particle leakage rate tester is used to measure the ratio of the particle matter concentration that leaks into the mask from all other parts except the filter element of the mask to ambient particle matter concentration outside the mask during inhalation. At present, there are many domestic manufacturers of mask respirator particle leakage rate testers, but there are some common problems such as inconsistent technical parameters and obvious differences performance of different instruments. However, the existing standards do not make requirements for the performance detection. In other words, under the current circumstances, the accuracy of mask particle leakage rate tests cannot be guaranteed. Thus, it is of great significance to ensure the measurement accuracy of particle leakage rate testers for controlling the protective performance of masks. 
The mask respirator particle leakage rate tester generally consists of an aerosol generator, aerosol concentration monitoring devices and a test chamber. The test chamber is airtight in which human subjects can complete the required motions. The aerosol generator generates aerosol particles with the specific concentration and size distribution. The generated aerosol particles are imported into the test chamber through the top interface. After active mixing, it is discharged from the exhaust port at the bottom of the test chamber. Human subjects perform multiple required actions. During each action, the particle matter concentration in the test chamber and the mask was monitored simultaneously. Thus, the leakage rate of masks can be calculated. 
As there is no standard test equipment or standard filtration membrane with metrological traceability for the leakage rate at present, the conditions for comparative evaluation are not available. According to the working principle of the tester, the performance of each key component of the tester needs to be measured and verified by the partial method to ensure the accuracy and consistency of the measurement, including aerosol generation performance, aerosol mixing performance and aerosol collection and detection performance.
In this paper, according to the technical route of aerosol generation-aerosol mixing-aerosol collection and detection, the metrological calibration method of the mask particulate leakage rate tester is studied. Specifically, it involves six items, namely flow rate of aerosol generation, test concentration of aerosol, particle size distribution and median diameter of tested aerosol, aerosol particle space uniformity in the test chamber, flow rate of aerosol collection, and indication error of aerosol mass concentration. These calibration items ensure the accuracy of aerosol generation, mixing and detection, respectively. Thus, the accuracy of mask particle leakage rate tests is guaranteed. 
In this study, the selection of calibration equipment and calibration methods are described in detail. The feasibility and effectiveness of the proposed calibration methods are verified by the analysis of the calibration results of the particulate matter leakage tester of different application institutions.

Key words: aerosol concentration, leakage rate, calibration, particle size distribution, spatial uniformity