Abstract：
In Europe, respiratory protective devices must be certified before they can be marketed. Among the parameters of interest, inward leakage (IL) characterizes the tightness between the face seal and the face, to verify that the device is well-designed. European standard EN 13274-1 (2001) and International Organization for Standardization (ISO) standard ISO 16900-1 (2019) specify that IL should be measured using sodium chloride (NaCl) aerosol or sulfur hexafluoride (SF6) gas. For reusable masks made of nonporous materials, both test agents are considered equally acceptable. However, the few studies that have compared IL values measured with various aerosols and gases have come to divergent conclusions. This work then aimed to measure IL with the test agents recommended by the standards to determine whether they are really equivalent. Since krypton (Kr) is an interesting candidate for replacing SF6 in standard tests, IL was assessed with SF6 and Kr simultaneously, and with NaCl aerosol using various calculation methods. Tests were carried out on 5 models of full-face masks donned on a headform connected to a breathing machine simulating 3 sinusoidal breathing rates of various intensities. The respirator fit on the headform was evaluated using a controlled negative pressure method to determine a manikin fit factor. Four scenarios were then tested to represent very poor, bad, good, and excellent fit. Gas concentration was measured using a mass spectrometer, and IL was calculated for SF6 and Kr. A combination of 3 devices allowed the determination of the number-based concentration of particles with diameters between 20 nm and 2 µm, and IL was calculated for each of the 33 channels, as well as using a cumulative number concentration. In addition, to comply with standards, a conversion was carried out to calculate IL using a cumulative mass concentration. The results of this work evidenced that the IL values measured with NaCl were systematically lower than those determined with gases. IL was also shown to vary with particle size, with a maximum value exceeding that calculated with cumulative concentrations (in number or mass). As part of the revision of the standards, protocols for measuring inward leakage should be redefined. On the one hand, acceptability thresholds should be re-evaluated according to the nature of the test agent (gas or aerosol), as it is clear that the 2 options do not give the same results for a given configuration. On the other hand, the aerosol leakage measurement protocol needs to be reworked to enable the measurement of a well-defined, robust, and reproducible inward leakage value.
摘要：
在欧洲,呼吸防护设备在上市前必须经过认证。在感兴趣的参数中，向内泄漏(IL)表征面密封件和端面之间的紧密度,以验证设备是否设计良好。欧洲标准EN13274-1（2001）和国际标准化组织（ISO）标准ISO16900-1（2019）规定，应使用氯化钠（NaCl）气溶胶或六氟化硫（SF6）气体测量IL。对于由无孔材料制成的可重复使用的口罩，两种测试剂被认为同样可以接受。然而,少数比较了各种气溶胶和气体测得的IL值的研究得出了不同的结论。然后，这项工作旨在用标准推荐的测试剂测量IL，以确定它们是否真的等效。由于氪（Kr）是标准测试中替代SF6的有趣候选者，同时用SF6和Kr评估IL，并与NaCl气溶胶使用各种计算方法。对戴在连接到呼吸机的人头模型上的5种全脸面罩进行了测试，模拟了3种各种强度的正弦呼吸频率。使用受控负压方法评估呼吸器在人头模型上的贴合性以确定人体模型贴合性因子。然后测试了四种情况，以代表非常差，坏,不错,和优秀的适合。使用质谱仪测量气体浓度，计算SF6和Kr的IL。3种设备的组合可以确定直径在20nm至2µm之间的颗粒的基于数量的浓度，并计算了33个通道中的每个通道的IL，以及使用累积数浓度。此外,为了符合标准，使用累积质量浓度进行转化以计算IL。这项工作的结果表明，用NaCl测得的IL值系统地低于用气体测得的IL值。IL也显示随颗粒大小而变化，最大值超过累积浓度（数量或质量）计算的最大值。作为标准修订的一部分，应重新定义测量向内泄漏的协议。一方面,应根据测试剂（气体或气溶胶）的性质重新评估可接受性阈值，因为很明显，对于给定的配置，2个选项不会给出相同的结果。另一方面,气溶胶泄漏测量协议需要重新设计，以实现定义明确的测量，健壮,和可重复的向内泄漏值。
