Myojo T, Willeke K, Chen C C
Department of Environmental Health, University of Cincinnati, OH 45267-0056.
Am Ind Hyg Assoc J. 1994 Sep;55(9):797-805. doi: 10.1080/15428119491018501.
Conventional fit-testing methods use HEPA filter cartridges to distinguish face-seal leakage from filter penetration and thereby test a respirator's ability to face-seal. These methods cannot be applied to low-efficiency filtering facepieces that also protect the wearer through aerosol particle retention by the filter material. Therefore, the ability of a filtering facepiece to face-seal is of interest to the developer for improving the design and to the user for finding the conditions for optimal face-seal. A unique difference has been found between the combined aerosol penetration through filter medium and leak site at low versus high flow rate. This feature has been used to differentiate face-seal leakage from filter penetration. A "fit index" has been introduced as the most sensitive indicator of fit. When normalized by reference to the aerosol penetration through the filter material, this index displays a unified behavior irrespective of the filter material used. The fit index is determined by relating the measured total aerosol concentration at a high flow rate to that at a low flow rate. Tests during normal breathing of a human subject compare well with the data obtained during breath-holding experiments. Available instruments may be used for this test, but need to be modified for tests on humans.
传统的适合性测试方法使用高效空气过滤器滤芯来区分面罩密封泄漏和过滤器穿透，从而测试呼吸器的面罩密封能力。这些方法不能应用于低效率过滤面罩，这类面罩也是通过过滤材料截留气溶胶颗粒来保护佩戴者的。因此，过滤面罩的面罩密封能力对于开发者改进设计以及使用者寻找最佳面罩密封条件来说都是值得关注的。已发现通过过滤介质和泄漏部位的组合气溶胶穿透在低流量与高流量时存在独特差异。这一特性已被用于区分面罩密封泄漏和过滤器穿透。已引入“适合性指数”作为适合性最敏感的指标。当通过参考通过过滤材料的气溶胶穿透进行归一化时，该指数显示出统一的行为，而与所使用的过滤材料无关。适合性指数通过将高流量下测得的总气溶胶浓度与低流量下测得的总气溶胶浓度相关联来确定。人体正常呼吸期间的测试与屏气实验期间获得的数据比较吻合。现有仪器可用于此测试，但需要针对人体测试进行修改。
