Huang C, Willeke K, Qian Y, Grinshpun S, Ulevicius V
Department of Environmental Health, University of Cincinnati, OH 45267-0056, USA.
Am Ind Hyg Assoc J. 1998 Jul;59(7):461-5. doi: 10.1080/15428119891010208.
Fibrous filter media are widely used in respirators to remove airborne particulate matter from the inhaled airflow of workers. The N95 half-mask particulate respirator appears to be the most frequently used respirator under the new NIOSH regulation, 42 CFR 84. Considerable spatial variability in light penetration through the fibrous filter medium of an N95 respirator can be seen by visual observation when it is held to the light. This variability is due to the way in which the fibers are manufactured and laid down to form the filter medium. Similar spatial variability is expected in the aerosol penetration through the filters. Therefore, a test method has been developed for measuring the spatial variability in aerosol penetration. The main components of this method are an aerosol generator, a filter test stand with a movable sampling inlet, an aerosol size spectrometer, and an aerosol photometer. Measurements with the filter media of N95 respirators, tested at average filtration velocities corresponding to light, moderate, and heavy work loads, have shown spatial variations in aerosol penetration in excess of 100% relative to the average aerosol penetration for the entire respirator. N95 respirators are required to be at least 95% efficient (i.e., less than 5% penetrating) at the most penetrating particle size, when tested at 85 L/min. Tests with the new method have shown that the aerosol penetration of the most penetrating particles of about 0.1 micron diameter may locally be higher than 5%, while the average aerosol penetration of 0.1 micron particles is less than 5%.
纤维过滤介质广泛应用于呼吸器中，用于从工人吸入的气流中去除空气中的颗粒物。根据美国国家职业安全与健康研究所（NIOSH）的新法规42 CFR 84，N95半面罩颗粒物呼吸器似乎是使用最频繁的呼吸器。当将N95呼吸器的纤维过滤介质对着光线时，通过视觉观察可以看到光穿透该介质时存在相当大的空间变异性。这种变异性是由于纤维制造和铺设形成过滤介质的方式所致。预计气溶胶穿透过滤器时也会出现类似的空间变异性。因此，已开发出一种测试方法来测量气溶胶穿透的空间变异性。该方法的主要组件包括气溶胶发生器、带有可移动采样入口的过滤器测试台、气溶胶粒径谱仪和气溶胶光度计。对N95呼吸器过滤介质在对应于轻、中、重工作负荷的平均过滤速度下进行测试，结果表明气溶胶穿透的空间变化相对于整个呼吸器的平均气溶胶穿透率超过100%。N95呼吸器在85 L/min的流量下进行测试时，要求在最易穿透粒径下至少具有95%的过滤效率（即穿透率小于5%）。使用新方法进行的测试表明，直径约0.1微米的最易穿透颗粒的气溶胶穿透率在局部可能高于5%，而0.1微米颗粒的平均气溶胶穿透率小于5%。
