Qian Y, Willeke K, Grinshpun S A, Donnelly J, Coffey C C
Department of Environmental Health, University of Cincinnati, OH 45267-0056, USA.
Am Ind Hyg Assoc J. 1998 Feb;59(2):128-32. doi: 10.1080/15428119891010389.
In 1995 the National Institute for Occupational Safety and Health issued new regulations for nonpowered particulate respirators (42 CFR Part 84). A new filter certification system also was created. Among the new particulate respirators that have entered the market, the N95 respirator is the most commonly used in industrial and health care environments. The filtration efficiencies of unloaded N95 particulate respirators have been compared with those of dust/mist (DM) and dust/fume/mist (DFM) respirators certified under the former regulations (30 CFR Part 11). Through laboratory tests with NaCl certification aerosols and measurements with particle-size spectrometers, N95 respirators were found to have higher filtration efficiencies than DM and DFM respirators and noncertified surgical masks. N95 respirators made by different companies were found to have different filtration efficiencies for the most penetrating particle size (0.1 to 0.3 micron), but all were at least 95% efficient at that size for NaCl particles. Above the most penetrating particle size the filtration efficiency increases with size; it reaches approximately 99.5% or higher at about 0.75 micron. Tests with bacteria of size and shape similar to Mycobacterium tuberculosis also showed filtration efficiencies of 99.5% or higher. Experimental data were used to calculate the aerosol mass concentrations inside the respirator when worn in representative work environments. The penetrated mass fractions, in the absence of face leakage, ranged from 0.02% for large particle distributions to 1.8% for submicrometer-size welding fumes. Thus, N95 respirators provide excellent protection against airborne particles when there is a good face seal.
1995年，美国国家职业安全与健康研究所发布了关于无动力微粒呼吸器的新规定（《联邦法规汇编》第42编第84部分）。同时还创建了一个新的过滤器认证系统。在已进入市场的新型微粒呼吸器中，N95呼吸器是工业和医疗环境中最常用的。已将未使用的N95微粒呼吸器的过滤效率与根据以前的规定（《联邦法规汇编》第30编第11部分）认证的防尘/防雾（DM）和防尘/防烟/防雾（DFM）呼吸器的过滤效率进行了比较。通过使用氯化钠认证气雾剂进行实验室测试以及使用粒度光谱仪进行测量，发现N95呼吸器比DM和DFM呼吸器以及未经认证的外科口罩具有更高的过滤效率。发现不同公司生产的N95呼吸器对于最易穿透粒径（0.1至0.3微米）具有不同的过滤效率，但对于该粒径的氯化钠颗粒，所有N95呼吸器的过滤效率均至少为95%。在最易穿透粒径以上，过滤效率随粒径增加；在约0.75微米时达到约99.5%或更高。对大小和形状与结核分枝杆菌相似的细菌进行的测试也显示过滤效率为99.5%或更高。实验数据用于计算在典型工作环境中佩戴呼吸器时呼吸器内部的气溶胶质量浓度。在没有面部泄漏的情况下，穿透的质量分数范围从大颗粒分布的0.02%到亚微米级焊接烟雾的1.8%。因此，当面部密封良好时，N95呼吸器可提供出色的空气传播颗粒防护。
