Willeke K, Qian Y, Donnelly J, Grinshpun S, Ulevicius V
Department of Environmental Health, University of Cincinnati, OH 45267-0056, USA.
Am Ind Hyg Assoc J. 1996 Apr;57(4):348-55. doi: 10.1080/15428119691014882.
This study investigated bacterial penetration of different bacterial shapes, aerodynamic sizes, and flow rates through a surgical mask and a dust/mist respirator. The bacterial penetrations were compared with those of spherical corn oil particles of the same aerodynamic diameter tested under the same conditions. The tests were performed at different levels of aerosol penetration. Bacteria, ranging from spherical to rod-shaped with a high aspect (length to width) ratio, were selected as test agents. Among these, Pseudomonas fluorescens physically simulates Mycobacterium tuberculosis by shape and size. The concentrations of bacteria upstream and downstream of the test devices were measured with an aerodynamic size spectrometer. This instrument was found to measure the total viable and nonviable bacterial concentration effectively and dynamically over the entire bacterial size range down to 0.5 microns in aerodynamic size. The results indicate that the spherical corn oil particles and the spherical Streptococcus salivarius bacteria have the same penetration in the size range from 0.9 to 1.7 microns. It has been found that rod-shaped bacteria penetrate less. The penetration difference between the spherical and rod-shaped bacteria depends on the aspect ratio of the bacteria. For an aspect ratio of 4, the penetration of rod-shaped bacteria is about half that of spherical ones. Thus, it is projected that a respirator with 90% efficiency against spherical microorganisms or test particles (10% penetration) will be 95% efficient against rod-shaped microorganisms of the same aerodynamic equivalent diameter with an aspect ratio of 3 to 4, such as Mycobacterium tuberculosis (5% penetration).
本研究调查了不同形状、空气动力学尺寸和流速的细菌透过手术口罩和防尘/防雾呼吸器的情况。将细菌透过率与在相同条件下测试的具有相同空气动力学直径的球形玉米油颗粒的透过率进行了比较。测试在不同的气溶胶透过水平下进行。选择了从球形到具有高纵横比（长度与宽度之比）的杆状的细菌作为测试剂。其中，荧光假单胞菌在形状和大小上物理模拟结核分枝杆菌。使用空气动力学尺寸光谱仪测量测试装置上游和下游的细菌浓度。发现该仪器能够在低至0.5微米空气动力学尺寸的整个细菌尺寸范围内有效且动态地测量总活菌和死菌浓度。结果表明，在0.9至1.7微米的尺寸范围内，球形玉米油颗粒和球形唾液链球菌具有相同的透过率。已发现杆状细菌的透过率较低。球形和杆状细菌之间的透过率差异取决于细菌的纵横比。对于纵横比为4的情况，杆状细菌的透过率约为球形细菌的一半。因此，预计对球形微生物或测试颗粒具有90%效率（10%透过率）的呼吸器，对具有3至4纵横比的相同空气动力学等效直径的杆状微生物（如结核分枝杆菌，5%透过率）将具有95%的效率。
