Chen Chun-Wan, Huang Sheng-Hsiu, Chiang Che-Ming, Hsiao Ta-Chih, Chen Chih-Chieh
Institute of Occupational Safety and Health, Council of Labor Affairs, No. 99, Lane 407, Hengke Road, Shijr City, Taipei County, Taiwan.
Ann Occup Hyg. 2008 Apr;52(3):207-12. doi: 10.1093/annhyg/men008. Epub 2008 Mar 7.
The performance of dust cartridge filters commonly used in dust masks and in room ventilation depends both on the collection efficiency of the filter material and the pressure drop across the filter. Currently, the optimization of filter design is based only on minimizing the pressure drop at a set velocity chosen by the manufacturer. The collection efficiency, an equally important factor, is rarely considered in the optimization process. In this work, a filter quality factor, which combines the collection efficiency and the pressure drop, is used as the optimization criterion for filter evaluation. Most respirator manufacturers pleat the filter to various extents to increase the filtration area in the limit space within the dust cartridge. Six sizes of filter holders were fabricated to hold just one pleat of filter, simulating six different pleat counts, ranging from 0.5 to 3.33 pleats cm(-1). The possible electrostatic charges on the filter were removed by dipping in isopropyl alcohol, and the air velocity is fixed at 100 cm s(-1). Liquid dicotylphthalate particles generated by a constant output atomizer were used as challenge aerosols to minimize particle loading effects. A scanning mobility particle sizer was used to measure the challenge aerosol number concentrations and size distributions upstream and downstream of the pleated filter. The pressure drop across the filter was monitored by using a calibrated pressure transducer. The results showed that the performance of pleated filters depend not only on the size of the particle but also on the pleat count of the pleated filter. Based on filter quality factor, the optimal pleat count (OPC) is always higher than that based on pressure drop by about 0.3-0.5 pleats cm(-1). For example, the OPC is 2.15 pleats cm(-1) from the standpoint of pressure drop, but for the highest filter quality factor, the pleated filter needed to have a pleat count of 2.65 pleats cm(-1) at particle diameter of 122 nm. From the aspect of filter quality factor, this study suggests that the respirator manufacturers should add approximately 0.5 pleats cm(-1) to the OPC derived from the generalized correlation curve for pleated filter design based on minimum pressure drop.
防尘口罩和室内通风中常用的筒式滤芯过滤器的性能，既取决于过滤材料的收集效率，也取决于过滤器两端的压降。目前，过滤器设计的优化仅基于在制造商选定的设定风速下将压降降至最低。收集效率作为一个同样重要的因素，在优化过程中很少被考虑。在这项工作中，一个结合了收集效率和压降的过滤器品质因数，被用作过滤器评估的优化标准。大多数呼吸器制造商将过滤器折叠到不同程度，以在滤筒内的有限空间内增加过滤面积。制作了六种尺寸的过滤器支架，每个支架只容纳一褶过滤器，模拟六种不同的褶数，范围从0.5到3.33褶/厘米（-1）。通过浸入异丙醇去除过滤器上可能的静电荷，并将风速固定在100厘米/秒。由恒流雾化器产生的邻苯二甲酸二辛酯液体颗粒用作挑战气溶胶，以尽量减少颗粒负载效应。使用扫描迁移率粒径分析仪测量褶式过滤器上游和下游的挑战气溶胶质数浓度和粒径分布。通过使用校准的压力传感器监测过滤器两端的压降。结果表明，褶式过滤器的性能不仅取决于颗粒大小，还取决于褶式过滤器的褶数。基于过滤器品质因数，最佳褶数（OPC）总是比基于压降的最佳褶数高约0.3 - 0.5褶/厘米（-1）。例如，从压降的角度来看，OPC为2.15褶/厘米（-1），但对于最高的过滤器品质因数，在粒径为122纳米时，褶式过滤器需要有2.65褶/厘米（-1）的褶数。从过滤器品质因数的角度来看，这项研究表明，呼吸器制造商应在基于最小压降的褶式过滤器设计的通用关联曲线得出的OPC基础上，增加约0.5褶/厘米（-1）。
