Department of Mechanical Engineering, University of Minnesota, 111 Church Street, Minneapolis, MN 55455, USA.
Department of Integrated Engineering, Minnesota State University Mankato, Trafton N141, Mankato, MN 56001, USA.
Ann Work Expo Health. 2017 Jul 1;61(6):737-747. doi: 10.1093/annweh/wxx044.
Elevated concentrations of diesel exhaust have been linked to adverse health effects. Filtering facepiece respirators (FFRs) are widely used as a form of respiratory protection against diesel particulate matter (DPM) in occupational settings. Previous results (Penconek A, Drążyk P, Moskal A. (2013) Penetration of diesel exhaust particles through commercially available dust half masks. Ann Occup Hyg; 57: 360-73.) have suggested that common FFRs are less efficient than would be expected for this purpose based on their certification approvals. The objective of this study was to measure the penetration of DPM through NIOSH-certified R95 and P95 electret respirators to verify this result. Gravimetric-based penetration measurements conducted using polytetrafluoroethylene (PTFE) and polypropylene (PP) filters were compared with penetration measurements made with a Scanning Mobility Particle Sizer (SMPS, TSI Inc.), which measures the particle size distribution. Gravimetric measurements using PP filters were variable compared to SMPS measurements and biased high due to adsorption of gas phase organic material. Relatively inert PTFE filters adsorbed less gas phase organic material resulting in measurements that were more accurate. To attempt to correct for artifacts associated with adsorption of gas phase organic material, primary and secondary filters were used in series upstream and downstream of the FFR. Correcting for adsorption by subtracting the secondary mass from the primary mass improved the result for both PTFE and PP filters but this correction is subject to 'equilibrium' conditions that depend on sampling time and the concentration of particles and gas phase hydrocarbons. Overall, the results demonstrate that the use of filters to determine filtration efficiency of FFRs challenged with diesel exhaust produces erroneous results due to the presence of gas phase hydrocarbons in diesel exhaust and the tendency of filters to adsorb organic material.
柴油机排气中污染物浓度升高与健康不良效应有关。过滤式面罩（FFR）在职业环境中被广泛用作针对柴油机颗粒物（DPM）的呼吸保护形式。先前的研究结果（Penconek A、Drążyk P、Moskal A.（2013 年）：商业用防尘半面罩对柴油机排气颗粒物的穿透性。Ann Occup Hyg；57：360-73.）表明，普通 FFR 的效率低于其认证批准的预期，因此不太适合此用途。本研究的目的是测量 NIOSH 认证的 R95 和 P95 驻极体口罩对 DPM 的穿透率，以验证这一结果。使用聚四氟乙烯（PTFE）和聚丙烯（PP）过滤器进行基于重量的穿透率测量，并与使用扫描迁移率颗粒谱仪（SMPS，TSI Inc.）进行的穿透率测量进行比较，后者测量颗粒尺寸分布。与 SMPS 测量相比，使用 PP 过滤器进行的重量测量存在较大的变异性，并且由于气相有机物质的吸附而存在偏高的偏差。相对惰性的 PTFE 过滤器吸附的气相有机物质较少，从而使测量结果更加准确。为了尝试纠正与气相有机物质吸附相关的假象，FFR 上游和下游串联使用初级和次级过滤器。通过从初级质量中减去次级质量来校正吸附作用，可提高 PTFE 和 PP 过滤器的结果，但这种校正受取决于采样时间和颗粒及气相烃浓度的“平衡”条件的限制。总体而言，这些结果表明，使用过滤器来确定受到柴油机排气挑战的 FFR 的过滤效率会因柴油机排气中存在气相烃以及过滤器吸附有机物质的趋势而产生错误的结果。
