Fängmark I, Wikström L E, Henningson E W
National Defence Research Establishment, Umeå, Sweden.
Am Ind Hyg Assoc J. 1991 Dec;52(12):516-20. doi: 10.1080/15298669191365144.
A modified personal impinger (MPI) for sampling airborne microorganisms was tested for collection efficiency with the jet nozzle placed at various positions above and below the liquid surface. The sampler was operated with 10 mL of water and sampling rates between 1.08 and 3.4 L/min. The collection efficiencies for a polydisperse aerosol of diethylhexyl phthalate (DEHP) and monodisperse aerosols of polystyrene latex particles (ULP) were determined with an optical particle counter. The results show that a test aerosol generated from a suspension, such as ULP, gives test results that agree better with theoretical predictions than a polydisperse oil aerosol such as DEHP. The measured aerodynamic 50% cutoff diameters (D50) agreed with those predicted from impaction theory with the jet nozzle 4 mm from the flask bottom. For preservation of viability during sampling of microorganisms, it is common to use impingers with the jet nozzle above the liquid surface. These tests showed that if the MPI is operated with the jet nozzle above the liquid surface, D50 will be displaced toward larger particle sizes because the jet-to-plate distance/jet diameter ratio increases substantially when a soft impaction surface such as the liquid is used. The increased D50 could to some extent be compensated for by increasing the flow rate. An increased flow rate will, however, result in more losses because of aerosol regeneration.
一种用于采集空气中微生物的改良型个人撞击式采样器（MPI），在将喷嘴置于液面上方和下方的不同位置时，对其采集效率进行了测试。该采样器使用10毫升水进行操作，采样速率在1.08至3.4升/分钟之间。用光学粒子计数器测定了邻苯二甲酸二异辛酯（DEHP）多分散气溶胶和聚苯乙烯乳胶颗粒（ULP）单分散气溶胶的采集效率。结果表明，由悬浮液产生的测试气溶胶，如ULP，其测试结果比多分散油气溶胶如DEHP更符合理论预测。当喷嘴距离烧瓶底部4毫米时，测得的空气动力学50%截止直径（D50）与撞击理论预测值一致。为了在微生物采样过程中保持活力，通常使用喷嘴在液面上方的撞击式采样器。这些测试表明，如果MPI在喷嘴位于液面上方的情况下运行，D50将向更大的粒径偏移，因为当使用诸如液体这样的软撞击表面时，射流到平板的距离与射流直径之比会大幅增加。增加流速在一定程度上可以补偿D50的增加。然而，流速增加会因气溶胶再生导致更多损失。
