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Prolonged exposure to respirable crystalline silica (RCS) causes silicosis and is also considered a cause of cancer. To meet emerging needs for precise measurements of RCS, from shorter sampling periods (<4h) and lower air concentrations, collaborative work was done to assess the differences between personal respirable samplers at higher flow rates. The performance of FSP10, GK2.69, and CIP 10 R samplers were compared with that of the Safety In Mines Personal Dust Sampler (SIMPEDS) sampler as a reference, which is commonly used in the UK for the measurement of RCS. In addition, the performance of the FSP10 and GK 2.69 samplers were compared; at the nominal flow rates recommended by the manufacturers of 10 and 4.2 l · min−1 and with flow rates proposed by the National Institute for Occupational Safety and Health of 11.2 and 4.4 l · min−1. Samplers were exposed to aerosols of ultrafine and medium grades of Arizona road dust (ARD) generated in a calm air chamber. All analyses for RCS in this study were performed at the Health and Safety Laboratory. The difference in flow rates for the GK2.69 is small and does not result in a substantial difference in collection efficiency for the dusts tested, while the performance of the FSP10 at 11.2 l · min−1 was more comparable with samples from the SIMPEDS. Conversely, the GK2.69 collected proportionately more crystalline silica in the respirable dust than other samplers, which then produced RCS results most comparable with the SIMPEDS. The CIP 10 R collected less ultrafine ARD than other samplers, as might be expected based on earlier performance evaluations. The higher flow rate for the FSP10 should be an added advantage for task-specific sampling or when measuring air concentrations less than current occupational exposure limits.

High flow rate respirable size selective samplers, GK4.126 and FSP10 cyclones, were calibrated for thoracic-size selective sampling in two different laboratories. The National Institute for Occupational Safety and Health (NIOSH) utilized monodisperse ammonium fluorescein particles and scanning electron microscopy to determine the aerodynamic particle size of the monodisperse aerosol. Fluorescein intensity was measured to determine sampling efficiencies of the cyclones. The Health Safety and Laboratory (HSL) utilized a real time particle sizing instrument (Aerodynamic Particle Sizer) and poly-disperse glass sphere particles and particle size distributions between the cyclone and reference sampler were compared. Sampling efficiency of the cyclones were compared to the thoracic convention defined by the American Conference of Governmental Industrial Hygienists (ACGIH)/Comité Européen de Normalisation (CEN)/International Standards Organization (ISO). The GK4.126 cyclone showed minimum bias compared to the thoracic convention at flow rates of 3.5 l min−1 (NIOSH) and 2.7–3.3 l min−1 (HSL) and the difference may be from the use of different test systems. In order to collect the most dust and reduce the limit of detection, HSL suggested using the upper end in range (3.3 l min−1). A flow rate of 3.4 l min−1 would be a reasonable compromise, pending confirmation in other laboratories. The FSP10 cyclone showed minimum bias at the flow rate of 4.0 l min−1 in the NIOSH laboratory test. The high flow rate thoracic-size selective samplers might be used for higher sample mass collection in order to meet analytical limits of quantification.

This article discusses the practical challenge of meeting USEPA requirements for equivalency between novel particulate matter monitoring instruments and the USEPA WINS PM 2.5 Impactor (i.e., the Federal Reference Method sampler for fine particulate matter). A project was undertaken to develop a new PM 2.5 instrument in which the WINS impactor was substituted by a cyclone, to give superior performance over long sampling periods under heavy loading. Empirical cyclone models were used to develop a new generation of very sharp cut cyclones (VSCC), together with a particular VSCC specimen suited to PM 2.5 sampling at 16.67 l min −1 . In laboratory tests, this VSCC demonstrated a precise 2.5 µm D 50 cutpoint and sharpness as good as the WINS. A formal application was then undertaken to achieve USEPA Class II Equivalency designation. The process included aerosol laboratory loading trials, with results showing no change in cutpoint after up to 90 days between cleaning cycles. Field trials to compare the VSCC to the WINS FRM were then performed in both western and eastern air sheds to demonstrate the precision and accuracy of the candidate VSCC FEM. The results showed that the VSCC instrument yielded precision and accuracy within USEPA requirements, although the USEPA data requirements for the field trials (in terms of aerosol size distribution and concentration) were not fully met. The outcome of the project was that the Class II equivalency designation was achieved, but not without major difficulties in gathering suitable and sufficient data to meet the stringent test requirements laid down by USEPA. Some changes in the designation procedure are recommended in light of this experience.