The design, testing and use of a 23 mm internal diameter cyclone for sampling of respirable dust are described. Calibration of the cyclone using an Aerodynamic Particle Sizer showed that the size selection characteristic of the cyclone gave a close match of the BMRC d50at a flow rate of 9.2 l. min−1.On this basis, field trials were conducted at this flow rate and measurements of respirable dust (by weighing) and respirable silica (by XRD) emissions from a number of mineral processing stacks are included. Computer modelling of the cyclone performance later showed that, owing to differences in the shapes of the size selection curves, the respirable mass collection of the cyclone was closest to that of the BMRC definition when operated at a flow rate of 10.2 l. min−1. At this flow rate, the cyclone should be capable of selecting respirable dust with a total mass error of less than
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