Health-based aerosol sampling should reflect how particles penetrate and deposit in various regions of the human respiratory system. Therefore, size-selective sampling should be adopted when monitoring aerosol concentration in the atmosphere. However, cyclone samplers, the most commonly used respirable sampler type in the workplace, show specific particle size-dependent bias toward the international respirable convention. Additionally, cyclone samplers are vulnerable to the dust loading effect resulting in an underestimation of respirable particulate matter. In the previous study, a virtual cyclone has been employed to overcome the dust loading effect, but still had the disadvantage of high aerosol penetration of large particle sizes. Therefore, in this work, the effects of key dimensions of virtual cyclones including chamber width (or inlet width), chamber size and inlet height on the separation performance were further studied and the configurations of virtual cyclones were modified to best fit the ISO/CEN/ACGIH respirable convention. Experimental results demonstrated that a better match with the ISO/CEN/ACGIH respirable convention curve can be achieved by increasing the chamber width to over 20 mm. Moreover, the new virtual cyclones can operate at a flow rate up to 21.5 L/min to collect more respirable particulate matter for the increasingly stringent respirable dust standards. The new virtual cyclones demonstrate accurate and constant measurement of the respirable dust for exposure assessment.
Keywords: Personal sampler; respirable convention; virtual cyclone.