This work examines the physical factors that contribute to sampling errors in an aerosol sampling system consisting of a sampling probe and a sampling line. Aerosol particles are more massive than gas molecules and therefore tend to deviate from air streamlines in response to sudden directional change, which potentially leads to sampling errors during sample transfer processes. Based on well-established studies involving particle transport and deposition, an analysis was performed to determine the sampling line transmission efficiency for 0.5- and 5-μm particles as these particle sizes are used in defining air cleanliness level in ISO 14644-1[1] and FED-STD-209E.[2]* Our analytical results indicate that significant particle losses for 5-μm particles can occur if bends exist in the sampling lines. In addition, particle losses typically can be reduced by lowering the air velocity in the sampling line, and this can be achieved by using a sampling line with a larger inner diameter (I.D.). The example calculations also showed that 0.5-μm particles, with their insignificant inertia, have nearly 100% transmission efficiency regardless of the sampling line bends.

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