Particle-collection efficiency of the CIP 10-M personal sampler’s rotating cup containing aqueous or viscous collection fluid

The CIP 10-M personal sampler measures worker exposure to airborne particles making up the conventional inhalable fraction by collecting particles in a rotating metal cup containing a few milliliters of a collection fluid. Aqueous liquids are generally used, but their rapid evaporation limits the duration of sampling; alternative collection fluids could alleviate this problem. Indeed, the particle-collection efficiency of the rotating cup has not been extensively studied, and the only data available relate to a discontinued model. This study aimed to measure the collection efficiency of the current rotating cup model containing an aqueous (water) or viscous (ViaTrap mineral oil) collection fluid. The kinetics of evaporation confirmed that ViaTrap does not evaporate, making 8-h sampling campaigns in constant volumes feasible. Particles with a wide range of aerodynamic diameters (between around 0.1 and 10 µm) were produced using various test rigs and mono- or poly-disperse test aerosols. Both new and older cup models performed similarly, with a collection efficiency of > 80% for larger particles (aerodynamic diameters > 2.8 µm), progressively decreasing to around 50% for aerodynamic diameters of 2.1 µm; with aerodynamic diameters of < 1 µm, the collection efficiency was generally < 10%. In physical terms, collection efficiency was unaffected by the type (aqueous or viscous) or volume (between 0 and 3 mL) of collection fluid used. Bias maps indicated that the inhalable fraction may be underestimated in occupational settings, particularly with aerosols mainly composed of particles with aerodynamic diameters of less than around 3 µm.