Particle collection efficiency of the rotating cup of the CIP 10-M sampler filled with aqueous or viscous liquids

The CIP 10-M personal sampler has been developed to measure worker exposure to airborne particles according to the conventional inhalable fraction. Particles are collected in a metal rotating cup filled with a few milliliters of a collecting liquid. The major drawback of aqueous liquids, which are normally used with the CIP 10-M, is the fact that they evaporate quickly during the sampling and then, the collection of particles may end in a completely dry rotating cup. There is few experimental data concerning the particles collection efficiency of the rotating cup and they only concerns a previous model of the rotating cup, which is no longer available; influence of volume or type of liquid also remains not determined. Starting from the hypotheses that a viscous non-evaporating liquid could increase the sampling duration and improve the physical performances, the aim of this study was to measure the collection efficiency of the new rotating cup filled with aqueous (water) or viscous (ViaTrap mineral oil). The collecting liquid evaporation kinetic (decrease of the volume vs. time) in the rotating cup was measured. It confirms that the ViaTrap does not evaporate and that it is possible to perform 8h-long sampling without any loss of the initial volume contained in the cup. Different test rigs and mono- or poly-disperse test aerosols allowed us to perform complementary measurements of the collection efficiency of the rotating cup according to a wide range of aerodynamic diameters (between around 0.1 and 10 µm). Neither the type (aqueous or viscous) nor the volume (between 0 and 3 mL) of the liquid influences the physical collection efficiency of the CIP 10-M rotating cup. The use of the CIP 10-M in order to make sampling related to the inhalable fraction in occupational areas may lead to underestimations of the worker exposure when the emitted aerosols are mainly composed of particles presenting aerodynamic diameters below around 3 µm.