High efficiency CIP 10-I personal inhalable aerosol sampler

Abstract

The CIP 10 personal aerosol sampler was first developed by Courbon for sampling the respirable fraction of mining dust. This respirable aerosol sampler was further improved by Fabries, then selectors for sampling thoracic and inhalable aerosols were designed. Kenny et al. evaluated the particle-size dependent sampling efficiency of the inhalable version in a large-scale wind tunnel using a life-size dummy. The authors found that the overall sampling efficiency decreases more rapidly than the CEN-ISO-ACGIH target efficiency curve. Görner and Witschger measured the aspiration efficiency of the CIP 10 omni-directional inlet. They found that the aspiration efficiency was high enough for inhalable aerosol sampling. This result led to the conclusion that the low sampling efficiency is due to some internal losses of the aspirated particles before they reach the final sampling stage, namely the CIP 10 rotating filter. Based on the assumption that the inhalable particles are selected at selector aspiration level, an experimental research project was conducted to improve particle transmission to the collection stage of the sampler. Two different inhalable selectors were designed by Görner and tested in a laboratory wind tunnel. The transmission efficiency of both models was measured by Roger following an experimental protocol described by Witschger. The T-shaped air flow circuit was finally adopted to draw the aspirated particles into the final collection stage of the CIP 10. Actually, in this selector, the almost horizontally aspirated particles should be conducted vertically to the rotating cup. In two previous prototypes, particles could be deposited in certain places by inertia (where the aerosol was forced to deviate drastically) or by sedimentation (where the aerosol decelerated). The aerodynamic behaviour of the adopted solution causes the particles to accelerate radially between two horizontal plates before they enter a vertical tube. This acceleration avoids the particles being deposited on the lower horizontal plate. At the beginning of the vertical tubing, the mutually opposing particle trajectories limit particle wall deposition by virtual impaction effect. The inner selector walls are polished to avoid particles being stopped by eventual surface asperities. Particle size-dependent sampling efficiency was measured in the laboratory wind tunnel. The experimental aerosol was composed of polydisperse glass micro-spheres. The size analysis of the particles collected was done by the Coulter Counter technique. The transmission efficiency (reciprocal to wall losses) was found to be close to 100 % for the entire range of particle sizes, and indicated no particle loss. The overall sampling efficiency was measured using a rotating bluff body at an external wind speed of 1 m/s. The rotating bluff body represents a scaled torso of an operator. The "high efficiency" CIP 10-I (I for inhalable) responds fairly well to the conventional CEN-ISO-ACGIH criteria for sampling the inhalable health-related aerosol fraction.