Collection efficiency for submicron particles of a commonly used impinger

The collection efficiency for submicron particles of an all-glass impinger, under conditions commonly used by industrial hygienists, was studied by me asuring the removal of particles from a polydisperse polystyrene aerosol. C ollection efficiencies for water and dimethylformamide as sampling liquids at Row rates of 0.7, 1.0, and 2.0 L/min were determined. The collection eff iciency at a flow rate of 1.0 L/min was found to be less than 20% for parti cles with a diameter between 0.02 and 0.7 mu m. When thermally generated pa rticles are a part of the exposure pattern and air measurements are made us ing the all-glass midget impinger as the collection device, the particulate contribution to the exposure could be severely underestimated due to poor collection efficiency in the submicron range.