NEW AEROSOL SAMPLER WITH LOW WIND SENSITIVITY AND GOOD FILTER COLLECTION UNIFORMITY

The overall sampling efficiency of many aerosol samplers is sensitive to wind velocity and direction. In addition, most samplers have internal losses due to gravitational settling, electrostatic interactions, and internal turbulence. A new sampling inlet has been designed to reduce these problems. The flow patterns over the new prototype sampler were visualized in a horizontal wind tunnel. Visualization of the streamlines over the new sampler and limiting-streamline quantitative analysis showed negligible turbulence effects due to the inlet's geometry. The overall sampling efficiency of the prototype sampler was compared to that of a 25 mm closed-face cassette. Uranine was used as the challenge aerosol with particle physical diameters of 13.5, 20 and 30 mum. The wind velocity ranged from 100 to 300 cm s-1. Evaluation of the data showed the new sampler to be less significantly affected by wind direction and magnitude. The particle distribution observed on the sampler's filter was found to be reasonably uniform, an advantage for several types of analyses.