Shift of Aerosol Penetration in Respirable Cyclone Samplers

Abstract

To investigate the effect of aerosol loading on cyclone performance, an ultrasonic atomizing nozzle was used to generate micrometer-sized particles as challenge aerosols. A 25-mCi Po-210 radioactive source neutralized the particles to the Boltzmann charge equilibrium. An aerodynamic particle sizer measured the particle size distributions and number concentrations upstream and downstream of the cyclones. A humidifying system controlled the relative humidity in the test chamber to study the effect of hygroscopic properties on aerosol penetration as a function of particle size. The change in cyclone collection efficiency curve was significant. For example, the aerosol penetration of 4 µm particles dropped from 50% to about 30% for the nylon cyclone when challenged with small potassium sodium tartrate particles (count median diameter [CMD] of 3.5 µm, geometric standard deviation [GSD] of 1.3, mass concentration of 4.6 mg/m3) for 3 hours. The deviation was less serious (from 50% to about 40%) for the multi-inl...