Design and Operation of a Batch-Feed Fluidizing Bed Aerosol Generator for Inhalation Toxicity Studies

Abstract

A fluidizing bed aerosol generator (FBG), designed for inhalation toxicity studies, was constructed and tested. A key design feature contributing to its operational stability was the partial masking of the screen supporting the bronze beads. This caused 20–80% of the bed to fluidize under normal operating conditions. The non-fluidizing areas functioned as reservoirs to “feed” the fluidizing areas. Using a bed volume of 1000 cc of bronze beads and 20 g of MnO2 dust, the mass output rate ranged from 0.1 to 1.0 mg/min when operated at plenum pressures of 1.04×102 to 2.42×102 kPa (minimum fluidization pressure was approximately 82.8 kPa). During daily operation at three different output rates, the FBG produced aerosols with little change in particle size distributions or concentration when operated six hours/day for five days. Furthermore, when the FBG was operated at a fixed output rate for 15 days with two recharges of MnO2 dust, the particle size distribution did not show any cumulative increase. Thus, long-term operation of this FBG should result in a reproducible range of concentration and particle size distribution.