PERFORMANCE, FLUID MECHANICS, AND DESIGN OF A SMALL-ANIMAL, WHOLE-BODY INHALATION EXPOSURE CHAMBER

Abstract

A 0.7-m3 inhalation exposure chamber was designed for continuous whole-body exposure of up to 64 small laboratory rodents to a variety of airborne toxicants using either single- or multiple-tier configuration. Though similar in design to conventional exposure chambers currently in use, several design modifications were incorporated to improve chamber performance with regard to both animal maintenance and toxicant distribution within the chamber. Several approaches were taken to assess chamber performance characteristics. Repeated, random-order serial sampling of 27 discrete loci within the exposure volume was used to determine both spatial and temporal distribution of polydisperse NaCl aerosols (1.3 m MMAD, 1.65) . The collective spatial and temporal deviation of aerosol cong centration within the exposure volume as a whole ranged from 3.5 to 5.2% as a function of single versus multiple-tier configuration. Application of a mathematical model of mixing characteristics in dynamic-flow reaction vessels demonstrated that the effective mixing volume in the chamber varied from 50 to 65% of total chamber volume, depending upon configuration. Computational fluid mechanics methods used to model flow structure within the exposure volume demonstrated that buoyant forces dominated flow structure development. Flow structure was shown to be sensitive to small changes in temperature. There was a marked agreement between assessment of chamber performance by flow structure analysis and assessment of performance by more conventional methods.