Effect of Equilibration Zones on Stability, Uniformity, and Homogeneity Profiles of Vapors and Aerosols in the ADG Nose-Only Inhalation Exposure System

Effect of Equilibration Zones on Stability, Uniformity, andHomogeneity Profiles of Vapors and Aerosols in the ADG Nose-OnlyInhalation Exposure System. GREEN, J. D., HELKE, W. F., SCOTT,J. B., YAU, E. T., TRAINA, V. M., AND DIENER, R. M. (1984).Fundam. Appl. Toxicoi. 4, 768–777. A commercially available,inexpensive, nose-only exposure chamber was modified to includeremovable equilibration zones, and the effect of these zoneson chamber performance was determined. Since limited performancedata were available concerning this unit, a more extensive characterizationwas performed. EPA limit concentrations (5 mg/liter) of toluenevapor or corn oil aerosol, and relatively low concentrationsof uranine aerosol (50 pg/liter) were produced by standard techniques.The presence or absence of equilibration zones did not affectthe stability or uniformity of toluene vapor atmospheres, withthe coefficient of variation (CV) not exceeding 3.33% in allexperiments. In contrast, the presence of two equilibrationzones was found to progressively enhance the uniformity of theinhalable test aerosols in the animal exposure zone (CV 3.16%).Matrix sampling revealed that in both uranine and corn oil experiments,the center matrix point concentration was consistently lowerthan samples taken in the actual animal breathing zone. Equilibrationzones markedly reduced the difference between breathing zoneand center point concentrations. These performance data indicatedthat the modified ADG nose-only exposure system performed exceptionallywell with the materials that were studied. Results were comparableto those describing whole-body chamber performance. The readyavailability of this inexpensive prototype lends itself to standardizationof techniques between laboratories