Abstract
The generation of dry dust aerosols for animal exposures, where a long-time stable output is necessary, is a difficult and many faceted problem. In order to control accurately the exposure levels in chambers for long periods of time a system is required in which concentrations are continuously monitored and modified on an instantaneous basis. A system has been built that monitors and controls the dust output from a dry dust generator using a long-path opacity device with a feed back loop. The design makes it possible for a microcomputer to scan all parameters in the chamber room and print out on demand an update of the accumulated data. An investigation of system parameters are herein described. It is essential that the system operate with a variety of different types of dry dusts at a range of concentrations. The laboratory experiments describe the use of flyash, silica, carbon, olivine and Arizona road dust at chamber concentrations of from 400 to 3500 µgms/m3 in the respirable fraction. Testing indicates that concentrations of the various dusts can be maintained over an 8 hour period with only small fluctuations in concentration.