The effect of air control systems on the indoor distributions of viable particles.

The filtering effects of three types of air control systems at two wastewater treatment plants on viable particles were investigated. Aspergillus fumigatus and other thermophilic organisms were used as monitors for viable particles. The indoor concentrations of viable particles were found to be affected by building design and the use of conventional mechanical air systems. Viable particles of approximately 4.0 microm and greater in aerodynamic diameter were filtered from the air while respirable size particles less than 4.0 micromwere not filtered as well. There was evidence of growth of viable particles within the mechanical air systems. Conventional air control systems may not be adequate for the control of viable particle contamination of the indoor environment without modifications and proper maintenance.