The use of ultra-high-speed floor burnishing instruments to polish hard-surface floors in health care facilities is known to produce elevated concentrations of dust particles and microorganisms in indoor air. Special air restraint assemblies can be fitted onto ultra-high-speed burnishers, with the net effect that significant increases in the levels of dust particles and microorganisms are prevented (Schmidt et al., 1986). Similar devices are apparently not available for vacuum cleaning devices used for carpet maintenance.

Renovation and repair work, such as replacing windows or repairing furniture in residences, generally results in increased concentrations of fungi in occupied spaces (Hunter et al., 1988). The disturbance of walls visually contaminated by fungi in both residences (Hunter et al., 1988) and commercial buildings (Morey, 1990a) generally results in a 2 to 4 order of magnitude increase in airborne fungi, generally of a single type, at various distances from the disturbance site. In large buildings, the disturbance of fungus-contaminated insulation in the HVAC system can result in order of magnitude increases of fungi throughout the occupied spaces (Morey and Williams, 1991). As an example, renovation on a floor above a renal transplant ward was causally associated with an outbreak of nosocomial Aspergillus infection (Arnow et al., 1978). Movement of heavy equipment on the floor above the transplant ward probably caused sufficient vibration to allow dusts, including Aspergillus spores, to aerosolize in the ceiling space above the ward and to disseminate into patient areas.

Once contamination of a building has occurred, exposure can be controlled by removing the contamination (source control), by cleaning the air (E in the model), or by dilution control (V_o). Air cleaning and ventilation control can be accomplished by using local and/or central ventilation system components.

Source control in indoor environments is most effectively achieved by limiting moisture, which promotes the growth of some microorganisms (xerophilic fungi), and by limiting the use of fleecy finishing and furnishing materials (e.g., carpet), which by their porous nature permit the accumulation of allergens. Restricting the use of carpets, for example, to those that can be removed from the house for periodic cleaning is an effective means of helping to control house dust mite allergens.

Removing the source is the most effective means of remediating existing contamination. Furnishings and construction materials that are visibly