Engineered solutions for mitigation of IAQ problems

Development of engineered solutions to mitigate IAQ problems requires understanding of several factors: (1) contaminant types, sources, and interactions; (2) nature of building occupants and their activities; (3) building HVAC equipment design and operation, and (4) climate. Control strategies are passive or active, and include the following options: source control, exposure control, ventilation, and air cleaning. Controls of sources and exposures are mostly passive and prescriptive. Engineered controls of specific contaminant classes, such as Volatile Organic Compounds (VOCs) and particulates (PM,), are more actively directed at design and operational aspects of ventilation and air cleaning. Ventilation is the historic approach for control of contaminants. It is essentially dilution of contaminated "dirty" air with fresh "clean" air, and/or separation and venting of "dirty" air. Air cleaning, by contrast, is treatment through removal and/or conversion of individual air contaminants. Five overlapping technologies can be addressed: (1) filtration of particulates, (2) electrostatic precipitation of particulates, (3) reaction of negative ions with VOCs and PM, (4) sorption of VOCs onto solid sorbents, and (5) oxidation of VOCs. Engineered solutions require: knowledge of the contaminants to be controlled, ability to determine the distributions of contaminants in time and space, and understanding of the degree of control achievable by a particular technology. Combinations of new technologies using multipoint monitoring systems coupled with low-level, real-time detectors now provide the potential for greatly improved quantitation of control strategies and technologies. Implications for sampling, monitoring, and control will be reviewed.