As indicated in previous chapters, built environments are subject to a number of potentially significant indoor air quality/indoor environment (IAQ/IE) problems that may cause acute symptoms, long-term health risks, discomfort, or odor. With the exception of severe cases of acute illness or unpleasant odors, most problems (or potential problems such as radon) go unrecognized. In the case of residential and nonresidential buildings, a need to conduct an IAQ/IE investigation develops only after occupants become aware that health and other problems may be associated with home or work environments. Awareness development is rapid when an odor problem or some type of physical discomfort occurs. In most cases, building occupants do not suspect a causal relationship between acute and chronic illness symptoms (which characterize classical air quality-related symptoms) and their building environment. High prevalence rates of sick building syndrome (SBS)-type symptoms in noncomplaint buildings suggest that most individuals so-affected do not realize that their building/work environment is in any way responsible.