As indicated in previous chapters, a variety of contaminants are generated within, drawn in as a result of infiltration and ventilation, or passively transported into indoor environments. Because of potential health risks and other factors such as comfort and odor, it may be desirable to control either airborne or surface contaminants or both. There are two primary approaches to controlling indoor contaminants. These include controlling the contaminant at the source (source control) or controlling contaminants once they are produced or become airborne (contaminant control). Contaminant control measures, ventilation, and air cleaning are discussed in detail in Chapters 11 and 12.