Workable and effective control strategies must be based on an understanding of several pertinent factors, First, contaminants need to be assessed in terms of concentration, reactivity, physical state and particle size. If applicable, second, emission source configurations should be taken into account. It is important to know that discharges are continuous or intermittent, point or area releases, and originate primarily indoors or outdoors. The nature of exposure response relations must be considered. The individuals are required to be protected from long-term exposures to even low concentration of certain pollutants, Finally the type of indoor enclosure is important. Some ameliorating measures are more suited to private residences than to public buildings