Buildings that serve nonresidential purposes, such as office complexes, a large diversity of retail and commercial units, and institutional buildings (schools, universities, hospitals, day-care centers, and convalescent and retirement homes), experience a variety of complaints that may be associated with poor indoor air/indoor environment quality. When a building is subject to complaints sufficient to convince management to conduct an indoor environment (IE) investigation, it is often characterized as a “problem” or “sick” building. Health complaints have been described as being due to buildingrelated illness, or tight building/sick building syndrome.