Typically, studies on indoor fungal growth in buildings focus on structures with known or suspected water damage, moisture, and/or indoor fungal growth problems. Reference information on types of culturable fungi and total fungal levels are generally not available for buildings without these problems. This study assessed 50 detached single-family homes in metropolitan Atlanta, Ga., to establish a baseline of "normal and typical" types and concentrations of airborne and dustborne fungi in urban homes which were predetermined not to have noteworthy moisture problems or indoor fungal growth. Each home was visually examined, and samples of indoor and outdoor air and of indoor settled dust were taken in winter and summer. The results showed that rankings by prevalence and abundance of the types of airborne and dustborne fungi did not differ from winter to summer, nor did these rankings differ when air samples taken indoors were compared with those taken outdoors. Water indicator fungi were essentially absent from both air and dust samples. The air and dust data sets were also examined specifically for the proportions of colonies from ecological groupings such as leaf surface fungi and soil fungi. In the analysis of dust for culturable fungal colonies, leaf surface fungi constituted a considerable portion (>20%) of the total colonies in at least 85% of the samples. Thus, replicate dust samples with less than 20% of colonies from leaf surface fungi are unlikely to be from buildings free of moisture or mold growth problems.

Indoor air in occupied buildings is always more polluted from human‐sourced contaminants than the air outside the building. This is true for modern buildings constructed during the past decade as well as for primitive shelters erected centuries or millennia ago. It follows that a continuous source of outdoor air is required to prevent the degradation of indoor air from contaminants arising from people and their activities. This was realized historically by the inventors of roof vents for exhaust of fire smoke and by early designers of openable windows for introduction of make‐up (outdoor) air. Major sources on indoor air pollutants are discussed, i.e., microbials, allergens, volatile organic compounds, pesticides, combustion products, tobacco smoke, radon, and particulates. Sampling of these pollutants and interpretation of data are included. Varied approaches to indoor air quality studies, ventilation, protocols and guidelines, and control are discussed.