It is estimated that even up to 30% of buildings worldwide may be the subject of complaints connected with the quality of indoor air. Potential sources of air pollution can be both organic and inorganic particles. This article focuses on biological air pollutants from living and dead biological sources, especially those connected with fungi. Fungi found in the indoor air of domestic dwellings in a large extent are similar in their species composition to those found on the outside of the building. Microorganisms enters into the buildings during the airing of rooms or through the different slots and can develop on the surfaces of various materials. Intensively develops in a poorly ventilated, damp and dusty environments. For this reason the exposure to the indoor air pollution might be stranger for inhabitants than the expose to the impurities of the outdoor air. Presence of fungi in domestic dwellings can be very danger because of most often is associated with allergic reactions, mycotoxins, volatile organic compounds or even with fungal infections.