ABSTRACT
Microorganisms are omnipresent indoors and their main sources include humans, domestic animals, soil and plants, and outdoor air entering the building through ventilation and air-conditioning systems. The development and spread of microorganisms depend on many environmental parameters, such as geographical location, temperature, humidity, the presence of organic and inorganic sources of nutrients, and electromagnetic radiation as well as urbanisation. This chapter discusses the influence of environmental conditions (season, temperature, humidity, geographical location) on the microbial quality of indoor air. The available data indicate among others that ventilation and air-conditioning systems are not without significance for the microbiological cleanliness of the buildings, which, if improperly maintained, may become an active source of such contamination. The importance of the impact of urbanization on microbiological contamination of the air was also pointed out.
